BU-808: How to Prolong Lithium-based Batteries

Discover what causes Li-ion to age and what the battery user can do to prolong its life.

Battery research is focusing on lithium chemistries so much that one could imagine that the battery future lies solely in lithium. There are good reasons to be optimistic as lithium-ion is, in many ways, superior to other chemistries. Applications are growing and are encroaching into markets that previously were solidly held by lead acid, such as standby and load leveling. Many satellites are also powered by Li-ion.

Lithium-ion has not yet fully matured and is still improving. Notable advancements have been made in longevity and safety while the capacity is increasing incrementally. Today, Li-ion meets the expectations of most consumer devices but applications for the EV need further development before this power source will become the accepted norm.

As battery care-giver, you have choices in how to prolong battery life. Each battery system has unique needs in terms of charging speed, depth of discharge, loading and exposure to adverse temperature. Check what causes capacity loss, how does rising internal resistance affect performance, what does elevated self-discharge do and how low can a battery be discharged? You may also be interested in the fundamentals of battery testing.

BU-415: How to Charge and When to Charge?
BU-706: Summary of Do’s and Don’ts


What Causes Lithium-ion to Age?

The lithium-ion battery works on ion movement between the positive and negative electrodes. In theory such a mechanism should work forever, but cycling, elevated temperature and aging decrease the performance over time. Manufacturers take a conservative approach and specify the life of Li-ion in most consumer products as being between 300 and 500 discharge/charge cycles.

Evaluating battery life on counting cycles is not conclusive because a discharge may vary in depth and there are no clearly defined standards of what constitutes a cycle (see BU-501: Basics About Discharging). In lieu of cycle count, some device manufacturers suggest battery replacement on a date stamp, but this method does not take usage into account. A battery may fail within the allotted time due to heavy use or unfavorable temperature conditions; however, most packs last considerably longer than what the stamp indicates.

The performance of a battery is measured in capacity, a leading health indicator. Internal resistance and self-discharge also play roles, but these are less significant in predicting the end of battery life with modern Li-ion.

Figure 1 illustrates the capacity drop of 11 Li-polymer batteries that have been cycled at a Cadex laboratory. The 1,500mAh pouch cells for mobile phones were first charged at a current of 1,500mA (1C) to 4.20V/cell and then allowed to saturate to 0.05C (75mA) as part of the full charge saturation. The batteries were then discharged at 1,500mA to 3.0V/cell, and the cycle was repeated. The expected capacity loss of Li-ion batteries was uniform over the delivered 250 cycles and the batteries performed as expected.

Capacity drop as part of cycling

Figure 1: Capacity drop as part of cycling. Eleven new Li-ion were tested on a Cadex C7400 battery analyzer. All packs started at a capacity of 88–94% and decreased to 73–84% after 250 full discharge cycles. The 1500mAh pouch packs are used in mobile phones.

Courtesy of Cadex

Although a battery should deliver 100 percent capacity during the first year of service, it is common to see lower than specified capacities, and shelf life may contribute to this loss. In addition, manufacturers tend to overrate their batteries, knowing that very few users will do spot-checks and complain if low. Not having to match single cells in mobile phones and tablets, as is required in multi-cell packs, opens the floodgates for a much broader performance acceptance. Cells with lower capacities may slip through cracks without the consumer knowing. 

Similar to a mechanical device that wears out faster with heavy use, the depth of discharge (DoD) determines the cycle count of the battery. The smaller the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine. There is no memory and the battery does not need periodic full discharge cycles to prolong life. The exception may be a periodic calibration of the fuel gauge on a smart battery or intelligent device. (See BU-603: How to Calibrate a “Smart” Battery)

The following tables indicate stress related capacity losses on cobalt-based lithium-ion. The voltages of lithium iron phosphate and lithium titanate are lower and do not apply to the voltage references given.

Note: Tables 2, 3 and 4 indicate general aging trends of common cobalt-based Li-ion batteries on depth-of-discharge, temperature and charge levels, Table 6 further looks at capacity loss when operating within given and discharge bandwidths. The tables do not address ultra-fast charging and high load discharges that will shorten battery life. No all batteries behave the same.

Table 2 estimates the number of discharge/charge cycles Li-ion can deliver at various DoD levels before the battery capacity drops to 70 percent. DoD constitutes a full charge followed by a discharge to the indicated state-of-charge (SoC) level in the table.

Depth of discharge

Discharge cycles
(NMC / LiPO4)

Table 2: Cycle life as a function of
depth of discharge.*  
A partial discharge reduces stress and prolongs battery life, so does a partial charge. Elevated temperature and high currents also affect cycle life.

Note: 100% DoD is a full cycle; 10% is very brief. Cycling in mid-state-of-charge would have best longevity.

100% DoD ~300 / 600
80% DoD ~400 / 900
60% DoD ~600 / 1,500
40% DoD ~1,000 / 3,000
20% DoD ~2,000 / 9,000
10% DoD ~6,000 / 15,000

Lithium-ion suffers from stress when exposed to heat, so does keeping a cell at a high charge voltage. A battery dwelling above 30°C (86°F) is considered elevated temperature and for most Li-ion a voltage above 4.10V/cell is deemed as high voltage. Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling. Table 3 demonstrates capacity loss as a function of temperature and SoC.


40% charge

100% charge

Table 3: Estimated recoverable capacity when storing Li-ion for one year at various temperatures. Elevated temperature hastens permanent capacity loss. Not all Li-ion systems behave the same.

0°C 98% (after 1 year) 94% (after 1 year)
25°C 96% (after 1 year) 80% (after 1 year)
40°C 85% (after 1 year) 65% (after 1 year)
60°C 75% (after 1 year) 60%
(after 3 months)


Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.0V/cell should deliver 1,200–2,000 and 3.90V/cell should provide 2,400–4,000 cycles.

On the negative side, a lower peak charge voltage reduces the capacity the battery stores. As a simple guideline, every 70mV reduction in charge voltage lowers the overall capacity by 10 percent. Applying the peak charge voltage on a subsequent charge will restore the full capacity.

In terms of longevity, the optimal charge voltage is 3.92V/cell. Battery experts believe that this threshold eliminates all voltage-related stresses; going lower may not gain further benefits but induce other symptoms. (See BU-808b: What causes Li-ion to die?) Table 4 summarizes the capacity as a function of charge levels. (All values are estimated; Energy Cells with higher voltage thresholds may deviate.)

Charge level (V/cell)

Discharge cycles

Available stored energy

Table 4: Discharge cycles and capacity as a function of charge voltage limit. Every 0.10V drop below 4.20V/cell doubles the cycle but holds less capacity. Raising the voltage above 4.20V/cell would shorten the life. The readings reflect regular Li-ion charging to 4.20V/cell.

Guideline: Every 70mV drop in charge voltage lowers the usable capacity by about 10%.

Note: Partial charging negates the benefit of Li-ion in terms of high specific energy.

[4.30] [150–250] [110–115%]
4.25 200–350 105–110%
4.20 300–500 100%
4.15 400–700 90–95%
4.10 600–1,000 85–90%
4.05 850–1,500 80–85%
4.00 1,200–2,000 70–75%
3.90 2,400–4,000 60–65%
3.80 See note 35–40%
3.70 See note 30% and less

Experiment: Chalmers University of Technology, Sweden, reports that using a reduced charge level of 50% SOC increases the lifetime expectancy of the vehicle Li-ion battery by 44–130%.

Most chargers for mobile phones, laptops, tablets and digital cameras charge Li-ion to 4.20V/cell. This allows maximum capacity, because the consumer wants nothing less than optimal runtime. Industry, on the other hand, is more concerned about longevity and may choose lower voltage thresholds. Satellites and electric vehicles are such examples.

For safety reasons, many lithium-ions cannot exceed 4.20V/cell. (Some NMC are the exception.) While a higher voltage boosts capacity, exceeding the voltage shortens service life and compromises safety. Figure 5 demonstrates cycle count as a function of charge voltage. At 4.35V, the cycle count of a regular Li-ion is cut in half.

Effects on cycle life at elevated charge voltages

Figure 5: Effects on cycle life at elevated charge voltages. Higher charge voltages boost capacity but lowers cycle life and compromises safety.

Source: Choi et al. (2002)

Besides selecting the best-suited voltage thresholds for a given application, a regular Li-ion should not remain at the high-voltage ceiling of 4.20V/cell for an extended time. The Li-ion charger turns off the charge current and the battery voltage reverts to a more natural level. This is like relaxing the muscles after a strenuous exercise. (See BU-409: Charging Lithium-ion)

Figure 6 illustrates dynamic stress tests (DST) reflecting capacity loss when cycling Li-ion at various charge and discharge bandwidths. The largest capacity loss occurs when discharging a fully charged Li-ion to 25 percent SoC (black); the loss would be higher if fully discharged. Cycling between 85 and 25 percent (green) provides a longer service life than charging to 100 percent and discharging to 50 percent (dark blue). The smallest capacity loss is attained by charging Li-ion to 75 percent and discharging to 65 percent. This, however, does not fully utilize the battery. High voltages and exposure to elevated temperature is said to degrade the battery quicker than cycling under normal condition. (Nissan Leaf case)

Figure 6: Capacity loss as a function of charge and discharge bandwidth.* 
Charging and discharging Li-ion only partially prolongs battery life but reduces utilization.

Case 1: 75–65% SoC offers longest cycle life but delivers only 90,000 energy units (EU). Utilizes 10% of battery.
Case 2: 75–25% SoC has 3,000 cycles (to 90% capacity) and delivers 150,000 EU. Utilizes 50% of battery. (EV battery, new.)
Case 3: 85–25% SoC has 2,000 cycles. Delivers 120,000 EU. Uses 60% of battery.  
Case 4: 100–25% SoC; long runtime with 75% use of battery. Has short life. (Mobile phone, drone, etc.)

Courtesy: ResearchGate – Modeling of Lithium-Ion Battery Degradation for Cell Life Assessment. 

Discrepancies exist between Table 2 and Figure 6 on cycle count. No clear explanations are available other than assuming differences in battery quality and test methods. Variances between low-cost consumer and durable industrial grades may also play a role. Capacity retention will decline more rapidly at elevated temperatures than at 20ºC.

Only a full cycle provides the specified energy of a battery. With a modern Energy Cell, this is 250Wh/kg, but the cycle life will be compromised. All being linear, the life-prolonging mid-range of 85-25 percent reduces the energy to 60 percent and this equates to moderating the specific energy density from 250Wh/kg to 150Wh/kg. Mobile phones are consumer goods that utilize the full energy of a battery. Industrial devices, such as the EV, typically limit the charge to 85% and discharge to 25% to prolong battery life. (See Why Mobile Phone Batteries do not last as long as an EV Battery)

Figure 7 extrapolates the data from Figure 6 to expand the predicted cycle life of Li-ion by using an extrapolation program that assumes linear decay of battery capacity with progressive cycling. If this were true, then a Li-ion battery cycled within 75%–25% SoC (blue) would fade to 74% capacity after 14,000 cycles. If this battery were charged to 85% with same depth-of-discharge (green), the capacity would drop to 64% at 14,000 cycles, and with a 100% charge with same DoD (black), the capacity would drop to 48%. For unknown reasons, real-life expectancy tends to be lower than in simulated modeling. (See BU-208: Cycling Performance)

Capacity Retention
Figure 7: Predictive modeling of battery life by extrapolation.
Li-ion batteries are charged to three different SoC levels and the cycle life modelled. Limiting the charge range prolongs battery life but decreases energy delivered. This reflects in increased weight and higher initial cost.
With permission to use. Interpolation/extrapolation by OriginLab.

Battery manufacturers often specify the cycle life of a battery with an 80 DoD. This is practical because batteries should retain some reserve before charge under normal use. (See BU-501: Basics about Discharging, “What Constitutes a Discharge Cycle”) The cycle count on DST (dynamic stress test) differs with battery type, charge time, loading protocol and operating temperature. Lab tests often get numbers that are not attainable in the field. 


What Can the User Do?

Environmental conditions, not cycling alone, govern the longevity of lithium-ion batteries. The worst situation is keeping a fully charged battery at elevated temperatures. Battery packs do not die suddenly, but the runtime gradually shortens as the capacity fades.

Lower charge voltages prolong battery life and electric vehicles and satellites take advantage of this. Similar provisions could also be made for consumer devices, but these are seldom offered; planned obsolescence takes care of this.

A laptop battery could be prolonged by lowering the charge voltage when connected to the AC grid. To make this feature user-friendly, a device should feature a “Long Life” mode that keeps the battery at 4.05V/cell and offers a SoC of about 80 percent. One hour before traveling, the user requests the “Full Capacity” mode to bring the charge to 4.20V/cell.

The question is asked, “Should I disconnect my laptop from the power grid when not in use?” Under normal circumstances this should not be necessary because charging stops when the Li-ion battery is full. A topping charge is only applied when the battery voltage drops to a certain level. Most users do not remove the AC power, and this practice is safe.

Modern laptops run cooler than older models and reported fires are fewer. Always keep the airflow unobstructed when running electric devices with air-cooling on a bed or pillow. A cool laptop extends battery life and safeguards the internal components. Energy Cells, which most consumer products have, should be charged at 1C or less. Avoid so-called ultra-fast chargers that claim to fully charge Li-ion in less than one hour.

Last updated 2018-10-20

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Comments (525)

On October 21, 2010 at 10:38am
John Vanderkooy wrote:

I am grateful to Cadex Electronics for the whole website explaining batteries.  It is really helpful to restore useful units, assess questionable ones, and the explanations are at a “university” level.  Thanks.

On October 26, 2010 at 5:29pm
pamela knowler wrote:

How long do I charge a new laptop battery before use?  The battery arrived partially charged and information suggests I charge it fully before using.  I can’t seem to find any information about how long to charge it…...it’s a lithium ion 9 hour (lenovo) laptop battery.


On October 28, 2010 at 8:48am
Dennis Lackey wrote:

10-28-10, I sell cell phones and other devices that use lithium batteries and I have been misinforming my customers inregardes to charging requirements of their batteries. ireally found the information reall useful. Thanks,  Dennis

On October 28, 2010 at 3:59pm
Taurug Baca wrote:

What is 1C?  What is a C?

On November 6, 2010 at 2:28am
Fred B wrote:

  Taurug Baca wrote:  What is 1C?  What is a C?
To quote http://en.wikipedia.org/wiki/Battery_charger:
“Charge rate is often denoted as C or C-rate and signifies a charge or discharge rate equal to the capacity of a battery in one hour. For a 1.6Ah battery, C = 1.6A. A charge rate of C/2 = 0.8A would need two hours ...  to fully charge the battery from an empty state, if supported by the battery. This also assumes that the battery is 100% efficient at absorbing the charge.”

On November 13, 2010 at 3:38pm
James wrote:

What about overcharging? What are the effects of leaving a Lithium-ion battery charging when at full capacity?

On November 13, 2010 at 3:41pm
James wrote:

Also, is there an ideal range to charge/discharge the battery in e.g. 40%-70%, ensuring a partial discharge?

On November 16, 2010 at 6:01pm
Carlos Jordan wrote:

I really appreciate your technical info on Lithium-ion batteries. I recently purchased a wonderful Panasonic Camcorder,  which uses such a battery,  and your advice not to fully discarge, before re-charging is so very helpful, as I thought according to the manual, it was necessary to discharge fully.

As James asked above, what is the ideal partial discharge, before charging again?

Thanking you kindly for your help.

On November 23, 2010 at 2:50pm
nygus wrote:

Sadly, macbooks (and other laptops) run much slower on fixed power (even 4x slower), when battery is removed… so battery dies very quickly. I think they use battery as capacitor to support short demands of higher power.

On November 23, 2010 at 7:03pm
David wrote:

If it is better to have the battery charged to 40% and then stored while on main power, why do the laptop manufacturers not program the BIOS to have an option to charge to 40% and stop? I am always on fixed power, the problem with removing the battery at 40% is that I would be vulnerable to power outages. With the battery still inside the laptop charged to 40% I would be saving my battery, saving power and saving my data in the event of a main-power failure. Does anyone know if there is a software out there which could charge to 40% and stop? If so, please let me know.

On November 24, 2010 at 11:21am
Patrick Woo wrote:

How frequent should I apply a full discharge to recalibrate the fuel guage?
Every 30 charges sound very frequent to me if your laptop alternate between battery power and fixed power many times a days.

On November 29, 2010 at 2:51pm
Andy wrote:

“Frequent full discharges should be avoided when possible”
“A deliberate full discharge and recharge every 30 charges corrects this problem”

How are these recommendations compatible? It is really safe to *completely* discharge the battery? Wouldn’t it die after a single *full* discharge?

On December 2, 2010 at 7:22am
Mehper C. Palavuzlar wrote:


Follow this question on SuperUser.com:

“Software to hold battery at 50% charge level”

On December 7, 2010 at 9:19pm
Dave wrote:

Does freezing cause dammage to the batery?  Or does using the battery in a cold or frozen state cause the dammage?  Can a battery be frozen allowed to thaw and be fine?

On December 17, 2010 at 9:09pm
Andrew wrote:


You do not want to leave your battery in your laptop even if would remain at 40% because your laptop generates quite a bit of heat from use which is harmful to the batteries. The lithium batteries should be stored at 40% AND in a cool place.

On December 19, 2010 at 8:15pm
Phil wrote:

This is one of the articles that I was reading about caring for your laptop batteries.

On December 24, 2010 at 7:30am
Carol Nemetz wrote:

I removed battery for a number of hours. Whn I replaced it the battery icon read"plugged in, not charging” I have had this problem with not chargeing a number of times. After 4 attempts, Gateway repaired it. The last time they replaced the motherboard and installed a new battery.All was well until I removed he battery and replaced it

On December 25, 2010 at 5:21pm
Fede wrote:

Most of the time I use my laptop at work. I use it without the battery and I keep it at 40%.
What I noticed is that if I put the battery again after a few days the charge had lowered to 30% for example.
So, If I the ideal storage is at 40% but after a few days the charge drops to 30%, how can you keep it stored at 40%?

On December 28, 2010 at 3:47pm
Daniel wrote:

Thank you for this infomation, people complain with the performance of their laptops, just maintain and look after your bleeming laptop!

Thanks to Battery University for this infomation

On December 30, 2010 at 10:08pm
Jaime Blanco wrote:

I have not seen that this question is answered… so I will add my question to the queue…. Is there an ideal rate of when to charge the battery ? eg.  40% ... or 70% ??  BTW… With this article I have finally understand how to use my battery… thx!!! I was living a lie.. and… in the past… I knew battery industry had evolved this years..

On January 1, 2011 at 8:32am
Gcat122 wrote:

The Verizon sales clerk insisted that I not leave my droid 2 on the charger for more than 4 hours or the battery would be damaged. I have trouble believing a new smartphone would be dumb enough to kill batteries. Is he wrong or is the manufacturer trying to sell more batteries?

On January 6, 2011 at 9:06am
Ike wrote:

Gcat122, properly made Li-Ions should have built-in protection that prevents problems caused by overcharge. However, you may have heard about massive battery recalls in the recent years due to quality problems causing overheating or even explosions - so his suggestion may have been related “just in case” caution.
Normally, a quality charger will notice when the battery is full and cease attempts to overload it. But it’been proven that all chargers aren’t that smart, especially generic brand ones that may apply charging methods unsuitable for Li-Ion type.

On January 6, 2011 at 6:22pm
Niall wrote:

would carging my battery whilst using it do any damage to it? this appears to be the only information i cannot find on lithium ion battaries

On January 10, 2011 at 9:17am
Mike wrote:

I just purchased a 20v “professional” cordless drill/driver (Craftsman brand) from Sears at 60% off the original price. This item was marked “clearance”. I’ve been congratulating myself on a great find until I read this article. I immediately checked the date on the two lithium-ion batteries enclosed and found it to be 10 2006. I think I know now why they have been reduced to clear. I’ve charged up the batteries and they seem fine, but I haven’t used the drill yet so don’t know what performance and battery life to expect. I have to assume that these items have been sitting in a warehouse or store uncharged for over four years.
What remaining life should I expect from a four-year old battery that has never been charged? Should I consider returning the drill?

On January 11, 2011 at 1:12pm
Tad wrote:

@Mike - if the drill carries the standard Craftsman “forever” warranty, you can always return the drill if the batteries prove to be unsatisfactory.

Lately my Blackberry 9700 has taken to powering itself off suddenly when the battery gets down around 1 bar, before it even reaches the “yellow” or “red” part of the gauge.  This may be due to my recently acquired habit of charging it every night. 

I’ll let it run down a few times and see if that makes a difference.

On January 12, 2011 at 5:23am
Michael wrote:

Great info!
One comment - a couple of your graphs are the wrong way around - the convention is to have the independent variable on the x-axis. So, in the last graph, you should be reading off the number of cycles on the y-axis, against each charge/discharge rate on the x-axis. (The number of cycles is *dependent* on the charge/discharge rate).

On January 13, 2011 at 8:50am
dewey hodo wrote:

Does the above care, use and charging instruction apply equally to EV lithium batteries?
What special care must be given for Li batteries hundreds of times larger and more powerful than laptops?

On January 13, 2011 at 2:31pm
John wrote:

Hi, great article, but I have one question. What about Li-Polymer batteries, does all this apply to them also or are there some significant differences?

On January 17, 2011 at 1:19pm
Victor wrote:

My battery can’t backup anymore, and I only get to have Power for 6hours a day. and I’m a Programmer. Getting another is just too expensive so how can I make it work again! I’m using a UPS for a LAPTOP.

On January 21, 2011 at 7:53am
Cobalt wrote:

“Keep the lithium-ion battery cool. Avoid a hot car. For prolonged storage, keep the battery at a 40% charge level.”

So i need charge battery every time when battery indicator is at 60%???

On January 21, 2011 at 10:02am
Ashley wrote:

This is an awesome article, it explains everything in detail and is backed up by evidence, making all the information very credible.
However, I still do not grasp the definition of “discharge”. Does it mean letting the battery run out; let it completely die?

My phone has been having battery issues I hope I can fix it!

On January 21, 2011 at 10:33am
Hilda Smith wrote:

Thank you for this very helpful information.

On January 23, 2011 at 1:28pm
Royce wrote:

I stored my lit. battery from my laptop to increase battery life. After six months I reinstalled the battery and it will not charge. Was storing it six months too long?

On January 24, 2011 at 4:11pm
Alex wrote:

It depends on the state of charge when you stopped using it.  If it is almost completely discharged 6 month might be too long.

On January 24, 2011 at 4:14pm
Alex wrote:

You should try leaving the battery 1 - 2 days plugged in, it might recover

On January 24, 2011 at 4:29pm
Alex wrote:

If it doesn’t seem to have charged after 1 - 2 days, it has to be taken apart and the cells have to be charged directly before the protection circuits. A power supply that can provide constant current is needed, for ex a lab power supply. The voltage should be set to the voltage written on the battery and the max current should be set to 5% of total capacity. Obviously the polarity has to be connected correctly and the charging process should be left alone for awhile until the constant current disappears. After that the battery should be placed in the laptop and it should charge normally.

On January 25, 2011 at 8:22am
Alex wrote:

And, there’s another thing.  if when you try to power the laptop with the bad battery the lights flash as if it tells you that the battery is bad that it might never charge and it also might not solve the problem charging the cells before the protection circuits inside. It is best to try something else before you charge the cells separately.  after taking the battery apart disconnect all wires from the cells that go to the protection circuits. it is easier to desolder them from where they are near the cells rather than from th pcb, but this might not be the case for all the batteries.  After desoldering all wires leave it like that for 10 seconds than resolder the wires back to where they were.  you should connect the battery into the laptop and try to charge it.  In a similar situation it worked for me.  Through this method you cut the power from the protection circuits and it resets some parameters related to the battery monitoring

On January 26, 2011 at 5:32am
Mescoda wrote:

I have translated this useful article into Chinese on my blog
If anyone get interest in it,you can visit

On January 28, 2011 at 6:55pm
ptah wrote:

Interesting to note that some laptop computers have the battery pack protruding from the main case.  That may be intended to reduce exposure to heat released by other components.

On January 31, 2011 at 6:55pm
DickL wrote:

I would like to know what is different, if anything, about charging and discharging Lithium Iron Phosphate (LiFePO4) batteries - relatively new chemistry in the Lithium family of batteries.  Folks at Batteryspace.com claim much increased number of cycles (>2000) if managed conservatively.  Any observations or recommendations?

  - DickL

On February 4, 2011 at 3:04pm
Ty wrote:

Excellent information on Li-Ion laptop batteries. Approximately 500 charge and discharge cycles is pretty accurate. However, some companies claim 1000 or more. It all depends on the quality and grade of the battery cells. Cheap battery cells will not last very long. Whereas a well build battery with high quality cells should have a normal lifespan, given it’s not put in abusive environments.


On February 7, 2011 at 9:13am
suman wrote:

wat about over charging?
do we hav problem in doping it

On February 8, 2011 at 9:11am
jean wrote:

what does discharge mean?

On February 11, 2011 at 4:36pm
steve wrote:

I’m wondering what the effect of freezing is on the lithium ion batteries in my Makita cordless driver/drill.  Working in the winter in Iowa, freezing temperatures are common at worksites.  Will frequent freezing reduce the total number of charge/discharge cycles I’ll get out of my batteries over the life of the tool?

On February 21, 2011 at 12:49am
Prem Dissanayake wrote:

It’s great place to study about battery as well as other related accessories.Good luck!

On February 23, 2011 at 7:26am
Pier Francis wrote:

Excellent info on batteries, thanks to Battery University

On February 25, 2011 at 3:53am
Andrew wrote:

I also wanted to express my gratitude on the information given about lithium based batteries.  Thank you!

On February 25, 2011 at 3:14pm
Cadex Electronics Inc. wrote:

We have updated this article as of today February 25, 2011.

On February 28, 2011 at 1:59am
Rob Smith wrote:

I tried to fgure out how to handle longevity and the best solution so far is by Sony VAIO laptops. During normal use in office I put charge limit to 40% and batter never goes above that, if I need to travel I simply increase it to 80% or 100%.
Capacity of battery remained constant for more than 2 years now, what might be due to such ‘soft charging’, but also due to quality of Sony batteries.
Dell Studio XPS has excellent utility which simply turned charging off whenever user wishes.
So I keep charge level somewhere around 50% and whenever I need laptop simply turncharging on.
IMO it should be standard on all laptops.

On March 1, 2011 at 11:13am
mike wrote:

Question:  I was told to leave the computer on at all times, just shut the lid.  This will add to the life of the battery.  Comments

On March 12, 2011 at 11:33am
genesis wrote:

people,please…..do not take everything you read on internet as a must. what this ....“article” acctually tells you is: 1) it is not recomended to keep your battery plugged in when fully charged for a long time periods.2)it is not neccessary to always fully discharge the LI battery(you can charge it anytime to any%). 3)do not keep/operate your battery in an owen.4) if you plan not to use your battery for a long time, it is better to keep it half charged.
thats about it - everything else is just a .... masochism.

On March 12, 2011 at 12:00pm
gendersis wrote:

smile thanks genesis, i will do as you said, hopefully my battery will survive another year :D

On March 20, 2011 at 11:07am
Kevin wrote:

Awsome sight…I have an Evo Shift and my battery gets up too 47 degree’s while using it and sometimes noy slowly? Sprint said that it’s ok? Please HELP!!!!!!

On March 23, 2011 at 3:44pm
SLy wrote:

****Tad wrote:
@Mike - if the drill carries the standard Craftsman “forever” warranty, you can always return the drill if the batteries prove to be unsatisfactory.****


Craftman “Hand Tools” are lifetime.  Cordless drills and other similar items are NOT lifetime.

The battery you bought has a 90 day warranty.  Same as the charger.  The tool has a year warranty.


On March 24, 2011 at 3:50pm
James wrote:

derp has a point.. and summarizes the article well

..but he came over as a an obnoxious braggart.

On March 27, 2011 at 10:02pm
Sagar wrote:

Great article…Thanks for sharing smile

On March 30, 2011 at 4:09am
wezz wrote:

ive just bought a new cordless lithium drill/driver for DIY use only have i made a costly mistake? thanks wezz

On March 30, 2011 at 6:58am
Paul wrote:

I have been looking at this and I think the data is a bit mis leading. Its not the number of re-charges that is important, but the total hours before the battery cannot get to above 70%.

I have been a geek and modelled this. If you take an average battery with a life of 600hrs in standby (the actual number dont matter here), then the total hours you get for the 100%DoD is actually more than the 10%DoD. Yes, you get more recharges, but less total hours of use. From the table in the article, the 50% DoD gives you the most number of hours out of the battery before it cannot get above 70%.

Its quality not quantity!

p.s. I havent read all the comments so I apologise if I am repeating what has been said!

On April 4, 2011 at 8:20am
Rich S. wrote:

“The question is often asked: Should I disconnect my laptop from the power grid when not in use? Under normal circumstances this should not be necessary because once the lithium-ion battery is full, a correctly functioning charger will discontinue the charge and will only engage when the battery voltage drops to a low level.” Does this same thing apply to the phone batteries?

On April 5, 2011 at 4:43am
Dave wrote:

Obviously, as derp left his own laptop mostly plugged in for a year, he is, by his own definition, a retard. What a jerk.

On April 7, 2011 at 7:37am
David wrote:

Table 2 states that for a full 100% discharge and full charge that the battery would last roughly 500 cycles, while one that has a 10% discharge and then charging back up to 100% would last roughly 4,700 cycles. I hope I understand that table correctly, if not please help me understand it better.

My question is that given that I would follow the 10% discharge cycle would that not cause the battery to ‘fail’ sooner since discharging 10% and then charging to 100% 4,700 times would roughly equate to 470 100% discharges? I’m sure I may be misunderstanding something, but I don’t see how the numbers add up.

On April 7, 2011 at 8:18am
Paul wrote:

The key isn’t the number of re-charges, it is the total hours you get out of the battery. So you are, approximately, right. Look at my comments above.

More re-charges does not necessarily mean more battery life. Just means more re-charges


On April 7, 2011 at 9:55am
David wrote:

Thank you Paul! That helped out greatly. I will include my findings doing similar calculations here:
Total capacity: 100 mAh

Dod     Cycles   Total Hours of use       Formula   (capacity * Dod) * Cycles
100%      500         50,000               (100 * 1.00) * 500
  50%    1,500         75,000               (100 * 0.50) * 1,500
  25%    2,500         62,500               (100 * 0.25) * 2,500
  10%    4,700         47,000               (100 * 0.10) * 4,700

Please let me know if I used anything incorrectly.

On April 7, 2011 at 10:23am
Paul wrote:

It is close, but it does depend what they mean by 10% DoD

If you look at the graph (figure 1), it shows that each time you charge, the ‘full’ level on the battery is a bit less each time. The failure is when it can only get to 70%. So lets say you charge 2000 times, the batt may only charge to 80%, say. Then 10% DoD in this case will be (in your example) 10% of 80mAh. If they meant 10%DoD of the orginal batt capacity in each charge, then you are right but I doubt it. I say that because if that is what they meant, then they could not have done a 100% DoD case (how can you discharge 100mAh when the batt is only at 80mAh?)

So in your cals, where you have (100*0.10)*4,700 the 100 needs to be a decreasing value for each charge e.g. (100*0.1) + (99.9*0.1) + (99.5*0.1) or similar

Does that make sense?


On April 7, 2011 at 11:18am
Ed Vim wrote:

Great article, thanks for writing this up.

Regarding derp’s comments, interesting but its value greatly diminished by immaturity.

On April 8, 2011 at 9:21am
David wrote:


Yes that makes sense. I would update the calculations to account for that but I have already had enough fun for the day. grin

Thank you for the response.

On April 8, 2011 at 6:01pm
Patrick B wrote:

I keep my laptop plugged in all the time at home to do work on. According to this article, it seems that by doing this, I am wearing out my battery prematurely. I take it the right thing to do would be to let it partially discharge, then take it out of the unit until I need to use it on battery power. Am I right?

On April 9, 2011 at 3:04am
thomas 09789989648 wrote:

hi i am a laptop service enginear how to check battery ok or bad . and how to create one lithiyam ion battrey on charging pls tell me

On April 9, 2011 at 10:12am
GenericM wrote:

I hope my laptop never needs servicing even more now.

On April 10, 2011 at 8:49pm
elf- wrote:

I just bought a new battery for my Huawei Ascend cell phone I have let the battery drain completly out then gave it a full charge then let it die out and gave it a complete charge again. From the reading above, If I want too prolong the battery life I should let it drain down to 50-60% battery life then put it on the charger? Or do I keep on letting it drain down to 10-15 % then put it on the charger for 4 hours or until 100% charged? Please respond back thanks!

On April 11, 2011 at 3:33am
Paul wrote:

Based on the data they show in the paper, the 50% DoD seems to give you the longest batt life.

But I am not an expert, I am just analysing their data.

On April 22, 2011 at 9:36am
PAUL J. wrote:

Funny, if you paid $200 to read David Linden’s Handbook of Batteries 3rd Edition it will tell you that lithium ion batteries have a good shelf life.  Primary lithium does, but not Li-ion.  This is straight from Linden’s $200 book:

            TABLE 35.1 Advantages and Disadvantages of Li-ion Batteries
Advantages                                                   Disadvantages
Sealed cells; no maintenance required                   Moderate initial cost
Long cycle life                                       Degrades at high temperature
Broad temperature range of operation               Need for protective circuitry
Long shelf life
Low self-discharge rate
Rapid charge capability
High rate and high power discharge capability
High coulombic and energy efficiency
High specific energy and energy density
No memory effect

On April 22, 2011 at 9:58am
PAUL J. wrote:

Elf, it does not matter with Li-ion.  Just charge it whenever you get a chance, but just so you know Li-ion is happiest around 40% state of charge.

On May 2, 2011 at 11:42pm
Mike wrote:

The question most raised is life.  Our batteries utilize precision GPS on job sites.  The manufacturer of the units is very attentive to detail as far as expansion with charging.  They utilize a gore valve to help with the hear when the batteries and components expand.  However, the replacement batteries we receive, which i believe are quality last almost half the time as the original manufacturers batteries.  Do you believe this to be a coincidence or quality factor.

On May 2, 2011 at 11:46pm
Mike wrote:

The question most raised is life.  Our batteries utilize precision GPS on job sites.  The manufacturer of the units are very attentive to detail as far as expansion with charging.  They utilize a gore valve to help with the heat when the batteries and components expand.  However, the replacement batteries we receive, which i believe are quality, last almost half the time as the original manufacturers batteries.  Do you believe this to be a coincidence or quality factor.

On May 3, 2011 at 6:17am
PAUL J. wrote:

There seems to be a lot of controversy on the subject of lithium-ion batteries and what you should do with them when you first receive them.  The experts will tell you that there is no “conditioning” needed with Li-Ion, however I have seen first hand experience which begs to differ. 
I have seen proof time and time again that Li-Ion DOES benefit greatly from “conditioning” the battery by letting it discharge fully (until the device shuts itself down) and charging it 8-12 hours (repeat process) for the first 3-5 days.
That could solve your problem, or you might just be getting old batteries.
Next time you receive a new battery, try this method, I think you will be surprised.

On May 4, 2011 at 8:14am
Rob wrote:

@ Paul J
That could also be just down to the fact that this sort of cycling is used to calibrate the battery mater in some equipment - Apple Macs spring to mind here. So repeating this until your battery is in peak form (usually 3 or 4 cycles) will keep updating the calibration values and hence give you the most accurate reading. This in turn will give the longest time before the software of the device thinks the battery is nearly flat and shuts down to protect your information.

Anyway, thanks for the thread. It’s amazing the amount of FUD that there is out there, not helped by the fact that most manufacturers are particularly vague with regards to their battery care and handling instructions. They could all do with having an article similar to this, but specific to their particular battery, charger circuit and typical usage patterns, in their manual.

On May 8, 2011 at 1:29pm
danceswithbongs wrote:

Thanks for an informative article.  Wasn’t it nice of derp to drop by, making use all feel better about ourselves.  Always good to notice that mans inhumanity to man is hard wired.  I would imagine derp could learn a bit from someone who is retarded, like how to treat others.
Again, great article, and first free thing I’ve ever heard of from a university.
Can people still major in 9 volts?
Appreciate you droppin knowledge like Galileo dropped the orange!(see The Beastie Boys)
From the law offices of danceswithbongs, esq.

On June 2, 2011 at 3:25pm


I BOUGHT A NEW ASUS Eee PC 1008P and i am facing problem with my battry charging…

my battery charges well when netbook power is off but when i switch the netbook on the battery light keeps on blinking and windows 7 tray shows at my battery is intermittently charging and disconnecting….(that is the reason why my battery light is blinking..which would remain static if it is charging normally)

please help…or should i be needing to go the ASUS tech help?


On June 8, 2011 at 7:34am
Charge Me wrote:

Sooo, why is it of the dozen laptops I’ve owned over the last ten years, that they still had less than 5% wear after one year and less than 15% wear after two years and kept them at 100% and had maybe 10-20 full discharges a year?

On June 14, 2011 at 7:47am
Marilyn wrote:

A few years ago a physicist friend explained to me that it doesn’t matter how far you discharge the battery but once it’s on the charger it should be left on until the battery is fully charged. My boyfriend (a chemist/scientist) says this is complete untrue with the current battery technology. He tends to charge his phone in short stints where I tend to never attach to the charger unless I can leave it long enough to fully charge. Any thoughts? (We both have the Samsung Galaxy S which is a great phone but a huge energy suck. I must recharge once a day which I do at then end of the day until the morning.)

On June 15, 2011 at 6:49am
Paul J. wrote:

Your boyfriend is correct.  Lithium Ion technology can accept a topping charge at any time and doe not require a full charge.  I also have a Galaxy S and I charge it whenever I get a chance.  You should prime the battery the first few days though by draining it completely and charging completely.  This will also help calibrate your phone’s battery meter to the new battery.

On June 22, 2011 at 10:26am
Crusty wrote:

Derp is certainly a character. OK, he’s douche. There, I said it. Anyone have any luck with freezing dead batteries and bringing them back to life? Some say it works—I’m skeptical. I’m trying it now with an HP dv7 battery (OEM HP from 9/2009) I guess it can’t hurt. Besides, this monster 7lb laptop is lighter without the battery. Works fine on straight AC.

On June 25, 2011 at 2:37pm
Alan Kanarbik wrote:

I appreciate the resourcefulness of the information you have provided here.

Another question has come to my mind regarding saving power on Li-ion batteries. Will it make no difference to plug the battery in and out with the laptop running on AC power or is battery life saved by turning the computer off first for the switch between power sources?

On June 25, 2011 at 10:42pm
Crusty wrote:

My guess is if you are going to have your laptop plugged in most of the time, as in a large, say 17” desktop replacement type, it would be best to just remove the battery altogether. Such is the case with my HP DV7 laptop with it’s beautiful 17.3 screen. Lugging around a nearly 8lb laptop (with battery installed) for any great distance will make a man pine for something much smaller (and lighter!) Seriously, if you’re leaving it at home or office most of the time, what’s the point?
Oh, and the ‘freeze your dead battery” thing I tried from another site? Well, unless it says Lazarus somewhere on the label next to the P/N, this appears to be bunk. It was worth a try, I guess. All you need is a dead battery and a freezer bag. . . . .

On June 30, 2011 at 9:57am
Niels-Erik Jensen wrote:

How many kWh do you have to get from the power supplier to get 100 kWh into the battery.
The heating up of the battery shows you have to tap (a lot, maybe)  more kWh from the power supplier than the energy that is charged into the battery.

Same question for discharging a battery which also gets hot during de-charging.

On July 14, 2011 at 1:47pm
Colin Macdonald wrote:

I am thinking of buying an electric bike, but I go away to Africa during the British winter, so the battery would be stored unattended for six months each year.  Is this going to be a problem?  Have you any advice?

On July 14, 2011 at 7:51pm
Marilyn wrote:

Thanks Paul, I’ve started taking both of your advice and charging the phone whenever I have a charger available. I still find myself draining the battery before I find a charger, today it was too many birds and not enough pigs, but I’m getting better. Phone is well primed based on my previous charging habits. wink

On July 15, 2011 at 7:10am
Gerge lopaz wrote:

Too much information, not specific, hard to find information that is relevent.

On July 18, 2011 at 7:58am
Walt Borntrager wrote:

I have found just the opposite of this “data” in multiple Li-ion applications.  In both notebook computers and cell phones, I’ve found that if I never recharge the battery unless it is fully discharged, and then always fully recharge it, I get years of full capacity.  My first cell phone would run 13 to 14 days continuously per charge for nearly 10 years using this rule.  (Then communication protocols changed from analog to digital.smile)
I had a notebook computer charging module with an intermittent connection at the output, charging a minute or so, then disconnecting and allowing the computer to discharge a minute or so, then charging a little…  In less than 1 day, the battery had no capacity - would not hold enough charge to hold up the computer for 10 seconds.  The previous day it would power it for nearly 2 hours.  The battery did not undergo any shock - the computer was sitting on a table.
I’ve found the same for Ni-Cad (obviously) and also NiMH.
My personal experience in using rechargeable batteries for the last 20 years consistently agrees with this rule.

On July 23, 2011 at 1:27am
Jeff Simon wrote:

Maybe I am the only one missing one aspect of the number of cycles verses depth of discharge: if you only get 500 cycles with 100% discharge, as compared to 4700 cycles with 10% discharge, those cycles are not equivalent.

That is, the 100% discharge got 10 times the power ouput as compared to the 10% depth. If assuming useful work was done in each depth, then in fact getting 500 cycles actually gets a bit more work than 4700 cycles of only 10% the depth.

This seems to me to say that the depth of discharge is much less important than you would initially think from just looking at the number of cycles alone, as the amount of output is actually slightly more under the deep cycle, but for practical purposes is close to equivalent.

That is, unless I am missing something that everybody else is seeing.

On July 25, 2011 at 3:53am
Jim H wrote:

I have a new netbook and want to preserve the Li Ion battery as long as possible.  I have no occasion to need to use the netbook on the battery, but I may someday.  I’ve had the netbook about a month and have not installed the battery.  Is this a good strategy? Should I charge the battery about half way and put it in the fridge sealed to prevent moisture incursion

On July 25, 2011 at 6:19am
Paul J. wrote:

My suggestion to you would be to read the article instead of just the comments.  It seems like only a few people actually took the time to read it, and everyone else wants answers without doing the reading.  I have read the whole book” Batteries in a Portable World” and I would recommend it to anyone who would like to have a better understanding of batteries and the characteristics of each chemistry.

On July 25, 2011 at 6:22am
Paul J. wrote:

Jeff, I think it is just stated to be equivalent for practical purposes because it is close enough.

On July 25, 2011 at 8:21am
Jeff Simon wrote:

Paul, yes what I am saying is that they are practically equivalent. But the article seems to imply that very small cycles is far better.

On July 26, 2011 at 6:35pm
Walt Borntrager wrote:

Paul, I read the article and am saying that my 20+ years of experience with rechargeable batteries disagrees with one primary implication:  The article implies that many partial cycles will allow the battery to keep full capacity longer.  The “memory” effect that plagued NiCad chemistry and supposedly is not present in Li-Ion, is the effect that, if the battery is only partially discharged, then recharged, it will soon only have the capacity to which it is used, i.e., if you only discharge it 10% and then recharge it each time, after a number of cycles, the total mAH available will only be about 10% of its original capacity.  My experience has found this true of NiCad, NiMH, and Li-Ion, although Li-Ion is the most forgiving.  As I stated before, a faulty charger connection caused very small cycles on my last Li-Ion and it destroyed the capacity in days.  I would certainly not recommend discharging any of these chemistries small amounts between recharges.  I’ve seen this habit destroy capacity very prematurely numerous times.
Most of today’s notebook computers have a hysteresis built into the charge cycle such that, if you fully charge it, no charging will occur until you have intentionally discharged it to some extent.  This allows you to keep it plugged in for periods of time without excessive short charge cycles.  Some also have the option to turn the charger off until it is really necessary at a low remaining charge.  This is a clue that notebook computer manufacturers agree with me on this aspect.

On July 27, 2011 at 7:40am
Paul J. wrote:

Walt, I agree with you that Li-Ion doesn’t always behave exactly as indicated in the article.  My comment about “reading the article” was not pointed at you or others who are here to discuss findings and experiences.  It was for the people who just come here for free answers without putting forth any effort to actually learn what the article is teaching. 

That said, bear in mind when you read this article that it was published in 2001.  Lithium-Ion technology has advanced and is better understood now than it was in 2001.

Isidor Buchmann has released a third edition just a couple months ago that I can’t wait to get my hands on.

On July 28, 2011 at 3:10am
Sandeep wrote:

Is it really a good practice to keep the charger on for my laptop even after my battery has reached 100%(fully charged)? If not does this have an implication on the life of the battery and by how much? Is energy wasted in the process becuase the charger tries to keep pumping into an already full battery and if so what is the loss like?

On July 28, 2011 at 5:42pm
Walter Borntrager wrote:

Sorry Paul - didn’t notice that this was an old study.  Good point - read and think through the article before asking a question that was already answered.

I tend to spout off a bit over this subject because of all the hype that Li-Ion has beat the “memory effect” syndrome.  I haven’t found a solid chemistry yet that has…
(By solid, I mean this primarily excludes lead acid, which thrives on a continuous full charge, within limits, and can be destroyed by a full discharge.)

Thanks for the comments…

On August 1, 2011 at 3:16am
NeilP wrote:

Jim H,
If you have still not plugged your batteryinto the laptop, then DONT.
I have heard, but cant confirm, that the batteries, factory fresh, are chemically stabilised, somehow.  The first charge cycle or two disapates this stabilisation, hence the need to cycle the battery a few times to get full capacity
Colin, Ref your E bike battery.  That totally depends onthe chemistry of the pack, It could be Sealed Lead Acid, or a LiFePO4 or?? Check out the Endless Sphere E bike forum for an answer,once you know battery chemistry

On August 8, 2011 at 6:23am
Retxirb wrote:

First let me thank you for this great article and this website, very informative. I recently bought new netbook and I’ve been charging the battery for around 40% to 80%. I charge it up 40% when I won’t be using the battery for a long period of time. I pull out the battery whenever I have access to power outlet.

Charging the battery while the computer is running may cause the battery serious stress because of heat. But I occasionally charge my netbook around 7pm when the temperature is cool so I can watch the netbook when its reached 80%.

I know that everything even computer battery has an end. If I reach that point, I would dissect the battery, ebay some Li-Ion and then solder it to place. That would save me a lot of bucks.

On August 9, 2011 at 6:36am
NeilP wrote:

Jim H,
If you have still not plugged your batteryinto the laptop, then DONT.
I have heard, but cant confirm, that the batteries, factory fresh, are chemically stabilised, somehow.  The first charge cycle or two disapates this stabilisation, hence the need to cycle the battery a few times to get full capacity
Colin, Ref your E bike battery.  That totally depends onthe chemistry of the pack, It could be Sealed Lead Acid, or a LiFePO4 or?? Check out the Endless Sphere E bike forum for an answer,once you know battery chemistry

On August 19, 2011 at 9:20am
Fabrice wrote:

Paul, note:

“On February 25, 2011 at 3:14pm
Isidor wrote:
We have updated this article as of today February 25, 2011.”

Still, I wish he would address the point raised about battery utility (i.e., total power delivered) vs. number of charge cycles.  It is a good example of how data presentation can define - and limit - our ability to understand what is really important.

On August 23, 2011 at 5:32am
John C. Crowther wrote:

Re. Charging / Discharging of Lithium Batteries - and useful life of the battery
The Article and many of the Comments, as well as stressing prevention of overheating, (in a hot computer or a hot car) seem to indicate that length of battery life is a matter of how much you discharge the battery, and how often you charge it. So it can take 500 cycles of total discharge (100% discharged to 0%) or 4700 cycles of 10% discharge (100% charged dischragd to 90%). [see exchange between David & Paul on April 07, 2011] They agree that the amount of work done by the Li-battery is pretty much the same whatever approach you take.

Many of the comments focus on avoiding overcharging - and some recommend keeping the Li-battery around 40% - 50%  discharged, and topping it up frequently. Sounds like “ïf you don’t use it, you lose it”

So far so good. But I have a confusion which is (unless I overlooked something - want to avoid a ‘flame’ from ‘derp’). I am concerned about undercharging a Li-Battery. This concern relates to a Lenovo Thinkpad system, but I imagine it could apply to many other Laptops.

I have a ThinkPad W520, and since the mains adapter is a brick 17cm x 8cm x 3.5cm weighing 750g (6.7"x 3.2” x 1.3” weighing 1.64 lbs) I figured from suggestions on thinkpads.com Support Community (http://forum.thinkpads.com/viewtopic.php?p=628326) that I can equally use a smaller mains Adapter also
available from Lenovo.

The “Brick” has an output of 170W, 20V charging at 8.5A
The smaller versions have an output 90W and charge at 4.5A
so accordingly I bought a Lenovo 41R4494 Ultraslim Adapter which is 11.5 cm x 7cm x 1.7cm and weighs 377g (4.5” x 2.75”  x 0.67” weighing under 12 ounces). I felt very pleased.

But now my ThinkPad is nagging me each time I switch on or close down:
“Ïncorrect AC adapter is attached.
This AC adapter may not provide enough power to your Thinkpad. Please reconnect the proper AC adapter.”
i.e they mean I am ündercharging the battery, right?
(That’s true, if I leave the UltraSlim attached while I work, the battery runs down.
Question: But is that bad? Maybe it runs down more slowly, than if the UktraSlim Adapter is *not* attached? Can it damage the control circuits in the battery or the mains adapter?

My compromise work routine uses the Li-battery for my working day, and I charge it overnight.
1. I hibernate the computer - with remaining charge in the battery ca. 30% - leaving it plugged in to the UltraSlim charger overnight.
2. In the morning I unplug the mains adapter, before waking up the computer (thereby avoiding the nag).
  It’s back to 98% - 100% - showing 8 or 9 hours work available in the battery (the 9-cell)
During the day, I use the computer on battery, in sporadic intervals of half to 1½ hours. Between each work interval I close the lid to hibernate. I rarely finish the day with less than 30% charge in the battery.

So now to my main questions:

A. is this routine harmful for the life of a Li-Battery?
B. if not, why does Lenovo nag me for using the 4.5A mains adapter?
  (it charges OK when I am not using the computer).
Many thanks for any insight or ‘light’ the Team can shed on this subject.

Regards = John

On August 28, 2011 at 11:19am
BIKIE wrote:

Hello I wonder if I put my computer without the battery charge and peude after I put my battery during charging is there a risk that the battery or the computer gate

On September 23, 2011 at 12:50am
Dee wrote:

The owners of this site deserve praise. great work and solid information.

On September 25, 2011 at 1:32am
Ashfaq wrote:

I heard the battery life reduces if we keep the charger plugged-in (charing) after the battery is 100% - is it true?

On September 25, 2011 at 2:25am
banmeet singh wrote:

After discharge the battery should be fully charged back because

1. Charging back to 70% restore the life

2.Prolonged discharge state of the plate causes sulphation

3. Partial charging after deep discharge is also causes sulphation

4.,Both B & C

On October 10, 2011 at 6:05am
Peppe wrote:


I find this article very interesting. With the aim of trying to put it in practice by moving to a more sound “maintenance” of my Li-ion batteries, I was quickly listing them in my mind: I ve Li-Ion batteries on my notebooks (Asus and MacBook Air), my two photo-camera, my videocamera, my mobile phone.

So, two main insight I want to apply: 1) never leave a li-ion battery inactive for too long time (i.e. months), but keep electrons move from time to time; 2) store the battery at the best possible conditions, i.e.: low temperature, low humidity, about 40% of charge.

I should have no problems with mobile phones and notebooks, as I use them everyday so keeping them at about the charge level I want is something I can someway control (plug/unplug them appropriately). The only problem is the Mac which heats often and there’s no way to remove the battery if I want to give it some relief.

The real problems are with the photo/video camera: I don’t use them everyday, sometimes I don’t use them for a few months. How can I simultaneously apply both insights ?
Suppose I charge them to some 40% (difficult to control, at least with the photo-cameras, while the Sony Videocam has a progress bar), and then I remove from the devices and leave them apart. I then go to re-charge them after 1 month (insight 1). How much charge can they loose in 1-month ? I imagine few enough so that to bring them back to 40% I should leave them plugged in 10 minutes ?

Is this something sound and workable ?

Because if not, then I should charge them more and then artificially use the devices intensely to make them discharge the battery again at about 40%. That’s because I don’t know if there’s any universal charger/discharger that I can use to control how much charge/discharge I want to apply to a li-ion battery before I store them.

All this is so much easier with the Ni-MH Hybrid batteries (used in strobes for example) for which I’ve bought a Maha Powerex MH-C9400 charger/discharger and every few weeks I run a Refresh&Analyze; cycle specifically designed for optimal storage of the batteries (then, every few months I run another “stronger” program to fully re-generate them).


On October 17, 2011 at 1:40am
Mr.Milcho wrote:

Thanks to Battery University for this information.

On October 18, 2011 at 6:41am
Cedric wrote:

The table shows numbers of cycles for different DoD.
But does 50% DoD mean cycling the charge between 50% charge and 100% ?
Given what the article says, would it not be best to cycle charge between 10%-60% for example ? (avoid full charge to not have high voltage in the battery) ?

And what I would like to know is what is best (ex. during working hours, at my desk) ??  :
- let the laptop/phone plugged, so with battery near 100%, but almost not used (except for peak power use, such as in phones for some radio communications).
- Or only plug sometimes, maintaining charge beetween 20%-80%. In this case we have lower voltage, but the battery is much more in use, enduring more (partial) cycles.

Note that for phone, they won’t work with battery pulled-off. I wish it could be set up to only charge to a partial charge (ex 75%).

On October 20, 2011 at 12:05pm
Tom wrote:

Very Useful…

On October 21, 2011 at 9:23am
Andrew wrote:

Hi - I have read this forum over various times and have seen the question “can Lithium Ion batteries be restored/saved”? asked a number of times. Often the discussion leads in tlo technical descriptions but no clear answer…

Once they no longer hold a charge, is there anything I can do to practically revive a lithium ion battery or is is straight to the garbage dump?

it’s just that i have a very large pile of, what were, high quality battery packs and would like to know if i can ever derive an practical use for them? ...beyond being paper weights?

i just figure that these 14.4v, 95Wh unite cost a bundle and certainly their must be a way to restore them…no?

please appreciate that while mechanically advanced, in the battery world I’‘m very much the lay person…

On October 22, 2011 at 4:31am
Sergey Verlinski wrote:

Could you please explain: which mechanical parameters describes aging of batteries? And second question: how Young’s modulus of Li batteries changes depend of temperature. Thanks in advance.

On October 22, 2011 at 8:52pm
Michael Nolting wrote:

I just want to know if keeping my laptop with li batteries connected to the AC charger is destroying my batteries.
I replaced my battery because it would not hold a charge in June and now it behaves very erratically.

On October 23, 2011 at 8:00am
mekong_nam wrote:

well.The information that you give is different from user’s manual of cellphone company. They said that user should full discharge, empty their battery before recharging to keep battery lasting longer. All sellers said that users should charge their battery 8 hours for first 3 times to maximize the capacity of battery.

On October 26, 2011 at 2:15am
Clement Lee wrote:

My Portable DVD is using Li-Polymer rechargeable battery. It is about 1.5years old. Now the battery swelled and the charge capacitive drop seriously.
Why the battery swell ?
Is it dangerous to keep on charge and discharge it ?

On October 27, 2011 at 12:13pm
resg wrote:

My mobile accepts charging both using AC adapter or USB port. Using the USB will apply a slower charge as stated in the owner’s manual. Question is: is the USB charge less stressful than the one with AC adapter? Is it better for the battery at all?

On October 27, 2011 at 9:09pm
Martin wrote:

So does anybody know if this article has been updated from 2001 to include more recent info?
As far as my logic goes then at least in 2011, it’s ok to keep your laptop plugged in with the battery attached, because
1. if you charge to 100% and keep to AC on the charger is intelligent enough not to really start charging the battery again until it naturally drops to about 95%
2. while on AC the laptop does not draw power from the battery (source Dell homepage)
You have to keep in mind though to discharge it / charge it once in a while (from this page here it seems the best is to let it go to about 25%?).
Only if your laptop gets very hot while using it on AC, is removing the battery a good idea as a hot laptop will also naturally heat up the battery (remove the battery and touch it, should give you an idea). This, as I understand, will make the battery loose it’s capacity more quickly.

On October 30, 2011 at 1:48pm
David Jones wrote:

I’ve just finished reading the article and all comments.  Not until nearly the last comment did I learn that the article was written in 2001.  I scrolled back up and found no date before or after the article.  My closest clue was when the comments began in 2010.  My fault for no thorough research of the source.  I simply Googled “how to care for Lithium Ion batteries”.  I must say that I appreciate the intelligent comments, especially Paul and Walter.  Many thanks for this information.  My Toshiba laptop and cell phone batteries will serve me longer and stronger.

On October 30, 2011 at 4:36pm
megan wrote:

i left my phone in outside and i fount it everything works fine but not less than 5 seconds after i turn it on it says battery is to hot powering off??? does anybody know wht tht means ???

On November 1, 2011 at 3:48pm
Ted Seifert wrote:

How do I store my lithium batters for the winter, I use them in my yard tools. I will not be using them for about 4 to 5 month.

On November 1, 2011 at 6:32pm
cristovian wrote:

Can a battery, namely Li-ion be charged and discharged at the same time,without a disruption in the output. The battery pack has two terminals one input and the other one an output.

On November 12, 2011 at 7:30am
bargainsbob@gmail.com wrote:

I just bought a Craftsman 20 v Li-Ion Professional drill (display model). When I got it home I tried to charge it and the charger indicated that it was defective and refused to give it a charge.
  So I stuck it in the freezer for a short while and then it charged ok.

Does anyone know why this happened?
Does anyone know if the pack is good or should I return the drill to Sears.
Thanks for any replies

On November 23, 2011 at 9:38am
Zubair Shahid wrote:

Hi! I have a dell inspiron 1520 laptop. I have a question…. If i use maximum time laptop on ac state although my battery is full so is it harmful for my laptop or my battery… plz guide me…

On November 27, 2011 at 1:16am
HHAH wrote:

very helpful, thanks very much

On December 2, 2011 at 12:10pm
brian wrote:

Laptops get hot when turned on especially bigger ones when the CPU and video cards are processing a lot of data. It can be detrimental when turned on 24/7 as the battery also maintains a 100% charge. Placing laptops on blankets or beds can block the vents and overheat it further. Fabric is also a good insulator. If laptop batteries are protected from excessive heat while running, wouldn’t the service life last much longer.

The advantage of Li-ion is that it is light. I prefer NiMH because apparently, they don’t age as fast when not in use and they don’t have that explosion risk.

mAh can be a bit misleading because it does not equal Wh. Wh is equal to V x Ah. So it seems if you connect cells in series, you find the Wh of each cell before adding it.

On December 5, 2011 at 1:44am
Ray Wells wrote:

I have a Samsung Galaxy, and left it charging overnight using the USB port of my HP Mini, which was plugged in the whole time. In the morning, the phone was good, but the laptop battery was 0% and has not worked since. My theory is the USB port stayed powered while the laptop cut it’s own charger off for some reason.  Before this, the laptop battery was doing fine.

On December 5, 2011 at 9:35pm
Katy wrote:

Well from first hand knowledge the quickest way to kill your Lithium Ion battery is to let it go completely dead. Another thing is to leave it in the car over night in the cold. Just trying to help so you guys don’t make the same mistake.

On December 12, 2011 at 6:48am
Guillaume wrote:


If you intend to use your laptop charged in for an extended period of time, remove the battery from it at 40% capacity.

You should not keep the battery on the laptop. The laptop will keep charging the battery as soon as it losses a little capacity and will eventually reduce the battery life expectancy.

On December 12, 2011 at 6:53am
Guillaume wrote:

So if I understand the Table 2 correctly, the optimal capacity to charge a Li-ion battery is 50% ?

100% * 500 cycles = 500 times full capacity
50% * 1500 cycles = 750 times full capacity
25% * 2500 cycles = 625 times full capacity
10% * 4700 cycles = 470 times full capacity

Did I miss something ?

On December 17, 2011 at 1:04pm
taz wrote:

Dont listen to these people thats crazy there saying if u store ur battery in ur fridge at 0c your battery will only lose 2% per year? So i can store my lithuium battey for 10 years and lose only 20% capacity? LOL

On December 18, 2011 at 3:51pm
Mike McMahon wrote:

My cell phone battery is Li-Ion 3.7 vdc. My USB output is 4.98 vdc. Is the 4.98 v going to significantly degrade the life of my battery?

On December 22, 2011 at 5:14am
Ray Wells wrote:

The underlying issue is “how humans should behave in order to handle technology”. Well, guess what, that’s backwards. Technology should behave in a way that humans can deal with. Assume they are all retards if you like, but expect them to: 1/ Leave rechargeable devices plugged in most of the time, 2/ Leave the battery in place when in use, regardless of being plugged in. 3/ Store things in a hot vehicle when convenient. 4/ Need a clear indication when a battery needs replacing. Like everything else, battery technology will evolve by natural selection. Utility and economics.

On December 22, 2011 at 5:24am
Ray Wells wrote:

I liked the original article, gives a good analysis of the challenges facing the industry.  There will probably always be “101 things to avoid doing” with any battery technology.

On December 30, 2011 at 11:14pm
Du Roi wrote:

I have a Nokia N70 Me for several years (may be 4 or 5) with a Li-Ion (BL-5C) battery, what i use to do is to charge 100 %, and use phone until the battery is full discharge. My BL-5C is in perfect condition i assure you. This is my own experience with a Li-Ion phone battery, and i think this contradict a little beat some of this theories. I hope this help in a way or another.

Happy New Year for all !!!

On January 2, 2012 at 7:35am
Ray Pipkin wrote:

@ Jeff Simon, who wrote:
“Maybe I am the only one missing one aspect of the number of cycles verses depth of discharge: if you only get 500 cycles with 100% discharge, as compared to 4700 cycles with 10% discharge, those cycles are not equivalent.

“That is, the 100% discharge got 10 times the power ouput as compared to the 10% depth. If assuming useful work was done in each depth, then in fact getting 500 cycles actually gets a bit more work than 4700 cycles of only 10% the depth.”
You are correct in your observation, but you should have taken it one step farther. Using the data of Table 2 which gives the number of cycles to 70% capacity as a function of depth of discharge, one can derive the relative amount of total energy extracted (a dimensionless quantity) from a Li-ion cell as a function of DoD:

100% DoD yields 500 units of energy from a Li-ion cell over its useful life;
50% DoD provides 750 units;
25% DoD provides 625 units; and
10% DoD provides 470 units.

The data in Table 2 indicate that recharging when the capacity reaches 50% is optimal over the other three options.

On January 2, 2012 at 9:50pm
Inpulpded wrote:

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<a >advanced system care torrent</a>
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On January 8, 2012 at 3:56am
Deyan wrote:

I have owned an Acer Aspire laptop with a Li-ion battery for 4 and a half years now. I use it predominantly on AC power and NEVER take the battery out. My battery now still has 86.9% of its initial capacity. Any comments? derp, what do you think?

On January 17, 2012 at 4:21am
Eric wrote:

If you look at table 2, it only says the number of cycles, which is irrelevant here. If we have a charger ready and need to know when to charge to prolong life, you can’t read it from the table directly. If I fully use the battery until it’s empty (100% DoD) you have to compare that to 10 cycles discharging to 10% DoD, because that’s fulfilling the same usage; any other comparison is useless. So looking at these four values, the 25% DoD seems to be the best, but more values would be helpful.

On January 18, 2012 at 1:58am
jessiefister wrote:

don’t charge your battery untiil it is used up.
more ideas please click:

On January 20, 2012 at 3:26pm
Luke Patrick wrote:

I work research and development and have tested lithium-ion cells for years. Here are some points I have learned on lithium ion:

0. If a battery is in a device, the device always has some sort of battery management system. Full discharge (to 0 volts) should not be possible and does cause irreparable damage. “full discharge” to about 2.7V (0% state of charge) is normal.
1. Storage will not rejuvenate or recover capacity.
2. If you need to store long term, store it at 50% charge. This reduces self discharge and/or active material degradation. 
3. Freezing can damage a cell by causing dendrites (crystalization) in the electrolyte components and piercing seperator or damaging material bonds.
4. The lower the operating temperature - the slower the ion exchange.
The higher the temperature - the higher the material degradation. Room temp is best.
6. Once in a while, discharge the battery until the device cuts it off, fully charge it and leave it on the charger for a short time. This moves as many ions as possible from one electrode to the other keeping them free to move instead of “stubbornly stuck”.
7. Remember different companies make different formulations of Lithium ion and Li-polymer that behave differently like High power, High capacity, long life ... there is always a trade off.

On January 24, 2012 at 5:23pm
shane wrote:

charge my battery

On January 27, 2012 at 2:44pm
Karen wrote:

I just moved to a new office.  Since moving my cell phone battery discharges (totaly- phone will not turn on) after about 3 hrs in the office with no use.  It has never done this and now does it daily.  There are several radars operating within 1/2 mile.  Could they be causing this?  Tempature is cool and humidity is about 20%.  The person who had the office before me said it did the same to her.  It does not affect my IPad or Laptop.  What could cause this and Is this damaging my battery?  Thanks

On January 30, 2012 at 5:05am
BigMart wrote:

I am even more confused now than when I started (not difficult!).  I used to use my Acer 5715Z series laptop battery running it off the mains all the time, where practicable.  Now I let it virtually fully discharge and then fully recharge.  I now believe that it is wrong

So I am to let it discharge to 50% and then recharge it back to 70% ???

Is it okay to run the laptop without the battery inside?

Please help a simpleton !!

On January 31, 2012 at 9:15am
Guillaume wrote:


You want to run the laptop without the battery if you can. Don’t leave the battery in the laptop when you are connected on the 120 Vca. A poor battery charger will reduce your battery life with an bad charging method.

As it was said earlier, the optimal charge level is around 50% of the battery capacity. You don’t want to go crazy with your laptop’s charge level. I suggest you to use the laptop between 40-100% of your battery capacity and then recharge it.

On January 31, 2012 at 10:22am
BigMart wrote:

Thank you Guillaume for your comments.

I am afraid you are bit too technical for me!  What is 120 Vca ?  The battery charger is within the laptop.

So I charge it up 50%, ie when it indicates 50% left.  So what is 40-100% then?

As you can see I am so confused !!

On January 31, 2012 at 10:39am
BigMart wrote:

Would you agree with this supplier’s instructions?


On January 31, 2012 at 10:41am
Pavlo Maksyutenko wrote:

“The smaller the depth of discharge, the longer the battery will last”
is WRONG based on Table 2. Battery life = (number of cycles)x(depth of discharge). Table 2 shows that 50% DoD is the best.

On January 31, 2012 at 4:59pm
BigMart wrote:

So what are you saying Pavlo?  Discharge to 50% and then charge up to ???

On February 1, 2012 at 3:48am
John Fetter wrote:

On December 22, 2011 Ray Wells wrote, “Technology should behave in a way humans can deal with”. He is 100% right. If batteries are powering computer equipment, it should be easy for equipment manufacturers to include programming that learns how the equipment is being used and to control battery charging accordingly for maximum life.

Simple. Unambiguous. The equipment would then be left plugged to a mains supply as much as possible. It would automatically apply optimum charging. If it detects excessively long absence from a mains supply, it warns the user.

They are not doing this simply because they want users to be confused and they want batteries to stop working, on average, just out of warranty, so that they can sell more batteries.

On February 4, 2012 at 6:57am
Des wrote:

A very in formative web page. I must admit that I have more than I knew about batteries. I will refer your site to my friends.
Thanks to all for your wonderful contributions.

On February 4, 2012 at 8:32am
BigMart wrote:

I wish someone could give me simple answesr
I just want to know if I am running it on battery power how long I should let it run down to - and then do I recharge it to full power.  If I am running it through the mains do I take that to full power?  When running it on the mains do I take the battery out?

Thank you.

On February 4, 2012 at 9:39am
John Fetter wrote:

Go to supermarket, pick up something from the fresh produce section. it carries details about the contents, cooking instructions, etc. Buy something with a battery, it carries instructions that look remarkably like threats. Don’t do this, don’t do that. Will burn, will explode. Hey, I just want to know how to use this thing!

On February 6, 2012 at 9:28am
Guillaume wrote:


Don’t let it drain out to maximize life expectancy. When you reach 25-40% remaining capacity, you should start recharging it.

On February 6, 2012 at 11:25am
BigMart wrote:

I concur with John Fetter’s comments.  Is there nobody out there that speaks plain English?

On February 6, 2012 at 11:29am
BigMart wrote:

I take a coach / train journey every few weeks which lasts approx 2 hours.  I use it then on battery power.  When I reach my destination I can then use mains.

So should I just run it off the mains when practical (removing the battery first?), or use battery power, but when I am down to 25 - 40% (a big range), plug it in until it reaches maximum?

On February 6, 2012 at 2:20pm
Guillaume wrote:

With that kind of use, I would recommend to recharge the battery the day before your coach / train journey. You may leave the battery at “whatever” remaining capacity for a few weeks if this capacity is over 25%.

If the remaining capacity is below 25%, recharge it until it reaches 40% and then store it until the next utilization.

Also, I suggest that you remove the battery from the laptop for an extended use on mains.

On February 6, 2012 at 5:04pm
BigMart wrote:

Thanks Gullaume

As I will be using the laptop over a couple of days, so I will need to charge it up, use it on batteries then use it on mains until it charges up again.  So should I continue this process until I get home?  I will want it fully charged for my return journey.

On February 6, 2012 at 5:05pm
John Fetter wrote:

My company was running a product ad on line that had absolutely nothing to do with lithium ion batteries. We inadvertently worded it in a way that was interpreted by unhappy lithium ion battery users to mean we could help them. The effect was like a tsunami. They clicked away the ad budget for the day almost in the blink of an eye. It appears there are very, very many very unhappy battery users out there.

The understand the advice that has been given. I personally do not find it difficult looking after batteries. The vast majority of users are primarily interested in using, not in mothering batteries. It is not right that the use of batteries requires user participation and decision making in a process that will hopefully help to overcome critical product design deficiencies.

On February 9, 2012 at 6:47pm
Kells2122 wrote:

I loved what Derp & Luke Patrick had to say.  It was in laymen terms that I could understand.  I just bought a new hi-cap battery for my hp laptop and want to make it mobile.  Now I understand how to do this.  Thank you for the article and all the info.

On February 11, 2012 at 10:16pm
Capt bob wrote:

have two 24 volt battery packs which run a 11 hp golf cart motor in my 10,500 lbs boat
Have been storeing batteries in insulated/heated garage 40 tp 60 F
outside temperature 10 to 30 F 40 to 60 days per year southern Utah
warmer rest of year

should I be leaving batteries outside in boat in the winter

On February 11, 2012 at 11:54pm
John Fetter wrote:

Capt Bob - Assuming your 24V battery packs are lead-acid, if they were mine, I would give them a full charge, ensure they are left disconnected and leave them outside in the boat in winter, under cover. Fully charged sulfuric acid will not freeze like water but freezes just above minus 40 degrees. Low temperature reduces chemical activity and therefore keeps the batteries from discharging.

On February 12, 2012 at 2:11pm
Jon wrote:

Great article but I still have questions:  I just bought a new laptop.  It will be used everyday and the battery will need to be used on most days.  I will have access to a power source about as much time as will need to use the battery.  Should I fully charge the battery to 100% everyday?  Should I remove the battery when I can plug the laptop in even though the battery is 100% or close to?  I’m looking for any suggestions you might have on how I should maintain my battery.

On February 18, 2012 at 7:25pm
zachary wrote:

is there any way to condition a LI-ION if you failed to do the 8 hour charge the first use. i was on the go when i recieved my cell. so it wasn’t charged properly the first two days? if i leave it on charge for 8 straight hours will that condition it if done with in the first week? cycle it? other procedure, or is it “day late dollar short”

On February 24, 2012 at 9:39am
Steven wrote:

I still use my 1st Gen iphone from 2007 and the battery capacity is still good. Everyday when I’m home, the iphone goes on the cradle and gets charged overnight, regardless of how much battery is left, (usually over 50%). Most of the modern gadgets that use Li-ion battery have smart charger that will cut off when the battery is fully charged. I guess charging my iphone every night since 2007 have prolong the life of the battery. So I concur with the article.

On February 24, 2012 at 4:05pm
Martin wrote:

What is the difference between taking out the battery from a laptop while not in use, and leaving the battery in there, switched off ?

On February 29, 2012 at 6:28am
Wombat wrote:

is there a safe way to “wake up” a Li-ion battery relatively safely at home? i have a number of batteries from drills that won’t charge and only show 11-12v (they are 18v packs)

On March 3, 2012 at 3:51pm
AlaskaPop wrote:

Great information, historical, evolving to present-future.  Should help me conserve some
legacy systems beyond ‘average’, which is better than I could have managed before reading this essay Now I need to figure out the charger actions of a couple of laptop/power-adapter combinations, and use habits of my associates.  Avoid heat, full discharge, prolonged idle, and on really old systems, overcharge, and we should see good use life.  Thanks all.

On March 9, 2012 at 12:22am
logo items wrote:

Li-ion or Lithium Ion are often used in newly produced laptop and mobile device. Actually i wrote about Laptop Battery Maintenance before, it’s about how to maintain your laptop battery by doing regular fully cycle (fully charge and then fully discharge). But, later i know that those methods are only work on Ni-Cad and Ni-Mh battery.

On March 9, 2012 at 8:08am
Rajdeep Singh wrote:

Following the advise of a blog, I started storing my Laptop and Mobile battery in an air tight container. After reading this article, I am confused whether to leave them there or store them in room temperature ? I live in India where summer temperatures soar to 45 degrees. Centigrade. Will room temperatures be safe ? Please advise. Thank you for this wonderful article and do convey my best wishes to derp ( honestly he is a good soul )

On March 9, 2012 at 2:51pm
haddy wrote:

should i disconnect after my battery is full or should i keep it connected to charger

On March 10, 2012 at 12:14am
Rajdeep Singh wrote:

You should disconnect

On March 14, 2012 at 7:34pm
Matt J. wrote:

Several commentators have confirmed what I long suspected: that a smart charger will detect when a battery is full and dial back the voltage. But they have also confirmed that not all chargers are this smart: so the natural question is: how do I tell if the charger I am considering buying, or the charger that came with my computer is that smart or not?

On March 14, 2012 at 7:58pm
Rajdeep Singh wrote:

Matt J., you just have to have confidence on the Charger which comes with the Computer. There’s no other alternative. if you buy a charger, make sure it matches the specifications and it is from the same company as that of the Computer.

On March 14, 2012 at 8:01pm
Rajdeep Singh wrote:

You just have to have confidence on the Charger which comes with the Computer. Should you buy a new one, the specifications should match the Computer’s requirement and should be from the same Company as that of the Computer.

On March 14, 2012 at 10:36pm
Matt J wrote:

@Rajdeep—That is asking a lot. Especially since the published specs for both the OEM and aftermarket chargers do not INCLUDE The information. They all claim, for example, to be capable of charging LiON batteries. The aftermarket chargers also come with a long list of model#s of laptops they claim to support. But since this article and the comments claim that many of them do not dial down the voltage when the battery is charged, no, I do NOT have confidence on the Charger which comes with the Computer.” Not without an explicit guarantee.

On March 15, 2012 at 4:19am
Rajdeep Singh wrote:

Ofcourse the specs in the Battery are mentioned. haven’t you noticed it ? In several articles and blogs you will read on the ways how to calibrate your Laptop Battery. Read that too.  Don’t go for any charger. Insist on the one you were using earlier. That way you are safe. My earnest submission to you ~ One, buy an original charger which came with your Laptop and second learn how to calibrate your battery periodically. There is no reason why your battery charging indication should be wrong. Let me know. I am just trying to help you.

On April 1, 2012 at 10:17am
Gary wrote:

wrt Bigmart’s question on Jan.31 “What is 120Vca?” - I believe he meant 120 VAC, which stands for volts AC, standard mains in N. America.


On April 3, 2012 at 2:42am
batman forever wrote:

mi psp no se quiere cargar.al ir a cargarla en unos segundos se apaga dazme soluciones

On April 3, 2012 at 9:32am
Rajdeep Singh wrote:

With my apologies ~ request you to kindly post your queries in English only

On April 3, 2012 at 7:44pm
Matt J wrote:

Charging a battery in just seconds is NEVER a good idea, ‘batman forever’. Remember what the article above says about heat shortening the life of the battery: charging too fast WILL raise the temperature too high and shorten its life.

On April 7, 2012 at 12:37pm
Tina wrote:

I am sorry about my lack of understanding but I just purchased a new battery for my laptop. I have an HP Pavillion. It came with 74% charge so I continued to charge it to 100%. Now I want to make sure that my new battery lasts longer than my old battery. I tried reading and understanding the article but my brain cannot seem to process it. Do I allow the battery to completely discharge and recharge? If so, how often? If not, how far down, percentage wise, do I allow the battery to discharge before I allow it to recharge. Again, my apologies for my lack of understanding. Thanks!

On April 7, 2012 at 1:39pm
Matt J. wrote:

@Tina The article was not THAT hard to read;) But the answers to your questions are all based on the following principle expressed in the article: shallow charge/discharge cycles are better for battery life than deep ones. So No, you do not allow it to completely discharge. 10% discharges allow the battery to last for much longer, but are themselves too small to really be practical. If your laptop and charger have good control over the charging current, (a question this article does not even try to answer), then you should just leave it plugged as often as possible.

On April 7, 2012 at 3:07pm
Big Mart wrote:

I have to agree with Tina.  I found the responses very confusing.

So, Matt J, are you saying you should leave the laptop plugged in with the battery as often as possible?  What I have gained from the article and responses, is I have left the battery drop to approx 50%.  I have removed the battery and running the laptop (where practicable) off the mains.  Is this right?  If not, please explain so myself and Tina can understand it.

Thank you.

On April 7, 2012 at 10:39pm
Matt J. wrote:

@Big Mart - Close, but not quite. What I said is that you “should leave the laptop plugged in with the battery as often as possible” IF the charging circuity is high enough quality. Unfortunately, neither this article nor the vendor specs tell us enough about the chargers: but overcharging is also bad for batteries, and poor chargers WILL overcharge the battery.

I am not sure which of my computers and chargers have high enough quality. I feel pretty confident of the Apple computers, less so of Radio Shack or Targus chargers bought for IBM compatibles.

On April 7, 2012 at 11:13pm
Rajdeep Singh wrote:

For Tina ~ All new batteries come in a semi discharged state. You should have charged it fully and even after that for atleast two hours before using your computer. Never mine…...Now charge the battery fully before using it. Let me know !!

On April 7, 2012 at 11:22pm
Rajdeep Singh wrote:

For Tina ~ Follow this. Allow the battery to charge fully ( with your Laptop off ) Once charged use your laptop on battery mode till it discharges and you get a pop up suggesting that you have to charge your battery.  Again charge your battery ( with your computer off ) and use your battery as above.  only once in a while you may use your Laptop plugged in with the battery fully ( A circuit in the battery stops the battery being charged once it attains 100%  so as to protect the battery from being over charged ) If you a using your Laptop more as a desktop for more than two weeks, it is better to take out the battery and keep it in a coll dry place. But please use your battery atleast once in a month. Please store your Laptop battery at 40% ~ 45 % charge level ` at which oxidation takes place the least.

On April 7, 2012 at 11:30pm
Rajdeep Singh wrote:

For Tina ~ Once in a while, in plugged in mode with the battery in your Laptop go to all programmes > H.P.Support Assistant > Trouble Shooting > Power and Thermal > Battery check. ( click on Battery check and wait )  Your Laptop will tell you the state of your battery. So far your battery is new, you should not a have a problem.  If you get a message saying CALIBRATE YOUR BATTERY, please feel free to contact me at rajdeep218@gmail.com

On April 8, 2012 at 2:46am
Big Mart wrote:

@MattJ   Thank you for your advice.  What should I do then with my Acer Aspire 5715Z.  The only charger I have for it is the charger within the laptop.

Should I put the battery back in and then use the laptop off the mains?  Do I do anything more when it reaches 100% charged?

I use my PC most of the time, and tend to only use the laptop when I away from home, ever 2 - 3 weeks for a weekend.

On April 8, 2012 at 4:55am
Tina wrote:

@Big Mart…thanks for agreeing with me.
@Rajdeep and @Matt J…I am a bit conflicted now with what you are both saying. Do I allow it to completely discharge then? I thought completely discharging a Lithium-ion battery was NOT a good idea.

Sorry again for my confused state of mind…lol!

On April 8, 2012 at 4:57am
Rajdeep Singh wrote:

if you are mostly on the PC it is better that you take out the battery and store at 40% to 45 % and store it till you work on your Laptop over weekends Once charged to 100%, power your laptop from the battery till it drains and again charge to 100 % preferably with your Laptop off. This will ensure that your battery is always in working condition Nothing to do when your battery is fully charged. Just remember never to store batteries at 100%, no matter what. Use your Laptop and bring it down to atleast 45% before storing. Remember your charger is only working when you are on plugged in mode. In battery mode your charger is off so nothing to worry !! please make sure before inserting your battery that the contact points are clean. Gently rub an eraser over the contacts and blow off the remnants from the points. If you follow thee points, i am sure your battery will give you good service. All the best !!

On April 8, 2012 at 5:18am
Rajdeep Singh wrote:

For Tina ~  Complete discharge is known as deep discharge. which means your computer hibernates. No this is not good especaially for the hard disk as a reverse voltage can cause serious damage. When the voltage drops to say 14% a pop up tells you to plug in before your Laptop hibernate. Rightly so.  So just charge your battery Preferably with your Laptop off till it attains 100%. A second Pop Up ( I too have a HP Pavilion g4 ) appears later when you are on 11%.PLEASE DONOT TAKE A RISK AND START CHARGING. Somebody suggested 10% to indicate a deeper discharge in an effort to calibrate the battery but that is different subject altogether which your new battery will not require now. And Tina please remember that all HP laptops reveal the correct battery reading as long as you have the applicable charger and battery ( which comes from HP )and you have not messed around trying to calibrate your battery.In the beginning every one is scared ~  but later it will be your Laptop which will teach you a lot of things so dont   have to feel embarrassed.

On April 8, 2012 at 7:59am
Tina wrote:

@Rajdeep Sing ...YOU ROCK!!! I am all set to go. See I have my Master’s Degree in Reading unfortunately not all types of reading…lol. Thank you very much for not letting me feel stupid or embarassed!

On April 8, 2012 at 9:18am
BigMart wrote:

Thank you Rajdeep.  However, if I am running the laptop using battery power it will probably run out of power while I am still using it (should I let it drain completely, or start recharging it at, say 10%?), so therefore I would have to recharge it with the laptop on.  Does that make much difference?

On April 8, 2012 at 9:34am
Rajdeep Singh wrote:

For Bill Mart ~ suppose you are on battery, wait till the second pop up arrives ( 11% ) and then start charging you battery ( plug in mode )  if you have important work to do, carry on. There’s no harm. Preferably put the laptop off cos a lot of heat is being generated ( while charging the battery gets hot otherwise too and secondly the Laptop generates enough heat when on ). Remember the biggest enemy of your battery is heat. Apart from this there’s no difference if you charge your battery with the Laptop on. All the Best.

On April 8, 2012 at 9:39am
Rajdeep Singh wrote:

For Tina ~ The objective of blogs and articles is to ensure people exchange ideas and learn. At one time, I too, was ignorant. today I feel happy   that   i am in a position to reassure people. Maybe one day people will ask you about Laptops and you will be able to answer their queries

On April 8, 2012 at 9:44am
Big Mart wrote:

Cheers for that.

If I have finished what I am doing and it has got to say 60%, do let it continue up to 100% and then run down, or just run down from that 60%?

Just want to be absolutely clear on what I am doing !

On April 8, 2012 at 7:04pm
Rajdeep Singh wrote:

Run down from 60%.  to 11%. Put off your computer and charge as usual to 100%. i agree, its better to be sure.

On April 9, 2012 at 4:43pm
Matt J. wrote:

@Rajdeep- Don’t feel too happy, your claims are quite contradictory to the basic claims of this article. No, he should NOT wait until the battery is discharged to 11% That would be one of the deep discharges that shortens battery life.

On April 9, 2012 at 5:42pm
Rajdeep Singh wrote:

@Matt.J ~ If my suggestion is in contradiction to this article, why does even a company like HP has pop ups coming at 14% and then again at 11% by DEFAULT.. The company insists that BEFORE YOU CHARGE YOUR BATTERY, YOU SHOULD DISCHARGE IT ~ KEEPING IN VIEW A FULL DISCHARGE CYCLE. Every one knows that if you go beyond 11%, the Laptop will hibernate, so the cut off point is 11% WHICH IS NOT A DEEP DISCHARGE. Had this been so, the companys would insist you charge your battery earlier, say at 20% or 25%, and the Pop ups would appear then…....... This has been agreed upon by HP too.. I don’t know which Laptop you have but I suggest you illicit their opinion too on the matter.And if you not agreeable to my suggestion, its better you don’t follow it. THERE IS NO COMPULSION !!

On April 9, 2012 at 5:59pm
Matt J. wrote:


Completely hypothetical speculation is no substitute for reading and understanding the article. Especially not when that speculation relies on unlimited benevolence of a company.

Discharging to 11% IS deep enough to have a significant effect on battery life, no matter what HP chargers say. That is clear from the article.

On April 10, 2012 at 2:33am
Big Mart wrote:

Well I am now even more confused.  Is there anybody that works in the battery industry that can give a definitive response?

On April 10, 2012 at 7:36am
Rajdeep Singh wrote:

@ Big Mart ~ Ask Matt J. ~ he seems to be an authority on this subject. !
@ Matt.J. ~  You’ve got me wrong again.  No where in the article it says that 11%  is ” deep enough   to have a significant effect on battery life ” This is purely based on your assumption. Throughout my comments I have bee n mentioning ” COMPANY ”  and you said ” no matter what hp chargers say “. For your kind information, no charger manufacturing company in the world specifies,  the level at which a battery should be recharged ( 11% / 14% ) that is purely the   responsibility of the Laptop manufacturing company. Chargers just indicate, basic specifications. its the laptop manufacturing company which tells you when to recharge..If you own an android mobile phone , you should be familiar with Lithium batteries. Just go to Google search and you will see hordes of articles and blogs on Lithium batteries ~ on how to maintain them, charging etc.WHATEVER INFORMATION I AM POSTING HERE IS NOT HEARSAY ~ THEY ARE BASED ON MY PERSONAL EXPERIENCE AND CONFIRMED BY H P .

On May 7, 2012 at 5:48pm
Eske Rahn wrote:

Thanks for a great article!

But I wonder if the conclusion drawn on table 2 are absolutely accurate?

Here I have extended it with a third column, taking the deterioration into account.

  DoD   Cycles   Total Usabilty
100%    500   435
  50%    1500   638
  25%    2500   531
  10%    4700   400

The added last column says how many times of “full charge” you will get out of the battery in total during its life time with each approach.
Assuming a linear deterioration of the battery from 100% to 70% of its original capacity (This assumption is backed by a graph in the article)
So the integration is simple, and can be replaced by a mean factor of 85% [*] to the pure product.

This would yield that the optimal total capacity gained from the battery over its lifetime is a DOD of around 50%
(Plotting the four points and combining with a smooth curve indicates that the maximum is around 60-50% DoD)

More precisely
Sum{n=0 to N-1 of DoD*(1-30%*n/N) }
=DoD*(N - 30%*Sum{n=0 to N-1 of n/N})
=DoD*(N - 30%(N-1)/2)
~DoD* N*85%

Best Regards
Eske Rahn

On May 13, 2012 at 10:39am
Gama Xul wrote:

This information has allowed me to fully recover the use of Lithium-ion cordless drill batteries for I had thought were irreversibly damaged. It’s good to understand a little bit of the science and practices of batteries and long-term storage. I’m taking far better care of my tool batteries now, and I’m running on a set of two I hadn’t previously cared for properly. Life extended by two years so far! Thanks for this information.

On May 14, 2012 at 12:43pm
Xiaopang wrote:

Matt J., you’re quite exaggerating by claiming that discharging down to 11% is already a deep discharge. Think logically for a moment: Companies have the legal obligation to deliver products who function within the expectations of their end users. If a product would actually be damaged extraordinarily (in this case a deep discharge would qualify for that) while its use is also within what could be expected from a normal user, then this might make the company vulnerable to law suits. Not just because they’d sell a falsely advertised product, but also because it would be dangerous.

A deep discharge should be avoided not just because it might ruin the battery, but also because such a battery might suddenly start to burn or even explode. Windows allows to go way below 11% (Xp 3%, Vista/7 5%), so as a result millions batteries would be damaged and a plethora might catch fire and burn…but that doesn’t happen…and for a reason:

A deep discharge per definition is when the cell voltage drops below a specified value. For 4.2V cell phone batteries this value is usually around 2.5V (60%). For notebook batteries that usually operate in the range of 10-12V I couldn’t find any values, but applying the same ratio as above, 60% would equal 6-7.2V.

To actually debunk your carelessly spit out claim I actually let my Notebook discharge the battery down to 30mW (0%) while I measured the battery voltage. The battery usually operated at 11.5V when the computer is connected with the charger. On battery the voltage is around 11V and goes down the more the battery is discharged. At 30mW charge the battery still had a cell voltage of 9.6V and thus was way above what would qualify for a deep discharge.

A deep discharge usually only occurs if a battery is used by devices that don’t turn off automatically on low charge and draw so little charge themselves that batteries can be discharged much longer and deeper than through normal devices.

Notebooks not just turn off automatically, they also need a pretty high charge level to even power up, so using up the battery entirely still leaves enough charge for the battery to not be damaged (anything else would be a pretty big oversight/design flaw, wouldn’t it). Li-ion batteries are equipped with small chipsets though that control the charging process and report stats back to the operating system. This also draws power, so discharging a battery down to 0% and storing it like that for weeks would eventually result in a deep discharge.

So, for all of those who are in doubt: try it out yourself if you are unsure. You can measure the battery voltage with hardware monitor.

On May 15, 2012 at 9:14am
Matt J. wrote:

I just cannot believe how many people comment here without having a clue what they are talking about. You, Xiaopang, are one of these. DId you even LOOK at Table 2? How did you miss the huge difference in number of cycles for a battery discharged to 10%? You are the one who completely missed what the article says, I got it right.

On May 16, 2012 at 6:17am
Xiaopang wrote:

No Matt, you just can’t read and throw any term into the ring that makes sense to you, regardless of its meaning. Your words:

“No, he should NOT wait until the battery is discharged to 11% That would be one of the deep discharges that shortens battery life.”

My reply was about explaining how 11% is NOT a deep discharge, because there is a clear definition of what a deep discharge is and which you apparently don’t know. I also never claimed that discharging the battery by 100% would not limit its recharge cycles. I didn’t even go near that.

You, Matt, need to learn to comprehend instead of just looking at a few isolated numbers in the desperate attempt to find proof for the twisted ideas you apparently try to convey.

You’re welcome to disprove what I actually said by using my own words, instead of just claiming that you got it right, while you clearly have no clue what you’re talking about…

Just to not just let your little statement die like it probably should, I’ll put table 2 into perspective. Something you should have done yourself instead of treating as the absolute truth.

First of all, table 2 is based on 4.2V cell phone batteries, while I was talking about notebook batteries. Both types are designed for totally different uses. While a cell phone battery is the sole source of energy for a cell phone’s life and is being recharged on a regular basis, a notebook battery is only there to deliver occasional power to a much greater extent. Charging also only takes place occasionally (granted the user/software/charging electronics) behave properly.

Secondly, the number of charges is determined by using an arbitrary value of battery life. The text even says so itself. Did you even read it or did you just look at the pretty graphs and numbers? The threshold value could be anything and the resulting measurements are of little use for other batteries. Proof lies in the numbers itself:

100% * 500 cycles = 50.000% total charge
10% * 4700 cycles = 47.000% total charge

Discharging a battery by 100% nets more charge over the battery’s life than only using it up by 10%. So, even if the words you laid in my mouth were actually uttered by me, I’d still be right due to the fact that you didn’t analyze what you argued with.

Even better: The arbitrary threshold of 70% is unrealistic. Who gets rid of a battery just because the cell phone only offers 3 weeks of standby instead of 4? Who buys a horrendously expensive notebook battery just because the battery only delivers 5 hours of work time instead of 7? A threshold of 30% would be much more realistic and would probably show that the 100% discharge nets much more charge than the 10% one. The gap between 50% and 25% discharge would probably also get a lot smaller, or may be even vanish at all. I don’t know and you don’t either, but the 10% - 100% discrepancy shows that this table is of little worth for your argument.

Repeat the test with a wide array of current notebook batteries of different brands with at least 10 per brand to minimize statistical flukes and then you have some numbers to argue with. Right now you have squat, let alone logic or analytical skills.

On May 16, 2012 at 1:29pm
Matt J. wrote:

No, Xiaoping, you are the one guilty of the lion’s share of the charges you fling at me. You were right about one thing: you should have “let my little statement die” instead of responding with your angry screed.

I never said anything about throwing a battery out after it is “deep discharged”. Nor if discharged to 11%. Neither does the article. Nor about throwing it out after three weeks of standby. That is your fantasy. But the difference between 11% and 10% is obviously small.

And how did you miss the title of the article? Despite your pretense, it is NOT specifically about 4.2V batteries, it is about Li-ion in general.

Your angry screed, full of equivocation, shows only your own inability to understand either me or the article. If anyone ever gets anything useful out of it—which is doubtful—it will be the article’s author realizing what he could have worded differently to better avoid confusion and needless arguments.

But even if he had worded it perfectly, there is nothing he can do for anyone clueless enough to believe as you do, that “Companies have the legal obligation to deliver products who function within the expectations of their end users”. That was funny. Why did you THINK most software license agreements disavow any “fitness of purpose”? They would not be able to do this if your ‘legal obligation’ were real. Newsflash: it is not.

On May 16, 2012 at 3:59pm
Tom V Martin wrote:


Refering to Table 2
Assuming a 10% DoD gives you 1 unit of use and you can recharge it 4700 times you’ve gotten 4700 units of use out of the battery.
Now if you have a 25% DoD you get 2.5 units of use per recharge. You can recharge it 2500 times you’ve now gotten 6250 units of use from the battery.
If you have a 50% DoD you now get 5 units of use per recharge. You can recharge it 1500 times you’ve now gotten 7500 units of use from the battery.
If you have a 100% DoD you’ve now gotten 10 units of use per recharge. You can recharge it 500 times you’ve now gotten 5000 units of use from the battery.

In addition keeping the battery topped off is contradictory to the information contained in Table 3.

I’ve found I obtain the best life and length of use between charges by allowing the battery to dischage till the device tells me it needs to be recharged, and then recharging it at that time.

On May 16, 2012 at 7:03pm
Craig wrote:

I must admit to being slightly confused. You say “the worst condition is keeping a fully charged battery at elevated temperatures, which is the case when running a laptop on the power grid” but then go to say “The question is often asked: Should I disconnect my laptop from the power grid when not in use? Under normal circumstances this should not be necessary because once the lithium-ion battery is full, a correctly functioning charger will discontinue the charge and will only engage when the battery voltage drops to a low level. Most users do not remove the AC power, and I like to believe that this practice is safe.”

Surely leaving the laptop plugged in all the time will lead to “keeping a fully charged battery at elevated temperatures”, no?

On May 21, 2012 at 12:33am
Xiaopang wrote:

Looks like a few comments were deleted, including my reply to Matt and that without an explanation…nice.

Matt: Here’s the gist of my last reply.

“You were right about one thing: you should have “let my little statement die” instead of responding with your angry screed.”

Yeah, try to sweep the fact under the rug that I cleared up your whole misconception about deep discharges and the erroneous “advice” you gave with it. That was also the sole purpose of my comment, so I guess I was right about two statements. Not a bad quota in a two statement post…

“I never said anything about throwing a battery out after it is “deep discharged”. Nor if discharged to 11%.”

Never said you did.

“Neither does the article. “

The article used 70% capacity as a threshold and called it “end of life”. I’d pretty much call a battery that has reached its end “dead”. What do you do with dead batteries? I throw them out…

“Nor about throwing it out after three weeks of standby. That is your fantasy.”

No, that was an analogy to show you how useless numbers based on such high thresholds are. By definition of the article, you’d have to get rid of batteries at that point because they are considered dead. The conclusion you should reach, other than being sidetracked by your own poor way of arguing, is that a more realistic threshold might show that the charge that could be expected would be pretty much even for certain charge levels. May be the opposite would be the case, but no one knows that. That’s why you can’t use the numbers as a basis of your argument. Their nature just doesn’t allow any conclusions.

“But the difference between 11% and 10% is obviously small.”

10% DISCHARGE of Table 2 != 11% CHARGE (=89% discharge). Yeah, the difference between 10 and 89% (or 90 and 11% if you want to look at the charge levels) is obviously small…

“And how did you miss the title of the article? Despite your pretense, it is NOT specifically about 4.2V batteries, it is about Li-ion in general.”

And where does the article say that the protection circuit is the same for cell phone and notebook batteries? You imply they work exactly the same, even though that makes no sense at all since both battery types are designed for totally different usage scenarios.

“Your angry screed, full of equivocation, shows only your own inability to understand either me or the article.”

Your obvious lack of understanding and your poor way of arguing make me rather smile than angry. How you get anger out of my reply is beyond me, but you’ve been misinterpreting the article and my replies so much that I’m not really surprised.

Btw, provide proof for your so called equivocations. My replies are right there. Use quotes for once in your life.

” If anyone ever gets anything useful out of it—which is doubtful—it will be the article’s author realizing what he could have worded differently to better avoid confusion and needless arguments.”

The article is very clear in what it says. It just doesn’t take amateurs like you into account who can’t even distinguish percentages of charge and discharge levels…

“But even if he had worded it perfectly, there is nothing he can do for anyone clueless enough to believe as you do, that “Companies have the legal obligation to deliver products who function within the expectations of their end users”. That was funny. “

Just because you found it funny doesn’t make it untrue. What I described is part of many case law and codified law based countries. You clearly are no lawyer and you also clearly lack proper common knowledge:

“If a defective product causes an accident that results in death, injury or property damage, the manufacturer, distributor, retailer and lessor of the product may be liable for the damages caused by the product. [...] The plaintiff must establish that a product has a defect that made it unreasonably dangerous at the time the product left the control of the defendant. [...] It may also be possible to show that the product was defective because it did not perform in keeping with the user’s reasonable expectations.”

Source: http://www.osbar.org/public/legalinfo/1047_DefectiveProducts.htm

“Why did you THINK most software license agreements disavow any “fitness of purpose”?”

Software != Hardware. Software doesn’t explode or catch fire when being deep discharged. Also, show me such an agreement for any non-Software product. You won’t find any, but just in case you do, it would be in violation of basically any western law.

On May 25, 2012 at 4:15pm
Celine Suchanek wrote:

I had a question.

I have a 2.3 android with the BL-4D 3.7 volt Li-on battery. I have found that overcharging does reduce battery life. I have had the phone only a couple of months and I do not use it a lot because each time I do after a couple of hours the battery is low. I received two batteries with the phone but it is still a problem. I have let it get to 0 percent a couple of times and recharged it to 100 percent. This has not helped. I know not smart but it was a suggestion I read before I read the article. I have not had problems with previous phones when it comes to battery life. Am I doing something wrong? I e-mailed the company but they have not responsed. Any help would be greatly appreciated. Also what android phone has the best battery life?

Is there an extended version of the battery I have?

On May 29, 2012 at 10:39am
Cadex Electronics Inc. wrote:

Hello all,

This article has been updated with lots of new information from Isidor.



On May 29, 2012 at 10:59am
Joe wrote:

These days, we have a lot of Smart Phones on the market like the Iphone which we cannot remove the battery for charging using other machine. Is there a way, we could analyze or using other accessories to charge it white the battery still inside the phone.

On June 8, 2012 at 11:15pm
azam uddin wrote:

This ‘tree-power’ article is pretty interesting. For those of you who may be well-versed in…charge an ‘e-vehicle’s’ battery pack? ‘Electrical circuit runs…39;s enough power in trees for University of Washington researchers to…

On June 12, 2012 at 1:25am
Andre Gardner wrote:


I’ve been monitoring my battery wear for a while now carefully with BatteryBar Pro v3.5.4 and my conclusion is that over-discharging and over-charging your battery is damaging and always results in wear.

So now I never allow the battery to trickle charge to 100% pulling out the plug before around 90% to 95% max. I then run the battery until around 50% to 35% and then start charging it again. By doing this all the time, BatteryBar Pro registers the minimum amount of wear. In fact a slip from this regime always seems to result in a few percentage points of wear. I think I basically do manually what some systems can do automatically through a setting in the BIOS (wish I knew about this feature before buying my laptop!).

So that’s my comment really. I really recommend BatterBar Pro so you can really keep an eye on what is going on. But remember the computer needs a restart for any wear level numbers to be updated.

Hope his helps!


On July 3, 2012 at 1:02am
demajoor wrote:

this is for laptops i presume
i dont think this works for phones like the htc one x or has that been tested to?

On July 3, 2012 at 1:34am
Big Mart wrote:


If you never charge it to 100%, what about when you want to use just battery power?  I will be going on a train journey tomorrow, and want to use it on the way. There are rarely mains sockets.  I want the maximum amount of time available.

On July 6, 2012 at 8:49am
Andre Gardner wrote:

To reply to Big Mart

I think the best thing to do is to charge to something like 97% to 98% and that will restrict the battery wear to the absolute minimum and won’t have to compromise too much batter capacity.

Having said that I think it is inevitable that you will need to fully discharge the battery from time to time when on the train for example but you just bear in mid that this will most likely damage you battery a bit unfortunately.

Hope this helps.


On July 6, 2012 at 9:41am
Big Mart wrote:

I think my battery for the laptop is now almost at the end of its useful life !  I can only get just over an hour from it when fully charged.

Is there anywhere that is recommended to buy a replacement one.  I did ask the laptop manufacturer (Acer) but it was horrendously expensive.

Thanks in anticipation

On July 6, 2012 at 10:18am
Andre Gardner wrote:

Just search for it in Google by putting in the model name with the words “replacement battery” in the search box. Note that laptop batteries are not that cheap you should expect to pay at least $50.

On July 6, 2012 at 10:23am
Big Mart wrote:

Thank you Andre.  I just wondered if anyone knew of a good reliable company.

On July 25, 2012 at 7:14am
Hassan wrote:

Hi….This is Hassan…i have hp probook 4530….The battery is PR06 Notebook Battery 3ICR19/66-2….10.8Vdc 4200mAh….I face power outages almost after every one or two hours. If i charge my battery to 40% and then put in fridge and during power outage i will use the battery. Is this practice a good one? If yes plz tell me the %charging that i should use for the battery.

On August 8, 2012 at 6:55pm
John Feltz wrote:

I’ve written a small program to perform unattended shutdowns of battery powered devices (such as laptops) at specific charges. It is for Ubuntu or Linux users, however if there is enough interest I’ll consider porting it for windows and mac:


On August 28, 2012 at 8:15pm
Daniel Dourado wrote:

The charger that came with my Motorola Razr is 5.1 v… How come? If the maximum is 4.2?

On August 29, 2012 at 5:34am
Herve wrote:

I read the original version of this article (whose only table was the very enlightening Table 3) many years ago, thanks to the authors for updating it with more tables and very informative data.
I’m afraid there are two typos left:
- in the comment on Figure 1: “A pool of new 1500mA Li-ionbatteries”—> should be “A pool of new 1500mAh Li-ion batteries”
- in the comment on Table 4: “Every 0.01V drop”—> should be “Every 0.1V drop” to match the table values (e.g. 4.2 to 4.1).

On August 31, 2012 at 4:38am
GEO wrote:

muito bom parabéns

On August 31, 2012 at 5:00pm
Janet wrote:

The battery university is a tremendous service.  Thanks for keeping it updated.  I agree with Herve’s typo corrections above.

I worked with batteries for many years, so I hope my words will take away some of the battery and charging anxiety that many have expressed in the comments.  Here are the key things to remember about Li Ion:
1.  Li Ion has a long shelf life, except if it is stored fully discharged.  Hence, the common recommendation to store at about 40% state of charge or above.  STORE BETWEEN 100% AND 40% STATE OF CHARGE..
2.  All name brand companies produce chargers that stop the LiIon charge at 100%.  It is the best practice to allow the charger to complete the charge.  Opportunistic charging (less than full charge) is ok and will not harm the battery.  There are electronic control modules either in the battery pack or the charger that decide when the charge is complete.  USE THE MANUFACTURER’S CHARGER AND ALLOW THE CHARGE TO COMPLETE MOST OF THE TIME.
3.  You do not need to store the battery in the refrigerator and it may be harmful to store the battery in the freezer.  Your battery is happy at the same temperature you are comfortable.  The most important thing you can do for the battery is do not leave it in the car on a hot day.  Same goes for your dog or your kids.  STORE THE BATTERY AT ROOM TEMPERATURE.
4.  If you are usually plugged in when you work, the battery does not even need to be in your laptop. (Check your instruction book or if you have children, use good judgment.)
Just make sure the battery terminals are taped so you do not inadvertently short it.  OR Try not plugging in the laptop some work sessions. Most will tell you when the battery is getting low and you have plenty of time to plug it in (but this is using up your battery life).  Either way avoids keeping the battery at full state of charge all the time and repetitive charging (starting charge on a fully chargd battery) which is detrimental to battery life.  There is a variety of charger quality on the market.  Some battery/charger combinations will detect this situation sooner than others.  TRY NOT TO KEEP YOUR BATTERY ON CHARGE OR FULLY CHARGED ALL THE TIME.

I understand the batteries are expensive and you want the most life out of them.  To get the most life from the battery really is as simple as the 4 BEST PRACTICES listed above.  Your life is too short to be babysitting your batteries trying to decide the depth of discharge for today and/or running to the fridge for a battery.  Enjoy.

On August 31, 2012 at 5:59pm
Matt J. wrote:


To which I reply:

But on what grounds do you assert that it has to be the manufacturer’s charger? Why wouldn’t a Targus Universal Charger (for example) have a control module capable of doing the control just as well?

On August 31, 2012 at 6:21pm
Janet wrote:

It is best to use a charger designed for the intended product.  If there is a reliable third party charger specificly intended to charge the battery for your product then it would also be acceptable.  This is for safety reasons so that the monitoring and control circuits usually within the battery pack operate correctly to control the battery charge.

On September 25, 2012 at 2:12pm
jay wrote:

What about using a Touchstone dock (Hp Touchpad) The general consensus on the touchpad forums is that it is safe to pop the touchpad on the wireless dock which also charges it to full capacity…Most people are leaving their touchpads on this dock every night and day and taking it off inbetween for minimal use. Ie checking email, browsing then throw it straight back on the touchstone.

This would seem to indicate that these touchpads are permanently living at 100% or near caoacity at all of the time….Can this be safe or healthy for long term maintenence?

Apparently their does seem to be a rash of issues re the hp touchpads battery not waking from powering off or discharging.
Maybe keeping it topped off can save it from accidentally deep discharging, as it seems the auto power off chip may not be functioning correct with the software/hardware

On October 20, 2012 at 8:32am
john h wrote:

thanks to (almost) all who contribute here. I have really enjoyed reading the articles and the comments/speculations.  I have a few of my own, and I would love to hear back from all (almost) of you. First, from reading the comments and seeing that there is not 100% agreement on the “do’s and don’ts”, it would seem to me there is a missing factor, which I would respectfully suggest is manufacturing quality of the battery.  From my own experience, I have had some devices which were abused, yet maintained good runtime capacities for long lifespans, as well as others that were “babied” and died ridiculously premature and expensive deaths. In the case of laptop packs and other multiple cell assemblies like those used with cordless tools, my forensic investigations reveal individual cells which have failed either by shorting or some form of diminished capacity which renders the entire pack useless.

My question today concerns the use of different charging connections and their effect on rates/quality of charge;  as was mentioned by some, the charging circuitry is contained within the device (cell phone).  As such, how is it that I get a faster charge from, say, the one that plugs into the cigarette lighter as compared to the one that is usb powered?  Obviously the voltage sources are different, but does that mean the phone is so “smart” it is deciding for me whether I want a quick charge or a very slow one? Shouldn’t the phone look at the incoming source and automatically regulate it down to the appropriate rate? All of the automotive and 120v receptacle charges I have charge at a rate that is much faster than usb.  Is then the usb the preferred way?

On October 30, 2012 at 2:10pm
carol wrote:

How about the larger Li Ion batteries used in yard tools?  Mine have decreased their life of charge time as well as the time it takes to charge them fully.  These are “green works” batteries.  Is there a way to turn this around and get the longer charge time back?

On October 31, 2012 at 5:25am
john h wrote:

Hi Carol
I will get my 2 cents worth in and then hopefully some others will have something to add.  From what you are describing, which includes both short run times and long charge times, I would have to conclude that your battery packs are reaching the end of their useful lives.  The condition you describe sounds to me like the internal resistance of the batteries is rising.  If you ascribe to the philosophies of B.U., then you understand that it is not possible to rejuvenate the lithium cells, and could also be dangerous to try. Unfortunately, the lesson you have learned is one I think most of us are perpetually repeating, and I am struggling to understand completely what the process is that destroys most of these cells.  I have had very very few of these lithium cells which lived up to their stated life expectancies.  My own experience would suggest 3 main factors: #1: Quality / proper use of charger circuit.  #2.: Quality of actual Lithium cells.  #3: Usage patterns and environmental (heat) considerations.  The comments listed above from Janet are along the same lines as what I believe; In effect, we are inadvertently “killing” a lot of these by putting them/ leaving them on chargers that are not well engineered.

On October 31, 2012 at 6:18am
carol wrote:

Thanks John H.  I was just hoping that there was a trick to actually getting the performance from the batteries that was promised in the sales pitch for the product. Silly me!

On October 31, 2012 at 10:12pm
Raphael wrote:

My Lenovo G480 and other current Lenovo notebooks as I know has a software called “energy management system” which you can tweak to make the battery fully charge in case you’re always using unit without the AC power or it will have the charger charge the battery up to 60% level if you’re frequently using the AC power. Now I know the rationale of this “60%” after reading this article. Thank you…

On December 23, 2012 at 3:31pm
Mohammad wrote:

tnx for useful artice… I have a new lenovo Y580 and I don’t know how to charge it for the first time….would u help me plz..

On January 4, 2013 at 10:37am
Andrew G wrote:

My Nikon digital SLR (D50) was bought in December 2005.  I’ve taken about 7000 pictures, so I guess the camera isn’t used a great deal.  It’s run by an EN-EL3a Li-Ion, 7.4v 1500 mAh battery pack.  I recharge the battery (8.4v, 0.9amp Nikon charger) as soon as the camera displays a ‘low battery’ symbol in the viewfinder.  I guess I recharge the battery 6 to 10 times a year.
But I’m worried as I’m still using the original battery…. 
I know I’ve only recharged it (maybe) 70 times.  Well short of the 200+ re-charge cycles.
But the camera / battery never get cold or hot.  As soon as the charge is complete, I put the battery back in the camera.  At the rate I use the battery, will it last another 7 years?  Or is there a finite time it will last?
I have a digital volt meter.  Is there a simple measurement I could make - that would give me an indication how much life there is in the battery pack?
FYI: Immediately after charging the battery measured 8.31v
One hour later is was 8.29v
Eight hours later it was still 8.29v

You expert thought would be appreciated!

Best wishes from the UK!


On January 12, 2013 at 11:06pm
Jason Lee wrote:

I think it’s rather impossible to do a partial discharge on Apple’s mobile devices. The iPad is equipped with three batteries, the MacBooks are equipped with six. But I’m not sure if they dishcarge one after the other or all together.

On January 17, 2013 at 5:24am
James Bond, Jnr wrote:

How about lithium ion battery safety? Hundreds, perhaps thousands of handheld and laptop devices have been burnt out by lithium ion battery fires.The Chevrolet Volt lithium ion battery caught fire several times. The Boeing 787 Dreamliner lithium ion battery caught fire several times. A submarine and several aircraft have been written off by lithium ion battery fires.

On January 17, 2013 at 7:51am
Dick Lawrence wrote:

Jason Lee, your iPad has its batteries wired in series. The voltage powering the device is the sum of the 3 batteries’ voltages, e.g. around 12V. They all discharge together. The MacBook probably has 2 parallel strings of 3 batteries but (like the iPad) they still all discharge together.
James B. - take a look at lithium-iron-phosphate (LiFePO4) battery technology and the abuse these take in order to be certified safe (to meet UN safety requirements) - I found a description of these tests on this site. They include pounding a steel spike through the battery. They still don’t overheat or start fires. Very tough technology and very long cycle life. I built a bicycle headlight / tail light system with them and they’re working great after 2 years.  -  DL

On January 17, 2013 at 9:37am
James Bond, Jnr wrote:

Dick L
You are reciting the sales blurb. I took the lithium ion battery fire information from news reports. The airlines that bought the 787 don’t want to fly them until the problem is fixed.

On January 17, 2013 at 12:12pm
Dick Lawrence wrote:

James: different technology. LiFePO4 is the variant that was the basis for the late great A123 Systems battery company, who were anxiously working to get into the electric car industry in a big way, before they went down and were acquired by a Chinese company (not sure it’s a done deal yet). BatterySpace.com sells LiFePO4 batteries by the way. Did you even look at the U.N. qualification test reports? It’s not marketing sales literature.

Plain old Lithium-Ion is more prone to overheat and risk starting a fire, as the unhappy folks at Apple know.  If you have information linking the 787 issues to LiFePO4 technology please let us know, with corroborating links supplied.

On January 17, 2013 at 2:35pm
James Bond, Jnr wrote:

I believe Boeing would only have used the best of the best lithium ion technology Yet it failed. Lithium ion battery technology is inclined to burn. You seem to be digressing.

On January 18, 2013 at 1:48am
Pier Luigi wrote:

I´ve been talked that to improve/increase the lifespan of out batteries, it is quite recommended to run discharging cycles every 6 months. Could anyone advice me about it?

I was serching on Internet for a Battery Discharger and i found out the item below:


I looking forward to hearing from your. Thank you very much for your collaboration.

On January 18, 2013 at 3:49am
Martin Rosen wrote:

Would this product be of any use?  http://www.mightydeals.co.uk/deals/national/Gadgets-Gifts/Power-Bank-Recharger-/4033?lsid=550200030&campaign=Affiliate_Window&utm_source=Affiliate_Window&utm_medium=Affiliate_Marketing&utm_campaign=Affiliate_Window_Sale

On January 18, 2013 at 6:11am
Dick Lawrence wrote:

Pier, the Battery Discharger you link to is mostly for testing batteries not for recommended maintenance or improving the battery.

The benefits of discharging a battery depends on the battery type (chemistry). For lead-acid battery, deep discharge is BAD for the battery and will shorten its lifetime. For nickel-cadmium some people recommend occasional full-discharge and the re-charge, citing the “memory effect” of nickel-cadmium chemistry - I think your question may be about nickel-cadmium. Other people claim the “memory effect” is a myth. You will find good information on this battery-university site, it is a very good source of info on batteries of all kinds.

Lithium-ion, like lead-acid, does not benefit from deep discharge - you will get longer life from lithium-ion chemistry by only discharging to 25-30% and re-charging to 80-90% - storing it at full charge (100%) for a long time is also not good - which is the topic of this forum, actually. There are some good articles and graphs here that explain it.  - DL

On January 18, 2013 at 6:32am
Dick Lawrence wrote:

James, I strongly doubt Boeing used LiFePO4 technology - it’s relatively new and the 787 was in design for many years. They are conservative about bringing in new technology especially where safety is concerned - even though LiFePO4 would have been a better choice, in retrospect.

Go to http://www.batteryspace.com/lifepo4cellspacks.aspx and then click on “Knowledge on LiFePO4 battery”. Look at the “Needle Test” - this is where they pound a steel spike right through the battery, causing a dead short through all its layers. Also the short-circuit voltage vs. temp test - the battery gets hot but does not burn, outgas, or explode. This is a nasty test but LiFePO4 does it more safely than traditional Li-ion as the presentation makes clear.

If you have evidence Boeing specified LiFePO4 for their batteries, please provide it here.
  - DL

On January 18, 2013 at 7:03am
John Fetter wrote:

Lead-acid automobile batteries are purpose designed to deliver very high currents briefly. They do not cycle very well. Most people are familiar with this type and mistakenly assume this type represents lead-acid technology.

Lead-acid motive power batteries, in contrast, are purpose designed for cycling and, dollar for dollar, will outperform every other chemistry when used on deep discharge cycling duty.

On January 19, 2013 at 2:42am
James Bond, Jnr wrote:

I believe you introduced LiFePO4 into the discussion. There is obviously a difference between a battery that powers a handheld drill, small enough to have a steel spike driven through it with impunity, and a very large battery, powerful enough to start one of the largest turbofan jet engines currently in use.

On January 20, 2013 at 10:36am
Jason Lee wrote:

Thanks, Dick. That was a very helpful post. +1 for you.

On January 29, 2013 at 12:49am
Silentcon wrote:

What level should i keep the battery? 30%-80% or 40%-90% ?

On February 6, 2013 at 9:46pm
Brad P wrote:

Seems like a lot of people more expert than me here. 

I just bought an expensive Li-ion powered car (no gas, only battery powered).  The batteries were manufactured by a leading global manufacturer.  The car was delivered to me with the batteries in sleep mode, in which state it had been for at least a week, probably two, possibly longer.  I believe the batteries discharged to 2.6% of their recommended full charge, sleep mode kicking in at about 5-6% of full charge.  I am being told orally by the car company that there has been no damage to the car’s battery (about half the value of the car), and that there is no chance of any copper shunts having developed, and that the car could have continued to sleep for another 4 months until any damage would occur.  After owning and charging it for a month, I see what looks like 25% more daily idle battery discharge from my battery than others are experiencing.  Should I believe them and not press any claim?

On February 12, 2013 at 1:25am
Greg Zeng wrote:

So many comments, so could you add the last date of the original, so that we can avoid reading old comments?

In case not covered:

1) Battery charger sometimes “breaks” e.g. inbuilt charger of mobile devices, especially if subject to heat, dust, vibration & fluids (including humidity). Most comon in old mobile phones.

2) Electrical contact deterioration, as in the first point, but between battery, charger or the device, or combination of all of these.  Repaired by cleaning & stopping vibration.

3) Premature aging (battery and/ or charger). Statistical bad “luck” of factory production, especially after ageing, heat, moisture, vibration effects.

On February 18, 2013 at 3:05am
Fin wrote:

Thanks for the good advice. I have a question if the laptop battery runs out very quickly (3-4 min), this means that it is already broken, and yet somehow you can recalibrate it, fix it?

On February 23, 2013 at 10:21pm
Avi wrote:

Samsung Galaxy Note II has a 3100mAH Li-ion battery. Some Internet sites suggest charging the battery when it reaches 10%, while other sites suggest connecting the charger when it reaches 50% - any ideas which might be correct?


On March 1, 2013 at 2:41am
KU wrote:

Does anyone know the improvement in the # of cycles if the charge discharge is 0.5C instead of 1C

On March 20, 2013 at 7:01am
James Bond, Jnr wrote:

Great news! Boeing sorted out their lithium ion battery problem. They seemed to have brushed the engineers aside, proudly brought in a team of legal-minded johnnies, who proceeded to tell everyone they had known about the problem since 2008, just did not use that solution because the paperwork was out of sequence.

On March 21, 2013 at 2:06am
Alan wrote:

@Avi: If you read the article above, you will see a Depth of Discharge (DoD) table with the following information:
100% DoD ==> 300 – 500
50% DoD ==> 1,200 – 1,500

Fudging the numbers in the table, you can get:
90% DoD ==> 480 - 700
80% DoD ==> 560 - 900
And so on. Based on that, I suggest you do not let your battery drop lower than 30%. In addition, if possible do not charge your battery to 100%.

On April 11, 2013 at 4:38am
James Bond, Jnr wrote:

Not such great news. Same lithium ion battery manufacturer, batteries fitted to Mitsubishi electric cars. Caught fire, at least one car totally destroyed. Simple problem + organization with vested interests + facility to hide behind lawyers = next to zero problem solving capacity.

On May 21, 2013 at 10:15pm
tOM wrote:

For desktop UPS use in a laptop, you probably want to maximise your battery years by charging only to 3.92v, which corresponds to 50% charge.

For portable use, you just want to recharge to 50% if it gives you enuff life, or whatever level does give you enough life.

Ideally, a battery management program would allow several charging targets:
- MAX portable runtime (ie, 100%)
- UPS use (eg, as desktop computer or low-usage phone days) (3.92v or 50%)
- several steps in between MAX and UPS for flexibility.

My Dell 5720 laptop has a “desktop usage” charging scheme which keeps the charge between 70 & 80%

On June 4, 2013 at 2:14pm
Martin Rosen wrote:

I have just bought an iPad.  When is the optimum time to charge it up?

On June 9, 2013 at 6:43am
John Gurski wrote:

I just purchased a cell phone and was wondering if I purchased a replacement battery but never charged it keeping as a spare would this be possible or do Lithium Ion batteries degrade with non use.  The phone is an off brand and I am worried when the original batteries loses storage capacity I may not be able to find a replacement.

Thanks for your great informative website.

On June 9, 2013 at 8:04am
Dick Lawrence wrote:

Many Li-ion batteries will hold charge and maintain their performance for a decade or more. If you’ve read everything on this forum you should have enough info to keep your spare battery good for many years. I would summarize it as: keep the battery in a cool place, charge it once, discharge it to 40-50% charge, and then leave it alone until you need it.  - DL

On June 13, 2013 at 1:48pm
Steve Mullis wrote:

I am using a Nikon Coolpix 8700 camera. The camera came with a 7.4v 700 mAh battery. I need replacement batteries. I see batteries advertised at anywhere from 700 -1500 mAh. I was told that due to the physical size of the battery it cannot be manufactured with greater than 800 mAh. I understand how to prolong the battery life (I suppose it wouldn’t hurt to put them into a refrigerator or surround them with a cold blue ice back). Is the information I received correct (re: mAh) or should I attempt to purchase a battery with the highest possible rating?

On June 28, 2013 at 11:07am
Alex wrote:

The study shows that 10% and 25% depth of discharge was not as good as 50% (table 2) but would have liked to see the 75% and 90% depth of discharge data as those would be more practical options. That is noone is going to regularly recharge battery at 90% charge or even 75% charge. It would be useful to know whether to target a recharge at 50% or would recharging at 25% charge or 10% charge be even better or substantially worse?


On July 19, 2013 at 6:47am
Derek wrote:

I must say the Galaxy S3 battery must be leaps and bounds ahead of the information here and on wikipedia.

I have discharged my battery below 5% about 10 times in the first 3 weeks and let it run to 0% twice. I have now taken steps to charge the battery at about 30%. However, the battery monitor pro app currently estimates it’s capacity as 2143mah so doesn’t seem to have affected it.

The spare battery (official GS3 accessories pack) has only lost 4% power after 1.5 months of storage time starting on 100%.

What I’d like more information about is table 3 because I dislike what is being said there and the numbers look suspicious relative to the words. Surely the battery does not lose 20% of its maximum capacity permanently after 3 months if it is sitting at 100% and 25 degrees? I mean if the spare GS3 battery only lost 4% temporarily (ie. can be recovered via charging), surely it has not lost 15% permanently in just 1.5 months.

If this statement was true then spare batteries can only ever have 40% of the original maximum capacity if stored at 100% for a year.

On August 14, 2013 at 7:01pm
Alvin wrote:

To: Walt Borntrager
Your statement about lithium ion memory has been backed up by some research.


“Here we report a memory effect in LiFePO4—one of the materials used for the positive electrode in Li-ion batteries—that appears already after only one cycle of partial charge and discharge”

It doesn’t say it’s ruined, but it “remembers” a partial charge….after one cycle.

On August 16, 2013 at 11:28am
Drew wrote:

I have seen that most Li-ion are charged to 3.7V. I have an application which requires 3.9-4V. Would anybody supply me a battery and charger charged to 3.9V-4V?

On August 19, 2013 at 9:25am
Fred Johnston wrote:

I recently purchased 6 Li-Ion batteries for our 2 Samsung Galaxy Note 2 Phablets, and the batteries only get 50-75% of what the OEM 3100mAh batteries that came with the phone, yet they rate their batteries at 3500mAh.  I complained, and they told me to fully charge and discharge 5-6 times as this would improve the capacity.  This will take me a long time to cycle through all of my batteries in this fashion.  Are they BSing me or can this be true???
Also, if possibility of being true (from what I’m reading here, that should not be the case) is there a good way to discharge them faster (eg rig up something with a resistor so I don’t need to run my phone through all of these exercises??

On August 19, 2013 at 10:05am
john h wrote:

There are some free Aps you can get which will discharge the batteries for you, so I would recommend doing that instead of the science lab version; although you can certainly connect them to a resistor and discharge manually.
My own opinion is that whoever sold you these is blowing smoke to stall you and prevent you from asking for a refund. I have heard mixed opinions both here and other places about the validity of exercising a lithium battery, but the technique suggested to you sounds more like a NiCad strategy to me.  I can’t find the link right now, but there is a guy who has a pretty good blog dedicated to reviewing the various replacement batteries out there.  Maybe you can do a search and locate it.  He has found that many, many of them are lying about the actual capacity of the cells. So what you have may be a decent quality battery, but it does not have the claimed capacity.

On August 19, 2013 at 10:31am
Fred Johnston wrote:

Thanks John… sort of what I’m thinking too (blowing smoke and delay tactic).  I do have, and have used, a fast discharger, but they chew up the phone and still make it unavailable for hours, and really heat it up… so I’m looking for a “kinder” way (as my previous Galaxy S2 died and I think part may be to trying this in the past to many batteries)... it is a LOT harder on the phone than the batteries!  If you happen to be able to locate that blog, what would be helpful (but only if easy for you to find)... many thanks!... good site, this one.

On August 19, 2013 at 11:21am
john h wrote:

I think this is the site:  http://www.batteryreview.info/  I purchased 2 of the Gorilla Gadgets high capacity for the Galaxy S3. I hated running from charger to charger. Now I have one in the phone, which averages about 3 days with my usage, and I carry the other charged one and simply change out. I don’t ever use the charger that connects to the phone-just a cube-style charger that plugs in to the wall; leave it overnight, and then take it with me.  I have concluded that the whole idea of obtaining maximum life and output is not as relevant as reliability and consistency- realistically nobody keeps devices that long any more. I probably throw away devices that have better batteries in them than what I was getting brand new 10 years ago.

  I love this site, I wish there was a more active discussion forum.  There are a lot of smart people who visit here.

On August 20, 2013 at 11:12am
Rupesh wrote:

I have a question - I see lot of experts here, I would be thankfull if someone can answer this question.

I am using a Mobile Device Sony Xperia Tipo inside the Bus and it has to be kept permanently charged as we are using its Bluetooth capability.

Will there be any safety problem related to this use, I would be using it 24x7 and the mobile would always be connected to the charger.

Please assist with your valuable feedback/comments/suggestion


On August 20, 2013 at 3:39pm
Vaib wrote:

I went through this article its true. being an electronics Engineer . it is well known that charging and discharging are Properties of a battery. but I had experienced I used my laptop hp mostly on AC . I still even after 50 months m getting 35 minutes battery back up . My ColleaguE s use their laptop on charging and disparaging process their batteries dies in just around 30months so s prefer to use it on ac but must be aware of heating phenomena . I tired it on my Samsung smart phone too it is giving back same when I buyed it 1 year ago. . . so nothing harm on using your li battery until it heats up . . thanks for this superb analysis . . .

On August 20, 2013 at 3:43pm
Martin Rosen wrote:

I have recently bought an iPad.  I would like someone to tell me how to keep it in optimum performance, in particular the battery.


On August 21, 2013 at 1:53am
Rahul wrote:

I still dont understand why any of the people above still hav’nt understood what the author means be a cycle. If DOD is 10% (100% to 90%) it constitute only 0.1 cycle and not 1 full cycle. So only by doing that 10 times will make a cycle. So total energy produced during the battery’s lifetime will be 100 times compared to 100% DOD. I hope atleast some of you are able to understand this now.

On August 22, 2013 at 7:19am
john h wrote:

From a pure engineering perspective, your point is taken.  However, many of the people here are seeking practical ways to extend the life of their batteries.  The extreme example is if you never discharge the battery, it should last forever.  Not only is this untrue, it also completely defeats the purpose of having a portable device in the first place. I believe the misunderstanding may lie in the definition of a cycle; even the author points out that there is disagreement among experts.  How many of us have had the experience of “taking care of “ a battery by keeping it constantly charged only to discover the capacity of the battery has diminished rapidly anyway? I think there are other factors that may override the basics of DOD and total number of cycles.  In one of these articles the author points out that the worst thing you can do to your battery is to use it while you are charging, yet that is what most of us are constantly doing with a cell phone; It gets low on charge, and you still need to use it, so you plug it in and continue your conversation. The author suggests that this induces many tiny cycles of charge/discharge, in turn creating lots of heat, which might account for the shortened battery life over time.

On August 22, 2013 at 1:35pm
John wrote:

My Samsung NC10 netbook when new ran on battery for 4 hours and 20 minutes. After three and a half years it still gave 3 hours and 30 minutes on battery. Hardly ever used on charger. The BatteryBar app showed 28% wear after around 1500 charge cycles. Is this battery exceptional?

On August 28, 2013 at 11:19am
Marc wrote:

This article sais: Environmental conditions, and not cycling alone, are a key ingredient to longevity, and the worst situation is keeping a fully charged battery at elevated temperatures. This is the case when running a laptop off the power grid. Under these conditions, a battery will typically last for about two years, whether cycled or not.

But what’s worse, running your laptop of the power grid (thus having a fully charged bettery) or stop charing when it’s at 80%, drain it to 30-40% and charge again?

I’m asking because in when you run it of the grid, the battery becomes warm whilst being full. When not running of the power grid, you’re causing another cycle, and it only has a limited amount of cycles. What’s the ‘least’ bad for my battery?

On October 3, 2013 at 1:17am
hasanat wrote:

informativesite. I like this.

On October 12, 2013 at 8:03pm
Sachin wrote:

I bought a tab with lithium polymer battery one part of the article stated charging it to lower voltage will extend battery life.. is it good to charge at 75% or 80% I can compromise with battery run time but cannot with its lifespan..
I have battery vehicle too and any suggestions are appreciated..

On November 23, 2013 at 5:57pm
highks wrote:

Very good to know that keeping LiIon batteries at full charge is actually not a good idea. I always thought, keep them all as full as possible to storage… but now I know I’d rather not do that anymore.

I also didn’t know that higher temperatures are that bad for LiIon batteries - and I always wondered why notebook batteries die relatively quickly coompared to other batteries, like in camcorders.

It really is a shame that no notebook manufacturer has a 50% charge option. It would still be good enough to use as a ups in case of a power outage, but the battery could last for 5 years or even more. But when you look at the prices for original spare batteries, I guess that is why they won’t do it. Rather make some dough on spare batteries every two years…

On November 24, 2013 at 3:32pm
Dr Jack wrote:

A modest genius.

On December 8, 2013 at 10:38pm
Abhishek Gupta wrote:

Nice Tips! Look, you must Dim your screen – Most laptops come with the ability to dim your laptop screen. Some even come with ways to modify CPU and cooling performance. Cut them down to the lowest level you can tolerate to squeeze out some extra battery juice.http://www.stensly.com/2013/12/how-to-extend-battery-life-of-your-laptop.html

On December 14, 2013 at 11:29pm
Niraj wrote:

I have a ASUS laptop and it’s advertised battery backup time is ~ 3-4 hours. However I have got more than 9 hours of battery backup. No I am not kidding. This was when I used my laptop somewhat sparingly and did this on purpose to find out the maximum battery backup.

My settings -

1. Display is always 0, the lowest brightness possible. The background is full black, screensaver is full black, browser background is full black. In general in every software if it is possible to have total pitch black background I go for it. Actually it looks very sleek and you may not recognize it is the same as your usual softwares. I do it primarily yo save my eyes [oh yes, i love my eyes more that the environment] but it also prolongs battery life.

2. when running on battery, my processor is underclocked to 60%.

3. my laptop is set to switch the display off after 1 minute. the laptop itself never sleeps or hibernates. i dont like to wait for my machine to switch on if i resume my work. the HDD is put to sleep after 20 minutes of inactivity.

4. my laptop is NEVER switched off. this one is about 6 months old and I have switched it off for more than an hour only 3-4 times. Moreover it is permanently connected to the AC power. so far my laptop has run on battery (for more than a couple of hours) only twice in the last six months.

the result is that my battery is almost as good as new. any battery shows strength decay only after about 100 discharge cycles. mine has been to only (maximum) five discharge cycles and I intend to keep it that way. no wonder I get such a long backup.

On December 17, 2013 at 10:04am
Bruno wrote:

I have a new Asus s400 ultrabook. It has a built-in battery so removal is not an option. I have read that partial discharges are the best for longevity of the battery. So my question is do I use the laptop on battery till it drops to about 70% battery life and then plug in and top it up. Do I use this method unless I need to be away from ac power.?I want to do the best for the battery. Thanks

On January 9, 2014 at 2:46am
James Johnson wrote:

Yes, partial discharge is better than full discharge, but also partial charge (meaning - not fully charging the battery) is better than full charge. Keeping the battery always at full charge and especially plugged on a charger for long time will shorten it’s life. http://j.gs/3HYu

On January 11, 2014 at 3:50pm
Jason Seibel wrote:

For my new laptop, I want to maximize its battery capacity so that when i have a big trip, i can make the most out of a full charge. Based on this article i am wondering which of these two methods would work best (unless i am wrong either way).

1. I keep battery between 40 and 70 percent charge all the time. My reasoning is that I want to keep the voltage per cell low by not charging it too high, and I want to make the depth of discharge as low as possible since i will be using it at home and will always have a charger available.

2. Keep battery between 20 and 50 percent. - same logic, but I think keeping the voltage even lower by not charging my laptop above 50 percent will also help improve battery life.


I am also wondering if even doing a cycle between 20 and 80 percent charge would be significant enough to increase battery life. I have an Acer V7 - 482PG-6629

On January 18, 2014 at 10:21am
David Smith wrote:

Great article and a lot of good info in the discussion.

While I know next to nothing compared to a lot here I just had to jump in wth my thoughts.
When you consider the cost versus the lifetime of these packs they are not that expensive, baby them and get say 12 months against using them without worrying about longevity, but not abusing them, and getting 9 months, say you pay $60 for the battery, thats $5 a month babying against $6.66 a month without worrying, is all the fuss worth $1.66 a month ?

I use 16650 3000mah batteries in high powered modded led flashlights, they are always fully charged when not in use, often have 3A or 4A load on them, never taken below 2.8 v although sometimes taken to 3v, the lights get hot, the battery compartment sometimes getting to 50c or so, is this abuse, you bet, will it shorten there lifespan, yes, but I am prepared to put up with it to follow this hobby, what I am getting at is sometimes you just have to do what you have to do, and if that means discharging the batteries until you laptop tells you they are flat, then just accept you have shortened the life of the battery a tiny little bit and move on.

I am in no way putting down anyone here, treat them nice and they last longer, of special interest to myself was not leaving a laptop pack out of the laptop for more than about a month, my wife has two packs and she just leaves one pack out fully charged until she needs it, not now she won’t smile

Cheers David

On January 24, 2014 at 10:46pm
riot wrote:

should i remove my hp625 battery while gaming or watching movies, the indicator says not charging when the battery reaches its full condition and i heard that if you remove battery it will cause damage to laptop while in serius actions that need some extra power and actually the battery can work as an back up power to save hardwares

On February 6, 2014 at 12:48pm
mehdi wrote:

Hi, I purchased a laptop computer with embedded battery (the battery can’t be removed) and I’m wondering if I need to calibrate the battery or not? The seller told me that it is needed and I have to discharge and charge it 3 times in order to be calibrated (I do it once till now).
Another issue: do you recommend keeping the battery charge in 40% or it’s not necessary?
My laptop computer will turn off by 7% of battery charge (my experience of first discharge). I use my laptop most of the time at home. Which strategy best maintain my battery health?
My laptop name: Sony VAIO Fit 15 SVF15A18CX
  Battery Type : Standard Lithium Ion Battery (VGP-BPS34 3650mAh)
  Battery Life : Up to 3 hours and 45 minutes10

On February 12, 2014 at 7:30am
Riot wrote:

Hi Mehdy
As the battery can not be removed never let it go below 80% or gradualy it will get old, you use it at home right? so why not plugged in while in home
Everyone knows that battery killers are charge and discharge plus heat smile live happy homie

On February 16, 2014 at 7:59am
Mehdi wrote:

Thank You for responding. As I understand the heat produced by keeping the battery in full charge condition is less harmful for battery health than charging and discharging of the li-ion battery each time?

On February 25, 2014 at 10:30am
Riot wrote:

My hp625 battery never gather heat because it is full charged and conected to the wall socket, do not place the machine on carpet, clothes or such stuff that cover fan holes.
off course discharging ages the battery

On March 8, 2014 at 1:05pm
Neil wrote:

great resource, thanks for all the info

have a quick question, if any gurus have an opinion it would be greatly appreciated

just got a Levono Z710 ideapad and it came with “Energy Manager” software that has a conservation mode.  from what the software says, it is intended to be used if you’re not going to be using the laptop for a week or longer, to keep the battery at a state of charge of 55% - 60% to avoid battery life reduction due to long periods of full charge state.

when i turn it on and use the laptop, the battery charges to: 60% available (plugged in, not charging)

so my question is, would this not be the best way to use my laptop while at home and AC is available (95% of the time), and turn conservation mode off and fully charge the laptop when I’m actually taking it somewhere AC is not available?

On March 10, 2014 at 1:04am
Riot wrote:

You doing office work or watching movies surfing net, better detach the battery but if you doing games or other heavy grahic duties attach the batt and turn of all conservative modes and let the machine flows..

On March 24, 2014 at 12:30am
Youngjae Cho wrote:

I wonder DOD 30% voltage.
About 4.2V full charged voltage battery, 3.9V is DOD30%, right?

On April 8, 2014 at 12:10am
Edward wrote:

Dear Youngjae Cho ,different Lithium battery from different company have different performance.. we need test the discharge curve to get the answer
more details please contact zzrm316@163.com

On May 9, 2014 at 3:06pm
Brian wrote:

It souds as if the best bet is to use an old battery that holds 50-70% charge for home use, when plugged into the mains. This will protect you from power outages etc, Then put in your nice new 100% chargeable battery when travelling and you need to be working umplugged.

On May 12, 2014 at 9:57am
brad wrote:

What is the source for Table 2? 

On May 15, 2014 at 11:11am
Migisha wrote:

gotta say,
best. lesson. ever!
Many happy returns to you from the 256

On June 1, 2014 at 10:53pm
yuri provase wrote:

Looking for table number 3, can I say that the best way to use your batteries is discharge them normally (80/85%) and then charge them back just a few hours before using them again?

On June 30, 2014 at 1:03am
Khayyam Akhtar wrote:

I have a smartphone with li-ion battery. It’s Sony Xperia SP and it has built-in battery. First it was great but then because of that useless battery doctor task killing app, one night I left my mobile with 22% charge left and tomorrow when I woke up, it was 0%.
Since then I feel like my mobile battery is not good. My habit is to charge mobile when it is below 15% and I never plug it out until its 100%. Last night at 4am I left it on stand by with 72% and today in the morning it was below 58%. There was only one message and the notification light was turned off in the settings.
What should I do?

On June 30, 2014 at 2:01am
Khayyam Akhtar wrote:

Another thing is that it drains power mostly in stand by. When I listen to walkman, watch videos or work on wifi, it works like before and only little charge is used mostly 2%-7% is used.

On June 30, 2014 at 2:43am
Edward wrote:

Dear Khayyam, how long do you keep this smartphone?? two years or three years? please email to me   zzrm316@163.com   Edward rechargeable boy

On June 30, 2014 at 4:55am
Oscar Ormond wrote:

Step 1: Check if the thing is properly plugged in and check if the power is actually on.

On July 1, 2014 at 2:46am
Mohamed Soheb wrote:

what should be the amount(percentage) of charging/discharging the battery to increase its life.

On July 2, 2014 at 2:15am
Edward wrote:

95% charging/discharge the battery can increase its life

On July 2, 2014 at 2:22am
Mohamed Soheb wrote:

thanks Edward,
and what should be the minimum amount to which we are suppose to drain battery to prolong its life

On July 2, 2014 at 2:46am
Edward wrote:

Dear Mohamed ,  no minimum amount requirement, for example, 10% discharge is not equal to one full discharge, and 10 times 10% discharge is equal to one full discharge.
please email to me   zzrm316@163.com   for detail information Edward

On July 5, 2014 at 4:18am
dialus wrote:

It is good post and informative post.Thank you.

On July 7, 2014 at 10:59am
Smurlin wrote:

Really great info in this article - much appreciated.

On July 16, 2014 at 11:56am
Shun wrote:

Fascinating, the underlying principle I found from reading this article is do not go to the extremes and stay balanced, reduce stress, prolong the life and avoid high temperature.  Applicable to many other aspects of life.

On August 7, 2014 at 9:00pm
Mark Paulo Yan wrote:

I’ve read the article mostly and searched the page for “usb”, for related info. I did not, however read all the comments, which are quite a lot.
Now my concern is that to my undertanding Li-ion batteries charge well in the 3.9 to 4.2 Voltz range, whilst usb ports have a 5V rating, which is way higher than the recomended 4.2V.
Does newer/current (2014) devices have voltages regulating circuits?
Or does current Li-ion batteries operate on 5V?
Or are we mangling our batteries using current common charging ways?

On August 20, 2014 at 1:57pm
Jack G wrote:

Looking for some clarity regarding the tests on Depth of Discharge (DoD). Is the voltage level 0.0V at 0% DoD? If so, perhaps a more realistic test would be discharging to a typical device’s cutoff voltage (say, 2.5V).

On August 20, 2014 at 7:22pm
Edward wrote:

mark paulo yan—the output voltage from USB is 5.0V ,and the lithium-ion max voltage is 4.2V, this because there is overcharge circuit in the lithium-ion battery to prevent from overing 4.2V. to charge the battery, the output voltage must higher than the battery max voltage. is that clear

On August 25, 2014 at 7:35am
Kenelm Ulric Dogcio wrote:

Okay, so im trying if someone can answer my question (by reading the comments from above. yes from 2010 comments) and still i was not able to get any answer.

My question is. What is the ideal charging percentage for my 2110mAh Li-Poly battery (From a smartphone, nondetachable) Is it discharing to 25% and charging to 90%? Or 10% to 80%/90%? Thank you in advanced for answering.

On August 25, 2014 at 6:28pm
Edward wrote:

Dear Kenelm Ulric Dogcio , I advise the better way is 10%—90%

On August 28, 2014 at 9:20pm
Kenelm Ulric Dogcio wrote:

Thank you for answering edward. Also, i’ve observed that everytime i charge i use DU Battery APP and when it charges for like 40mins or so, the voltage im seeing is above 4.20. And its advisable to have lower than 4.20 right? What should i about it? Or is the app accurate?

On September 13, 2014 at 12:46pm
Rich wrote:

I just bought an iPod classic after the discontinuation, and I already have a working one, so I just want to store this one until its needed.

How long is it ok to just leave it in the box? I read once that you’re not supposed to let a battery sit with no charge in it, and the date on the iPod box says 2009, meaning this thing almost definitely has no charge right? Should I start it on charge cycles or just leave it in the box?

On September 14, 2014 at 6:41pm
Edward wrote:

Dear Rich, If the Ipod battery is not used for a long period, it should be replenish charging one time for every six month.  zzrm316@163.com

On September 14, 2014 at 9:28pm
Feanor wrote:

I assume that the number of charge cycles in the table above are complete charge-discharge cycles?

So, for a 10% depth of discharge, the battery should last for 4700 FULL recharge cycles - not 4700 recharge cycles of just 10%?

On September 17, 2014 at 12:25am
Edward wrote:

Dear Feanor,  full charge and discharge cycles can not to 4700 cycles

On September 19, 2014 at 5:31am
Luca wrote:

Is it worse for a lithium polymer battery (phone or laptop) to be charged while the device is on?

I would think yes, but I am not sure.

On September 24, 2014 at 4:19am
Quantum PC Support wrote:

These type of posts are forever. Battery saving tricks are always welcome. We often ignore basic things and we have to repent for those. Follow the video http://vimeo.com/65740042

On October 2, 2014 at 11:12pm
Feanor wrote:

Hi Edward - I don’t understand your response. I’m not sure I was clear myself though.

My question is, whether the 4700 figure means a) 4700 charge cycles from 90% to 100%, or b) whether it means 1 charge cycle = 10 cycles from 90% to 100%, in which case the battery would last 47 000 charge cycles from 90% to 100%.

Both seem unlikely to me; a) would provide no increase in battery cycle life, which goes against what’s been said, while b) seems excessive but meets the definition given of one charge cycle being 0-100%.

On October 2, 2014 at 11:16pm
Feanor wrote:

Luca - no; you’re better to use the device while it’s being charged, as this reduces battery use and wear. With one caveat though - you shouldn’t leave the device on charge all the time; normal use for a portable device is to disconnect it for at least a few hours a day when you move it around, so I generally stick to that. Just use it normally, but avoid excess charging or excess use (unless your usage pattern requires excess use, then use it - it’s a tool, after all!).

On October 3, 2014 at 1:06am
Edward wrote:

Feanor, the 4700 figure means a) 4700 charge cycles from 90% to 100%, if you charge from 90% to 100% and then discharge from 100% to 90% you can use 4700 cycles.. yes the a no increase the total discharge time in theory, but in fact , you can hard to control the 0% to 100% charge and discharge, discharge to 0% maybe means over-discharge.  anyway, it is a battery ,do not too worry about the cycle life. just use it

On October 3, 2014 at 7:43am
Luca wrote:

Thanks Feanor & Edwad,

I am really glad to learn so much here!

On October 5, 2014 at 11:22am
Feanor wrote:

Thanks Edward. I don’t think that the article is clear on this point though. Cycle is at one point (if not here, then elsewhere) defined as 0-100%, and the article goes on about how reducing depth of discharge (DoD) will increase cycle count. But if we’re counting a cycle as charging from any DoD to 100% then it achieves nothing and all the discussion about DoD us pointless.

Most consumers don’t need to worry about over-discharge as the equipment (mobile phone, laptop, etc) will prevent that unless they store their batteries for weeks or months at 0%.

On October 18, 2014 at 10:52am
ali mufit cetingul wrote:

comple condition chamber test solar battery

On October 31, 2014 at 9:53am
Anup Chapain wrote:

Why should we users bother on these details?? Don’t you think its wisest move to implement the optimum cut-off circuit in the laptop itself by the manufacturers in order to maximize the battery life?

On November 22, 2014 at 1:04pm
pankaj wrote:

Simple question:
How much time battery(2080mAH) take for fully charged?
charger:5.0v=550mA (50/50Hz 0.2A)

On November 28, 2014 at 1:16pm
Morteza wrote:

Simple answer: 2 hr

On December 24, 2014 at 12:34am
akash wrote:

This piece of information helped me a lot.I used to charge my tablet at 7v/cell but now I know that I should charge It at only 4.20v/cell.Thanks a lot.

On December 28, 2014 at 10:17am
Vaughn Hartsell wrote:

I’m still confused as to when and how much to charge my battery in my MacBook Pro. Is there no simple answer? 
(1) Charge it 4 hours every day (2) only charge it when it dies and stops functioning.
(3) Keep the charger on all the time. (4) Never worry about it. (5) Use it plugged in until the battery dies! (6) See why I’m still confused.

On January 8, 2015 at 12:08pm
bilalorignal wrote:

i am using my laptop with li ion battery 6 cell for almost 3 years and its battery power is as good as new what i do is always plug in my laptop in trust worthy power source like UPS (urgent power supply) and keep using it on it and take out my battery hence i am saving my battery charge cycles that the secret

On January 20, 2015 at 4:27pm
JC wrote:

I have a 4400mAh Li-Ion laptop battery from Batteries Plus.  It is model: RAYCL2809B, it is made by Rayovac.

This battery works well but only as long as I do not allow it to fully discharge.  If it fully discharges, then the charger is not able to recharge the battery. I have tested the charger with my friend’s battery (he has the same laptop but with the original battery) and it works just fine.  The guys at BatteriesPlus also tested the charger and said it was fine.

Anyway, whenever the battery fully discharges, I have to take the battery back to BatteriesPlus and they hook it up to a machine for like 8 hours in order to revive it.

Anyone know why this happens to the battery?  It is quite annoying that I have to keep going back to the store to get this rayovac battery revived.

Anyone have a method to revive the battery at home?

On January 21, 2015 at 1:03pm
Raphael wrote:

i agree! where is the short simple answer? what i’ve understood is this and i’m not even sure its correct.

you buy a new laptop… after turning on discharge to 10%, recharge fully to 100%

form there on… discharge to no further then 40%, recharge no further than 80%

once a month… discharge to 10% and then recharge to 100%. repeat cycle!

Could anyone please confirm this? Great info and all but jeeeez! can there not be a more concise version for people that actually want to play with their new toy, like, today without the stress of damaging it?

On February 20, 2015 at 9:43am
Richard Coleman wrote:

Question: In table 2, the cycles and DoD relationship seem to imply that 50% discharge is ideal. Reasoning is that for e.g., 50% DoD, you must charge twice as many times as 100%, therefore to make the two operating schemes comparable, you must divide the apparent cycle life by two, i.e., you really got the equivalent number of 675 full cycles. If you adjust the data in this way, the graph seems to peak at about 50% (I fit a 2nd order polynomial to the adjusted cycles. I’m still reading this article ... so there may be something I missed.
Glad to discuss, please email me with contact information if possible. I have an MS in Operations Research and a BS in Naval Engineering, so I’m not just flailing here ... but I may be wrong.

On March 19, 2015 at 12:05am
ikenna wrote:

Is there any stand alone appliance that can be used to protect a battery from exceeding a 50%DoD for gel batteries?

On March 28, 2015 at 10:43am
Rob Chandler wrote:

I was about to post my reasoning that based on Table 2 it would appear that charging at 50% DoD is the sweet spot. Then I saw that Richard Coleman had reached a similar conclusion.

What I found interesting is that frequent recharging when DoD is at 10% appears to be almost as bad as waiting until the battery is fully discharged.


On March 29, 2015 at 11:13am
peter wrote:

There is sentence:
The shorter the discharge (low DoD), the longer the battery will last.”

In table 2 they said if 10%DoD then 3750 cycles. We know that one cycle in this case is 10x10DoD.

Maybe we should charge battery more often than 50%DoD.

On April 19, 2015 at 2:09am
Peter Baillie wrote:

I wondering if anyone could recommend where you could buy a Battery Management System (BMS) for a 36v electric bike battery which can be plugged into the battery for diagnostics; to read recharge cycles, kms distances etc. Your article and discussions on DoD is interesting, to work out the number of DoD vs kms travelled and to try and work out the lifecycle capacity left on a battery and the kms remaining to be run. Thanks Peter Baillie

On April 19, 2015 at 6:27am
John Fetter wrote:

Peter - There are so many variables in batteries and battery usage, it is impossible to achieve with any reasonable degree of accuracy, what you say you want to do. Having said that, there are such systems on the market, because demand, not technology, drives these kinds of things.
Battery purchasers look for the lowest possible price. Hence battery manufacturers are obliged to manufacture to the lowest acceptable standards. Batteries are a grudge buy. There is nothing that can be made that cannot be made by another more cheaply. This has been the driving force over the last 40 years in an industry that is 130 years old. The only place you can find quality is on the sales brochures. Hence some batteries will last eight years, some will last four years, some will last two years.

On April 20, 2015 at 1:09am
Peter Baillie wrote:

John, thanks for the feedback, appreciated. Would you have any recommendation on where to buy one? Or even a shop that deals in this kind of thing? Peter

On April 30, 2015 at 2:39pm
peter wrote:

i think edward is wrong: 10-90% charging/discharging is not the best way to prolong battery life.

Also i think feanor is wrong: using device while charging is not good for battery life coz battery is making a lot of micro cycles and wearing battery.

On April 30, 2015 at 5:56pm
Alice wrote:

peter,  Why? Without any explanation your comments are worthless.

On May 1, 2015 at 5:34am
peter wrote:

It is obvious like 1+1, i dont wannt to be smartass but please, read this article(s), see the tables…
- best is charging @ 50%DoD
- best is charging while device is turned Off
  “A device should be turned off while charging. This allows the battery to reach the threshold voltage unhindered and reach a low saturation current when full. A parasitic load confuses the charger.”


On May 1, 2015 at 7:37am
Alice wrote:

peter, The reason why most people pay good money is to use what you disparagingly call the parasitic load, as and when they want. “Look ma, my battery lasted ten years. I achieved this by hardly ever using the computer.” It is as easy as 1+1 for a charger to “read” the battery, look after the battery, and at the same time deliver power separately to the rest of the system.

On May 1, 2015 at 11:14am
peter wrote:

information and advice about turning of device while charging is from this site. And we are discussing it very precisely what are the facts from theory and how is it in practise.

also, please give us info and any valid link about delivering power separately to the rest of the system while charging li-ion battery.


On May 1, 2015 at 4:29pm
Alice wrote:

peter, You accused two people of being wrong. It is easy to drag information from a source. Anyone can do it. Means nothing. Opinions vary. Can you explain why these two people are wrong?

On May 2, 2015 at 12:28am
peter wrote:

Everything is in my post, there is no need to repeat it again.

But you didnt explain “delivering power separately”.. Explain? Link? Pdf?
Please be constructive as others are.

On May 2, 2015 at 5:34am
Shelagh Delves-Broughton wrote:

I apologize if this has been asked or answered but if one using a laptop, as a desktop should take out the battery, store it safely but use it once every 2 weeks or so, what do you do if the laptop wont allow you to take out the battery and you use it as a desktop?


On May 2, 2015 at 5:53am
Alice wrote:

peter, You said they were wrong, gave an opinion, did not explain, were not constructive. Lithium ion, like all batteries should be charged at constant current, up to a suitable preset voltage. Impossible with computer directly in parallel with battery, computer drawing variable current. Simple solution, in common use by circuit designers who understand batteries. Feed computer directly and feed battery via simple current sensor. The current sensor output is compared to a reference value. The difference between the two is used to correct any error in the current and can maintain an exact charging current value. The end-of-charge voltage can be preset to optimized values that will terminate charging a desired state-of-charge.

On May 3, 2015 at 11:25am
peter wrote:

ok, now you are talking. thanx for informations, means a lot to community.

Need to ask: does it apply to smartphones as for laptops you said?

On May 3, 2015 at 6:52pm
Edward wrote:

I think Alice is right ,She must be the professional battery expert or electronic expert!!

On May 14, 2015 at 8:32am
Ty wrote:

I’ve read this article and others and have scanned all comments here and read many.  But I still haven’t found a recommendation or what seems to be a simple and obvious question.  maybe it’s above and I missed it.

Here’s the question.

My laptop is always connected to the power grid except when I travel.  However I do move it between my office and my deck and don’t want the hassle of shutting down between those moves so my battery remains in my laptop at all times.

I saw the recommendation in the article to let it discharge only to 50% before recharging.  At least I think that’s what I read. 

My questions is, how often should I let it discharge at all?  Once a day?  Once a week? Once a month?

Thanks in advance for any knowledgeable answers.

On May 17, 2015 at 4:01am
Amith wrote:

After reading through this article, I went and did some measurements on some of the phones I own. I basically did a full charge, waited for about 5 minutes, pulled out the battery and measured with my multimeter.

On a Samsung Galaxy Note 3, it seems to go upto about 4.3 V. On a Lenovo A606, It goes to about 4.21 while on my old Nokia 1110, it seems to stop at 3.8 V.

I also did a comparison of actual voltage measurements against the readings I get from battery apps. They’re pretty close ( ~ +- 0.01V) and also require a certain ‘settling’ time.before the readings stabilize.

I guess it’s a trend here that modern phones tax the battery a lot. So, it’s no surprise that they lose quite a lot of the capacity within the first year of usage. Maybe the best approach is to only charge our phones to about 75% or so and stop.

On May 25, 2015 at 2:03pm
voyance internet wrote:

Your article is very well written, which are much less appreciated is that I once again thank you.

On June 1, 2015 at 2:37am
MARTIN wrote:

So they are arguing that if you charge your battery at a higher level of discharge, the phone will have a higher cycle life.

WELL DUH. if you divide the 10% DOD by 10 you actually only get 470 total cycles out of each 100% that it drained. Which it actually below the maximum suggested charge cycles for charging at 100%DOD.

Now if you look at the 50% DOD cycles and calculate the cycle it gets per 100% then you will get 750 max. So is it suggesting we charge our phones at 50% ? LOL wtf is this non sense

it may reduce the possbiility to temperture wear to the battery however, charging for shorter period of times

On June 1, 2015 at 3:05am
Alice wrote:

MARTIN, Can you explain how one might charge at a higher level of discharge? You probably don’t want to acknowledge that people with less knowledge compensate by making more rude noise.

On June 1, 2015 at 5:42am
TTMartin (not MARTIN) wrote:


Referring to Table 2
Assuming a 10% DoD gives you 1 unit of use and you can recharge it 4700 times you’ve gotten 4700 units of use out of the battery.
Now if you have a 25% DoD you get 2.5 units of use per recharge. You can recharge it 2500 times you’ve now gotten 6250 units of use from the battery.
If you have a 50% DoD you now get 5 units of use per recharge. You can recharge it 1500 times you’ve now gotten 7500 units of use from the battery.
If you have a 100% DoD you’ve now gotten 10 units of use per recharge. You can recharge it 500 times you’ve now gotten 5000 units of use from the battery.

In addition keeping the battery topped off is contradictory to the information contained in Table 3.

Good data in the article, but, poor interpretation of the data by the author.

I’ve found I obtain the best life and length of use between charges by allowing the battery to discharge till the device tells me it needs to be recharged, and then recharging it at that time.

On June 1, 2015 at 11:40pm
Alice wrote:

MARTIN ? ... The electrochemistry that relates cycling to DoD in batteries is not linear. The only way to obtain that information is by hands-on testing.

On June 7, 2015 at 1:52am
peter wrote:

@TT Martin:
We need to clea what is 1 discharge cycle?

1 dis.cycle = 4 x 25%DoD = 2 x 50%DoD…etc..)

On June 8, 2015 at 3:19am
Amith wrote:

          I think you’re confusing charge levels with depth-of-discharge. 50%DoD just means the capacity level to which you would discharge your battery below the ‘original’ capacity.

          For e.g. Say a battery has a capacity of 10,000 mAh. Discharging it to 5,000 mAh(50% charge) is 50% DoD, so is discharging from 7,500 mAh (75% charge) to 2,500 mAh (25% charge).

          The author isn’t being contradictory, don’t fully charge it (maybe charge to 75% Charge) and don’t discharge it completely before recharging (75% to 25% charge, i.e. 50% DoD).

On June 15, 2015 at 7:22am
Andy wrote:

From all the information I’ve gathered over time, this is what I really recommend:

Remove your Li-Ion battery if you don’t need portability or are not doing anything important on your device (if you don’t need backup power in case of a power outage).
This prevents ambient temperature and heat from the device from degrading your battery much much faster than as it would be on the shelf. Just run the device directly from the charger if it allows.

If you want to take it a step further or for longer-term storage, you can tape the terminal of the battery with electrical tape (to prevent accidental conduction and short circuits) and store it in a sealed ziplock bag inside your fridge (to prevent moisture). NOT YOUR FREEZER. The idea is to keep it just above freezing temperature but not to freeze your battery. 5 degrees Celsius is a good temperature.

As for charging and typical usage or If you have a hard-to-remove internal battery, try to keep your battery level from 30% to 80%, hence charging only 50% of the battery at a time. In other words, not too low and not too high battery capacity and not too short and not too long charging cycles. By doing this, you also follow the 50%DoD in this article that appears to statistically give the most hours of use for a Lit-Ion battery.

On a side note, when you buy a new battery, the first 3-4 charge cycles are very likely going to give you a lower total capacity than what the battery is capable of, but this should be amended after about 10 cycles. I don’t recommend fully discharging and charging your batteries for these first few times to “prime” your battery, just use it normally unless your battery percentage meter is inaccurate and needs to be calibrated then do a full cycle.

On June 15, 2015 at 7:48am
Andy wrote:

Adding to what I missed above:

When you are planning to store your batteries, charge the battery between 45% and 65% to compensate for gradual discharging and depending on how long you plan to store your batteries for.

Make sure you take them out once in a while (every month, few months or so) to check they still have charge in them and charge them back up to storage capacity if they are too low.

It goes without saying that you don’t store a battery with 15% or less battery or you could risk it going into “sleep mode” or being too weak/damaged to charge.

On June 15, 2015 at 9:31am
Alice wrote:

Andy, Brilliant idea! Or is it? Have you not worked out that your suggestion is more or less the same as buying an expensive automobile, locking it up in the garage and using buses and trains for transport instead? Much, much later, there is a emergency and you need the car in a hurry. And guess what? You have a flat battery, flat tires and find the rats made their nests out of the bits and pieces that used to make the car go.

On June 19, 2015 at 2:09am
Andy wrote:

Alice, this is only recommended as a measure if you don’t need portability or are not doing anything important on your device that needs a backup power supply. And like any car owner, they should take the inactive car out once a month to ensure the battery doesn’t completely go dead.

With OEM laptop battery replacement packs at times costing an arm and a leg and manufacturer customer service being so poor in general, it’s only an ideal suggestion and does not represent what the typical user must do. We all make sacrifices to the detriment of the battery and that’s okay because it is meant to be used.

But I have to admit at the very least, removing your battery while plugged in is a smart thing to do. In my experience with laptops, especially high performance aluminum or full-bodied metallic laptops heat up considerably, and the heat conducts to the battery along with heat from charging combine to easily equal 50-60c. An excellent example would be the first few generations of HP Envy laptops notoriously known for heat and cooking the battery.

Under heavy use while plugged in with the battery fully charged, these batteries typically did not last more than a little over a year without holding any useful amount of charge and most definitely needed replacing soon after.

On June 19, 2015 at 2:42am
Alice wrote:

Andy, If removing the battery is the smart thing to do, then perhaps a woman could provide an optimum solution. A plug-in extension cord arrangement that would have the battery out of the oppressively hot laptop and at the same time fulfilling it primary function.

(By the way, taking a car that is very infrequently used, for a run once a month is a battery killer.)

To sum up, lithium is a SERIOUSLY problematic technology.

On June 19, 2015 at 3:28am
Andy wrote:

You are definitely right in this regard that it is problematic but it is not limited to lithium. Batteries are an inherently weak technology that struggles to keep up to the demands of the power consumption in wake of constantly evolving technology.

Lithium technology is already considered a mature battery technology and almost at capacity of what it can be capable of and further advancements are slow and progress is minimal until we can switch to another type of battery.

For your typical lead-acid car battery, taking an inactive car out once in a while is actually beneficial for its health since when a lead acid battery is partially discharged, lead sulfate forms. This sulfation causes a permanent loss of capacity of the battery. So the batteries should only be stored in a fully charged condition and the charge should be topped up from time to time by taking the car out to charge it with the alternator to compensate for the self discharge of the cells.

On June 19, 2015 at 4:39am
John Fetter wrote:

Andy - I am not going to join this discussion about lithium ion but I think I might be able to throw some light on the lead-acid situation. A lead-acid battery that isn’t receiving any charge for a month, and is probably being drained slowly by the electronics in the car, will likely have been reduced to between 60 and 80% state of charge. Starting an engine that has been standing takes more out of the battery. The alternator voltage regulator will limit the charging voltage to a maximum of 14.4 volts. It is impossible to bring a 12V lead-acid battery that has been subjected to this form of treatment to a full state of charge with a normal average trip. The battery begins the next month of inactivity in a partial state of charge. Each successive month will deprive the battery of charge. After a few months of this kind of treatment the battery will give up the ghost.
There are trickle chargers on the market that begin charging the battery until the voltage has risen to well beyond 14.4 and then drop the voltage to about 13.5 and hold it there. Batteries thus maintained last eight years or more.

On June 21, 2015 at 11:53am
Sally G wrote:

Interesting… I have an e-bike with a lithium battery. After commuter cycling on it for 27 months (year round), it’s still as good as when I got it (actually, better since getting a new console which seems to be more efficient at extracting energy from the battery). I only discharge it 50-75% per trip before recharging (50% in summer, 75% in winter - cold weather does seem to consume more energy out of the battery). So from above, this battery should last a goof 5-7 years - far more than the 1 year the manufacture’s warranty!
However, I do hear of people who don’t use their ebikes having problematic batteries from the get go - which would make sense as the charge does dissipate with time if I don’t ride it (usually within a month) so I presume that that would be equal to a full discharge. Must be said not having trickle charge on the charger also doesn’t help - if I put the plug in on Friday and don’t pull it out to Monday, I’ve lost 20% of my charge!

On June 28, 2015 at 6:51am
Tom Wiersma wrote:

We are very disappointed in the lithium ion life we experienced on two different bike batteries.  While initial life produced a range up to 20 miles on our 24 volt emoto bikes, that range degraded to 1 mile after 2 years on the first bike, and the second bike is now at 8 mile maximum after 22 months and degrading rapidly.  The bikes are stored indoors with periodic charging in winter and are recharged after each use in summer.  The factory that made the batteries is out of business, and a rebuild costs $300 a piece.  We have $1200 total in the two bikes new.  The first sat around Menards till I purchased it for $400.  It short life lead us to believe shelf life was a factor.  On the second bike we had to wait for the factory to produce the batter!  Same results.  Could have been worse.  It could have been a $35,000 lithium ion car!

On July 19, 2015 at 4:39am
Timar wrote:

The dispute whether to keep the battery permanently attached to the notebook, thereby providing flexibility and protection against power outages, or to store it half charged, thereby greatly improving the battery’s lifespan, can easily be resolved if one has a fresh and a worn down battery. I simply leave the old battery, which is below 10% capacity but still holds more than sufficient power for finishing some tasks and providing hibernation power, permanantly connected to the notebook and keep the new battery tucked away after charging it to 60%. If I plan to use my notebook on battery, it suffices to connect the battery to the computer for one hour in order to charge it to 95%, but even if I don’t have the time to top it up, it still provides at least 50% capacity and a decent runtime.

On August 13, 2015 at 9:10am
Rudy Rash wrote:

Do the comments and suggestions of this article also apply to AGM (acid glass mat) and SLA (sealed lead acid) batteries used in UPS’s (uninterruptible power supplies) or those used in power wheel chairs?

On August 27, 2015 at 5:39pm
guest wrote:

i charge my battery when it is 1% 2 % and charge up to 5%  6% and use it because i need. i do it maybe 5 times every day for months. it is no problem for me now.

On September 14, 2015 at 11:32am
corky wrote:

I just wanted to know the shelf life, like can I buy two batteries, use one, save the other? or will the unused one get old? I spent wanna read a physics paper

On September 15, 2015 at 11:55pm
Bayu Murti wrote:

Actually I’m little bit confused with that DoD theory.
Given that 100% lasts a day, if we apply 100% DoD, then we’ll get 300-500 charging cycles, means 300-500 days. If we apply 10% DoD, we’ll det 3750-4700 charging cycles, but we also need to charge our phone 10 times a day, means we’ll get only 375-470 days. Where is the differences?

On October 8, 2015 at 2:15am
Michal wrote:

@Bayu Murti: Well the thing is that one charging cycle is defined for whole capacity of battery, that means if you discharge your battery to 50 %DoD and then fully charge it two times - it is count as one charge cycle. Theoretically discharging to 10% of DoD in your case can be done 10 times and that is count as one charge cycle.

On October 8, 2015 at 2:38am
peter wrote:

The practical sweet spot seems to be 4.1v and dont top up if you don’t have to. After 500-1000 full charges, you will be sick of the battery, given improved cells over time.

Given that, perhaps out batteries ought be say 26v or 38v etc., and our chargers set to charge .1v lower.to give a net 24 or 36v.

The article concurs with what I hear from cruising yachties. Keep them between 20 and 80% charge, and they last forever.

I also hear flattening the battery isnt so bad. Its storing them flat that’s the problem. Put a flat battery on charge immediately you get home and its tolerable practice.

On October 14, 2015 at 10:33pm
kpr wrote:

Hi, I would like to know whether a Li-ion battery in a laptop if leaked due to exposure to heat, will it discharge acid / will the discharge from the battery be acidic and corrosive such that it damages the motherboard or chips.


On October 16, 2015 at 10:04am
Lilith wrote:


I sell batteries in Holland to customers and the most asked question is why the battery needs to be 40% charged for storage. Every resaler tell this to their customers, but this bulletin gaves me the best oppertunity.
Storage is best at 3.92 volt 58% SoC. I appreciated it that this bulletin gave me the best answer. Also for my electric bike is this the best SoC to maintain capacity at a prolonged period.

Thanks BU and Cadex for this usefull information. I like that.
[my English is not so good, sorry]

On October 20, 2015 at 9:57am
MIKE wrote:

PLS my hp laptop battery even when fully charge will not power on my laptop or any other laptop unless made active by just charging it for few seconds(sometimes 3sec), and its last for 3hours when fully charged. what can i do to stop this?

On November 11, 2015 at 1:06pm
Marcin wrote:

I use my laptop mostly at home. Does it mean it’s optimal to keep the charger plugged in all the time (since the more shallow the discharge, the better - so by extrapolation, the most shallow discharge - no discharge, would be the best)

On November 12, 2015 at 8:14am
naima wrote:

I am having a problem with the battery life of my Samsung galaxy pro tablet.
It`s not charging while I am using you tube although the sign of charging is showing it is charging but the percentage of charge keeps decreasing.
but if I stop using the tablets it gets charged.
please can you help me solve this problem because if I am watching a film I can`t just stop it and carry on watching it few hours later.
kindest regards.

On November 17, 2015 at 4:51am
plymjack wrote:

All (nearly) very useful (especially Alice).
I have a lot of experience with large lead-acid batteries (from Submarines)  but most does not translate here to Li-on.  I am just getting a BMW i3 (without backup generator) and am keen to maximise life and range.
The car comes with monitoring but no voltage information so I will look for a way to see this.  Range is around 120Km, but expect to be used for around 320-40km a day.  Will follow the guidance above and on charge when down to 50% (where possible).
If anyone has an i3 info or advice I would like to hear it.  thanks.

On November 27, 2015 at 7:31pm
Jordan wrote:

Great write up BUT I still don’t know if a new phone battery needs to be fully charged from the beginning or not.  If its not fully charged then will the memory and life of the battery be affected (diminished)?  These are points I would have appreciated knowing about at the beginning of the article rather than slogging through rheams of data (which I appreciate) but honestly do not have time to read through smile

On December 14, 2015 at 2:11pm
shoaib wrote:

There is obviously a lot to know about this. I think you made some good points in Features also. Keep working, great job!recipe

On December 15, 2015 at 12:20pm
Clive Skeggs wrote:

Many articles are written about charging Li-on batteries, but I am surprised nobody seems to have come up with a method of safeguarding against over discharge. When I used to condition Ni-cad batteries, I built a recycler which used relays to automatically cut off the charging and discharging cycles. This was so simple, after finding suitable relays that would release the holding coil when the voltage dropped below the desired level. This should be even easier with Li-on batteries, seeing that their voltage is much easier to match with a 6 or 12 volt relay.
Does anyone have any smarter methods of easily controlling the usable voltage level? It needs to be dead simple so that each separate battery could be protected, i.e. Using 4 ex laptop Li-on cells in a 12v drill battery case.

On December 29, 2015 at 7:27am
Ishara wrote:

I have a galaxy note 4 mobile…
I didn’t understand about the correct battery percentage to plug my mobile in to the charger and correct percentage to discharge it from charger.
can you please tell me the best healthy percentages.

On December 29, 2015 at 9:15am
Clive Skeggs wrote:

Amy standard commercial battery operated device would have these safety features built in and can be seen as miniature circuit boards when disassembling a battery pack. What I am referring to in my previous note was the use of just the actual cells from for example s laptop or similar type of battery pack. These Li-ion cells would not normally be protected from either overcharge or over discharge when used for other purposes than originally designed for.
I have purchased a Nitecore D4 battery charger (recommended) which will ensure the proper charging cycle but am still missing a suitable discharge protection.

On January 22, 2016 at 8:49pm
sarath samarajeewa wrote:

Very useful article

On January 23, 2016 at 9:34am
Herschel Specter wrote:

How much of the 7kw-hr Powerwall can one discharge before significantly limiting the battery’s number of cycles?

Thank you

On January 24, 2016 at 8:58am
Clive Skeggs wrote:

I would recommend reading the following article, lots of interesting facts which will probably answer your question about the 7KW Powerwall batteries.


On February 5, 2016 at 5:42am
karthik wrote:

Hey guys. Is it okay to leave the laptop plugged in. I pretty much use it as a desktop. Means its almost always connected to the AC power and runs 15 hrs daily. I have limited the charge level to 50% and leave it plugged it. And once in a while when there’s a power cut i let the battery discharge to 7% ( which is the default setting it came with before it would ask to to connect to a power source) And Once in a few months i discharge it down to 7% and then charge it up all the way to 100%. and then remove the battery and leave it out for 6-12 hrs before i put it back on my laptop and then discharge it down to 50% and leave it plugged in. as mentioned earlier.

So is it okay to do the above routine? Is it really okay to leave it plugged in at 50% almost all the time.?

On February 6, 2016 at 1:29am
Arnfinn wrote:

Hi. Thank you for this informative page. I dont understand the table 4; many car manufactors like Tesla and Kia let the car charge the battery cells to about 4,3V. Wouldent this destroy the EV battery within about 2 years?

Best regards Arnfinn

On March 23, 2016 at 8:50am
Michael Kusch wrote:

Very informative page.
I remember many years ago when electric cars were in dipers (late 90’s?), reading an article that to maximize life, they would only have the battery charged up to 60% and discharged down to 40%, but I don’t remember which chemistry they were using at that time. Rest assured that electri car maker are making everyting to prolong battery life without the user having to watch for battery voltages. The most they will let you do is select between “optimize for runtime” and “optimize for battery life”.

I bought my Dell Laptop with the extended battery on Dic 2010. The original capacity was about 9.8Ah. The battery has been used and abused. I’ve had it stay at maximum charge for ages, I’ve it cycle from 7% to 100% constantly, I even have had it shutting down due to overheating several times. After 6 years it still holds more tha than 6.8 Ah. Runtime has gone down from about 3.5 hours to about 2.2 hours. I’ve never seen another notebook battery last as long as this one. My wife’s notebook is not quite as old and is already on its third battery.

I’ve a questionabout that doubling of lifetime for each 0.1/V lower top voltage. Say you have a battery with an original 1000mAh capacity. If I lower the charging voltage to 4.1 its starting capacity should be around 840mAh. Now for the lifetime calculation, what is the end of life capacity used? Is it 70% of 1000mAh or 70% of 840mAh? In my opinion, “doubling” the lifetime should mean doubling the time it takes for the battery to drop down to 700mAh of usable capacity.
However I’ve seen (on other cources) that they use 70% of the “new” starting capacity, as for 3.9V the starting capacity is already far below 70% but they claim a 8x cycle life.
To me this is nonsense, because at 4.1V, 19% “new” capacity loss is already below 700mAh (81% of 86% is below 70%).
It also means that supposing a linear loss of capacity (for clarity), it is only by the time a 4.2V charged battery reaches 750mAh capacity that it would have less capacity than a 4.1V charged battery which would have fallen to 752mAh. This also means that for the first 83% of the charging cycles, a 4.2V charging voltage would have provided more capacity than a 4.1V charging voltage.

@Tom Wiersma:
Electric bike batteries are normally made up of LiFePO4 lithium ion cells. The advantage is that you can put them in series to directly replace lead-acid batteries, and charge them with standard lead-acid battery chargers. The rapid loss of capacity in these battery packs is however due to a completely unrelated factor: cell unbalance. Unless you use a balancing charger, little differences in internal resistance between cells will keep growing the unbalancing problem. The charger stops charging when the most charged cell is at maximum voltaje, and protection circuitry within the battery pack or the bike will stop discharging when the lower cell is at its cutoff voltage.
Balance charge your battery pack and it will probably go back up to nearly 20 miles again. Life cycle in LiFePO4 are much higher than other lithium chemistries, about 1000-2000 cycles.

On March 28, 2016 at 5:25am
palemoon wrote:

I have a Toshiba Satellite L50-A-161 with a Li-ion battery. The removal of my Toshiba battery is quite complicated: it is necessary to open the case unscrewing 14 screws and remove the dvd unit. The battery itself is fixed to the motherboard with 4 screws and a pin connector.
This kind of notebook was plainly designed to prevent the user from removing the battery.
Knowing this, my main concern is that I need to use my notebook for a prolonged period of time, many hours a day, often from morning to night, and I rarely need the battery as a source of power, working in places where the AC power is always available. To some extent I mainly use the battery as an AC filter.
With this in mind, I am wondering what practice suits me best: keep the laptop connected to the AC grid and calibrate the battery once a month with occasional partial discharges/charges would be safe?
You wrote that “Most users do not remove the AC power, and this practice is safe”, but of course this goes against the “Partial charge better than a full charge” guidance rule: keeping the laptop connected to the AC grid would keep the battery always at 100% charge.

On March 29, 2016 at 7:47am
Neville Walters wrote:

the charger for my lithium battery (for my golf cart) has a red light when charging and green when fully charged.  it was supplied with the battery.
it is now showing the green light, but not charging.

the battery is usually never run down completely, nor charged fully.  it has had about 170 of these cycles, i.e. about twice per week.

the make is ULTRA MAX, bought from AMAZON.

I don’t know much about batteries and would be grateful for your expert advice

On April 13, 2016 at 4:54am
sakthivel wrote:

For a LI-ion battery , what is the operating voltage range.(100% means = what is the voltage range and for 0% = what is the voltage )

On April 21, 2016 at 1:47pm
Kibber wrote:

@sakthivel: There’s a multitude of different li-ion battery chemistries, each with different maximum and minimum voltages, ranging from 2.5-1.5v for LTO (Lithium Titanate) all the way to Li-CoO2-NMC with 4.35-3.0v. Electric vehicles often use a combination of two or more different chemistries, to achieve both high-current and high-capacity benefits. Modern cellphones typically have 4.35v as their 100% voltage and go down to about 3.4v as 0% (which is probably more of a phone’s electronics limitation than a battery limitation per se). Numbers cited in this article are probably for the original implementations of Lithium Cobalt Oxide (LiCoO2), which goes from 4.2v to 3.0v. Whether the same suggestions for prolonging battery life apply to other chemistries is a question I don’t know the answer to, but if I had to guess, I’d say they probably do.

On April 25, 2016 at 12:17am
Axel wrote:

i`v got newly launched Galaxy S7 with Li-Ion battery. It`s habit for me to charge to 100%
even when i had another phones with Li-Poly i`v did same… but this one is expensive piece of glass so i`m wondering about that… Apple done some trick to preserve cycling, i believe samsung would`v done same but…
how safe is to charge my battery from 25-30% to 100%, will this decrease lifespan a lot? and what is recommended range of charging for S7`s kind of battery?

Thanks in advanced

On May 1, 2016 at 10:57am
ted wrote:

Question on using Li-ion battery for industry use as back-up battery.

If the battery is just charge up and sit there without discharging it, it is used for backup in-case of power outage.

How long will the battery life last? Longer or shorter life than applying the discharge method?

So, base on this article, if we keep the voltage at about 3.92, it should prolong the battery life. Correct?


On May 6, 2016 at 6:24am
Wowlaulau wrote:

Anyone here noticed that this comment thread has been active since 2010? That is crazy. But even crazier is the subject of the article that has racked up idk how many actual comments but for sure approximately 6 years worth And they’re all about BATTERIES! I WTF! DERP/DURP from back in 2010, if you’re out there,feel ya.

On May 13, 2016 at 8:04am
Curious wrote:

1) Can someone give more info about Bayu’s question and Michal’s response?
2) Ideally, to what DoD should I let my cell phone drain to before I charge it again to 100%? 
3) Is keeping my cell phone plugged in after it’s been charged to 100% a good practice, both from the standpoint of extending battery lifetime and safety? (I’m extrapolating to cell phone batteries the paragraph stating that unplugging laptop batteries from AC grid is unnecessary and keeping it plugged in is safe). 

On September 15, 2015 at 11:55pm
Bayu Murti wrote:
Actually I’m little bit confused with that DoD theory.
Given that 100% lasts a day, if we apply 100% DoD, then we’ll get 300-500 charging cycles, means 300-500 days. If we apply 10% DoD, we’ll det 3750-4700 charging cycles, but we also need to charge our phone 10 times a day, means we’ll get only 375-470 days. Where is the differences?

On October 8, 2015 at 2:15am
Michal wrote:
@Bayu Murti: Well the thing is that one charging cycle is defined for whole capacity of battery, that means if you discharge your battery to 50 %DoD and then fully charge it two times - it is count as one charge cycle. Theoretically discharging to 10% of DoD in your case can be done 10 times and that is count as one charge cycle.

On May 19, 2016 at 8:10am
Mohammad Hoque wrote:

It is clear from the figure that relation between charging cycle and capacity is linear for a specific charging/discharging rate. Now I am confused here how the measurements are done. Say battery capacity is 1500mAh and after few charging cycles with charging/discharging at 1C, they capacity is 1400mAh. 1C is equivalent to 1500 mA. Now since the capacity is reduced 1C is not equivalent 1500 mA anymore. Do the above measurements should be interpreted accordingly? Any reference is appreciated.

On June 2, 2016 at 2:15pm
Patrick wrote:

This article seems to be from 2010.  Motorola now uses “IMPRES” chargers on their portable radios with Li-Ion batteries to condition the batteries every so often by fully cycling them (full discharge followed by full charge).  I’m guessing Li-Ion battery research has changed the way we treat Li-Ion batteries in the last 6 years?

On June 9, 2016 at 4:13am
Mara wrote:

I’m traveling to a country with frequent power outages and changes in power supply. I am worried that the variation and peaks in power will damage the battery of my laptop. How can I avoid this? I already use a surge protector but I think this only works in case of extreme peaks, right?


On June 9, 2016 at 1:09pm
Michael wrote:

First of all, IMPRES batteries come in different flavours: NiCd, NiMH, Li-Ion.

Contrary to NiCd and NiMH, there is no such “conditioning” needed for the Li-Ion batteries nor does it present any advantage to the battery capacity.

For Li-Ion, all that it really does is recalibrate the battery “fuel gauge”, which is an IC embedded in the battery pack that tracks battery capactiy. Usually this is accomplished with a “coulomb counter” which tracks the amount of current that has been charged/discharged from the battery.
The “propietary algorithms” refer to the use of voltage and temperature measurements (and impedance tracking algorithms) in addition to the coulomb counter to more accurately predict battery total and current capacity.
This is also the real reason cell phone and battery manufacturers still tell you to let the battery charge completely before the first use. It’s not for conditioning like the old NiCd and NiMH batteries, but to let the battery fuel gauge be properly calibrated.

On June 10, 2016 at 1:47pm
DickLawrence wrote:

=>Mara If you have a typical charger it will work at any voltage from 90V (Japan) to 240V (much of Europe) so it will ride through voltage sags and spikes OK. A surge protector will make it more resilient to voltage spikes.

On June 13, 2016 at 12:36pm
Patrick wrote:

So all the IMPRES charger is doing with the Li-Ion batteries is recalibrating the fuel gauge?  It sure does take a long time when it conditions.

On June 13, 2016 at 3:16pm
Michael wrote:

The battery has to be fully drained and then fully charged. The time it will take depends on:
1) Current charge % of battery.
2) Maximum discharge current of both the charger and the battery
3) Maximum charge current of both the carger and the battery
4) Battery capacity.
Plus, for calibration purposes, it might discharge/charge at a lower rate, or at a higher rate to test for temperature dependency, and it might do the full discharge/charge cycle more than once.

On June 14, 2016 at 5:55am
Kad wrote:

I don’t get one thing (don’t laugh, I’m as far from understanding physics as one can) I don’t get. How come, that almost all smartphone chargers (verified randomly 3 at home) have an output of 5V and 1.0A, while my battery clearly states, “Limited Charge Voltage 4.35V,?

The charger only reach peak voltage when fully charging the battery?

On June 23, 2016 at 5:20pm
alex wrote:

I’d like to use a couple of 18650 batties in a small hobby kit with a small solar panel that will always remain on and transmitting data. What would increase battery longevity most?
1) Using a charge controller and a 5V solar panel - thus fully charging the batteries each sunny day
2) Using no charge controller and a 4V solar panel - thus never fully charging the batteries and having my voltage float up and down each day (never a complete cycle)

Naturally both would need over discharge protection. I guess the question is whether to use a TP4056 with 5V solar or just go with 4V solar and no TP4056

On June 30, 2016 at 5:34am
vale wrote:

The article and comments are really helpfull but i’m having trouble concluding how to care for my battery…

I just bought an ASUS X555LJ with not-removable LiPoly battery and i’d like to extend as possible it’s battery lifespan (as is the firs thing that declined of my previous, adorable, 5 year old Toshiba Satellite, all from misuse).

Long story short, what exactly should I do:
a) Never let it go under 40% or over 70%//40%-80%//20%-80%// 50%-80%
b) Keep it between 70% and 90-95%?
c) keep it always plugged when possible (i understand not)

On July 15, 2016 at 12:54am
Tarun Jhamb wrote:

What is the mathematical relation between No. of Charge Cycle and Life time estimation of Li ion Battery?
e.g. for NiMH batery
                      Lt = Lt (New)                    if C<=300 charge cycle
                          {1.3 - 0.001C} . Lt(New )    if C>300 charge cycle

I want this kind of relation for Li ion Battery.

On July 15, 2016 at 5:58pm
Jorge Feitosa wrote:


I got all day researching for the better strategy to take care of my laptop batery and I have some questions to make, if anyone can answer it would be good:

1 - Can I remove my battery for 3 hours and then put it back without any damage to the same? I work all day at home and my laptop keeps plugged all day on AC charge

2 - If I remove my battery should I put inside something to protect more? Like put inside a drawer?

3 - Before remove my battery, do I need to charge him between 40%~70%?

On July 23, 2016 at 3:28pm
Alex wrote:

1. You don’t need to remove the battery, because it doesn’t charge when full. Keep an eye on temperature - the most evil for batteries. If you play games, better to do this without battery. But if you use notebook for taping, and frequently move between room, houses - leave it in case. It is designed to be used, not stored )
2. No need to put it in a freezer or something - battery degrades by itself. After 3-4 years it will loose half of life.
3. Yes, charge it to 75% level, because internal schematics draw energy. Li-ion element by itself has very low self-discharge rate, but not charging scheme. After half of year it will discharge to lowest level, and even can die. So charge it sometimes, if you desided to store it (again - no point in doing this)

On July 25, 2016 at 4:22pm
Michael wrote:

The smartphone chargers don’t charge the smartphones battery, that job is done by the smartphone.
The chargers output 5V because that is the USB standard (actually it allows for 4.75 to 5.25V).
The smartphone is the one that limits both battery charging current and voltage.
If the charger says 1.0A, that is the maximum current it is designed to deliver, but that doesn’t mean the smartphone will send that much to the battery.

First of all, a bare solar panel will deliver a voltage that is dependant on both the amount of solar radiation hitting it AND the amount of current being consumed by the load. If there is no load or a very little load, you can get 50% higher voltage, meaning under no circumstances are you to connect a solar panel directly to a lithium battery. If the battery is full and there is still solar light, it will continue to charge the batterty.
To get the longest life cycle, do as the article says and lower the maximum charge voltage and increase the llow voltage cut-off voltage. There are chips that will let you program both voltages, or use fixed voltage parts accordingly.
Or you can switch to LiFePO4 chemistry if your circuit can handle the lower voltages.

On August 9, 2016 at 6:18am
Spuffler wrote:

In early 2015, I purchased a Novatel T1114 WiFi hot spot with Voice router (Verizon), it uses a Lith-ion cell for operating the voice telephone segment during power outages. I used the device normally for about 5 months, then, knowing it would be put into temperature controlled storage while I relocated, I disconnected the Lith-ion cell from the T114 so as to minimize self discharge. When I disconnected it, the battery should have been as near to 100% charge as the T1114’s internal charge circuit could have done.

A year after putting the T1114 into that temperature controlled storage, I put it all back together (correctly) and fired it up.

No joy, the T1114 declares ‘no battery’ and immediately shuts down. I’ll have to get a voltmeter to test the cell, but I’m guessing that during storage, the cell somehow self discharged to zero volts, despite being disconnected from the T1114 (there is a third wire coming from the cell package, probably a thermal circuit uses the battery and outputs temperature data on the third wire).

I’m also guessing that the T1114 charge controller is not a well fleshed out design, being incapable of recovering this cell from this state of discharge. Note that the T1114 uses the battery for times when AC power has failed; in my neck of the woods, AC power goes out for several days at a stretch about every 18 months or so.

This further indicates that the designer of the charge cicuit should have reasonably expected the cell to completely discharge. Sigh. I miss working in power conversion design development. I would have had the designers head for missing this condition.

The cell is made by Palladium Energy, no obvious results on Google.

Oh well, at least it has a class designation of ICR19/66, and thus it might be available off the shelf. Maybe that online battery retailer….

Would love to jump charge it with a different battery pack for a few seconds, in hopes of getting the terminal voltage high enough that the T1114 stops treating it as ‘no battery’; I’m thinking that if there was voltage at the packs terminals, the T1114 might resume operation and also resume charging the battery. Otherwise, until the T1114 recognizes a battery, it will refuse to boot, it will shut down, and ... for want of a nail, the kingdom was lost, so to speak.

On August 9, 2016 at 2:07pm
John Fetter wrote:

Battery charger designers generally have only limited knowledge about battery technology, and design chargers according to their beliefs and assumptions. They are inclined to be overconfident and arrogant about their technical prowess, assuming batteries to be electrochemical devices in need of rescue and assistance by electronics experts.

On August 13, 2016 at 6:05pm
me wrote:


On August 22, 2016 at 3:13pm
David S wrote:

Thank you for the excellent information.
It would be useful to see an article about the effect of high charge rates on battery life.

On September 3, 2016 at 3:35pm
Nwodo Chidi wrote:

Thanks for the information! I used a laptop 12 cells of each 1200mAh, 3.7v to build power bank.The cells were stalked in parallel. I charged it with a laptop charged output of 19.5v, 3.33A. I monitor it to avoid over charging. Sir, my question is this is there any ‘gauge’ or IC that I can add to the charger to shot down current entering the battery to avoid the same over charging when the battery is full. Moreover, circuit is needed? I am an amateur in this filed. Please I need a solution. Thank you once again!

On September 9, 2016 at 9:10am
Gale wrote:

I recently purchase chainsaw that uses 80 volt and 40 volt lithium batteries need any and all help in regards to keeping these usable

On September 17, 2016 at 7:09pm
Tina wrote:

I have just bought a “Powerguard Notebook protector chargeall” which the salesman insisted prolongs the life of a battery for iphone, tablet, laptop etc. He was very persuasive and assured me that charging any of these devices using this device which seems to be some sort of surge protector would virtually double the life of the batteries. I haven’t opened the packaging yet but have read through as much as I could of the very helpful information on this site but cannot see any mention of these supposedly marvellous inventions. Can anyone enlighten me please. Have I been had? Or will this little intermediary between device and power source really extend the battery life? Thanks in advance..

On September 20, 2016 at 3:44pm
Chad wrote:

I continue to be confused by the author’s DoD table, even after reading many of the related comments above.

Does the depth of discharge refer to how much of the battery’s capacity is used up, or to the absolute charge level?

In other words, what is the depth of discharge when I go from 75% charge to 25% charge? Is it 50% or 25%?

In the same article it says that the ideal charge voltage is 3.92V, representing a capacity of 58%. So does that mean we should be cycling our batteries between 58% and 50%? It can’t be right to recommend that we only use 8% of the battery’s design capacity.

Historically I have got excellent life from my laptop and iPhone batteries when cycling between about 75%–80% and 20%–25%. But should I instead be cycling between 90% and 40%? Or something else?

Also, I assume that when Table 2 gives 1,200–1,500 cycles for a 50% DoD, that isn’t full cycles but just number of charges, right? I.e, if one cycle is defined as one discharge and recharge of the entire capacity of the battery (or, say, using 50% of the capacity twice), then I assume the correct way to interpret table 2 is that you get 300–500 full cycles with a 100% DoD, but 600–750 full cycles with a 50% DoD, right?

On September 22, 2016 at 1:49pm
Chad wrote:

One follow-up question to my questions above: When Table 2 refers to a depth of discharge of 100%, what voltage level is that? We know from this article that “full” is something like 4.2V or 4.35V. But what is “empty”? Is it the 3.0V at which some equipment shuts down? Is it the 2.5V–2.7V at which the battery permanently goes to sleep? Something else?

I noted last night that just before my iPhone powered down the voltage was 3.5V. At that voltage the indicator was reporting 1% capacity. So is 3.5V a 99% DoD? I doubt it. Perhaps some device manufacturers are preventing deep discharges, so the advice to not discharge too far may need to be taken with a grain of salt if you’re using a device that has already taken this into account.

Finally, it would be good to know which is most damaging: Full charges or full discharges (and here I don’t mean full discharges below 3.0V; I mean full discharges as reported by a piece of consumer electronics). I expect it’s full charges. But there is insufficient information here to know whether it’s better to cycle a phone or a laptop from 90% to 40%, or from 80% to 30%, or something else. (And it’s further complicated by the fact that “30%” as reported by the device may not actually be a 70% DoD (see my comment above about the voltage at which your device reports 0%).

On September 25, 2016 at 8:46pm
Feaver wrote:

Can anyone please please answer the most asked but never really answered question here?
“a) Shall I keep my laptop/smartphone (in my case surface pro 4, so taking battery out is not possible) plugged in while I’m for example at home/office or b) is it better to prolong battery life by using it until XX%? and charge it again to YY%?”
If b) please also tell us the XX and YY percentages.
Thanks a lot!

On October 17, 2016 at 4:50am
sachit koirala wrote:

my old smartphones lithium ion battery takes 24 hrs to charge fully and in some case charge remains constant.what should i do please advise.will it explode

On November 1, 2016 at 4:14am
Bruce Campbell wrote:

The article seems to explain matters exceptionally well to me.  But highly effective communication is a terribly daunting challenge - even excellent composition can partially fail to convey information well, especially when complicated subjects are involved.  I’m not a student of energy cell (battery) technology, so please don’t confuse me with an expert.  But the article seems quite clear to me, so the following is an effort to express some key points in an alternative way in the hope that they’ll be more clear.  Beware though - I won’t try to cover everything.

As the article said:  “Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life.” and “In terms of longevity, the optimal charge voltage is 3.92V/cell.  Battery experts believe that this threshold eliminates all voltage-related stresses; going lower may not gain further benefits but induce other [degradation processes].”  (The actual quote was “symptoms”, but my sense is that degradation processes is more accurate language.)

And “The smaller the discharge (low DoD), the longer the battery will last.”

A dominant theme in these public comments seems to be a desire for maximum cell life management.  Me too - I want my cells to remain healthy for as many years as possible, and that’s usually much more important to me than availability of full capacity.

Here’s the unfortunate rub:  Due to marketing related specsmanship pressures, cell management systems (charging and other management circuits) have different priorities.  Portable use time specs are a major competitive matter - device manufacturers seek to publish superior use time specs, so they’re inclined to design their cell management systems to charge to about 4.2 V.  That seems to be contrary to our actual desires, and for inaccessible cells such as in most portable devices there’s little or nothing we can do about the charging voltage, alas.  Hopefully insightful engineers will eventually provide a utility in a device’s operating system which will allow us to select our own desired peak charging voltage within a range of 3.92 V/cell to 4.20 V/cell.  (Frankly this should have been implemented in all significant portable devices years ago.)

As the article states temperature is also a major degradation factor.  (And not just for the cells, but the electronics in the device too.)  Per the article:  “The worst situation is keeping a fully charged battery at elevated temperatures.”  But lower temperatures prolong life under all other conditions too.

Other degradation processes take place at low states of charge - just as the cell encounters degradation processes at high voltages, it encounters other degradation processes at low states of charge.

In my personal estimation middle range charge and discharge cycle stresses degrade much less than higher temperatures, higher charge voltages, or deeper discharges.

So for longest overall life, keep the cells as reasonably cool as practical, charge them to 3.92 V/cell, and discharge them as minimally as practical - recharge them to 3.92 V/cell as quickly after use as practical.

You have some control over temperature and depth of discharge.  As to charging voltage, we all need to pressure vendors to provide charging voltage control in their products.  They can do this, and rather easily, but evidently need tangible consumer pressure to prompt action.  Be bold - advise them clearly that you want this, are significantly displeased that it’s not yet available, and will purchase from whichever vendor first provides this capability.

For accessible cells such as in common LED flashlights, you might have full control, or nearly so.  Ideally find a charger with a selectable charging voltage, if such a product exists, and set it to 3.92 V.  If not, and you have some electronics technical skill, modify the best charger you can find to reduce its charging voltage to 3.92 V.

(Or construct your own - fabricate a high precision current limited regulator circuit with a very precise 3.92 V output.  Which, ideally, fully disconnects from the cell about five minutes after 3.92 V is achieved.  Very inexpensive (roughly $3) power converter modules which provide both current and voltage regulation are readily available from Chinese and perhaps other vendors for example.)

Multi-cell batteries, such as in laptop computers, present more challenges.  But just as with portable devices, we consumers should demand that vendors provide charge voltage control from 3.92 to 4.20 V/cell.  Again, they could - and rather easily.  But they probably won’t until significant pressure to do so exists.

In the meantime we can keep our systems as cool as practical, and discharge the battery as minimally as practical during portable use.

Again, I’m not an expert in these matters - I’m just trying to articulate my personal understanding.

On November 1, 2016 at 5:27am
Bruce Campbell wrote:

Also:  In the Macintosh world a third party free or contribution ware utility called “MacsFanControl” is available.  I have several fan equipped Macintosh devices which all utilize MacsFanControl at its highest cooling settings (which are far more aggressive than Mac OS defaults).  My fans thus make more noise and drain my battery faster.  But they keep my systems quite cool, which I view as far more important.  Maybe a similar utility is available for other devices.  Thermal physics is very clear about heat - it degrades systems, including electrochemical and electronic.  As best I recall, roughly speaking every 10 °C rise decreases life by about 50% - that is, life is halved.  Heat kills.  So I prefer to keep my systems as cool as I can.  (Even when I must thus discharge my battery a bit more deeply, to a point.)

(BatteryUniversity.com:  If you think my thoughts in this or my previous comment are of some benefit feel free to utilize them as you please, except that if you quote me directly, please attribute me responsibly.)

On November 1, 2016 at 9:33am
Tom V Martin wrote:

Bruce Campbell,

The data doesn’t seem to match the conclusions of the article.

Referring to Table 2
Assuming a 10% DoD gives you 1 unit of use and you can recharge it 4700 times you’ve gotten 4700 units of use out of the battery.
Now if you have a 25% DoD you get 2.5 units of use per recharge. You can recharge it 2500 times you’ve now gotten 6250 units of use from the battery.
If you have a 50% DoD you now get 5 units of use per recharge. You can recharge it 1500 times you’ve now gotten 7500 units of use from the battery.
If you have a 100% DoD you’ve now gotten 10 units of use per recharge. You can recharge it 500 times you’ve now gotten 5000 units of use from the battery.

In addition keeping the battery topped off is contradictory to the information contained in Table 3.

I’ve found I obtain the best life and length of use between charges by allowing the battery to discharge till the device tells me it needs to be recharged, and then recharging it at that time.

On November 2, 2016 at 10:05am
Hoda Youssef wrote:

Hi there,

What is the safe range of SOC for large scale Li-ion battery energy storage system (2 MW-4 MWhr) ?
I found most of the literature assume a range between 30% <SOC<90% , is it practical ? Also, where can I found a good reference to determine the safe SOC range of large scale BESS.

I thank you in advance for you help

On November 2, 2016 at 3:13pm
Bruce Campbell wrote:

Tom, I’m skeptical of Table 2 from the perspective of those who seek maximum lifespan (in total years of use) of their cells.  Table 2 presents discharge data from a default charge voltage which isn’t stated, but I suspect is 4.20 V.  (“DoD is assumed from a fully charged battery to said percentage level regardless of SoH.”)  But charging to 4.20 V degrades the cell irrespective of depth of discharge.  So my sense is that the data in Table 2 represents a mix of two degradation processes:  Depth of discharge related degradation plus maximum charge related degradation.

My sense from the public comments is that most people seek to maximize the lifespan of their cells, or at least express that desire.  Me too, even above total use (total of ‘units of use’, that is, sum of all depth of discharge times number of discharges) - I want my portable devices to remain usable in portable mode for as many years as possible.

Viewing the matter on a fundamental level, a cell has a primary electrochemical reaction, its charge / discharge reaction, which is 100% reversible and infinitely repeatable with no degradation.  But alas there are also an array of independent secondary chemical and electrochemical reactions which cause degradation.  They’re minimal at low temperatures and near the middle (ideally 58%) of the charge state.  They’re stronger, and thus more damaging, at high temperatures and high or low charge states.

So those who seek maximum lifespan in total years of use should keep their cells as cool as practical and as close to a 58% state of charge (3.92 V) as practical.  I suspect it’s that simple.

Or it should be.  But the problem - a big one - is that most device manufacturers make such management extremely difficult (as a practical matter impossible) because they fail to provide a means to manage the peak charge voltage.  (They also fail to provide a means to operate their fans more aggressively.)  They’re immersed in competitive specsmanship, including portable use time, and highly resistant to anything they perceive might threaten their specsmanship posturing.

However, clever engineers could convince their firm’s shallow minded MBAs that they can have it both ways - they can quote portable endurance based on 4.20 V charging in their specs, yet provide a utility which allows users to manage their cells for maximum lifespan by lowering the default 4.20 V peak charge voltage to more lifespan friendly levels, including of course 3.92 V.  Evidently a very rare few do - in his February 28, 2011 comment above Rob Smith advised that his Sony VAIO laptop provides such a utility (except that it evidently presents charge level information as percent of capacity rather than voltage).  Big kudos for Sony!  But availability of such control should be pervasive rather than rare.  Bitter raspberries to the majority of vendors…

We consumers need to pressure vendors to provide a utility like Sony’s in all their portable products.  We should aggressively demand it.  And vote with our purchase dollars whenever an opportunity arises.

In the meantime I hope a Battery University member will conduct a precision test focused on conditions for maximum lifespan.  In particular I’m very interested in capacity endurance for cells cycled between 58% charge (3.92 V) to 48%, 38%, 28%, 18%, and 8% charge.  At 23 °C and, if time permits, some lower and higher temperatures too.  I’m very interested in lifespan results under those conditions, and suspect many others are too.

Again I’m not a student of energy storage cell technology.  These are just my personal impressions.

On November 4, 2016 at 1:26am
Hoon wrote:

I just recently found that you can stop charging a Macbook that use Magsafe2 connector (probably same with Magsafe1) by blocking the center pin which is used for signaling. Had I known this, I would have used it like this for the last 3 years as most of the time I was on AC. Current cycle count is 100 on my late 2013 rMBP13. The battery still lasts pretty long (6+ hours).

I knew Thinkpads have a battery utility where you can limit the charge range by percentage.

On November 4, 2016 at 11:47pm
Bruce Campbell wrote:

That’s a terrific tip Hoon, thank you!

I studied a bit deeper hoping that common Mac hardware has general purpose access to that line such that software could control or influence it, thus allowing a utility to control state of charge of the battery like the Sony Vaio and Lenovo ThinkPad, but evidently it doesn’t.  Thus there appears to be no possible software means to control the battery’s charge level in a Mac due to lack of hardware support.  Bitter raspberries to Apple…

Thus when we’ll be on line power for extended periods we must charge or discharge our Mac’s battery to about 58% and then insulate the mag-safe connector’s center pin, a stone knives and bear skins class primitive solution.  Bitter bitter raspberries Apple…

I gather Windows 7 has provisions to control battery charge levels but they’re only effective when the system’s active - in sleep or shutdown mode those provisions can’t function, so the battery then charges to the level set by hardware (probably 4.2 V/cell or very close).  Microsoft probably did the best they could but are handcuffed by their open hardware environment, and most hardware isn’t battery management enlightened.

I haven’t studied the landscape in detail, but as far as I know the Sony Vaio and Lenovo ThinkPad are the only systems which have truly enlightened battery management design and thus deserve hearty kudos - very good for them!  They may rightly claim a far more advanced design in terms of battery management.

The other vendors need to open their eyes and tend to their tardy homework.

All just in my amateur opinions…

On November 5, 2016 at 4:46pm
Bruce Campbell wrote:

That’s a terrific tip Hoon, thank you!

I studied a bit deeper hoping that common Mac hardware has general purpose access to that line such that software could control or influence it, thus allowing a software utility to control state of charge of the battery like the Sony Vaio and Lenovo ThinkPad, but evidently it doesn’t.  Thus there appears to be no possible software means to control the battery’s charge level in a Mac due to lack of hardware support.

Thus for maximum life management we must charge or discharge our Mac’s battery to about 58% and then insulate the MagSafe connector’s center pin when we’ll be on line power for extended periods, a stone knives and bear skins class primitive solution.  Bitter bitter raspberries to Apple…

I insulated my MagSafe 2 connector center pin for my MacBook Air 7,2 running Sierra 10.12.1, and your method does indeed work. However, the OS illustrates a lightning bolt over the battery icon at the top of the screen which suggests the battery is charging when in fact it isn’t.  But the LED indicator in the mag-safe 2 connector remains dark.  So the combination provides a positive indication - the icon can be interpreted to indicate that the laptop is receiving line power, and the dark MagSafe 2 LED interpreted to indicate that the battery is not charging.

I tested one of my older MagSafe 1 equipped MacBook Pros running legacy OS 10.6.8, (for important legacy application compatibility) with basically the same positive results.  The laptop is powered, but the MagSafe 1 connector’s LED remains dark and the battery doesn’t charge.  The Finder’s battery icon has a lot of response latency, but ultimately (after a restart for me) indicates that power is connected and that the battery is not charging.  But the “Not Charging” message overwrites the state of charge percentage information, alas, so the user has to refer to System Profiler / Power and do a little math to acquire that information.  Or, for a rough indication, press the physical button for the battery charge state indicator to momentarily see it.

I gather Windows 7 has provisions to control battery charge levels but they’re only effective when the system’s active - in sleep or shutdown mode those provisions can’t function, so the battery then charges to the level set by hardware (probably 4.2 V/cell or very close).  Microsoft probably did the best they could but are handcuffed by their open hardware environment, and most hardware isn’t battery management enlightened.

I haven’t studied the landscape in detail, but as far as I know the Sony Vaio and Lenovo ThinkPad are the only systems which provide truly enlightened battery management design and thus deserve hearty kudos - very good for them!  They may rightly claim a far more advanced design in terms of battery management.

The other vendors need to open their eyes and tend to their tardy homework…

All just in my amateur opinions of course…

On November 6, 2016 at 4:18pm
Hoon wrote:

This got me thinking, which is worse for a sealed smartphone battery, keeping the battery full and plugged in most time when possible (with twice a day discharge to around 50%), or very frequent shallow cycling anywhere between 20-80%?

On November 14, 2016 at 8:56am
Guenter Kloepper wrote:

For what it’s worth, here is some experience that may be useful :
We have designed an App for Android which turns the phone into a Time Reporting Terminal. We use the NFC capability as a Badge Reader. What this usage implies is that the phone will be connected 100% of the time to its charger.

For the first batch of 100 units units we used a Samsung Core Prime phone. Well, after about 9 months in use, the batteries bloat to such en extent that the entire phone bends into an egg shape and we fear that some units are liable to explode. So we analyzed what actually happens between the phone and the battery. When the battery is fully charged, Samsung continues with a small trickle charge that starts at around 50 mA and drops off to 5 - 10 mA (phone switched on, screen on and App running). After 40 minutes they disconnect the charger for around 4 minutes and then repeat the 40-minute cycle. The charge current is different with the phone switched off, on but idle, and on with screen on and App running.

When you calculate the total charge into the battery during the 40 minutes and the charge drained during the 4 minutes you discover that the battery is being overcharged slightly with each cycle. When you extrapolate that over a month you discover that the overcharge is about 25% of the rated capacity of the battery (2000 mAh). So after 4 months the battery is overcharged by 100% and so it goes on until something (don’t yet know what) happens . . .

On November 21, 2016 at 10:44pm
Ajoy wrote:

What is the better practice for keeping battery well?
We will do full charge and discharge to a certain level or always keep in AC power.

On November 22, 2016 at 5:15pm
petey pablo wrote:

Does anyone know what would happen to a samsung phone which has 3000mah battery but was shipped with 0% battery and subsequently was stored in storage in warehouse for a year and the protection cut off switch was activated so did not turn on upon receiving.

I think the voltage was around 3500mv so 3.5v at 0% maybe a bit less say 3.4v , how much damage to the lithium ion battery would their be if it’s been in storage at low voltage for a year brand new?

Trying to decide whether to send it back. The voltage for my previous phone which i need to send back at 61% battery is 3920mv so 3.92V but on this one (due to damage i suspect of being stored at 0% and sleep switch activated ) at 61% reads 3855mv (3.85V) is the difference of 70mv (0.7V) a significant difference?

It seems to me the damage caused by the sleep switch circuit activated for nearly a year in low state of charge will have damaged the cells in the battery right?

Especially where everywhere preaches storing at 40%. I dont know why that samsung factory is so stupid and storing it at 0% and sending the phones out that way.

On December 11, 2016 at 5:17pm
BillV wrote:

I use a custom battery pack on a motorcycle consisting of eight A123 (LiFePO4) cells in a series/parallel arrangement.  I found that the bike’s ECM and instrument cluster will drain the pack in about 6 weeks of non-use so I’ve started making use of its quick disconnect.  A Battery Tender Jr. will bring it up to about 14.2 V and it will drift down to about 14.1 V in several days while disconnected.  Any drift beyond that seems to be very slow.  The bike’s charging system will leave it at around 13.5 V, which is also associated with very slow downward drift while disconnected.  All of that is at 65-70 °F.  It’s relatively easy to drain the battery to a desired voltage. Do you have any recommendations on what it should be in terms of prolonging its life while in storage?

P.S.  The Dreamliner battery was a lithium cobalt oxide type.

On December 25, 2016 at 11:19pm
Daniel wrote:

The article states that the optimal charge level is 3.92 volts/cell and that 3.92 V represents 58% capacity. However, the company that manufacturers the charger I am using for my lithium ion pack (a Panasonic NCR18650GA type) says that 3.92 volts represents a 73% state of charge. Why the difference in percentages?

On December 30, 2016 at 12:06pm
BillV wrote:

I’m suspicious of that information as it relates to LiFePO4 batteries.  Their voltages are lower such that 3.92 is unachievable.  Fully charged my batteries are only around 3.5 V.  See page 2 here: http://www.a123systems.com/Collateral/Documents/English-US/A123 Systems ANR26650 Data Sheet.pdf.  I haven’t looked at this in any detail but it seems to me that recommendations for optimum voltage for long storage life need to reference the specific type of battery instead of only stating lithium ion.  This could be what is going on with your 58% vs 73% values.

On January 3, 2017 at 3:47am
rangamaniiyer wrote:

is there any laptop battery with screw fitting that can be opened up to replace li ion batteries instead of throwing out the good electronic parts?

On January 13, 2017 at 4:32pm
geok wrote:

HELP. My battery for Dell 6230 dont charging (0%) and after the check show these:
What is all of that ? I am litle unrelated…...Is my battery DEAD ???

Power Efficiency Diagnostics Report
Computer Name GEO1-PC
Scan Time 2017-01-13T22:39:32Z
Scan Duration 60 seconds
System Manufacturer Dell Inc.
System Product Name Latitude E6230
BIOS Date 10/08/2012
BIOS Version A06
OS Build 7601
Platform Role PlatformRoleMobile
Plugged In true
Process Count 95
Thread Count 1017
Report GUID {4c1be59a-4825-4928-86fe-85fb4c23ba61}.


USB Suspend:USB Device not Entering Suspend
The USB device did not enter the Suspend state. Processor power management may be prevented if a USB device does not enter the Suspend state when not in use.
Device Name USB Root Hub
Host Controller ID PCI\VEN_8086&DEV;_1E26
Host Controller Location PCI bus 0, device 29, function 0
Device ID USB\VID_8086&PID;_1E26
Port Path

USB Suspend:USB Device not Entering Suspend
The USB device did not enter the Suspend state. Processor power management may be prevented if a USB device does not enter the Suspend state when not in use.
Device Name USB Composite Device
Host Controller ID PCI\VEN_8086&DEV;_1E26
Host Controller Location PCI bus 0, device 29, function 0
Device ID USB\VID_0A5C&PID;_5801
Port Path 1,8

USB Suspend:USB Device not Entering Suspend
The USB device did not enter the Suspend state. Processor power management may be prevented if a USB device does not enter the Suspend state when not in use.
Device Name Generic USB Hub
Host Controller ID PCI\VEN_8086&DEV;_1E26
Host Controller Location PCI bus 0, device 29, function 0
Device ID USB\VID_8087&PID;_0024
Port Path 1

CPU Utilization:Processor utilization is high
The average processor utilization during the trace was high. The system will consume less power when the average processor utilization is very low. Review processor utilization for individual processes to determine which applications and services contribute the most to total processor utilization.
Average Utilization (%) 27.56

Platform Power Management Capabilities:PCI Express Active-State Power Management (ASPM) Disabled
PCI Express Active-State Power Management (ASPM) has been disabled due to a known incompatibility with the hardware in this computer.




On January 15, 2017 at 1:16am
geok wrote:

My battery has that information. What it show? Are good on not? Why my battery dont charging (0%)?

Battery:Battery Information
Battery ID 1816Samsung SDIDELL KFHT82B
Manufacturer Samsung SDI
Serial Number 1816
Chemistry LION
Long Term 1
Design Capacity 65490
Last Full Charge 65490

On January 17, 2017 at 2:46pm
Pouly G wrote:

Some of you don’t understand meaning of term cycle. 1 cycle is a full discharge from 100% to 0%.
So some of your math in comments is wrong it should be like this:
100% DoD   300–500

50% DoD gives you 1,200–1,500 full 100% cycles meaning 2,400-3,000 50% charges.

25% DoD gives you 2,000–2,500 full 100% cycles meaning 8,000-10,0000 25% charges

10% DoD gives you 3,750–4,700 full 100% cycles 37,500-47,000 10% charges

But it all comes down to Li-Po, Li-Ion batteries age really quickly. A 2 year old Li based battery is considered old doesn’t matter if you used it or not and probably is holding 80% of initial charge.

On January 28, 2017 at 3:13am
Dominik Nožka wrote:

Hello everyone,
I have developed the smart charging adapter which prolongs battery lifespan more than 2 times. It is called GentlyCharge and it  solves problems of modern batteries like deep discharging and overcharging and protects battery from heat during charging. It is compatible with all the Android phones and tablets, and also with an Apple iPhone or an iPad.

For more info visit: www.gentlycharge.com

On January 30, 2017 at 12:40pm
Hoon wrote:

Hi Dominik,

Nice idea on the hardware implementation. I checked out your website and I’m impressed. One question, on your test data, does 10% battery level mean 10% reported by the Android/iOS phone itself, or does it refer to a specific voltage? I think modern phones have a safe low level (cutting off early enough) so it doesn’t wear out the battery too much, but nobody knows for sure as they can mess with both the 0% and the 100% and make sacrifices on the usable life.
Another question, is it capable of dealing with Qualcomm’s QC which raises the voltage to 9V? It’s still less than 1C charge rate on my Galaxy S7 Edge, so I think it’s ok as long as the heat is in check so I tend to use it when I’m in a hurry or have a fan to cool my phone while charging.


On January 30, 2017 at 12:44pm
Theodore wrote:

Based on the information provided in this article, isn’t it the best practice to remove the battery for as long as you are home and let the laptop run solely from the power supply?Say that your battery is 50-60% drained or even 40% isnt it still better to save it from several hours everyday of being topped off as being in full charge stresses the cell a lot? You can always charge it when you wake up or at work depending on your schedule.This practice is employed on experia XE and newer smartphones too. They ry to avoid both toping off and complee draining based on the users lifestyle.

On February 3, 2017 at 3:02pm
John wrote:

I recently bought two smartwatches - Samsung Gear S2 Classic and S3 Classic and I am concerned about the lifespan of the batteries. I am not a science-minded person, so much of the article and nearly all of the comments are a bit over my head. That said, from the information I have gathered from forums where I posted my question, I was led to believe that the battery should, in the end, last anywhere from 2-3 years, depending of course on usage, temperature, number of charge cycles, percentage of charge cycles, etc.  One person stated that it sounded like the battery in the S2 looked to him to be a classic 300 cycle battery, so if fully discharged and recharged daily, it wouldn’t last a year!  However, in the article above, it says:

“Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.0V/cell should deliver 1,200–2,000 and 3.90V/cell should provide 2,400–4,000 cycles.”

Given this info, since the battery in question (Gear S2 Classic) is a Li-ion 250 mAh 3.8 V 0.95Wh, which, I would assume, is close to the 3.90 V mentioned above, shouldn’t it provide roughly 2,4000-4,000 cycles, taking into account, of course, the variables I mentioned above?

I would greatly appreciate any and all input regarding this questions, smartwatch batteries in general and those for the S2 Classic and S3 Classic in particular.

Many thanks!


On February 3, 2017 at 3:51pm
Theodore wrote:

Hello there. You mention that the battery is a 3.8 volts 250mAh cell but i think the 3.8 refers to the nominal voltage. Its a bit strange to be referenced as 3,8v because most of the cells i ve seen are referenced 3,6-3,7 but that being said i think its highly unlikely to be charged only until 3,8v. If i were the designer i would want the full 250mAh which is achieved at ~4.2. Therefore what i would do if i were you to increase the lifetime is make sure to charge it only at 80-90% and disconnect it afterwards, effectively restricting the charge to somewhere after 4.0v close to 4-05ish and i think this would extend the charge cycles but would reduce the RUNTIME between charging too.

On February 6, 2017 at 4:56pm
Jeremy wrote:

Pouly G said this:
Some of you don’t understand meaning of term cycle. 1 cycle is a full discharge from 100% to 0%.
So some of your math in comments is wrong it should be like this:
100% DoD   300–500

50% DoD gives you 1,200–1,500 full 100% cycles meaning 2,400-3,000 50% charges.

25% DoD gives you 2,000–2,500 full 100% cycles meaning 8,000-10,0000 25% charges

10% DoD gives you 3,750–4,700 full 100% cycles 37,500-47,000 10% charges

But it all comes down to Li-Po, Li-Ion batteries age really quickly. A 2 year old Li based battery is considered old doesn’t matter if you used it or not and probably is holding 80% of initial charge.

At first I was confused as the table said discharge cycles, this implies that it is the amount of cycles when discharged by the DoD and fully charged to 4.2V. This results in 50% DoD giving the most cycles.
Paula is correct, according to the chart on http://www.mpoweruk.com/life.htm , the lower the Depth of Discharge, the higher the average cycle. Average cycle defined as a complete discharge and charge (0-100%). Roughly it seems halving the DoD gives twice the amount of cycles. This also seems correct with Table 2, going from 50% to 25% DoD roughly gives double the cycles, 1200 to 2000.

Also Table 6 here seems to match with MrPowerUK and Tesla forums again, the lower the State of Charge after charging, the more cycles you will achieve.

From what I read here and other studies I can conclude that it is best to make frequent, short charges, 10% or less ideally, and keep maximum charging voltage to a minimum. Though of course realistically that is difficult, it is better to do frequent top ups, and disconnect the charging as soon as possible, within reason.

On February 7, 2017 at 11:55am
Hoon wrote:

Jeremy wrote:
“... From what I read here and other studies I can conclude that it is best to make frequent, short charges, 10% or less ideally, and keep maximum charging voltage to a minimum. Though of course realistically that is difficult, it is better to do frequent top ups, and disconnect the charging as soon as possible, within reason.”

According to the guys that make the AccuBattery app for Android, keeping it between 90% to 100% will cause similar wear on the battery as doing:
charging from 70%-90% (using 20%)
charging from 40%-80% (using 40%)
charging from 10%-60% twice (using 100%)
or something like that. All numbers are made up by me just to show the point.
Keeping the voltage high (besides heat) wears the battery, so try to stay in the lower bound.
Smartphones have a low voltage cut-off point so the voltage doesn’t go dangerously low before powering off. With this in mind, I’m keeping my Galaxy S7 Edge between 20-60% most times, and try to avoid charging over 80% on my iPhone SE.

On February 8, 2017 at 6:44am
Jeremy wrote:

I agree definitely charging from 90% to 100% will wear the battery faster because it is hitting a higher voltage, and the battery is stressed all the time at 4.2V since it is never given a chance to drop down and relax. Going from 90%-100% will probably kill the battery faster than charging from 25%-100%.

My point was, in theory, the shorter you keep the charge times (lower depth of discharge), the more life you can squeeze out of the battery.

Based on the table and graph going from 40%-60% is better than 20%-60%. Doing this will increase the amount of cycles because there is less stress. Of course this doesn’t apply to 100% cutoff, because constantly staying at high voltage alone will kill it.

Ideally if there is always an outlet nearby, the best time to charge it is 40%-50% so that it minimizes voltage cutoff and DoD to extend cycle life. As I said before this is unrealistic, so we try to charge it as soon as possible and disconnect it at the earliest, whether it is 50% or 70%.

On February 10, 2017 at 10:50pm
Tahseen Javaid wrote:

my question is that i have s6 edge, i want to expend his battery life as long so what can i do, which percent age % i can charge my phone 15 or 40 % to till 100% percent please tell me about this situation.
as s6 edge has 9 volts battery?

On March 20, 2017 at 10:54pm
Rob Zilla wrote:

Someone told me a metaphor.. think of your Li-ion battery as 2 flavors of pudding.  When the vanilla mixes with the chocolate, the charge depletes.  If only a little mix it can be separated easier, but allowing them to completely “swirl” makes it real hard to separate the flavors (the positive and negative charges).  I don’t have any proof of this but it makes it easy to think about.  I keep my system plugged in most the time but if I wanna take it somewhere I just let it get no lower than 3/4 or so. 

Not like the old days where you had to “train” your Ni-cad’s (and I think NiMH wanted full to 0 too iirc)

So best I can tell don’t quixk charge Li-I batteries and don’t let em run all the way out.  Heck my 3DS has been on for 3 days and still has 2/3 charge, tho a lot was in standby mode.

On March 23, 2017 at 11:38pm
revant wrote:

can a lithium ion battery used to charge a electric bike , be used to charge a electric stove(like a hot plate) ?

On May 26, 2017 at 1:46pm

The figure 6 is just mind blowing! I’ll try my best to prolong my smartphone or anything’s battery life that uses lithium ions as much as possible. Thank you so much for this useful article!
However, I use a battery monitoring app on my phone and it shows battery voltage. And while charging, above 70% the voltage is 4351mV and it seems constant. But it can be as high as 4470mV. When unplugged, the voltage drops to around 4200mV in several minutes.
My question is, is this normal? I mean, is it OK for my battery? The article says no to above 4.2V. But I don’t think this is just my device, which is Moto G4 Plus. My previous phone was Nexus 5, but the voltage while charging was also above 4.3V, I believe. Are current smartphones’ batteries are different from ones that are described in the article?
Should I abandon the manufacturer’s charger with Quick Charge and always charge from my PC’s USB port though it’s super slow? Because when I charge it that way, the voltage is kept much lower. (The phone doesn’t get hot also.)
Is it OK if I disconnect the charger before it reaches, say 80%, or is it that high voltage harms my phone’s battery no matter what the final SoC is?
I hope someone will answer my questions.

On May 29, 2017 at 2:15am

My another question is, which is worse, 0% to 50% every day or 50% to 100% every day? The figure 6 doesn’t show any result tested below 25%. So my question ultimately would be: which is worse, overcharging or overdischarging? I don’t know if they’re the correct words.
I have a feeling that 100% will be worse than 0%.

My yet another question is, which is good, 50% to 70% 1000 times or 60% to 70% 2000 times?
I really want to know if an amount of energy (=electrons?) you give to a battery at a time matters or only SoC (=voltage) is important in this case.

And apparently, if you use Chrome and have its data saver turned on, you can’t add a comment on this site.

On June 9, 2017 at 10:01am
Jeremy wrote:

I don’t know if you will read this since this is a couple weeks late but I’ll reply anyways since it might be helpful to others.

I know that for smartphones they use varying lithium chemistries that change their nominal voltage, and thus their charge terminal voltage. In fact I’d argue the majority of phones nowadays use lipo’s that terminate far above 4.2V, 4.4V is probably the norm. No need to worry, just look at percentage, 100% is still 100%. Totally fine to disconnect at 80%, just look at figure 6 to charge how you want it. 80%, is good, less then that is better.

Now for quick charging, “in theory” quick charge 1.0/2.0 will reduce the amount of cycles the battery has left. Their specs indicate a faster amp draw, which will result in more heat and stress on the battery as you experienced, and thus amount of cycles. However quick charge ONLY activates from 0%-50 or 60%, after which it will switch back to standard charging. With the large battery capacities nowadays, any phone with more than 2000 mah will safely quick charge below 1-1.5C, which won’t significantly affect battery capacity. This means in reality stress is limited, current is tightly controlled to avoid overheating, and the damage is minuscule you may not even notice the change in capacity.

With quick charge turned off, you can charge from your mains adapter much faster than your USB port with nearly no difference in longevity up to 0.5C. WIth a Moto G4 (3000mah), that is any adapter up to 1.5A. Ultimately it’s up to you, if you want to maximize longevity and/or you keep for phone for 3+years you can just turn quick charge off, and charge with the mains adapter. More info on charge rates at BU-401a: Fast and Ultra-fast Chargers.

0-50% is definitely better. There was a military study done on it, it was on Tesla forums but I don’t remember the link. Reason being that 100% keeps the battery stressed more at high voltage than at 0%, and you are normally above 0%. Of course 0% is still bad, the cell begins failing, but the phone will protect from that (0% is not actually 0%). This is why I recommend 20-50% or even better, 40-50%. Of course that only gives you only 50% of battery for emergency, so you can up that to 60 or 70% with a slight reduction in battery life.

60-70% is better than 50-70%. Look at table 2. You reduced the depth of discharge by 10%, but gives nearly 10x more cycles. Why 10x? I don’t know, but it’s just the way the battery is and with mpoweruk.com/life.htm saying the same thing as Table 2, it must be right.
The answer is the less energy, electrons, you give to a battery, the more cycles you get. They even claim cells in microcycle applications (charge and discharge pulses) can get 300,000 cycles. Again, in reality you won’t see it, but those are the conclusions.

Hope this helps!

On June 9, 2017 at 10:02am
Tom Brantley wrote:

Trying to figure out what voltage equates to 40% SoC?

My batteries are Li ion (NCA)....I thought that the voltage range was approximately 3.0v-4.2v and that would mean that 40% SoC was approximately .4 x 1.2 + 3.0 = 3.48v.

I read on the Battery University site that “At 40 percent charge, most Li-ion has an OCV of 3.82V/cell measured at room temperature.”

What am I not interpreting correctly?

My sincere Thanks for all of your help.

On June 26, 2017 at 6:37am
sakthivel selvam wrote:

What is the maximum discharge voltage / deep discharge voltage of Li ion battery.

What will happen if i discharge the battery (li ion)  to 2.3V.

Battery part no: ICR18650B3
Manufacture : LG Chem

On July 28, 2017 at 11:19am
Yura wrote:

Is keeping battery at 100% as bad as deep discharge to 0%?

What should I do? I have a MacBook Air but I use it as a laptop - connected to power, its battery always at 100%

How often should I disconnect it and how deep let the battery discharge?

Why don’t manufacturers explain this? This is the most ignored question ever! :(

On September 6, 2017 at 2:45am
MKING wrote:

We have a new Macbook Pro and it gets warm when charging. I am considering the purchase of a lower-wattage (amps) charger which will charge slower and at maybe a lower induced temp. for the battery. I have used a lower powered charger on my mobile phone and it does seem to help re temp. and battery longevity.

Am I on the right track or deluded?


On September 22, 2017 at 3:19pm
Rudi wrote:

Suppose I want to charge my cells to 4.08 volts.
What is best in order to minimize the stress:
1. Charge to 4.20 volts with high current (1-2 amps) en then stop when voltage is dropping. The end result then will be about 4.08 volts.
2. Set my charger (SkyRC MC3000) to charge to 4.10 volts and let charging go on till the voltage drop to 0.1 - 0.2 volts. Also here the result will be about 4.08 volts.

The first method is of course the fastest, but will bring the cell shortly at 4.2 volts.
The second method takes much longer (also stress), but never make the cell’s voltage above 4.1 volts, being 90%.

On September 23, 2017 at 1:02am
ZVI wrote:

Lead Acid batteries during charging emit toxic gases during charging and especially at electrica fork lift trucks.
What about the large batteries charging gassing of EV vehicles?

On September 25, 2017 at 4:22pm
John Fetter wrote:

Lead-acid batteries emit hydrogen and oxygen at the end of charging. Neither is toxic. The mixture is flammable.

On September 30, 2017 at 4:26am
Pablo Kho wrote:


Nice information! Definitely helps!

On October 11, 2017 at 12:47pm
Claudio wrote:


Explanatory text. Thank you
About new smartphone charging technologies, do they hurt the battery? Or are they functional and secure?

Thank you

Claudio (Brazil)

On November 2, 2017 at 10:26pm
Evi1M4chine wrote:

One thing missingg in all of this, seems to be, that longevity seems to be measured in charge-discharge cycles, instead of total use time!

Because, of course you get more cycles if you only use it for a part of the capacity. Duh. The total amount of discharging/use might still not be better!

I hope you can answer this, as it is really preventing me, from being able to draw any useful conclusions from this. :/

On November 17, 2017 at 1:09am
Mogens wrote:

Table 3 figure text says that the numbers are for 1 year, but in the lowr right corner of the table it says “(3 months)”... So which is correct? And what does the 3 months refer to if not the period of storage?

On December 1, 2017 at 2:32pm
Jesse wrote:

I have a question, so if the best percentage to store a lithium battery is 40 percent, why is it the the longest cycling is 65- 75 percent? Shouldn’t you try to keep the percentage to 40 as much as possible? So maybe 45 - 35 percent? or is there something i am missing out?

On December 5, 2017 at 4:49am
MKING wrote:

On September 6, 2017 at 2:45am
MKING wrote:
We have a new Macbook Pro and it gets warm when charging. I am considering the purchase of a lower-wattage (amps) charger which will charge slower and at maybe a lower induced temp. for the battery. I have used a lower powered charger on my mobile phone and it does seem to help re temp. and battery longevity.
Am I on the right track or deluded?

I still don’t know what to do?  Do I charge slower or as rapidly as possible?  I am doing 20% to 90% at present but it seems I should be recharging at 40% and unplugging at 80% to prolong the life?

I am now using an older HP laptop as a TV streamer and am actually removing the battery when it it ‘on the mains’  - this ought to help the battery stress by no being connected or in use - yes?

On December 7, 2017 at 3:41am
Vortex wrote:


In response to Evi1M4chine on November 2, 2017 at 10:26pm

Have in mind please I am not an expert.

If we consider the whole energy transferred to the device by means of the battery we, I think, could better understand the “cycles vs. use time” thing.

Discharging the battery 10 times by 50% (let’s say from 100 to 50 percents) gives the device the energy equivalent to 5 full 100% discharge, or 5C, “5 batteries”, to say smile

I’ll try to calculate this energy from the data plotted in
“Figure 6: Capacity loss when operating Li-ion within given charge and discharge bandwidths”.

Let’s consider the battery started to degrade and it’s full state of charge is at 90% as compared to the initial state which was 100%. From the data plot we see that if the battery discharge is driven at 100% to 25% range it reaches 90% capacity retention after 1000 cycles. On the other hand if the battery discharge is driven at only 75% to 65% it reaches 90% capacity retention after 9000 cycles (extrapolated). Much more cycles but with less energy transferred to the device in a single cycle.
So the whole energy transferred to the device when sycling at 100%-25% is
75% multiplied by 1000 which gives 750 C. “C” is the full virgin capacity.
In the case of 75%-65% we have
10%*9000 = 900 C.

Calculated this way we obtain the following:
75%-65% - 900C
75%-45% - 1500C
75%-25% - 1500C
85%-25% - 1200C
100%-50% - 800C
100%-40% - 720C
100%-25% - 750C
till the battery reaches 10% capacity degrading (90% retention).

As one can see there is an optimum in this therms and I would prefer 85%-25% or 75%-25% discharging.

On December 8, 2017 at 4:42am
Vortex wrote:

I extrapolated graphically the data from Figure 6 to more cycles using an intrapolation/extrapolation program with default settings assuming there’s a linear decay of the capacity retention with the number of cycles:


If so it can be expected a drop of battery capacity retention to 75% after 13000 cycles in the “75%-25%” scenario, drop to 70% after 11000 cycles in the “85%-25%” scenario and, the worst case, drop to 70% at about 7000 cycles when using 100%-25% scenario.

On December 10, 2017 at 1:52am
tOM_Trottier wrote:

Many devices do not show how charged they are - headphones, speakers, flashlights, and more.

One strategy with them is to use an in-line meter that shows the current used. These are readily available for USB on ebay & elsewhere. Once you have the meter, you can watch it to see the maximum charge reached when recharging from empty & then charge to the level you want. You can time this & then use a timer to tell you when to shut it off. This works if you always completely discharge the device or battery.

Another strategy, with a device, is to watch the current flow. Devices are smart enough to cut down the current as it reaches full, by monitoring the voltage or temperature. So if you see the current steady for a while, then start to drop, you can stop charging the moment you see the drop in current. My guess is that this happens when approaching 80% full, a reasonable tradeoff between battery life and battery longevity.

On December 11, 2017 at 12:37pm
robert wrote:

Id be grateful to anyone that could provide a viable solution.

I need to “balance” 12v 110Ah LiFeMgPO4   “lithium iron magnesium phosphate” batteries.

There are 2,544 in total / 48 packs of 53 in series.
Each battery has 4 cells approx 3.5v
Un-terminating them is an unreasonable option. 

If there is a good method to charge/ balance in bulk, while in series id sure like to know.
this has been an epic tedious undertaking.

so far we’ve been charging the whole pack until one of any cell in any module reaches 3.8v.  Then using truck chargers topping off the low modules.  After that discharge the entire pack, charge again and repeat until they get tighter.

There has to be a better way.


On December 28, 2017 at 12:54pm

Kudos to Vortex.  My thoughts exactly.

You can believe me, I am a chemist.

On December 29, 2017 at 11:42pm
boopathiraja m wrote:

I read about this website it will very useful for basic understanding about batteries
i will suggest you to read this site very carefully ....thanks for all other comments

On January 24, 2018 at 9:16pm
Dcharte (mofo ) wrote:

I have booked marked the page for future reference , that voltage information is invaluable understanding of battery life and how are care plays a role in it. an .Ive been honing the charge / discharge skills these last few days in prep for this weeks test rides with a new ebike build and its combined 25AH of batteries.
I want to add for those who use their laptops plugged in predominately you can install a app to set the charge to charge to 60% capacity (or what ever you choose) as it can/will extend the battery life by years. I myself have been using the lenovo battery saver app on a lenovo notebook since new.. I expect to get 20 years out them as they have 25 cycles on them now after 2 years..
My adice to all li ion users is to charge to 60 to 80% and top up to 90-95appy charging

On February 22, 2018 at 5:16am
tuinx518 wrote:

Now apply all this on Tesla battery, which is also lithium…...so imaging how fast the car is charging and discharging compare to a phone, no one gonna charge the car to only 75% anyway and charging a tesla at around 90kw will cause the battery temperature at around 40C, which is basically at the temperature of a phone working on full time benchmark running…...base on these…....the tesla battery will probably only have 50% of battery after 3 years…depend how often you charge it.

On March 14, 2018 at 1:16pm
Paul McGuire wrote:

Regarding the comments on teslas - they’re holding up fairly well.






On March 21, 2018 at 9:31pm
Peter wrote:

Hi, I would like to start by thanking the author(s) for gathering all these helpful data and informing the public.

I have, however, noticed a huge discrepancy between the number of discharge cycles presented in Table 2 and Figure 6 that I hope someone can provide more insight. Table 2 presents that an 80% DoD, which I interpret as charging a battery to 100% and discharging it to 20%, will cause the maximum battery capacity to drop to 70% after ~400 discharge cycles. However, in Figure 6, the dynamic stress test indicates that, by charging a battery to 100% and then discharging it to 25% (black line), the battery will retain 79% of its maximum capacity even after 4,000 cycles. In other words, Figure 6 presents that a 75% DoD will results in 21% loss in maximum battery capacity after ~4,000 discharge cycles, whereas Table 2 presents that an 80% DoD will results in 30% loss in maximum battery capacity after only ~400 discharge cycles (10 times fewer cycles compared to Figure 2!). Which one is correct?

As someone who is prepared to replace my electronics in 3 to 5 years, I am expecting my battery to undergo between 2,190 (3 years) to 3,650 (5 years) discharge cycles with an average of 2 charges per day. According to Figure 6, if I charge my battery to 100% and discharge it to 25% (75% DoD) every cycle, after 2,190 cycles, my maximum battery capacity will be at 85% and after 3,650 cycles, my maximum battery capacity will be at ~80%. I find this level of degradation acceptable and will not make any changes to how I charge my battery. However, according to Table 2, an 80% DoD (charging to 100% and discharging to 20%) will decrease the maximum battery capacity to 70% after only 400 cycles (roughly 7 months) and will warrant a change in my battery-charging behavior. Again, I am curious to know which of these two is correct.

Note that both Table 2 and Figure 6 does not consider battery degradation over time and for the purpose of this discussion, let’s not consider the effect of ageing on the battery. I am aware that Li-battery starts to degrade as soon as it leaves the manufacturing line. However, if the response to my question is simply, “Li-battery degrades naturally, so after 2 years you are expected to get a new one”, then there is no point to this discussion. Why bother making changes to your battery-charging behaviour if natural degradation is more detrimental. 

On March 22, 2018 at 1:50pm
Paul McGuire wrote:

At the above poster (Peter)—- a difference of 30% and 20% is not a massive difference when you’re considering lithium ion batteries. That’s in the same general ballpark. Every battery is going to act a little bit different.

Just remember that when you say you expect an average of 2 charges per day, you aren’t talking charge cycle, right? A charge cycle is a complete 100% to 0% drain (this is 1 cycle). Charging from 100% to 50% and back to 100% - doing this twice is 1 charge cycle even though I charged the phone twice. So doing 2 charge cycles a day is extremely rare unless you’re a super heavy cellphone user.

My wife uses her phone a lot and only averages 360 cycles on her iPhone 6s+ after 1.7 years. I an a more moderate usage and I only use about 220 after 1.7 years (I had a 6s+ as well).

You are very correct - most people will get a new phone at or around 2-3 years. Most users will not have consumed enough cycles to really make an effect. My wife’s iPhone lost about 3% design capacity after 360+ cycles. My phone stayed the same (design capacity). You’re absolutely correct, most people will not keep their devices or phones long enough. Those that do, however, can benefit by the information above.

Batteries are incredibly variable - some will hold designed capacity after many cycles, some aren’t so lucky. On average, if you do a 40-80% charge, your battery will keep its design capacity over a much longer period of time than someone who does 0-100% or keeps their phone at 100%.

I think your expecting to use 2,190 - 3,650 cycles is incredibly high. My wife is a heavy user of her phone and she’d be lucky to hit 400 after 2 years.

On March 23, 2018 at 3:48am
Chris wrote:

Thanks for this valuable article. Over the years, this information has proven to be accurate.

For the first 2 years, I used to keep my laptop plugged in all the time with 100% charge state. Unsurprisingly, the battery capacity had degraded by about 25% over that time. After reading this article, I started storing it at 40% and charging it to 80% at most ( while seldom charging to 100% just to calibrate).
Seven years after the purchase, my laptop can still get at least 2-3 hours of moderate usage, while colleagues with 2014 or newer models need to carry their chargers with them.

Another example is with two LG android phones, which I bought in late 2014. One of them (mine) was charged using the 40-80 method, while the other one was used normally.
Over 3.5 years later, my phone has retained about 85% of it’s battery capacity, while the other one is roughly at half or less. The problem is that battery replacements available for sale are as old as the one currently being used, and they have also degraded over time. That perfectly functioning phone will need to be replaced for this very reason. So, take care of your batteries, better do a 40-80 charge once a day (i use an app to limit the charging) instead of 10-100 charge every two days. And charge to 100% when you know you are going to need it!

On March 27, 2018 at 6:05pm
Peter wrote:

Hi Paul. Thank you for your response. The discrepancy that I am referring to, however, is not in regards to the maximum battery capacity. It is in regards to the number of discharge cycles presented in Table 2 and Figure 6. Table 2 states that a certain level of degradation will occur after ~400 cycles, whereas Figure 6 presents a lesser level of degradation after exceeding ~4,000 cycles. That’s a 10 times difference in the number of cycles! (and the huge discrepancy that I am referring to). I hope someone can provide more insight.

For ease of reference, I will quote my previous post:
“Figure 6 presents that a 75% DoD will results in 21% loss in maximum battery capacity after ~4,000 discharge cycles, whereas Table 2 presents that an 80% DoD will results in 30% loss in maximum battery capacity after only ~400 discharge cycles (10 times fewer cycles compared to Figure 2!). Which one is correct?”

On March 29, 2018 at 9:49pm
elijah smith wrote:

You’re absolutely correct, most people will not keep their devices or phones long enough. Those that do, however, can benefit from the information above.

On April 6, 2018 at 6:40am
Dorian Diaconu wrote:

Can someone give me some feedback related to BATTERY LIFE in terms of wired vs wireless charging (fast charging disabled)?

I already know that fast charging CAN reduce battery life. Do we have any info on wireless charging? Since it’s an inductive charging, some part of it’s energy it’s released as heat (not used for charging) and I think it SHOULD affect the battery.

The wireless charger I bought is a Wireless Qi Fast Charge Standing Samsung EP-N5100 with fans incorporated to reduce the heating. (Yeah, I use it on a compatible Samsung smartphone)

I made the mistake to have the fast charge active for some time (didn’t know it was active by default), but I only charge it from 40 to 80 so I hope no less damage has been done. Since I plan to keep the phone for a while (I doubt I’ll switch in 2 years), I want to try and be careful with the battery.

On April 13, 2018 at 3:28am
John Donegan wrote:

Thanks for a great site. I have been trying to estimate lion battery capacity SOC from voltages. I know its inacurrate at best - BUT on this page; http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
you indicate 3.8v approximates to 60% charge(table 2).
But on this current page(table 4) you indicate 3.8v is around 35-40% charge. Can you offer more info on this?
Thanks John

On May 4, 2018 at 7:02pm
Mike wrote:

Great info - for the tech oriented folks. Thanks. Really.

But how about a bullet point explanation for those of us who don’t want to read 5000 words and just want the basic idea of what is best for our smart phone?
For instance how about a bullet point explanation of the following:

*Best to let it get to X% charge before recharging
*Best to charge it to Y%
*Is it ok to leave it charging all night?
*Is it okay to remove it from charging at any time?
*Is it okay to use it while charging?
*How bad is it if it runs down to 0 charge?
*How much does it reduce the life of the battery if I pay no attention to any of these best practices and just charge it when I want and remove it from charging when I want?

On May 7, 2018 at 6:58pm
tOM_Trottier wrote:

*Best to let it get to X% charge before recharging,
—0% if single 4.2v battery 10% if greater voltage
*Best to charge it to Y%
—60% best.
*Is it ok to leave it charging all night?
*Is it okay to remove it from charging at any time?
*Is it okay to use it while charging?

On May 10, 2018 at 11:17am
Don Gilleis wrote:

If I am eyeballing Figure 6, I get the following numbers.  I am looking at the total amount of energy (in full cycles) I get before I hit 90% battery capacity:

75%-65% = 0.1 x 9000 = 900 full-cycles
75%-45% = 0.3 x 5000 = 1500 full-cycles
75%-25% = 0.5 x 3000 = 1500 full-cycles
85%-25% = 0.6 x 2000 = 1200 full-cycles

So I would conclude that 75%-25% is the best recharging schedule, since it gets you 1500 full-cycles worth of power before the battery degrades to 90%.

On May 29, 2018 at 3:27pm
Jan van der Zanden wrote:

Table 2: Cycle life as a function of
depth of discharge.*  A partial discharge reduces stress and prolongs battery life, so does a partial charge. Elevated temperature and high currents also affect cycle life.

Note: 100% DoD is a full cycle; 10% is very brief. Cycling in mid-state-of-charge would have best longevity.

100% DoD ~300 / 600
80% DoD ~400 / 900
60% DoD ~600 / 1,500
40% DoD ~1,500 / 3,000
20% DoD ~1,500 / 9,000 IS THIS NOT AN ERROR? SHOULD BE 4.500 / 9.000???
10% DoD ~10,000 / 15,000

On May 29, 2018 at 4:07pm
Don Gillies wrote:

20% DoD ~1,500 / 9,000 IS THIS NOT AN ERROR? SHOULD BE 4.500 / 9.000???

I am guessing that the ‘1500 cycles’ should have been > 3750 cycles and < 4500 cycles, giving 750-900 full-cycles of power from a battery that is cycled at 20% Depth of Discharge (DoD).

On June 10, 2018 at 10:37am
Sam wrote:

Is it ok to buy an aftermarket device to lower charge Voltage on a laptop?

I’m trying to extend a battery life, but can’t work on a slow and dim PC. I don’t do games, but run diagnostics and/or math related calculations, sometimes charts/graphs. If I were to slow performance there is a lag in response.


On July 6, 2018 at 4:22am
viral lad wrote:

what is the weight of 1 cell in NMC based lithium ion battery

On July 18, 2018 at 11:59am
Yang wrote:

I have a question , i recently changed my battery but searched the battery discharged cycles and it show 500 and a battery health of 93% , but it is a new battery , is that normal ?

On July 22, 2018 at 5:49pm
Jezzaaaa wrote:

Errata in the text relating to figure 7:

“If this were true, then a Li-ion battery cycled within 85%–25% SoC would fade to 74% capacity after 14,000 cycles. If this battery were charged to 85% ...”

Changing the charge level from 85% to 85%?

The first “85%” should be “70%”, to be consistent with the graphs.

On July 25, 2018 at 9:41am
Jesse wrote:

Does this information apply to a 3.85 (nominal) li-po (OnePlus 6)? What I mean, does going past 4.2 on it while charging have the same effect as going past 4.2 on a 3.6/3.7 li-ion?

On July 25, 2018 at 10:19am
Jeremy wrote:


That is normal, it is a new battery so it will have brand new set of cycles and 100% health. The cycle count is only an estimate from charging 0-100% and not that accurate. Also depends on the device.


Yes the information still applies, but voltage capacity is different. For a 3.85v battery,  4.4v is at 100%. Doing the same for a 3.6/3.7v will drastically reduce cycle life. Reducing Depth-of-Discharge and Charge Voltage still benefits the 3.85v battery.

Battery University goes into depth here: http://batteryuniversity.com/learn/article/confusion_with_voltages

On July 27, 2018 at 7:28am
Vicente wrote:

To charge the battery exactly 80% and download it up to 40% as advised in the article I recommend this Battery Limiter program, it is really useful, it allows you to configure those percentages


On July 30, 2018 at 9:47pm
tOM_Trottier wrote:

More discussion at

On August 22, 2018 at 4:33am
Mobile sentrix wrote:

if you’re really want to maintain your cell phone battery’s life, you should be charged your cell phone around 80 percent in one go.

On October 2, 2018 at 10:51pm
Francesc wrote:

Gracias por tan exhaustiva información, me ha servido para ampliar mis escasos conocimientos sobre baterías de Litio

On October 7, 2018 at 9:58pm
Keerthikrutha Seetharaman wrote:

Hi I want to use an ultimate lithium battery in a camera trap for 30-days continuously. How long would it last?

On October 18, 2018 at 12:42pm
Jim wrote:

As far as I can tell, the study cited for Figure 6 indicates that they use a constant charge rate of 1C for recharging in the study, but most Li-Ion chargers use a tapered rate and avoid 1C near 100% SoC.  Doesn’t this mean that the curves ending in a 100% SoC are unrealistically inflating the degradation of the batteries?

Also, this page and graph are cited a lot in the Electric Vehicle forums, but again the graph is based on ambient temperature cycling (the study indicates that the legend only lists the room temperature, not the cell temperature).  Many of the newer EVs are coming with active battery temperature management to fight the negative effects from the heat generated from charging (something the Leaf models that had issues in warmer climates lacked in the first iterations), so again, does the graph need a footnote indicating that it may not apply to EVs with active cooling?

On November 3, 2018 at 4:57am
Sam wrote:

If I buy a lithium ion “new battery”(no named brand) that has a date stamped on it from 2016 should I use it in my Samsung cell phone?
I bought it on Amazon.

On November 5, 2018 at 9:48am
Mike wrote:

The articles here are great but getting answers on these discussions is even better. I just wanted to say thanks to all who contribute!

On November 9, 2018 at 1:24pm
Jason wrote:

Hey guys, just wondering in terms of preserving battery lifespan, is it better to keep a lithium-ion device at 100% (using it while plugged in) or cycling it at 50%?

The reason I ask is because there is a device called a Nintendo Switch, which is a video game console that can be plugged to a TV via a dock or taken on the go. The dock also doubles as a charger. I understand keeping it between 80%-40% is probably ideal but for this kind of device it isn’t really doable without large disruptions to the experience.

I like to hook it up the TV which means it’s usually at 100% for long periods of time but I can start switching it between docked and handheld mode (to discharge to 50%, which is as much micromanagement as I’m willing to do) if that’s ultimately much healthier for the battery lifespan.

Thanks a lot!

On November 11, 2018 at 9:26pm
Mike B. wrote:

As most of the posts here are in reference to smaller batteries and smaller voltages, I’m not sure as anyone can help out, but here goes…..
I bought a 58v battery powered lawn mower on 12th May this year and have charged the battery 6 times up until now ( 12th November ) but now it will not charge at all. There is zero charge showing in the recharge window.
I have contacted the supplier of the mower and I’m told there is no warranty on consumables i.e. the battery.
Surely this $158.00 battery is only fit for the tip? Can anyone suggest anything I can do to bring it back to life?  Thanks.

On November 14, 2018 at 2:56am
Akshara Malhotra wrote:

Great, thanks for sharing information about how mobile battery can be kept healthy. You have really listed nice points to take care of the mobile battery life. From my side, I would recommend not to use animated wallpapers which might eat not just the battery but also the processor speed.

I would also suggest not to drain the battery to 0%. Everyone should apply charger when battery get down to 5 or 10%.

Anyways, very nice article. Couple of points which I was not aware of are mentioned in your post. Keep sharing and good luck.

On November 15, 2018 at 4:12am
mendip wrote:

in respond to Vortex :

i think you wrong in calculating ‘cycle and use’...
a cycle is from 0 to 100%, 10 to 110%, 20 to 120%... (100% capacity, not only from 0..)
(i.e charge the battery 10*10% is 1 cycle. (times*capacity percentage)
so all the charging method here giving the same amount of charge to use, but with diffrence in life expentancy.

in respones to Hoon :

i have galaxy s7 edge in use also…
i have 63% capacity from a ‘full charge’ lol (~2250 mAh from 3600 mAh)
i didnt followed any advice (=didnt know..). charged to top, and drained to 0% lol
and in hot climate. i have it for 2 yrs and 2 month now.

On December 4, 2018 at 7:21pm
Cassim Rahuman wrote:

For a battery of full capacity 40kWhr, if total number of (lifetime) Charge cycles obtainable with a 75% – 50% charging regime is 4,000 and total number of (lifetime) Charge cycles obtainable with a 75% – 25% charging regime is 1,800
The 75% - 50% regime gives a total energy for use during its lifetime [0.25 x 40 x 4,000 = 40,000 kWhr] compared to the 75% - 25% regime which gives an energy for use during its lifetime of [0.5 x 40 x 1,800 = 36,000 kWhr].

Thus, the comparison should be between 40,000 kWhr & 36,000 kWhr and not between 4,000 cycles & 1,800 cycles.

The actual comparison can be made to reflect this if ‘weighted’ lifetime cycles are used where: actual life cycle number is multiplied by the fraction of full (100%) charge of the charge regime used. In the preceding case, ‘weighted’ lifetime cycle for the 75% - 50% regime would be 0.25 x 4,000 = 1,000 cycles & for the regime of 75% - 25% the ‘weighted’ lifetime cycle would be 0.5 x 1,800 = 900 cycles.

Thus 1,000 compares with 900 and reflects the actual performance difference of 10% that is applicable. Comparing 4,000 cycles with 1,800 cycles in not very meaningful as the energies stored per cycle vastly differ.

On December 6, 2018 at 12:41am
Cassim Rahuman wrote:

await response

On December 7, 2018 at 7:20am
Michael White wrote:

Cassim makes a great point about kilowatt hours but let us talk practically speaking.

If you charged to 100% and down to 25% average roughly 600 cycles per year (that’s more than 1.5 per day) - you’d only reduce your battery capacity 5% in THREE YEARS and that is absolutely a worthwhile tradeoff to having 3 years with 15-20% less battery capacity with you! If you can get one battery replacement after 1-2 years, your phone should last 5 years charging to 100% and a much superior experience while you’re using the phone.

On December 10, 2018 at 7:47pm
Finn wrote:

I liked it

On December 11, 2018 at 9:58am
Cassim Rahuman wrote:

Michael - I think the validity of your observation will also be graphically supported if the graphs were based on the ‘weighted’ cycle lifespan that I proposed. I am hoping that by and by, the weighted cycle lifespan will displace the presently used numerical cycle lifespan.