How to Prolong Lithium-based Batteries
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 shelf life, cycling and temperature affect the performance. Because batteries are used under many demanding environmental conditions, manufacturers take a conservative approach and specify a battery life between 300 and 500 discharge/charge cycles. Life cycle testing is easy to measure and is well understood by the user. Some organizations also add a date stamp of three to five years; however, this method is less reliable because it does not include the type of use.
Figure 1 illustrates the capacity drop of 11 Li-polymer batteries that have been cycled at a Cadex laboratory. The 1500mAh pouch cells were first charged to 4.20V/cell at 1C rate (1500mA) and allowed to saturate to 0.05C (75mA) as part of full charge procedure. The batteries were then discharged at 1500mA to 3.0V/cell, and the cycle was repeated.
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Figure 1: Capacity drop as part of cycling. A pool of new 1500mA Li-ionbatteries for smart phone istested on a Cadex C7400 battery analyzer. All 11 pouch packs show a starting capacity of 88–94 percent and decrease in capacity to 73–84 percent after 250 full discharge cycles (2010).
Courtesy of Cadex
Designed for a smart phone, the packs were already a few months old at time of testing and none of the batteries made it to 100 percent. It is common to see lower than specified capacities and shelf life may have contributed to this. Manufacturers tend to overrate their batteries; they know that very few customers would complain. In our test, the expected capacity loss was uniform over the 250 cycles. All sample batteries performed as expected.
Similar to a mechanical device that wears out faster with heavy use, so also does the depth of discharge (DoD) determine the cycle count. The smaller the depth of discharge, the longer the battery will last. If at all possible, avoid frequent full discharges and charge more often between uses. If full discharges cannot be avoided, try utilizing a larger battery. Partial discharge on Li-ion is fine; there is no memory and the battery does not need periodic full discharge cycles other than to calibrate the fuel gauge on a smart battery.
Table 2 compares the number of discharge/charge cycles a battery can deliver at various DoD levels before lithium-ion is worn out. We assume end of life when the battery capacity drops to 70 percent. This is an arbitrary threshold that is application based.
|
Depth of discharge |
Discharge cycles |
Table 2: Cycle life and depth of discharge A partial discharge reduces stress and prolongs battery life. Elevated temperature and high currents also affect cycle life. |
|
100% DoD 50% DoD 25% DoD 10% DoD |
500 1500 2500 4700 |
Specifying battery life by the number of discharge cycles is not complete by itself; equally if not more important are temperature conditions and charging voltages. Lithium-ion suffers stress when exposed to heat and kept at a high charge voltage.
Elevated temperature is anything that dwells above 30°C (86°F), and a high voltage is higher than 4.10V/cell. When estimating longevity, these conditions are difficult to assess because the battery state is in constant flux, and so is the temperature in which it operates. Exposing the battery to high temperature and being at full state-of-charge for an extended time can be more damaging than cycling. Manufacturers do not like to talk about these environmental conditions and release information only in confidence when so requested.
In this essay we do not depend on the manufacturer’s specifications alone but also listen to the comments of users. BatteryUniversity.com is an excellent sounding board to connect with the public and learn about reality. This approach might be unscientific, but it is genuine. When the critical mass speaks, the manufacturers listen. The voice of the multitude is in some ways stronger than laboratory tests performed in sheltered environments.
Let’s look at real-life situations and examine what stress a lithium-ion battery encounters. Most packs last three to five years, less if exposed to high heat and if kept at a full charge. Table 3 illustrates capacity loss as a function of temperature and state-of-charge. One can clearly see a performance drop of recoverable capacity caused by environmental conditions and not cycling. The worst condition is keeping a fully charged battery at elevated temperatures, which is the case when running a laptop on the power grid. Under these circumstances the battery will typically last for about two years, whether cycled or not. The pack does not die suddenly but will produce decreasing runtimes as part of aging.
|
Battery Temperature |
Permanent capacity loss when |
Permanent capacity loss when |
|
0°C 25°C 40°C 60°C |
2% loss in 1 year; 98% remaining 4% loss in 1 year; 96% remaining 15% loss in 1 year; 85% remaining 25% loss in 1 year 75%; remaining |
6% loss in 1 year; 94% remaining 20% loss in 1 year; 80% remaining 35% loss in 1 year; 65% remaining 40% loss in 3 months |
Table 3: Permanent capacity loss of lithium‑ion as a function of temperature and charge level. High charge levels and elevated temperatures hasten permanent capacity loss. Newer designs may show improved results.
Batteries are also exposed to elevated temperature when charging with wireless chargers. The energy transfer from a charging mat to the portable device is 70 to 80 percent and the remaining 20 to 30 percent is lost mostly in heat. Placing a cellular phone on the heat generating charging mat stresses the battery more than if charged on a designated charger. We keep in mind that the mat will cool down once the battery is fully charged. Read more: Charging without wires.
Equally stressful is leaving a battery in a hot car, especially if exposed to the sun. When not in use, store the battery in a cool place. For long-term storage, manufacturers recommend a 40 percent charge. This allows for some self-discharge while still retaining sufficient charge to keep the protection circuit active. Finding the ideal state-of-charge is not easy; this would require a discharge unit with an appropriate cut-off. Users should not worry too much about the state-of-charge; a cool and dry place is more important.
The voltage level to which the cells are charged also plays a role in extending longevity. For safety reasons, most lithium-ion cannot exceed 4.20V/cell. While a higher voltage would boost capacity, over-voltage shortens service life. Figure 4 demonstrates the increased capacity but shorter cycle life if Li-ion were allowed to exceed the 4.20V/cell limit. At 4.35V, the capacity would increase by 10 to 15 percent, but the cycle count would be cut in half. More critical than the extra capacity is reduced safety, which would be the results of a higher charge voltage.
|
|
Figure 4: Effects on cycle life at elevated charge voltages Higher charge voltages boost capacity but lower cycle life and compromise safety. Source: Choi et al. (2002) |
Chargers for cellular phones, laptops and digital cameras bring the Li-ion battery to 4.20V/cell. This allows maximum runtime, and the consumer wants nothing less than optimal use of the battery capacity. The industry, on the other hand, is more concerned with longevity and prefers lower voltage thresholds. Satellites and electric vehicles are examples where longevity is important.
We have limited information by how much lower charge voltages prolong battery life; this depends on many conditions, as we have learned. What we do know, however, is the capacities. At a charge to 4.10V/cell, the battery holds a capacity that is about 10 percent less than going all the way to 4.20V/cell. In terms of optimal longevity, a charge voltage limit of 3.92V/cell works best but the capacity would be low. Besides selecting the best-suited voltage thresholds, it is also important that the battery does not stay in the high-voltage stage for a long time and is allowed to drop after full charge has been reached.
The voltage threshold of commercial chargers cannot be changed, and making it adjustable would have advantages, especially for laptops as a means of prolonging battery life. When running on extended AC mode, the user would select the “long life” mode and the battery would charge to only, say, 4.05V/cell. This would get a capacity of about 80 percent. Before traveling the user would apply the “full charge mode” to bring the charge to 4.20V/cell. This saturation charge would take about an hour and would fill the battery to 100 percent capacity.
Realizing the stress on the battery, some laptop and cellular phone manufacturers choose an end-of-charge voltage that is less than 4.20V/cell. A slightly larger pack compensates for the reduced runtime. Another option to extend battery life is removing the pack from the laptop when running on the power grid. The Consumer Product Safety Commissionadvises the public to do this out of concern for overheating and causing a fire. Removing the battery has the disadvantage of losing unsaved work on power failure.
Heat buildup is always a concern and running a laptop in bed or on a pillow may contribute to this by restricting airflow. Not only will heat stress electronic components, elevated temperature causes the electrodes in the battery to react with the electrolyte and this will permanently lower the capacity. Placing a ruler or other object under the laptop to increase floor clearance improves air circulation around the enclosure and keeps the unit cooler.
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.
Everyone wants to keep the battery as long as possible and use it in a way that is least stressful. This is not always feasible. Sometimes we need to run the battery in environments that are not conducive to optimal service life. As a doctor cannot predict how long a person will live based on diet and activity alone, so also does the life of a battery vary, and it can always be cut short by an unexpected failure. Batteries and humans share the same volatility.
To get a better understanding of what causes irreversible capacity loss in Li-ion batteries, several research laboratories* are performing forensic tests. Scientist dissected failed batteries to find suspected problem areas on the electrodes. Examining an unrolled 1.5-meter-long strip (5 feet) of metal tape coated with oxide reveals that the finely structured nanomaterials have coarsened. Further studies revealed that the lithium ions responsible to shuttle electric charge between the electrodes had diminished on the cathode and had permanently settled on the anode. This results in the cathode having a lower lithium concentration than a new example, a phenomenon that is irreversible. Knowing the reason for such capacity loss might enable battery manufacturers to produce future batteries with longer life spans.
Power loss through Protection Circuit
Besides common aging, a Li-ion battery can also fail because of undercharge. This occurs if a Li-ion pack is stored in a discharged condition. Self-discharge gradually lowers the voltage of the already discharged battery and the protection circuit cuts off between 2.20 and 2.90V/cell. Some chargers and battery analyzers (including those from Cadex) provide a wake-up feature, or “boost,” to re-energize and recharge these seemingly dead Li-ion batteries.
* Research is performed by the Center for Automotive Research at the Ohio State University in collaboration with Oak Ridge National Laboratory and the National Institute of Standards Technology.
Comments
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.
thanks
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
What is 1C? What is a C?
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.”
What about overcharging? What are the effects of leaving a Lithium-ion battery charging when at full capacity?
Also, is there an ideal range to charge/discharge the battery in e.g. 40%-70%, ensuring a partial discharge?
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.
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.
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.
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.
“Frequent full discharges should be avoided when possible”
and
“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?
@David:
Follow this question on SuperUser.com:
“Software to hold battery at 50% charge level”
http://superuser.com/questions/217480/software-to-hold-battery-at-50-charge-level
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?
@David
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.
This is one of the articles that I was reading about caring for your laptop batteries.
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
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%?
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
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..
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?
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.
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
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?
@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.
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).
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?
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?
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.
“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%???
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!
Thank you for this very helpful information.
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?
It depends on the state of charge when you stopped using it. If it is almost completely discharged 6 month might be too long.
You should try leaving the battery 1 - 2 days plugged in, it might recover
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.
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
I have translated this useful article into Chinese on my blog
If anyone get interest in it,you can visit
http://mescoda.com/2011/01/how-to-prolong-lithium-based-batteries/
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.
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
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.
-Ty
www.ebatts.com
wat about over charging?
do we hav problem in doping it
what does discharge mean?
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?
It’s great place to study about battery as well as other related accessories.Good luck!
Excellent info on batteries, thanks to Battery University
I also wanted to express my gratitude on the information given about lithium based batteries. Thank you!
We have updated this article as of today February 25, 2011.
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.
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
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.
thanks genesis, i will do as you said, hopefully my battery will survive another year :D
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!!!!!!
****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.****
COMPLETELY WRONG!!!
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.
Most of you are absolutely retarded, especially genesis. This article is not telling you to avoid putting your battery in an oven (or “owen” as you so aptly put), but to instead avoid using the laptop while on the power grid with the battery fully charged.
For all you derps out there (most of you, judging by your comments), this means that you should not keep the battery in the laptop while it is plugged in and you are using it. Laptops generate heat (hurr durr) and since the battery is in the laptop (again, hurr durr), it is exposed to the heat, AND is kept constantly at full charge while plugged in. So, no, genesis, one doesn’t require an oven to expose your battery to heat (derp). Laptop internals regularly get to 60-70 degrees Celsius, well above the stated ideal temperature for batteries.
And I CAN’T believe one of you actually stored a laptop battery for SIX MONTHS to GAIN battery life. What a tard. Never using a battery will zap the power quickly.
Here’s another thing. I left a laptop mostly plugged in for a year. It had VERY few discharges. Yet the battery lasted for only a 1/2 hour or so. So you tards be the judge as to whether or not keeping it plugged in with the battery installed leads to excess wear.
As for actually using the battery (when not plugged in), just use it. Avoid full discharges and don’t keep it in a hot area.
And for all you idiots wanting to magically make your depleted batteries work again: you are, as I mentioned, idiots. Everything has a lifespan. If you’ve had your battery for a while and used it often, then guess what? It’s old and used and you have to buy another one! YAY! HURR DURR!
And some derp mentioned people complaining about laptop performance: WTF are you talking about? Someone said that laptops function slower without the battery while on power, but that’s the only complaint I heard. You’re just a retard.
And someone here actually doesn’t grasp the concept of a discharge. Are you serious? Look up the word. Good Lord. Mega tards.
Anyway, thanks everybody for decreasing my hope in humanity even more than previously. The internet does that quite often. Bye, retards.
derp has a point.. and summarizes the article well
..but he came over as a an obnoxious braggart.
Great article…Thanks for sharing
ive just bought a new cordless lithium drill/driver for DIY use only have i made a costly mistake? thanks wezz
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!
“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?
Obviously, as derp left his own laptop mostly plugged in for a year, he is, by his own definition, a retard. What a jerk.
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.
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
Paul
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.
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?
Paul
Great article, thanks for writing this up.
Regarding derp’s comments, interesting but its value greatly diminished by immaturity.
@Paul
Yes that makes sense. I would update the calculations to account for that but I have already had enough fun for the day. 
Thank you for the response.
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?
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
I hope my laptop never needs servicing even more now.
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!
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.
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
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.
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.
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.
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.
@ 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.
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.
CAN SOMEONE HELP ME?
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?
thanks
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?
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.)
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.
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.
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?
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. . . . .
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.
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?
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. 
Too much information, not specific, hard to find information that is relevent.
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.)
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.
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.
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
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.
Jeff, I think it is just stated to be equivalent for practical purposes because it is close enough.
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.
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.
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.
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?
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…
Walt
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
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.
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
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.
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
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
The owners of this site deserve praise. great work and solid information.
hi
I heard the battery life reduces if we keep the charger plugged-in (charing) after the battery is 100% - is it true?
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
Hi,
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).
Peppe
Thanks to Battery University for this information.
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%).
Very Useful…
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…
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.
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.
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.
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 ?
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?
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.
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.
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 ???
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.
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.
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
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…
very helpful, thanks very much
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.
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.
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.
@Sandeep
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.
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 ?
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
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?
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.
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.
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 !!!
@ 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.
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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?
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.
don’t charge your battery untiil it is used up.
more ideas please click:
http://www.batterymag.co.uk
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.
charge my battery
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
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 !!
@BigMart
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.
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 !!
Would you agree with this supplier’s instructions?
http://www.ebay.co.uk/itm/ws/eBayISAPI.dll?ViewItem&item=290565009405&
“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.
So what are you saying Pavlo? Discharge to 50% and then charge up to ???
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.
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.