Charging Lithium-ion
Charging and discharging batteries is a chemical reaction, but Li-ion is claimed as an exception. Here, battery scientists talk about energies flowing in and out as part of ion movement between anode and cathode. This claim has merits, but if the scientists were totally right then the battery would live forever, and this is wishful thinking. The experts blame capacity fade on ions getting trapped. For simplicity, we consider aging a corrosion that affects all battery systems.
The Li‑ion charger is a voltage-limiting device that is similar to the lead acid system. The difference lies in a higher voltage per cell, tighter voltage tolerance and the absence of trickle or float charge at full charge. While lead acid offers some flexibility in terms of voltage cut‑off, manufacturers of Li‑ion cells are very strict on the correct setting because Li-ion cannot accept overcharge. The so-called miracle charger that promises to prolong battery life and methods that pump extra capacity into the cell do not exist here. Li-ion is a “clean” system and only takes what it can absorb. Anything extra causes stress.
Most cells charge to 4.20V/cell with a tolerance of +/–50mV/cell. Higher voltages could increase the capacity, but the resulting cell oxidation would reduce service life. More important is the safety concern if charging beyond 4.20V/cell. Figure 1 shows the voltage and current signature as lithium-ion passes through the stages for constant current and topping charge.
Figure 1: Charge stages of lithium-ion. Li-ion is fully charged when the current drops to a predetermined level or levels out at the end of Stage 2. In lieu of trickle charge, some chargers apply a topping charge when the voltage drops to 4.05V/cell (Stage 4).
Courtesy of Cadex
The charge rate of a typical consumer Li-ion battery is between 0.5 and 1C in Stage 1, and the charge time is about three hours. Manufacturers recommend charging the 18650 cell at 0.8C or less. Charge efficiency is 97 to 99 percent and the cell remains cool during charge. Some Li-ion packs may experience a temperature rise of about 5ºC (9ºF) when reaching full charge. This could be due to the protection circuit and/or elevated internal resistance. Full charge occurs when the battery reaches the voltage threshold and the current drops to three percent of the rated current. A battery is also considered fully charged if the current levels off and cannot go down further. Elevated self-discharge might be the cause of this condition.
Increasing the charge current does not hasten the full-charge state by much. Although the battery reaches the voltage peak quicker with a fast charge, the saturation charge will take longer accordingly. The amount of charge current applied simply alters the time required for each stage; Stage 1 will be shorter but the saturation Stage 2 will take longer. A high current charge will, however, quickly fill the battery to about 70 percent.
Li-ion does not need to be fully charged, as is the case with lead acid, nor is it desirable to do so. In fact, it is better not to fully charge, because high voltages stresses the battery. Choosing a lower voltage threshold, or eliminating the saturation charge altogether, prolongs battery life but this reduces the runtime. Since the consumer market promotes maximum runtime, these chargers go for maximum capacity rather than extended service life.
Some lower-cost consumer chargers may use the simplified “charge-and-run” method that charges a lithium-ion battery in one hour or less without going to the Stage 2 saturation charge. “Ready” appears when the battery reaches the voltage threshold at Stage 1. Since the state-of-charge (SoC) at this point is only about 85 percent, the user may complain of short runtime, not knowing that the charger is to blame. Many warranty batteries are being replaced for this reason, and this phenomenon is especially common in the cellular industry.
Avoiding full charge has benefits, and some manufacturers set the charge threshold lower on purpose to prolong battery life. Table 2 illustrates the estimated capacities when charged to different voltage thresholds with and without saturation charge.
|
Charge V/cell |
Capacity at |
Charge time |
Capacity with full saturation |
|
3.80 3.90 4.00 4.10 4.20 |
60% 70% 75% 80% 85% |
120 min 135 min 150 min 165 min 180 min |
65% 76% 82% 87% 100% |
Table 2: Typical charge characteristics of lithium-ion. Adding full saturation at the set voltage boosts the capacity by about 10 percent but adds stress due to high voltage.
When the battery is first put on charge, the voltage shoots up quickly. This behavior can be compared to lifting a heavy weight with an elastic band. The lifting arm moves up quickly but the weight lags behind. The voltage of the charging battery will only catch up when the battery is almost fully charged (see Figure 3. This charge characteristic is typical of all batteries.
|
|
Figure 3: Capacity as a function of charge voltage on a lithium-ion battery The capacity trails the charge voltage, like lifting a heavy weight with an elastic band. Courtesy of Cadex
|
Relying on the closed circuit voltage (CCV) to read the available capacity during charge is impractical. The open circuit voltage (OCT) can, however, be used to predict state-of-charge after the battery has rested for a few hours. The rest period calms the agitated battery to regain equilibrium. Similar to all batteries, temperature affects the OCV. Read "How to Measure State-of-Charge".
Li-ion cannot absorb overcharge, and when fully charged the charge current must be cut off. A continuous trickle charge would cause plating of metallic lithium, and this could compromise safety. To minimize stress, keep the lithium-ion battery at the 4.20V/cell peak voltage as short a time as possible.
Once the charge is terminated, the battery voltage begins to drop, and this eases the voltage stress. Over time, the open-circuit voltage will settle to between 3.60 and 3.90V/cell. Note that a Li-ion battery that received a fully saturated charge will keep the higher voltage longer than one that was fast-charged and terminated at the voltage threshold without a saturation charge.
If a lithium-ion battery must be left in the charger for operational readiness, some chargers apply a brief topping charge to compensate for the small self-discharge the battery and its protective circuit consume. The charger may kick in when the open-circuit voltage drops to 4.05V/cell and turn off again at a high 4.20V/cell. Chargers made for operational readiness, or standby mode, often let the battery voltage drop to 4.00V/cell and recharge to only 4.05V/cell instead of the full 4.20V/cell. This reduces voltage-related stress and prolongs battery life.
Some portable devices sit in a charge cradle in the on position. The current drawn through the device is called the parasitic load and can distort the charge cycle. Battery manufacturers advise against parasitic load because it induces mini-cycles. The battery is continuously being discharged to 4.20V/cell and then charged by the device. The stress level on the battery is especially high because the cycles occur at the 4.20V/cell threshold.
A portable device must be turned off during charge. This allows the battery to reach the set threshold voltage unhindered, and enables terminating charge on low current. A parasitic load confuses the charger by depressing the battery voltage and preventing the current in the saturation stage to drop low. A battery may be fully charged, but the prevailing conditions prompt a continued charge. This causes undue battery stress and compromises safety.
Battery professionals agree that charging lithium-ion batteries is simpler and more straightforward than nickel-based systems. Besides meeting the voltage tolerances, the charge circuits are relatively simple. Limiting voltage and observing low current in triggering “ready” is easier than analyzing complex signatures that may change with age. Charge currents with Li-ion are less critical and can vary widely. Any charge will do, including energy from a renewable resource such as a solar panel or wind turbine. Charge absorption is very high and with a low and intermittent charge, charging simply takes a little longer without negatively affecting the battery. The absence of trickle charge further helps simplify the charger.
Overcharging Lithium-ion
Lithium-ion operates safely within the designated operating voltages; however, the battery becomes unstable if inadvertently charged to a higher than specified voltage. Prolonged charging above 4.30V forms plating of metallic lithium on the anode, while the cathode material becomes an oxidizing agent, loses stability and produces carbon dioxide (CO2). The cell pressure rises, and if charging is allowed to continue the current interrupt device (CID) responsible for cell safety disconnects the current at 1,380kPa (200psi).
Should the pressure rise further, a safety membrane bursts open at 3,450kPa (500psi) and the cell might eventually vent with flame. The thermal runaway moves lower when the battery is fully charged; for Li-cobalt this threshold is between 130–150C°C (266–302°F), nickel-manganese-cobalt (NMC) is 170–180°C (338–356°F), and manganese is 250°C (482°F). Li-phosphate enjoys similar and better temperature stabilities than manganese.
Lithium-ion is not the only battery that is a safety hazard if overcharged. Lead- and nickel-based batteries are also known to melt down and cause fire if improperly handled. Nickel-based batteries have also been recalled for safety concerns. Properly designed charging equipment is paramount for all battery systems.
Over-discharging Lithium-ion
Li-ion should never be discharged too low, and there are several safeguards to prevent this from happening. The equipment cuts off when the battery discharges to about 3.0V/cell, stopping the current flow. If the discharge continues to about 2.70V/cell or lower, the battery’s protection circuit puts the battery into a sleep mode. This renders the pack unserviceable and a recharge with most chargers is not possible. To prevent a battery from falling asleep, apply a partial charge before a long storage period.
Battery manufacturers ship batteries with a 40 percent charge. The low charge state reduces aging-related stress while allowing some self-discharge during storage. To minimize the current flow for the protection circuit before the battery is sold, advanced Li-ion packs feature a sleep mode that disables the protection circuit until activated by a brief charge or discharge. Once engaged, the battery remains operational and the on state can no longer be switched back to the standby mode.
Do not recharge lithium-ion if a cell has stayed at or below 1.5V for more than a week. Copper shunts may have formed inside the cells that can lead to a partial or total electrical short. If recharged, the cells might become unstable, causing excessive heat or showing other anomalies. Li-ion packs that have been under stress are more sensitive to mechanical abuse, such as vibration, dropping and exposure to heat.
Charging Lithium-ion Polymer
Charging Li‑ion polymer, also referred as Li-polymer, is very similar to a regular lithium-ion battery and no changes in algorithm are necessary. Most users won’t even know if their battery is Li‑ion or Li‑polymer. The word “polymer” has been used as promotional hype and does not reflect special attributes other than to know that the battery is built in a different way to a standard Li-ion.
Most polymer batteries are based on a hybrid architecture that is a cross between Li-ion and Li-polymer. There are many variations within the polymer family, and the true dry polymer battery for the consumer market is still years away. Also know as the “plastic battery,” this system was first announced in early 2000 but was never able to attain the conductivity needed for most applications at ambient temperatures. Read more about the Lithium-polymer battery and the Pouch Cell.
Simple Guidelines for Charging Lithium-based Batteries
-
A portable device should be turned off while charging. This allows the battery to reach the threshold voltage unhindered and reflects the correct saturation current responsible to terminate the charge. A parasitic load confuses the charger.
-
Charge at a moderate temperature. Do not charge below freezing.
-
Lithium-ion does not need to be fully charged; a partial charge is better.
-
Chargers use different methods for “ready” indication. The light signal may not always indicate a full charge.
-
Discontinue using charger and/or battery if the battery gets excessively warm.
-
Before prolonged storage, apply some charge to bring the pack to about half charge.
-
Over-discharged batteries can be “boosted” to life again. Discard pack if the voltage does not rise to a normal level within a minute while on boost.
Comments
Very usefull information here, good thing I fond this page first before designing a charger for my custom-made battery pack.
P.S. You’re alwais talking about a 4,2V like they are the the standardwhat about 3,6V cells?
Facinating stuff, although I doubt I will ever have the ambition to put it use.
Grosser,
3.6 is the nominal delivery voltage of a Li-ion cell, while 4.2 is the max charging voltage. They are the same battery. It’s the same situation with other battery chemistries, e.g. for a 12V lead-acid battery, you’d be charging to ~14V
My Li-ion battery is used in a Canon 50D DSLR camera; The charger blinks to indicate the level of charge. The indications are 1-blink series, 2-blink series, 3-blink series, and steady-on to indicate full charge. Often I leave the battery in the charger and go to bed if the LED is at the 2-blink state. When I wake up 4 to 5 hours later, the LED may have been steady-on for 4 hours. I have two questions. (1)What harm am I doing to my battery by following this practice and (2)Is the battery fully-charged if I remove it from the charger as soon as the steady-on state is reached?
I need to do the following test:
1 Question;
Have my charge Battery is Full. How time (day) can battery disconnect?
and
2 Questions
What time need battery recharge for has charge Full ?.
PD: My power Supply is 3,7 volt
what is the work of that circuit inside a lithium ion battery?
Thak You, unanswer.
The Batery is connected circuit 3,6 volt constant (regulable according to load) and this support a circuit for memory and a processor primary.
Thanks again.
Eduardo
Does it benefit a lithium-ion or lithium-ion-polymer battery to periodically discharge it “fully” (ie, down to the above mentioned 2.7V-3.0V range)?
I have read several OEM’s offering differing strategies for optimizing battery life.
Thank you for your time and efforts—I very much appreciate the above instruction.
What about chargin vehicle batteries? This will be a big issue if they ever become popular.
How would the graph look if it were for vehicles?
Can lithium polymer cell phone batteries be over charged if left on charge to long and if left on to long will it diminish battery life.
I’ve inherited an electric vehicle powered by two 38V/90Ah lithium-ion batteries. The voltage of both packs read around 9V only! The engine management system reports that a mere 21 hours of operation have been logged thus far. Are these battery packs truly dead-DEAD or is it possible to resuscitate them again in one way or another? Please advise. Cheers.
I am looking for alternative charges for my HTC Desire. The standard charger that came with it is 5V and 1000mah. Since the charger uses a standard micro USB tip, there are a lot of available chargers out there with different Amp rating. Is it advisable to get a low Amp rating such as 500mah, higher amp such as 1200mah or stick with the same 1000amp? Is slow charging better than fast charging?
My HTC EVO cellphone shuts down when the discharge voltage reaches 3.6 volts. Isn’t this reducing the use-capacity of this battery quite a bit?
I’ve read somewhere that a charger with a lower voltage rating (e.g., 3.2v) cannot recharge a lithium battery with a higher voltage rating (e.g., 3.7v). Is this true? Something to do with electron transfer, I think… If this is true, I’m confused. How can a 3.7v charger charge a 3.2v battery to 4.2v if, when they reach the same voltage level (3.7v), it can no longer push said electrons around the battery?
Another question, if it’s alright: USB chargers have a rating of 5v. Would this cause problems with lithium batteries since as stated above, charging above 4.3v causes plating of the metallic lithium on the anode?
Thanks and more power!
Jovy
how can you trickle charge a 12v batt @ 2v trickle and get a full charge . the battery is like a tank, with a limitation of it"s rateing ie. 4.2v or 12v ,is the limit that the battery will hold, forceing anything over that will start to burn the core of the battery in one way or the other ... do i win a cuppie doll??
@ Flynn Siy, the ratings of the charger mentioned misguiding me as the standard charger rating should be in terms of volts and Amps/milli amps(mA) but not in mAh. If your concern is about a charger(i’ll interpret it to 500mA/12mA ) then go for 1200mA. There’s no harm in it. If you go for 500mA, it’ll charge but it become hot due to it’s inability to supply the rating current(say 1000mA).This inturn drop the voltage. If your concern is about a battery(a standard battery rating will be in volts and mAh), go for either one but in reduction in back up, in case if you chose 500mAh.Hope it cleared your doubt.
Cheers,
Vass.
How Li-ion battery gets recharged? Why at elevated temperature the battery life gets shortened? Does frequent charging pratice without being fully discharged affect bttery life span? Plz help..
“My HTC EVO cellphone shuts down when the discharge voltage reaches 3.6 volts. Isn’t this reducing the use-capacity of this battery quite a bit?”
—This is to protect the battery: further discharge could destabilize it and next charging could be risky (you may have heard of exploding LiIon batteries…).
Despite more strict cutoff liit, LiIons can store more energy than previous technologies iin same cell size, so you should not consider this a design fault/drawback, just a essential characteristic feature of this different chemistry.
—
Shiwakoti, you will find answers to your questions on the articles at this site: esp. in “Is lithium-ion the ideal battery?”. Shortly said, elevated temperature speeds up battery aging (it’s a chemical reaction a bit like how iron rusts faster in humid climate compared to dry circumstances) and it’s MUCH better to recharge often than let LiIons drain fully.
Thanks for the answer..
GOED UITGELEGDE TEKST
Excellent material. I now know how to properly charge a 3.7 volt Li-Ion pack I took out of a Blackberry phone that is since defunct. Tnx.
So in this article is states that Lithium Ion batterys are charged upto 4.2v, where each cell can handle 4.2v +/- .05v. So the upperbound here is 4.25v to 4.15v. So, if you have a charger that is push the cells to 4.21v or 4.22v, then it is theoretically fine.
“A continuous trickle charge above 4.05V/cell would causes plating of metallic lithium that could lead to instabilities and compromise safety. “
Here though you say that raising the cell above just over 4v may cause plating. So by specification, charging lithium ion cells to 4.2v will cause plaiting?
i observe (via an application) that my smartphone is reaching till 4191 volts during re-charging the battery by usb cable.
can we say that battery is died a bit? cos it is not reaching 4.2 or above.
i know that it is very small numbers but curious about it.
and also what shold i do max charge the battery?
The article mentions how dangerous it is to attempt charging cells that have been @<1.5v for just a few days. Well, that has not been in agreement with my experience. I occasionally salvage discarded Li-ion laptop battery packs…disassembling them to harvest the 18650’s for personal r/c and flashlight use. I commonly pull cells that are totally flat: 0v, sometimes even with polarity reversed by a few millivolts. In addition, some of the battery packs I ripped into were prehistoric by lithium chemistry standards (10 years+). More often than not all cells would recharge to their FULL original rated capacity and perform as new. I always test each cell individually with my iMAX B6 charger, manually putting them through at least a couple 500mA to 1Amp discharge/charge cycles. I have *never* experienced any safety nor reliability issues to date.
I would also like to brag of having had success restoring substantial capacity to the occasional cells that truly were worn. I will never share my method_IT’S MINE !_do not ask. ...Additionally, that procedure IS potentially dangerous and requires mandatory attentive supervision.
I suppose I’ve been laughing all the way to the battery bank. I know, horrible joke!
What i have believed is keeping my laptop plugged in all the time at my desk and using the battery power in case of power failure or so. We have very frequent power cut-downs for brief spans. I also use BatteryCare to notify me of recalibration.
AFAIK Li-ion does not have memory effect and they have PMS circuit built-in so don’t overcharge.
A vendor of notebooks recently opposed and recommended to cycle discharges and recharges regularly to keep the battery healthy and prolong its life.
What’s the bottom line?
What i have believed is keeping my laptop plugged in all the time at my desk and using the battery power in case of power failure or so does no harm to my battery pack. We have very frequent power cut-downs for brief spans. I also use BatteryCare to notify me of recalibration.
AFAIK Li-ion does not have memory effect and they have PMS circuit built-in so don’t overcharge.
A vendor of notebooks recently opposed and recommended to cycle discharges and recharges regularly to keep the battery healthy and prolong its life.
What’s the bottom line?
I just bought a Bushnell GPS and it has a Li-Ion battery pack. The instructions said to charge the li-Ion batteries for four hours. But upon plugging the charger to the batteries the green light immediatley came on, indicating a fully charged pack. But the pack is not charged at all. The unit will not turn on with these batteries. So my question is; Why is the charger displaying a Green LED when in fact the batteries need charged. And is there something I can do to make it start charging because the charger doesn’t charge when displaying a green light.
Mike, I have been thinking of doing some EV experiments using some old laptop cells. They flat and packaged in plastic bags. What do you think about using this type of cell?
i got a new phone. and it says b4 i do anything, i need to charge it for a total of 12 hours for it 2 run right, and battery life, blah blah…. but my question is, simple and plain… do i need to really charge it for the full 12 hours? can i just charge it until it says 100% charged, which would be in a hour or two…. i’ve google’d my question, and i’ve read mixed answers… “yes you should” “no, you don’t have to, because its a lithium-ion” whoop this, and whoop that…..
i would jus like a simpe answer.. yes or no… and why?
Thanx yous
hi, i would like to know about the first charge lithium baattery ?
should i live chargim for 24h ?
thanks
Thanks so much. All the new gadgets (laptops, cell phones, portable TV-DVD kits, etc) don’t specify anything about the Battery “rules’ like they used to in the day of NiCad and NiMH. This article is very VERY informative and helpful. NOW, i better start unplugging my laptop… thought i was ‘saving’ the battery by keeping it plugged in while using. I guess i probably shouldn’t be charging my cell phone overnight for 8+hours either?
Great article, very informative. Can anyone help me with the following:
I have a Gibson Robot Guitar, the manufacturer states that it runs on:
(2 x 14500) 2.4v 2100mAh lithium rechargeable battery system.
These batteries have been run down for some time now and do charge, the manufacturer cannot replace them.
How can the voltage be 2.4v when the minimum cell voltage for lithium batteries is 3.6v What should I buy to replace these?
dear sir
i have a vemar jiano helmet with integrated bluetooth. by mitake i’ve charged it with a nicd charger so the batterie was distroyed and does not work anynore.
when i opened the divice i found a li ion battery 3.7v 800ma reference stilo b001011.
please i would like to know if there is a way to fix it or recharge it again
if not can i use a a 1cell lypo battery to replace it
You made some respectable points there. I looked on the internet for the issue and located most individuals will associate with together with your website.
So should I do my best to keep the battery at 40%? For instance I’ve been letting it hover around 40% by continually plugging and unplugging it. Is that a good idea?
IS IT POSSIBLE TO CHARGE A PACK OF SIX 1.2 LI-ION BATTERIES WITH THE ORIGANAL
CHARGER THAT WAS BUILT FOR CHARGING A PACK OF 6 1.2 BATTERIES
THE BATTERY PACK IS FOR A SCREW/DRIVER DRILL
I WOULD BE VERY GRATFULL FOR ANY HELP
EDWARD.
This article has been updated as of March 10, 2011 with all new information. Enjoy!
Nice work Isidor. Thank you.
Mar. 13, 2011
To : Robert
I am looking for a 24V bicycle dynamo.
Is it available ? Please help me if you possible.
Thank you.
kunkiw77@gmail.com
What i have believed is keeping my laptop plugged in all the time at my desk and using the battery power in case of power failure or so does no harm to my battery pack. We have very frequent power cut-downs for brief spans. I also use BatteryCare to notify me of recalibration.
AFAIK Li-ion does not have memory effect and they have PMS circuit built-in so don’t overcharge.
A vendor of notebooks recently opposed and recommended to cycle discharges and recharges regularly to keep the battery healthy and prolong its life.
What’s the bottom line?
Hi,
I have a simple ARM7 gadget and I want to run it on the Li-ion batteries which are available cheap. Is there any singly IC chip solution which could
a. Charge the battery when connected to mains/ USB
b. Indicate the content of charge to ARM7 (ARM7 can query and stop working if there is no charge left to function properly)
With best regards,
Subbu.
I have an elerctric bike with a 600w - 36v motor.
It uses a li-Ion battery.
Usually each time I use the bike its charge drops about 20% of the total battery charge.
WHAT IS BETTER DO DO:
1 - CHARGE THE BATTERY EACH TIME I USE THE BYKE (battery with 80% of charge)
2 - CHARGE THE BATTERY ONLY WHEN IT REACHS 60% OR 40% OF CHARGE
I would like to make a battery pack charger for 4 Li ion cells. Would it be detrimental to limiting the charger voltage to ..say..15 volts. This would be within the voltage limit for each cell if the distribution is even.. However, if a cell is shorted there wpuld be excessove voltage on the other cells in the series string. Would it be better to design the charger for 4.0 volt peak and charger the 4 cells in parallel?
Excellent article. Thanks.
to
kunkiw77@gmail.com
most dynamo give an AC ourput,
you could try to use a transformer to UP the voltaje
Michel Kun
How to remove the charging time li ion battery ? Is there any alternatives way ?
Informative article but the voltage drop in stage 3 would indicate a cell in poor condition. A good cell will drop less.
My observation on using batteries after being badly discharged:
About 5 years ago I purchased 40 nearly unused 18X65 cells in 2 cell packs with protect circuit. They ware all discharged to cell voltages of .01 to 1.1 v. I charged them for 10 hrs at c/100 (Now I think c/10 would be OK) and 10% failed shorted. The remainder charged well at c/10 to 4.2 V. Letting them set 24 hrs, I looked at the voltage drop and classified the lowest 10% as weak. Then making a 12 V pack from the remainder I had 2 unused cells classified as good. I have had no failures though they have not been treated roughly. I checked the voltage on the unused cells today. Those marked weak are above 3.7V and those marked good are above 3.9V.
Hey guys,
Just want to get this clear in my head. When charging the battery up, I get a controller to put constant current into the battery, then when I sense 4.2v/cell, I get the controller to go into constant voltage (of 4.2) mode and the current will die away naturally till fully saturated?
Cheers
MD
Michael, NO, the manufacturer recommends that when 4.2 v is reached, let the current fall to c/10 then turn it OFF. I think a constant voltage charge can be done but it takes a long time and must be done at a lower voltage. When the above charging is done and the battery sits 12 hours, measuring the voltage and setting the float voltage to that is safe and gives maximum capacity but that voltage goes down as the battery ages. A float voltage of 4.1 is reasonable to get best capacity but as the battery gets old, that MIGHT make it age faster. Using the 2 step process of charging at 4.2 v till the current reaches your chosen value (>= c/10) then dropping the voltage to a float value would be the way to quickly charge then float it.
Hey Wayne,
Thanks for the reply. So is the current we are measuring the battery current or the current from the charger.
MD
Hey sorry Wayne I think I’m becoming confused. Do you apply a constant voltage in stage 2 until the current reaches c/10 OR manually bring the current down to c/10 with a controller?
Cheers
MD
Why can the the battery pack in a Tesla automobile be charged considerably faster when the charging unit is 240v vs. 110-120v?
I iam a complete novice, and am wondering if higher voltage input decreases charging time.
Thanks for any insight you can offer.
Michael,
Not all Li cells are the same so the numbers I use below are for the most common ones, some can be charged much faster.
The algorithm is to check the voltage and if it is < ~3 charge at no more than c/10. If it is >3v charge with limits of c/2 and 4.2 volts until a current of c/10 is reached, then stop . As mentioned in the article a voltage < 4.2 increases battery cycle life, shelf life, and reduces discharge capacity for the current cycle. A charge rate < the maximum rated is easyer on the battery. I think charging with variable current is satisfactory if current is limited as specified on the data sheet and the voltage is limited to 4.1 volts. This is good for float charging and charging from a variable source.
Erick
There is no inherent reason. It was designed that way to account for commonly available power connections, commonly limited to 20A (use at < 80% of limit) at 120v but commonly available at 50 A or more at 240V.
I am unable to decide which is better - to select a Li-ion battery pack with multiple cells or single cell. For example, how to choose between a 3.7V, 1500mAhr and a 7.4V, 1500mAhr ?
i am
CONFUSED
got some PSP battery from HK
I measuered 4.8 volts on end of charge
4.5 volts after 3 days standing
THEN WHY IS 4.2VOLTS MAXIMUM in all litterature
is this value ABSOLETE???
the battery seem to work OK.
thanks in advance for any help or informations
Amazing website… well written .. very very useful
Great Job
Great article!!
what happens if you let a li-ion battery connected indefinitely at 4.0V?
So I am building a solar powered usb charger for an android device. I know that my available curent and voltage at the time of charging will vary depending on the panel so in addition to overcharging I am wondering if capacitors to buffer power is necessary. I have also considered a 3000mAh battery with an integrated charging circuit would be better. That would offer me more consistent ouput to the device and be a contingency for a lack of or poor lighting. Any ideas would help. Kudos on the page, very informative.
i brought a new battery sony lithium-ion NP-BG1, WHEN I BUY IT , IT WAS IN SLEEPING MOOD, i plugged the charger for charging, but it did not charge, so please suggest me what should i do…
Great article. Well written and very informative - just what i was looking for. Thanks and keep up the excellent work.
Great informative article. For a “12volt” pack, I would charge 3 or for Li Ion cells with a constant current source and limit the volts per cell by connecting a 4.0 volt zener diode across each cell. This would allow parallel charging but also protect the cells from ‘over voltage’. Does this make sense? The total charging current would be limited by the charging source circuitry and shut off after all cells reached 4.0 volts.
Li-Ion (Poli)bat
Min V=2.7V ? 3.0V
Midle=3.6-3.7 (Li-Ion Li-Pol)
end of Charging 4.2V Sel Kill 4.3V+
Kill it Fast 4.35 +
what about voltajes for
LiFePo4
thanks
Higher charge voltages boost capacity but lower cycle life and compromise safety.
Li-ion battery to 4.20V/cell. This allows maximum runtime
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.
V4.20 end of Charging 100 MA (Panasonic ?)
4.20 400+ capacity 80%
4.25 400 bat capacity 25%
4.3v 250 Cycles 50%
4.35v 190 Cycles 25%
My laptop has a battery rated at 10.8V, 85Wh, 8800mAh. The charger outputs 18.5V, 3.5A, and 65W. I have an old charger that is rated 19V, 3.4A and 65W. Would it be safe to use the old one?
Hi,
i want to charge a 7.5 v 400 mAh li-ion battery from a small solar panel (6V - 1W).
I would connect the solar panel and the battery with a voltage regulator or with a MPP circuit that fixed the output voltage adjusting the output current of the solar panel catching always the maximum power from it. In this way it’s difficult charge the battery using the constant current/constant voltage method because i can’t control the charge current and i haven’t enough power from the solar panel.
In conclusion the charging of the battery is done with a small and variable charge current. Is that a problem? Can i charge the battery always in slow charge fase and with a variable current? If yes, which are the drawbacks?
Thank you. regards!
Andrea
Excellent!!! Love the detail…!
why lithium can perform fast charging between range 20% to 80% SOC only?
Why after 80% SOC charging became slow?
My son and I have the same cell phone. His battery charge lasts 1 days and mine only one day. I came here to find out why. We thought it was because I was charging too frequently. I now believe its because I always left the phone on while charging whereas he turns his off. Thanks for the info!
oops! 5 days vs 1 day…
Great article, thanks for the writeup.
One question: Would charging a Lithium battery with a higher amperage charger (but same voltage) cause any damage to the battery? I’m looking at +300mA to +500mA increase.
Hello,
I have a cell phone with a lithium battery. Is it true that it is better to let the battery almost completely die before charging? I was told the battery has a memory. Someone also told me that was only true with NiCd.
nteresting article but it seems to be contradicted by information here:
http://www.electricbikehub.co.nz/?p=919
which states that Lithium Polymer can be left on charge between bike rides without detriment.
Which is correct please?
Hello, my protected 18650 cell faced a high current draw and the protection circuit went to sleep mode.. the cell now measures just 0V!.. Do anyone know how can I wake up such a cell?.. Your help will highly be appreciated.. thanks..
Hey, very good article.
1. Where it says “The battery is continuously being discharged to 4.20V/cell and then charged by the device” I think you mean “The battery is continuously being CHARGED to 4.20V/cell and then DISCHARGED by the device”
2.¿Its ok to charge to a safe level, say 80% (thus preventing minicycles and overcharging the battery) with the device on?
3.¿How can you tell if the charger and/or the device has taken measures to prevent minicycles,overcharges,etc..?
Very vey thaks. Usefull informations.
Hi everyone
I just wanna ask some of the experts here, whether it’s is OK for me to charge a lithium-ion battery (let’s say a 2Ah), with a constant current of 50mA and a float voltage of 4.1V?
Despite the slow charging rate (longer time of course), would this work and would there be any other problems?
So, let me just make sure i have this straight.
I am building a charger and here is my what i am doing:
1. When battery is first connected charge at c/5 (as recommended by battery manu)
2. While in this stage continually read the voltage i am charging at to produce this current. (Question here: is this correct? or do i need to shut off my charge voltage and wait about a second for voltage to settle to battery voltage then read?)
3. When the voltage i am CHARGING at hits 4.2 at this current i charge at a constant 4.2 volts from this point on until the current drops below c/100 (as recommended by battery manu), or the total charge time exceeds 10hrs (as recommended by manu).
4. When my current hits this low i simply cut out the charge. Question - should i float the charge line at some value after charge?
So, basically i just want to make sure my method is basically correct. Am i reading the correct voltage to determine when to stop fast charging and when i am fully charged should i just leave the charge line at high impedence or should i float it to some value?
again, huge amount of misleading info here doesn’t mean everything is wrong. The author actually read these comments, but doesn’t reply to them, as he has deleted my previous post regarding the reliability of the info presented in this page.
To JC22:
2, you don’t need to cut off your charging voltage to see the stage of your battery.
3, no true; you are risking over-charging the battery at c/100 and more than 10 hours.
4, you shouldn’t float charge a lithium battery
5, When you are fully charged which shouldn’t be, you are not a battery. you should just stop risking over-charging yourself.
To Amkul:
You can charge with low current, but you shouldn’t float charge it. float charge means keep charging without stop; you have cut the charging current when this current is lower than 50ma; or you risk over-charge your battery.
to Javier:
1, yes, you are right.
2, It is totally fine.
3, there is no way you can tell; other than taking apart the charger and reconstruct the circuitry yourself.
To determan:
If your battery doesn’t charge up in the charger, the circuit probably is damaged.
To Craig:
You can charge lithium any time; memory effect is for the very old nicd only.
To Nolan:
You can, but never charge with more than 1C; and that is if you have a 1800mah battery; you shouldn’t charge it with 1.8A (1800ma);
Joseph:
It is not true; If you use your cell more than your son; then obviously it will last shorter.
I am afraid that you can’t charge a 7.5V battery with only 6v solar panel. You need 8.35V, so you need a dc to dc booster with regulation,but charging the battery with variable current is fine.
To skip:
It depends on the charger; but if the output voltage of those 2 charges is more than 12.3 Volt, both are not safe to charge your 10.8v battery.
To Ryan:
Your battery is your buffer. no cap is needed.
To zz:
You will over-charge the battery. It will expose eventually.
zz wrote:
what happens if you let a li-ion battery connected indefinitely at 4.0V?
TO MICHEL KUN:
As I know, PSP uses 5 volts power source. This either means that there is an internal circuit in the battery that boost the voltage from 4.2 to 5+ volts; or the battery is not made out of lithium. Either case, your battery should be safe to use.
To Jayk:
Depends on your needed voltage and power; higher voltage means higher voltage and higher power stored.
Jayk wrote:
I am unable to decide which is better - to select a Li-ion battery pack with multiple cells or single cell. For example, how to choose between a 3.7V, 1500mAhr and a 7.4V, 1500mAhr ?
An enterpreneor claiming, new technology can charge Lithium Ion Battery can charge eight times more life ????
Comments Please ???
you mean explode… interesting, I figured current must be 0 once voltages equalise, so no overcharge
To zz:
we are not in a perfect world. The charging voltage maybe more than 4.20, which means there is current going into the battery, and explode it eventually. On the other hand, due to the age of the cell itself, it may not has its maximun capacity voltage of 4.2. Normally when you charge the cell to 4.2 volt, it will drop a little bit. If a 4.2 volt charging current is kept charging that battery, eventually heats and pressure will built up and explode the battery.
To Garry D,
Yes. technically, it is possible.
if i have a 3.7volts li-ion battery what is the output specification of my battery charger?
Which new company has come up with this 8 times more life For Lithium Ion Rechargable Battery.
you misunderstood the question
I’m really not clear…..
I have a Dell laptop which I only use at home. Should I leave it plugged in? should I only plug it in when it needs to be charged? I have noticed that it has been getting very hot and at times the charger seems hot. We have been leaving it plugged in most days, then unplug it at night.
Thank you for clarifying for me!
Most likely 4.2V, but it is also limited in current.
jin, the charging voltage is 4V, no more
TO ray:
Output of your charger should be 4.2V at 200mA-1000mA
@ray
4.2V at 100ma-1000ma
4.2V at 100mA-1000mA
To ray :
4.2V at 100mA-1000mA
Most likely 4.2V, but it is also limited in current.
jin, you misunderstood my question
Thank you very much. It helps me a lot. Very good material.
Most likely 4.2V, but it is also limited in current.
jin, you misunderstood my question
Probably 4.2V, but it is also limited in current.
jin, you misunderstood my question
hi evry1..
for my application of voltage(72V) , i connected 23 li-ion cells in series. each cell have 90 AH of capacity.now each and every cells have voltage have 3.3V.
so my question is that how would i know that what is the current SoC of the cells.
and second question is while charging it when current starts decreasing, at till what point of current i should wait for the complete charge.
please any1 help me in finding above.
Is slow charging (via USB-Port) better then fast charging (wall plug)?
I’ve not heard of any entrepreneur but there is a team of scientist at the DOE who are on the verge of expanding capacity 8x…
http://www.labspaces.net/113675/Better_lithium_ion_batteries_are_on_the_way
Great article, helped a lot. Do you have by chance a similar article about proper discharging a Li-ion cell? I’m especially interested in detecting the lower threshold where discharging should be stopped. A diagram similar to the one here would help a lot. Would you detect voltage? If yes, what is the low threshold? Would you detect internal resistance? (If the latter, how?)
Probably 4.2V, and also limited in current. Better measure.
jin, you’ve misunderstood
I bought a Li-ion battery/pack with charger (in the form of an adapter). Unfortunately, I mixed it up with another adapter, so I used a 12V-1.5a charger instead of the 12.6V-0.350A I should have used. I noticed that the battery only outputs 9V max now, with charge dropping rapidly. Did I permanently damage it?
hello sir
i want to charge a 1.5v cells used in dc pumps
by switching it to main supply
probably 4.2V, but it is also limited in current.
you misunderstood the question jin
Wow, jin is really smart? Maybe she should be the one writing the articles!
I have a Toshiba C655-S5056 laptop with li-ion battery. Specs say 6 cells, 48Wh. The AC adapter is 65W (19V, 3.42 A). The laptop is dead and I want to manually charge the battery to determine if the problem is the dc jack.
Can I remove the battery and connect it directly to the adapter for an hour to partially charge the battery? I know it’s not safe to leave it connected. I just want to charge it enough to power up the laptop for a few minutes before I go to the trouble of replacing the dc jack.
Thank you.
erb2000@gmail.com
I want to use 3 AAA size of these in series in a headphone amplifier. There is no chemical recombination applicable as in NiCd or NiMH, they are more like capacitors in that way. So it seems they can’t be charged in series. It would quickly ruin the lowest capacity one. Is this correct? Can you suggest some really simple but safe way of charging them, one at a time if necessary, using only a regulated variable power supply with constant current limiting, a good quality analogue multimeter (Avometer) and maybe a resistor? I don’t need anywhere near maximum capacity. Are they easily damaged if the strongest ones reverses the weakest and therefore should be protected with diodes maybe? Can you suggest any good information about using them in series? Sorry, I should be paying you a consultancy fee for this lot! Thanks.
I have an electric car with Lithium ion batteries. I have a data logging voltmeter across the 170 volt series pack. When I hooked up the meter after stopping the car it took 2 hours for the meter to stop jumping all over the place in its voltage readings. After that it became super stable. What is this agitation you are speaking about?
When the switch is off and the battery pack is opencircuit no electrons can flow. However ion can still flow to equilibrium conditions. Will this look like a slow rise in cell voltage?
Dear sir,
I am using the 3.7V/3700mA li-ion battery for my electronic instrument. this battery gets dry after some time. Then i have to remove battery from ckt and directly connect it to the adaptor(4.1v/1500mA). but that is not possible to do all the time.
Please suggest the solution.
Interesting article. I have just started using li ion, and the charger I have charges to a voltage of 4.10 volts. I have a lot of experience with li po and the charger uses 4.20 volts as the cutoff for that variety. According to the article, I guess that’s a good idea. I just found it a little unusual. Thanks for the info.
How can I reset my Li ion 14.4 Hilti battery, peeps say it can be done I only get one single green light and no charge need help on this please, Thank you
I am working with an off grid dc motor that requires 48v and 250 ah and i plan for 24 hrs running. I plan to connect to lithium ion battery bank to store energy for later usage. Let say batteries are in series of 4 it means about 12 v. So how many battery shall i have and what is the charger size.? Anybody advise? Tq.
yes i have the same question as ray. my charger specifications are output 5v, 700mA. My battery is 3.7v 1500 mAh li-ion battery… if i want to avoid entering stage 2(saturation charge) region, at what % should i stop charging at? is it 85% which is cut off capacity at 4.2 V/cell, or perhaps somewhere near 60% which is cut off capacity at 3.7 V/cell?
thanks for any help 
Is it better to charge the Li Pp/Li On faster or slower as I have a variable current charger
I’m having a discussion with someone on a forum. It’s going like this:
I’ve got 4 7.4v batteries.
2x1000mah + 2x1200mah
I’m parallel charging them at 8.4v, no balancing at this point.
The charger hits 8.4v and cuts off when the current draw drops below a certain point.
My understanding is that each battery will saturate at 8.4v line and no further current will enter a saturated battery.
He’s of the opinion that I’m probably screwing up my batteries.
Anyone have some info?
THanks
Thanks for this wonderful info! really helps
Dear,
what is the equation to find the instant value of charging or discharging of a Li-ion battery ?
I have a Lipo battery (11.1V 3 cell / 1100maH) which I have a 12V AC adpator to DC charger with a amp regulator from 0-4 Amps. Firstly can I charge the battery higher than 1100maH or does it have to be lower…secondly it has been on for hours at 1000maH but still it doesn’t charge it? What is wrong? Thank you
Regarding Figure 1: Current is listed as being in Amps (A), but is this a typo? Should it be C, where C is the number of amps that would discharge a cell in one hour? For example, I have a 3500mAh cell for my Droid phone, so would not C equal 3.5A? Is 3.5A then the amount I would want to use to initially charge my cell until it’s voltage reaches 4.2V, at which point the cell itself will determine how much current it draws?
The article later states “The charge rate of a typical consumer Li-ion battery is between 0.5 and 1C in Stage 1”. I would LOVE to have that, but can’t find ANY! So is this another typo in the opposite direction? Did they mean between 0.5 and 1A instead of C? Because that’s the range most charges seem to max out at.
I have one charger that outputs 300ma (which is 0.085C), a few 500ma, and 800ma, and one that does a full 1A, but even that one is only 0.3C. These take TOO LONG to charge my cells.
To Ryan who posted on May 3, 2011, how’s your project going? That is my need also. I will be backpacking for a few weeks with my Droid. I have four 3500mAh cells, and a 10W solar charger. If 1C for my cells is 3.5A, at 4.2V that would be 14.7W, so my solar panels will never be able to provide more than the battery should be able to handle. Right??? The problem is that I can never count on ideal sunlight, so I pretty much want to pump everything the panel can generate straight into the cell. However, all of my adapters that output 4.2V have severe current restrictions as I mentioned above, so I don’t think I can get a full charge from the sunlight available. Any advice???
I have a Samsung Galaxy s and please tell me if I use my phone while charging the battery is damaging in any way. When charging the phone is using charger electricity or battery electricity ? (the phone has a Li-ion 1500mAh 3,7 V and original charger output 700mA 5V )
P.S. Thank you ?
No, that is not bad, and sometimes is necessary.
If your draw is less than the charger is putting out, then power from the cord is going both to the phone and the battery. But if you are drawing more than the cord can supply, then the phone is drawing from both the cord and the battery.
In extreme cases, the charger may not be able to keep up with the draw from the phone, for example if you are providing a wifi hotspot, recording a HD video with the light on, and geotracking your position simultaneously, all while trying to sling mad birds at swine, your battery may continue to discharge even while plugged in, but that’s the only way to make it last as long as possible.
The battery will charge fastest when phone is turned off because all of the power from the cord can be directed to charging the battery instead of also running the phone, but that is not practical for most people.
Same goes for laptops.
Another clarification that I think should be understood: The thing that plugs into the wall at one end and your phone at the other end is not really the charger. The charger is inside the phone. The wall cord provides 5v to the phone, and the charger inside the phone provides 4.2v to the battery. Although there are (and I have one) actual chargers, where you take the battery out of the phone and set it in the charger, which plugs into the wall.
The difference is that a charger is (or should be) smart enough to first supply a conditioning charge, then a constant current, and finally a constant voltage, and preferably a shutoff. The charger in the phone does this. The cord from the wall to the phone is not smart, it just provides a constant 5v.
Thank you Vince ! very usefull ; another question :
I have in my android phone a program that tells me much about battery status and tells me that when fully charged is about 4.2 V, above in this article I saw that charging is recommended under the maximum voltage to extend battery life (which you think that is the maximum voltage that the battery should be charged for above recommendation?) the program shows also battery temperature (which you think is the maximum temperature would have to be?)
If i’m watching a movie , or play some games or surf web is better for battery to keep phone connected or not to charger ?
P.S. Thank you!
From what I’ve learned from these websites, here are the answers: First to your last question:
What is really best is to keep your battery around half charged, 40%, 3.7v. So if you’re fully charged, it’s best to unplug it regardless of what you’re doing, and if it drops to less than those numbers, plug it back in.
Two things are bad for the battery: First, to let it completely discharge, which is almost impossible in normal operation because the phone itself will turn off long before the battery is empty in order to prevent such a thing. The battery itself also most likely contains a similar monitoring circuit, although at a lower threshold. Second bad thing is to keep it at a high voltage like 4.2v.
Think of it as you breathing. In your normal daily routine, you don’t empty your lungs as far as they will go, nor take as deep a breath as you can. You work best somewhere in the middle. But if you know you’re going diving underwater, then you’ll want to first fill up with as much oxygen as you can hold, so you can stay under water for as long as possible. But to live your daily routine that way would be very stressful on your body.
Now in regards to your first question, and with the understanding of the above, no 4.2v is not recommended for extending battery life. 4.2v is a rather arbitrary value that’s been agreed on by the industry as providing a reasonable balance between long term longevity and short term runtime. If you don’t need to survive all day without access to electricity, you’d be better to stop at maybe 4.0v or even 3.9v. However, the tradeoff is that you’ll get fewer hours without the charger.
People tend to be less concerned with how many years their battery will last, than how many hours it will last, and will often throw out the whole phone in two years anyway.
As for temperature, I personally feel that the heat is generated more by the phone than by the battery. Put a healthy battery in a phone and use it hard for a few hours, and the phone itself will raise the temp of the battery, simply because the battery is inside the phone.
Finally, as for what the phone app reports, it’s mostly guesswork (except for temp and voltage). But the voltage is not a reliable indicator of remaining charge, because the voltage can stay close to 3.7v most of the time. The percentage left is guessed by trying to track and count how many amps the phone is drawing from time to time, sampling it maybe every few seconds, and comparing that to the expected capacity of a new healthy stock battery.
On my phone with an extended battery, the phone will drop to 5%, and then continue to run fine for another day. So while voltage isn’t real accurate, it’s what I watch and I know that when it falls around 3.4v, it’s approaching empty. Then again, if you’ve been using it heavy and let it sit, the voltage will come back up a bit.
I have a need to overcharge a Lithium battery until failure. However, the charger we have limits the current as the voltage is reached. What kind of a charger will allow me to overcharge a battery?
@David, my understanding is that it’s the battery itself, not the charger, that limits the current once it’s getting full. With a typical 4.2v charger, once the cell is saturated at 4.2v, it simply won’t draw anything more. Zero current.
In order to force more in, you’ll need to increase the voltage. Maybe you can find a 4.3v charger? Or just hotwire it to 3 fresh alkalines in series, giving you 4.5v. I don’t want to be standing anywhere near you when you do this. When you say “failure”, I assume you mean loud noise, smoke and flames, and lithium shrapnel killing everything around you. You also could hook it to your car battery. Any DC source of significant voltage should cause the catastrophic failure you seek.
Legal disclaimer: Don’t actually do any of this. In fact, forget that I even wrote it. These are bad ideas, and nobody but you will be responsible for the consequences.
http://www.youtube.com/watch?v=vS2hGoJVmlA
Thanks Vince ! You are almost correct on the failure scenario (they do burst into flames, but no real loud noise or shrapnel). This testing will be performed in a stainless steel tank for the purpose of analyzing the gases that are made through this type of failure. We have previously induced battery failure through external heating, case crush and internal shorting. The next method we wanted to cover is the possibility of a failure in the charging mechanism that might allow an overcharging situation.
Regards, Dave
@David, ah, glad to know you know what you’re doing. I never know who I’m responding to, so I often lean toward dramatic caution. 
But you your goals, a conceivable failure might result from a USB charger somehow shorting the 5v input straight to the intended 4.2v output, resulting in what you’re looking for. The USB out from wall chargers sometimes can supply over an amp.
yeah men
-)
Just bought a Li Ion receiver battery pack and the istructions say i should plug the balacing plug in the charger, as well. The pack only comes with one plug, the one the plugs into the receiver. So how is it possible to balance the cells?
Hello!
I have a question that I have not fully satisfied by reading this website.
Using a laptop in a continuosly way, is it better to fully charge the battery and then to fully discharge it or is it better to have the charger always connected?
@Juan, the question to your question is “is it better for what?” Better for the longest long-term life of the battery? Better for the longest runtime the next time you need it?
In any case, the worst thing to do is to use it if you don’t need to, to run the laptop off the battery when there is AC available. 1.) Batteries will last for a few hundred charging cycles. Fully discharging them and recharging uses those cycles. 2.) If you suddenly need to hit the road, you will only have a partial charge.
The best thing to do for the longest runtime when you need it is to keep it fully charged. However, this will reduce the long-term life expectancy of the battery.
The best thing to do for the long-term life of the battery would be to charge it to 50%, take it out of the laptop and don’t use it, and just run the laptop on AC. Recheck it every few months to keep the charge around 50%. If you are planning a trip, then put it in and top it off before you go. But this all seems a little inconvenient.
So the bottom line is that you’ll have to choose a balance between long-term, short-term, and convenience, based on your own personal goals.
Well Vince, thank you for your reply.
My question was….better for longest long-term life of the battery.
I mean if you have to work with battery on because you need to move in the office you cannot put and take off the battery every time.
I read about someone that think it is better to charge the battery and then take off the charger to let the battery discharge and then re-connect the charger and more over!
Instead some other one assure that is better to leave the charger always connected to also get the battery always balanced…
I don’t know…you reply is quite clear and I know the better way is to not use the battery but I’d like to know your reply in this scenario.
Thank you.
@Juan, yes, in your case I recommend plugging it in whenever convenient. There is no advantage to unplugging it for the purpose of intentionally discharging the battery. That only hurts it.
Remember that the power cord is not the charger. The charger is inside the computer, and it will stop charging the battery when the battery is full, even when the power cord is still connected. At that point the computer is running AC, not the battery, and it will take a long time before the battery drops low enough on it’s own for the charger kick back in again. But when that happens it will quickly top off the battery again, and you probably will never notice it switching. So the battery will always be kept very close to full, so it’s ready when you do need to use it.
@Vince: thanks for your answer. I know the charger circuit is in the laptop…It’s just the name we usually give to it.
Your answer let me get a question too: If the charger stops to charge the battery and the computer will run AC for a while, why in the article is mentioned that the battery can reduce its life because to some chemical effects.
What do you say about this aspect?
Thank you very much
@Juan, I’m not sure I understand your question correctly, but if I do, this is my answer:
Keeping the battery at full capacity does reduce it’s life because of the internal chemical stresses it suffers at high capacity. But this is how most chargers are designed. This is the tradeoff, the downside to being prepared for maximum run-time.
Batteries are most comfortable at half capacity. This is why I say it would be best to charge to 50% and then remove the battery if you know you won’t be needing it for a long time, because the chargers are not designed to stop and leave it at 50%.
Well the question was a little different but that’s ok about your answer.
Thank you very much.
Bye bye.
How does this apply to an iPhone? If I want to maximize the life of the battery should I charge approximately to 75% then let it drop to 25% and then keep repeating?
And why does apple recommend draining your battery completely at least once a month? http://www.apple.com/batteries/iphone.html
@Sapan, I’m sure the info on this site would apply to all Lithium-Ion cells, including those used by an iphone.
Yes, your 75% to 25% sounds good, trying to keep it around half way.
Their recommendation to completely drain it monthly makes no sense for getting the most out of the battery, but it may be useful for calibrating the phone.
Over their lifetime, the maximum useable capacity slowly decreases. By periodically topping it off and letting it run down to where it turns itself off, your phone can learn what the new capacity is, and thereby giving you a more accurate percentage remaining indicator.
Phones have no way of knowing or measuring how much charge is really left, because the only measurable value of the battery is voltage, and as you can see from the charts at the top of this page, the voltage can stay around 3.7v for a very long time and then drop to dead very suddenly. So what they try to do is keep a running total of how many milliamps were drawn over frequent small intervals. It’s kind of like a printer trying to estimate how much ink is left based on how many pages you’ve printed since installing the new cartridge. Not real accurate, but it’s the best it can do.
So by topping it off and then running it to completely dead while the phone counts how much it’s using every second, it can get a pretty good idea what the total expected capacity should be, and use that info to calculate a percentage remaining.
Did someone now some tips for charging unused and new li-ion batteryes ?
I recently bought a new 3,7V ,1650mAh samsung battery for mai GALAXY S , I’ll wait your answer before first battery use.
Also the old battery (1500mAh) it’s in a good condition (not even 30 charge cycles)
, do you have some advices for preserving and alternative use uith the new one ?
THANK YOU !
Super post there! Comprehensive and well collated material. Thanks for sharing.