BU-808a: How to Awaken a Sleeping Li-ion

Learn what you can do to prevent a Li-ion battery to fall asleep.

Li-ion batteries contain a protection circuit that shields the battery against abuse. This important safeguard also turns the battery off and makes it unusable if over-discharged. Slipping into sleep mode can happen when storing a Li-ion pack in a discharged state for any length of time as self-discharge would gradually deplete the remaining charge. Depending on the manufacturer, the protection circuit of a Li-ion cuts off between 2.2 and 2.9V/cell. (See BU-802b: Elevated Self-discharge)

Some battery chargers and analyzers (including Cadex), feature a wake-up feature or “boost” to reactivate and recharge batteries that have fallen asleep. Without this provision, a charger renders these batteries unserviceable and the packs would be discarded. Boost applies a small charge current to activate the protection circuit and if a correct cell voltage can be reached, the charger starts a normal charge. Figure 1 illustrates the “boost” function graphically.

Sleep mode of a lithium-ion battery

Figure 1: Sleep mode of a lithium-ion battery.

Some over-discharged batteries can be “boosted” to life again. Discard the pack if the voltage does not rise to a normal level within a minute while on boost.

Do not boost lithium-based batteries back to life that have dwelled below 1.5V/cell for a week or longer. Copper shunts may have formed inside the cells that can lead to a partial or total electrical short. When recharging, such a cell might become unstable, causing excessive heat or show other anomalies. The Cadex “boost” function halts the charge if the voltage does not rise normally. 

When boosting a battery, assure correct polarity. Advanced chargers and battery analyzers will not service a battery if placed in reverse polarity. A sleeping Li-ion does not reveal the voltage, and boosting must be done with awareness. Li-ion is more delicate than other systems and a voltage applied in reverse can cause permanent damage. 

Storing lithium-ion batteries presents some uncertainty. On one end, manufacturers recommend keeping them at a state-of-charge of 40–50 percent, and on the other end there is the worry of losing them due to over-discharge. (See BU-702: How to Store Batteries) There is ample bandwidth between these criteria and if in doubt, keep the battery at a higher charge in a cool place.

Cadex examined 294 mobile phones batteries that were returned under warranty. The Cadex analyzer restored 91 percent to a capacity of 80 percent and higher; 30 percent were inactive and needed a boost, and 9 percent were non-serviceable. All restored packs were returned to service and performed flawlessly. This study shows the large number of mobile phone batteries that fail due to over-discharging and can be salvaged.

Last updated 2016-03-07

*** Please Read Regarding Comments ***

Comments are intended for "commenting," an open discussion amongst site visitors. Battery University monitors the comments and understands the importance of expressing perspectives and opinions in a shared forum. However, all communication must be done with the use of appropriate language and the avoidance of spam and discrimination.

If you have a question, require further information, have a suggestion or would like to report an error, use the "contact us" form or email us at: BatteryU@cadex.com. While we make all efforts to answer your questions accurately, we cannot guarantee results. Neither can we take responsibility for any damages or injuries that may result as a consequence of the information provided. Please accept our advice as a free public support rather than an engineering or professional service.

Or Jump To A Different Article

Basics You Should Know
The Battery and You
Batteries as Power Source

Comments (115)

On April 19, 2011 at 1:25pm
fhhuber wrote:

Note that some low voltage cutoffs are programmed for a SET voltage, others are based on RELATIVE voltage.

A set voltage cut-off would turn off power at the same voltage regardless of charge state when the battery was plugged in.

A relative voltage cut-off “detects” the battery voltage at plug-in and then the cut-off is a percentage of that voltage.

Because many hobbyist Radio Control system ESCs (Electronic Speed Controllers) use the RELATIVE voltage, it is imperative that a battery used in these applications be FULLY charged when it is plugged in.  A partially charged battery being plugged in can result in the cutoff being low enough to damage the battery.

On February 14, 2012 at 12:47pm
tytower wrote:

I had such a battery Hit it with a 40V pulse for 500 nsecs and it came good immediately

On April 3, 2012 at 7:59am
guy00 wrote:

I’ve tried to charge a battery that was not used for a year, but when i stopped using it it had a partial charge… now i measured it with a multimeter and it showed 0v (the protection kicked in). But when measuring between the negative and positive terminal AND the middle terminal (cell phone battery), it showed 1.09 and 1.04, respectively. I thought the battery is @ 2.13v, and tried to recharge it directly from the cell phone charger (red wire to the positive and black to the negative). A spark flied, but i continued to charge for another minute. Then i took a multimeter, measured, and it showed 3.2v smile. Then i continued to apply charging for another 2mins and got the battery up to 3.48v. Currently left the battery like that, it lits up a white LED very bright. I’m wondering is that battery safe for using now, i dont really need that battery, but if its working fine maybe i’ll find use for it since the cell phone i got it from is dead smile

On April 22, 2012 at 3:36am
Brian wrote:

Too involved and way off the topic.  How do I prolong lithiom ion battery life? :/

On June 25, 2012 at 10:44am
jake wrote:

What no one has said here is that Lion Batteries are prone to explode…Just see youtube.

Be very careful while resurrecting batteries always work under a perspex sheet with gloves., You can do almost any batteries..

On July 16, 2012 at 10:11pm
krist0ph3r wrote:

can i boost a cellphone battery using the regular charger, or do i need some special equipment to do so? would 5V/1A be enough?

On December 13, 2012 at 11:47am
Mad Monty wrote:

If Li ion batteries become unpredictably dangerous if left discharged too long, it would seem that no “found” batteries (e.g., old laptop unused for a “long time”) would be safe to use.  Have I got that right?  And following up, how best to dispose of them?

On January 11, 2013 at 2:37am
fred hreyer wrote:

How do you estimate when a lithium battery is at 40%?

On January 29, 2013 at 1:10pm
AbdEl-Rahman wrote:

That’s actually very great what you guys are writing , but actually needs some simplification on what should be done to boost it again on duty ,ya know.
So my request is for you guys to offer me a solution (SAFE Of course) to do to my iPhone Li-ion polymer battery ,that also doesn’t include removing it out of the phone .
I would be very grateful to have an expert opinion ,because I am done with those videos that never give a solution straight to a person,ya know .
Thank you for your time all

On April 5, 2013 at 11:32am
sam wrote:

guys can you please help me to restore my fully discharge li ion battery on my laptop,its about 5 months later after i bought it,i frequently using ac connection so the battery i’ve only used it ones a week,,but now its already fully discharge and i don’t how to awaken it..i already put it on my laptop but it;s not charging anymore,,,


On April 13, 2013 at 2:26am
Oscar Ormond wrote:

Take a technology that is very very difficult to get right then after spending hundreds of millions of dollars on research and it still not very good, knowing people want to use it simply go ahead and put it on the market. Take the money and run. Simple explenation.

On April 13, 2013 at 2:10pm
Mad Monty wrote:

So you want simple instructions on bringing a Li-ion back to life?  Here it is:  Choose either (1) to buy an expensive smart charger (like Cadex, above - no , I don’t have any stake in the company); or (2) Replace the battery.  That’s it.

Only those who can tolerate a brief explanation should read further. 

The reason not to try to fool with it yourself is that it really can go up in your face.  Literally.  Lithium-ion chemistry is not only more dangerous but also more complicated than NiH.  All the stuff you don’t want to read or try to understand is exactly the stuff in need to do to prevent a serious accident.  A smart charger figures it all out for you so you don’t get burned or blinded or destroy your laptop or whatever.  If you try to do it yourself, you have to think through all the algorithms, make complicated measurements, and administer the charge, all the while continuing to monitor and measure and make adjustments until either the battery reaches its maximum charge or you determine it is beyond hope.  (Ever look inside a laptop battery?  There is a whole slew of sensors and circuitry attached to each cell, whose primary requirement is to prevent harm and lawsuits.)

Yes, some people – many people – have been lucky when they have tried to rejuvenate batteries in simple ways.  If they played Russian roulette, five out of six would think that was pretty safe too.

Madly yours,

Mad Monty

On May 4, 2013 at 5:21pm
Parker Thornton wrote:

Any Batteries Plus or Batteries Plus Bulbs can recycle them for you. Please don’t throw them away.
They also have a Cadex and a laptop battery reconditioner and can restore batteries for you if you ask, usually for free

On May 21, 2013 at 2:57am
carribawhore wrote:

If you have an old camera li ion cell charger, like canon. You can easily bring dead batteries back to live. Without danger. Just connect the + and ~ of the charger with wires directly on the poles of the li ion akku. Then insert an empty camera battery in the charger and there you go.

On June 20, 2013 at 2:47pm
Mike wrote:

to AbdEl-Rahman: unfortunately you would have to take to battery out of your iphone, you need to jump start the li-ion battery with a high voltage at a low amperage which in turn would fry the circuits on you phone, there are tons of walkthroughs on how to remove and replace iphone batteries online, its not that difficult especially if you document where each screw goes and how you took it apart piece by piece.

MAC/Windows professional with 10+ years tech experience

On June 28, 2013 at 12:36pm
Sean M wrote:

“How do you estimate when a lithium battery is at 40%?”

As a rough example, if your battery pack normally lasts, say 10 hours under continuous use, you’ll reach 40% of usable capacity after six hours.

If all you go on is variables, you won’t know.  the simplest is to use the above method.

On July 10, 2013 at 2:52am
s.pirie wrote:

my wife has been using e cigarettes for three months now using ego t brand who give no back up for faults , these use lithium ion batteries , the fault is no operation of the atomiser although the battery voltage shows around 3.8 which is what is expected although the 3.8v is showing at the battery without pressing the operating button which you would expect this to make the atomiser work constantly with no need to press the button, this does not happen . Does anyone have any idea how i can fix this fault ? My wife is in desperation as all of her 5 batteries faulted on the same day which is very curious .

On July 20, 2013 at 2:52am
emmit wrote:

The batteries you have for the e-cig have a turn on / off sequence 5 pushes in 3 seconds or less will turn the device on (push on/ push off non latched)...and the same will turn the battery off..the battery also has a fail safe It will auto shut off if the button is depressed for more than 10 seconds (could be 7/8/9 seconds depends on battery type eg.ego

On September 24, 2013 at 12:26am
Yu Jun Gu wrote:

Just brought two efest 14500 protected batteries back to life. Thank you for this article!! They must have been in storage for a very long time, got them from a friend who didn’t want them anymore. Was having a helluva time. Charger didn’t register them. The way I woke them up was sticking them into a AA battery box I had laying around and connecting an 18650 (Positive to positive negative to negative) to the lead wires for 30 seconds or less. Freaked me out the first time around because the 14500 got real hot and I thought I had thermal runaway on my hands. But it cooled off again and when I checked the voltage it was at 3.07v. Repeated that step with the second battery just much shorter duration of charge with the 18650 this time around, like 10-15 seconds. Woke it right up. In the charger now recognized and charging as usual.

On September 25, 2013 at 3:18pm
mark wrote:

Does anyone have a working battery for a schwinn Transit bicycle i can buy?

On November 6, 2013 at 7:24am
Rodelion wrote:

Often I get frozen cells (showing 0V) to work again by putting it in a universal li-ion charger several times. Universal li-ion chargers give all kinds of pulses to the cell to figure out what kind of voltage and polarity the cell has. I think those pulses make the battery work again.

On another instance, with a Nikon EN-EL5, this didn’t work…
After a lot of effort I found out there are two hidden contacts underneath a little seal, so five in total. Through trial-and-error I found out that the hidden contact next to the ‘+’ corresponds with the positive terminal, and the one next to the ground, corresponds with the negative terminal. I think there’s a condenser between these two contacts, and I used a 6V lithium battery to charge it. When I got at about 3.7V, the battery suddenly started working again.
While doing this, both batteries became warm, but not quite hot. If a cell becomes really hot, I think you’re on dangerous ground.

On November 23, 2013 at 10:08pm
David wrote:

I have a weird issue with a protected 14500 battery. The battery shows 3.4v and will lit up a small LED (not a Cree or high output LED), but will not take input charge by the charger (charger light green like if it was not charging instead of orange) and when trying to boost it up using another 4.2v 14500 battery connecting + and - together, like mentioned above, it doesn’t seem to work at all, i.e. the defective 14500 won’t accept any input. It has about 200ma left out of ~600mh max capacity and will not power up my Cree P4 LED flashlight at all while the other 14500 battery will (even a 1.2NiMh battery doesn’t have problem powering this light).

Now I’m thinking the protection circuit might be defective and locked itself up whenever I try to input voltage/current or draw too much current out of it. Would there be anyway to save this battery by either resetting/bypassing the protection or simply physically removing the protection PCB ? It’s a brand new battery fresh from the store, and although they’re sending me a replacement one anyway, I’d hate to waste a salvageable product.

Thanks !

On December 17, 2013 at 7:31am
RKSINGH wrote:


On December 29, 2013 at 4:18pm
johny wrote:

according to what i’ve read, you can revive a dead li-ion with a low-current trickle charger. if the battery does not spring past 2.5 volts within one minute of trickle-charging, then the battery should be discarded. even if keeping on the trickle longer than one minute revives it!

is because the battery chemistry changes after it’s discharged and unused too long, making it dangerous to revive or use.

if it takes longer than one minute to revive, then the battery is dangerous, and should be discarded.

how to revive:

i don’t understand what this guy is doing:

On January 24, 2014 at 10:09am
jach wrote:

read again what mad monty wrote above. wise words. lithium chemistry is POTENT, experimenting with advice provided in a forum without understanding the basics of what your dealing with isnt recommended.and is literally russian roulette ,attempting to duplicate what worked in someone elses case , may explode in your face

On February 6, 2014 at 4:34pm
Sailor Jo wrote:

Very enlightening article. Still, I need to do some more research in order to understand the intricacies between the various types of lithium batteries.
The reading made me aware of the charger PIXO C4. I thought I found the ultimate charger until I checked the German manufacturers web site and the batteries that cannot be charged with this unit. A real eye opener, especially as it cannot charge the 18650 batteries that I have a problem with. Just too bad.

On March 4, 2014 at 9:43am
Emil wrote:

I just waked to life two 18650 batteries that came from a dead laptop battery I opened, the battery had 8 cells, four was complete dead, two was good and two had around 2V.
I used a iMax B6 charger and used NiMH charging with 0.1A current limit, charged the battery untill it shown 3.2V and then swopped over to lithium charging.
I put a iron pot over the battery lying on my concrete floor in the garage while I charged, in case the battery was blowing up or starting to burn.

On March 28, 2014 at 12:32am
e2cc_guru wrote:

I have designed a system which uses a 7.4 V, 6,6AH Li-Ion battery pack (18650) in the configuration 2S-3P. It is charged using a uC based software algorithm which is CC till 8.4V and then CV till current falls below 0.05C. I charge the battery using a 12V DC charger or a 12 V Solar Panel. Obviously there is a bick-converter in between which manages the voltage applied to the battery.

Recently I am getting field complaints that batteries which go to sleep would not revive using the software charger.

Can any one suggest what is wrong or what I should try? Please ask if you need more information.

On September 1, 2014 at 11:37pm
Paolo wrote:

Can I try to awaken a li-po battery from a Thinkpad notebook?
The Thinkpad don’t charge it.

On September 9, 2014 at 8:41am
usmc_0143 wrote:

I just got my Defeat 2500mAh IMR 18650 3.7V LI-MN batteries in the mail on Saturday (and today is Tuesday). I charged the batteries on Sunday and got my vapeing mod on Monday. I went to put the battery in and shortly after “trying” to Vale the battery got hot. I took it out and it looks like on the bottom of the battery the purple skin either peeled or got burned. I waited awhile for to cool off and the charger doesn’t even recognize there is a battery there. Any ideas what happened and if I can do something to get the battery working again?

On September 10, 2014 at 2:40am
emmit wrote:

Hi what EC mod have you tried to vape using this battery/ Most vaping mods have built in battery protection..
Is this the corrent battery for that mod? is it flat top,nipple top? some mods only accept non protcted batterise, and some with battery protection will accept protected batteris

I have many modss i mainly use a vamo with 3.7v non protected flay top

Art smile

On September 10, 2014 at 7:13am
usmc_0143 wrote:

I have a Stingray X MOD. I don’t know if only accepts protected or non proctected, but the two batteries that I do have are I believe non-Protected. It is a flat top. How do you know if the mechanical mod has a built in battery protector, and whether or not it only accepts protected or non-protected?

On September 10, 2014 at 7:56am
emmit wrote:


Stingray X Style Stainless Steel + Copper Mechanical Mod 18350 / 18500 / 18650
  510 threading connection
  Copper body wrapped with stainless steel
  Copper top cap wrapped with stainless steel with floating pin and vent holes
Is this the mod you have? 

Bottom magnetic firing button, the locking ring is NOT reverse-threaded
  Locking ring material: Polished stainless steel
  Silver plated copper battery contacts
  Comes with a hybrid adapter and a 510 drip tip
  Houses single 18650/18500/18350 battery (batteries sold separately)
  22mm external diameter
  18.6mm internal diameter

Connection Threading 510
Telescoping Mod No
Variable Voltage (VV)  No
Variable Wattage (VW)  No

Defeat 2500mAh IMR 18650 3.7V LI-MN

cant find this battery on web search

can I take it that you are from the USA?

where did you get that battery from? was it fast tech same as the stingray X

sounds like a short to me,Glad it didnt happen in your pocket!!! ...very painful

what atomizer are you using? have you checked for shorts on that and what

ohms/resistance on atty



On September 10, 2014 at 8:05am
Usmc_0143 wrote:

That is the exact mod that I have except mine is black but same one. No I haven’t checked for shorts. I friend at work is my expert. He is the one I go to for questions and to build my coils and stuff. I really new to the mechanical mod universe. I got the battery from Amazon. It’s Effest brand.  My atomizer is TOBH V3 Atty.  I got my mod from fluid apes.com as well as the atomizer.

On September 10, 2014 at 9:27am
emmit wrote:


have it checked for shorts on mod ans atty if okay try this type of battery as a test 18650 3.7V UltraFire4500mAh PCB Protected Li-ion Rechargeable Battery $5.00 on fleebay.com cheap as chips..the effest is the rolls royce of battery but not for your mod….you need protected batteries..you have proll fried the effest analso you can get an all in battery and mod protector using a Authentic Sigelei Variable Wattage Kick Module for Mechanical Mod from your supplier for about $10.00

once you have it sorted buy effest or sony protected batts


On September 29, 2014 at 8:12pm
Li wrote:

I have a Hitachi drill with 10.5V battery (BLC1015).  after 3 years of not using, the battery does not charge any more.  checking the voltage reveals that it has only 2.6V left.  I took a USB charger (an old LG cell phone charger 0.2A, 5V) and cut the end and exposed the wires.  stripped the end, and connected with the battery red to +, yellow to - with two metal paper clips.  there is not much change after 15 minutes, so I let it go over night.  the voltage became 3.1V.  I placed the battery to its original charger, and bingo! it started to charge.  the battery works now with the drill.  Interestingly, the spare battery would cost 50 dollars, but buying a new drill with two batteries and the charger would cost 90.  I got the idea from here and a youtube video, and figured that it could be useful to some folks who would get to this site.  it saved me fifty dollars and reduced waste.  I think the key is the slow charging of the battery to over the limit set by the charger.

On September 29, 2014 at 9:39pm
sahafdeen wrote:

my li-ion mobile battery 2500mah , working well upto 50% ,after sudden drain and directly come to 11%,,  only 3 months completed (buying), anyone give solution????

On November 19, 2014 at 1:37am
Stan wrote:

I had suffered the same “battery dead, not charging after complete discharge” scenario some two weeks ago on a brand new hp06 battery that had barely lasted a month. The older one “died” in the same way, although it was well within its final leg after a couple of years of usage and it barely lasted half an hour on idle! I took it apart for curiosity and some newbie studies. Anyway, the replacement would not charge at all so I decided to try reviving it from its deep sleep. I used an ordinary multi-voltage AC-DC adapter and applied 12v and 1A for a second and voila! The battery is now charging in the laptop. The current capacity is steadily rising by the minute and the temperature is normal. I’m keeping an eye out for any abnormal rise in temperature, but so far nothing alarming. I plan to recalibrate it after this charge cycle and will definitely post on any success or failure. If this works, I will be saved lots of money replacing the battery and the inconvenience of returning it to the dealer in pursuit of warranty facilitation.

On November 19, 2014 at 7:59am
Stan wrote:

More good news! The battery charged to full capacity as it normally would, without any unusual occurrences. As I type this comment, it still has 8% charge as it has been gradually discharging for the past three and a half hours on light usage (non-stop music playback, screen set to not dim or turn off and minimal work on some worksheets. The music is playing back from an external hard drive without an external power source). I know that it could have lasted even longer with the laptop sitting idle, but I wasn’t so patient to wait for a slow discharge. I’m never gonna discharge it completely again, but I want it to get critically low (3%) and let it shut down then charge it full capacity while the laptop is off. I must say I’m happy with the results, it’s like nothing ever happened to the battery despite having stayed “dead” for at least three weeks. I was mostly concerned about permanent damage to the cells due to staying in that state for too long, but my fears are no more! Thanks battery university for this priceless piece of information, saved me bucks for a smart charger or God knows what else I was gonna spend on to get out of this situation!

On January 11, 2015 at 3:18am
nihal wrote:

i have a ipod . with the same kind of battery.but i lost it and got it after many days.so the battery is completely drained.now how to fix it.do anyone have a solution other than changing the battery

On February 16, 2015 at 12:43am
prince ashiru wrote:

please my aspire one laptop battery was run down and i try to charge it in the 3rd day but its doesnt charge and the battery is last for upto 4 hours before ...
now its said plugged in, not charging…
please what can i do to get the battery on back

On April 14, 2015 at 12:31pm
Rick Whitehouse wrote:

Dear Battery University:
  I have a Ravpower 5600 mAH external battery, and charger for recharging my cell phone. The unit comes with a handy flashlight; unfortunately after placing the unit in my lunch bag, I think the flash light accidentally came on. After a few days I took out my Ravpower 5600 to charge my cell phone. I found my poor little charger completely dead. Is there a safe procedure for recovering my cell phone charger now? If I figure out what to do before getting my answer, I’ll be sure to share the info with Battery University.
Best Wishes,

On June 21, 2015 at 7:56pm
Clague wrote:

Left my phone in car in direct sunlight. It was over 100F in car. Phone shut off and was burning hot. Battery was performing poorly needing daily recharges even with little use. To cool phone down I stuck it in freezer and forgot about it. About three hours later I took it out. After thawing for about an hour I tried turning it on and was surprised that it started up and the battery was 85%. It has been over a day now and battery is still at 57 percent without having been charged.

On September 11, 2015 at 9:04am
Gaser wrote:


  My son HP Touchpad was left till it is drained. Left it in the charger for more than a week with no hope. I decided to crack it open and get the battery out to check if the battery or the circuit has an issue.

  At the first, the battery didn’t read any volt. The battery has 5 connectors 2 Red, 2 Black, 1 Green, 1 yellow, and 1 blue

Tried to charge it on Red & Black terminal using my Smart Charger, but since the charger couldn’t read the volt it reported over voltage error.

So decided to remove the rapping and see the battery, so I found that the battery has a circuit inside it, and the actual battery has 3.4 volt. So remove/desolder the battery from the circuit and charged it using my charger, and not it is 4.18v, but when connected to its circuit still doesn’t read anything.

I purchased another replacement and has the same issue with it, so not sure if there is something is needed to be done to activate the circuit, or am I done and should get my son another tablet.


On November 29, 2015 at 9:33am
Stub Mandrel wrote:

You can get little chips from Avago technologies that will put a very low current into a discharged LiON until it rises to a safe threshold and then charge normally.

Better idea than blasting with a high current IMHO.

On December 16, 2015 at 2:53pm
Caleb wrote:

If my battery pack from cordless tool was affected by water, would that cause the li ion batteries to go into hibernation mode? I looked over the circuit board and found nothing damaged. Can I bring the li ion 18650’s in this pack back to life or are they garbage?

On January 8, 2016 at 2:18pm
Ray Aguilar wrote:

Segway battery drained completely down now won’t take a charge,

On January 25, 2016 at 11:15pm
mohsen.m.shabestari wrote:

Segway battery drained completely down now won’t take a charge,

hi with all my respect
my lenovo le z500 laptop le =ion battery is in good condition capacity and other-are all
OK it coult not able to charge compactly i starts to calibrate the battery from that time it dost accept any charge and has been remain in zero charge please let me know if i can save my battery

thanks so much

On February 5, 2016 at 7:45am
Dania wrote:

Will a battery from a Bluetooth device like a headset need this boost?

On February 18, 2016 at 1:14pm
Dania wrote:

I figured, thanks Mad Monty

On February 25, 2016 at 4:26am
jorge arraiol wrote:

hello , that feature that you say is a BMS (battery management system) right ? i was searching for a charger that has a special feature to awaken lithium battery’s and i am in doubt if this charger from optimate has it or not…

1.    Pre-qualification / BMS reset: The charge program is selected according to battery voltage. For batteries with internal BMS (battery management system) that includes a low voltage cut-out; OptiMate Lithium has a BMS reset program to reconnect the internal cells with the battery posts so that charging can commence.

http://accumate.co.uk/optimate lithium 0.8.htm

Can you confirm it to me ?

thank you

On March 10, 2016 at 10:50am
Ashanta Abdur-Rauf wrote:

I have a number of Wahl Arco Se cordless clippers and even more of the Type 1854/1855 NIMH batteries to go with them. They are super expensive to replace but seem to die quickly even after fully charged. Is there a way to prolong their life or somehow bring them closer to how thwy originally worked?

On March 10, 2016 at 11:24am
Mad Monty wrote:

“Bring nearly any type of battery back to life so it’s just like new again”?  I don’t think this is possible.  Most battery chemistry is NOT reversible (and manufacturers warn you not to try to recharge them as they may burst).  There is a wealth of information on this site, and others as well, that disproves such claims. 

Of the truly rechargeable batteries (NiMH, LiOn, NiCad, etc.), all will lose capacity over time.  Some can, under exceptional circumstances and complex protocols, have some of their lost capacity restored.  (For example, NiCads have a memory effect such that if you repeatedly discharge them only say, half-way, they stop providing power when they reach the half-way point.  You may be able to restore them to some extent by repeatedly charging and discharging them almost completely - sort of exercise them back into shape.  But this is exceptional, and you have to do each cell individually - not the whole battery at once - to avoid reverse-charging and ruining the weakest cells.)

People want miracle devices all the time, and other people want to make them happy by selling them.  They’re usually cheap enough that it’s not worth returning them, and if you do, good luck getting your money back.

On April 4, 2016 at 12:40am
John wrote:

I bought two walkie talkies and they come with Li-ion 3.7V battery pack
the charger broke and i’ve not charged the batteries for 1.5 Years now.

When i measure the tension with a multimeter in the external terminals the tension is 0V
but when i measure the tension of the battery (terminals) itself, before the protection circuit, (yes i opened the plast battery enclosure… inside i found a battery connected to a protection circuit) then i get 3.11V

if i measure the tension between the (+) External Terminal of the battery and the (-) Internal Terminal of the battery case i get 3,11 Volts too

On April 4, 2016 at 12:42am
John wrote:


My question is:

Is the battery still good?
why is the protection circuit opening the circuit , in a manner that measuring by the external terminals i get 0V as reading?


On April 15, 2016 at 11:16am
Larry wrote:

I have two paralleled 3.7v, 2400mAh each, with a thermistor that reads 3.4v and will not charge any higher. The charging port is MINI USB. I do not get any voltage were the leads terminate on the unit. Could it be the batteries are finished or is the thermistor faulty? Thanks

On April 26, 2016 at 11:35pm
karl wrote:

With which tester did you do that:

Cadex examined 294 mobile phones batteries that were returned under warranty. The Cadex analyzer restored 91 percent to a capacity of 80 percent and higher; 30 percent were inactive and needed a boost, and 9 percent were non-serviceable. All restored packs were returned to service and performed flawlessly. This study shows the large number of mobile phone batteries that fail due to over-discharging and can be salvaged.

On May 26, 2016 at 12:19am

Good day everyone, please where can I get laptop battery cells. Am here in Nigeria and am into dead laptop battery re-celling.thanks

On June 10, 2016 at 9:42pm
Wayne wrote:

Several years ago I piurchased a large number of 2 cell packs useing 18650 c ells that had been shelf discharged, many to below .1 volt so none should be restored according to this article but I removed the cells and started charging them at .01c (have since leared that .1c is ok) then at .1c till they reached 4.1 volts or failed to charge. About 2/3 of them were in good condition (about 1/2 in neer new condition) and none have failed since then. Rather than protection circuits, I build a pack with a series of paralelled cells then use a charger that balances the voltage of each paralelled group. When not on charge there is no discharge so can be stored at 40% charge as long as wanted. for best life, store them in refirgerator.

On June 14, 2016 at 1:50am
Anna wrote:

Hi! I hope someone can help me(sorry for my english, it’s not my first language).
So i have this sony vaio battery (li-ion VGP-BPS26A 11.1V)that i used it on a laptop i had 3-4years ago.
Didn’t charged the battery at all and i tested it on a friends laptop and it pop up a message “no battery” it doesn’t recognize the battery. She wants to use the battery but I don’t know if it will work ever again. I don’t have any universal charger or any solution to try to charge it. Can anyone tell me what to do about it and if there is a way to possibly make it work again? To mention it’s pretty expensive a new one. I hope i can make it work someone, i don’t really have clue about batteries but i did researched and i didn’t found much about it.  Thank you!
P.S. I also had another battery from a dell from 3-4years ago that i didnt used (li-ion) and it did worked and charged, had no problems with it.

On June 14, 2016 at 2:45am
MadMonty wrote:

Wayne was lucky.  The thing about Li-ion batteries is that there are not just the two possibilities [it charges | it doesn’t charge], but three [it charges | it doesn’t charge | it goes into thermal runaway and bursts into flame]. 
The explanation quoted from this website, is this”.  “Do not boost lithium-based batteries back to life that have dwelled below 1.5V/cell for a week or longer. Copper shunts may have formed inside the cells that can lead to a partial or total electrical short. When recharging, such a cell might become unstable, causing excessive heat or show other anomalies.”
The argument often heard here is that “I read about it working, so I tried it and nothing bad happened.  So it must be safe.”  Yeah, and five out of six Russian Roulette players think it’s perfectly safe too.

On June 15, 2016 at 7:03pm
Anurag wrote:

I have a Sony xperia m phone. It was working fine. I once have touched positive and negative terminal of the battery with my tounge. After that when I put back the battery into phone it was not getting switched on. Even when tried to charge it, it was not getting charged.  Is the battery gone dead?  Would I have to buy new one?  Is there anyway I can fix it?  Please do reply. Thank you

On June 26, 2016 at 5:25pm
Dave wrote:

I have a replacement Li-Ion battery for a Toshiba laptop. I did nothing to break it in. I have subsequently been told that I need to run the battery down to 15% or so which I’ve done a couple of times now. I plug in the AC and the battery takes a ‘full’ charge. The problem (?) is that if I let the PC remain on, say an hour or two where I walk away, at some point the battery no longer is being charged and is running solely on battery power. If I unplug the AC and immediately re-plug the battery icon indicates that now the battery is taking a charge. Question: is the ‘problem’ with the battery or something with AC power management.

On July 6, 2016 at 10:37pm
John wrote:

@ Dave, I don’t think the battery for your Toshiba laptop is actually taking a full charge, you might be nearing the EOL (end of life) of the battery. you can check to see if the battery is near EOL via the control panel, then select the battery option

On August 18, 2016 at 4:32pm
Shelly wrote:

I bought a Lightning Pak RP2 (multi-function battery charger) recently. It came with a wall plug and a 12v adapter. Plugged it into the wall to charge the device and it’s not taking a charge. Made the mistake of plugging in the cord to the output 19v, 3.5A instead of the input 14v, 1A for less than a minute. Would this affect the battery?

On September 15, 2016 at 8:35am
Silvio wrote:

I bought a replacement lithium battery for my Asus TF300T tablet from Amazon. When I replaced it, the charging LED did not even come on.

I tested with a multi-meter on the motherboard points where the battery connects to whilst having the charger connected and my old battery shows two pins at 8.0V and two at 3.5V whilst the others show 0V.  The replacement shows two pins showing 8.05V on whilst the others showing 0. I was using the 20V range.

How can I boost this new battery as most probably its shelf charge has gone too low and the tablet’s charger is not able to wake it up. Do I require special chargers or equipment to boost it and if so to which points do I connect the boosting voltage?

Any help would be greatly appreciated as I cannot return the battery back. Thanks.

On October 13, 2016 at 9:47am
JohnA wrote:

I managed to reactivate a flat 18650 lithium ion battery that had been left in a discharged state for several months. The battery voltage read 0V on a voltmeter and would not take any charging current when a 4.2V power supply was applied to the terminals. Here’s what I did: Using a variable power supply set to 9V with 1A current limit, briefly (1 sec) connect it to the battery (+ to + and - to -). The power supply may clamp, but that provided enough charge to reactivate the battery protection circuit. Then recharge it fully with a standard lithium ion battery charger. Worked a treat!

On October 17, 2016 at 12:49pm
Allen wrote:

I managed to revive an 18v Li-Ion drill battery sort of like this after it apparently sat discharged in the cold over the winter.  It was reading about 2.5v if I remember correctly (minimum voltage should theoretically be ~15v, however these batteries also seem to “sleep” or “hibernate” after a while and will show ~8v on a full charge so take that for what you will).  The charger said it was bad. 

I have to say I don’t recommend doing this especially in light of the “one week rule”, but it could work in a pinch… I used a 12v lead-acid battery and a couple wires.  Hold for 5 seconds, let off, wait 5 seconds, and repeat.  The voltage slightly climbed.  Then move up to 10 seconds once I was sure it wasn’t overheating or anything, and wait 10 seconds.  Did this a few more times, then went to 15, 20, 30 seconds keeping an eye out for heat and noise.  Once it was holding at around 7v I was able to put it on the charger without it being declared bad.  It took probably 2.5 hours to fully charge which is a lot longer than normal, but it worked and I still use it sometimes about a year later.

I had another bad battery (same model) I tried to resurrect the same way that was holding 0.55v, it was not recoverable.  Never would hold at more than ~1.5v and I gave up before I messed anything up.

On November 24, 2016 at 3:57pm
petey pablo wrote:

How much damage would there be if a brand new samsung phone with 3000mah battery was shipped at 0% battery switched off by itself i.e. the sleep protection circuit activated and left up to 12 months in storage at amazon warehouse?

What kind of damage would there be? I think the voltage cuts off at 3.5V with samsungs switch so possibly it dropped to 3.4V min but what damage capacity self discharge etc would there be in this state?

On November 30, 2016 at 1:26pm
Steven wrote:

Have been working on the problem with my laptop battery for nearly a month. I never gave up. I performed many of the methods out there. For a little while, running off the battery until the laptop turned off, close the lid and let it charge overnight improved the battery status a little, but the wear percentage had gone up to over 90 and the charge wouldn’t even reach 50%. I kept performing another method of closing the lid, unplugging the a/c adapter overnight. Finally, after doing this again last night, this morning the laptop was still in sleep mode instead of turned off. When I opened the lid, the battery charge showed 78% and wear at 37%.. 2 hours later, it’s still charging and it’s at 92% charge. An enormous improvement.

On January 30, 2017 at 5:09pm
Tony wrote:

We use 3 LIR2450 coin cells in a portable instrument. Battery manufacturer is Power-Stream, but we buy through distribution. Some of the batteries are coming in from the supplier completely discharged (less than 1V), while others in the same batch are almost fully charged (~4V). Can the fully discharged batteries be “rejuvenated”, or should I be asking for replacements.

On February 10, 2017 at 8:47am
Kathryn Hodgson wrote:

I’ve just read that heating the battery with a hairdryer until it is nice and hot wakes it up. There were loads of ” yes this works ” comments. I’ll be trying it out myself later on. I chucked out the last battery that did this. Another suggestion was to use a USB cable. Strip the micro end down to the wires and jump start it like a car battery. This appeared to work as well. I think we both need some luck.

On February 17, 2017 at 3:41pm
roy grantham wrote:

i have a 36v li-on electric bike i discharged to much and sent it into sleep mode, its showing 37v from discharge terminals but my charger goes to green when trying to charge how do i wake the battery up

On February 17, 2017 at 5:14pm
Kathryn Hodgson wrote:

I have 3 nunchaku batteries
. 2 are completely dead and one has a little charge left but won’t recharge. They are nunchaku vapros brand for ecig. They are my favourite batteries for my set up and they also are getting harder to buy. They don’t have an obvious + and - otherwise I would try the slow wake up charge with a micro USB wire. Any suggestions and if there is a charger that I can buy I’d like advice. Don’t really want the cadex item unless guaranteed to work.

On February 19, 2017 at 7:58am
Geoffrey Mason wrote:

I dropped my spare Alcatel PopD1 mobile phone battery into a stream about nine hours ago. It was fully charged at the time. It took me about 3 minutes to fish it out. I don’t know how to test its voltage. It seems to have four terminals on it. It won’t begin charging in my phone. Can it be woken?

On February 20, 2017 at 1:33am
Kenny Thomas wrote:

I’m only writing with my experience - do not take as a recommendation, as may be dangerous!
I worked in an electronics store for a few years, and lost count of the number of customer’s ‘dead’ batteries I got working using our 2A bench power supply. I used to set the voltage slightly higher than the total cell voltage, leave for a min or two, then attempted to charge normally in the device. I only had one battery this did not work for.
The reason I am here at the moment is my windows tabled with it’s 3 cell battery has been in the drawer for 2 years. I just repaired the fault that was stopping power-on, but battery was dead. I applied my 19v charger across it’s terminals (after unplugging from board) for a few mins. It is now charging fine. It is up to 50% after 2 hours in Windows.

TLDR - if you are desperate, apply PSU straight to the battery for a min or two. In my experience it works 95% of the time.

On March 14, 2017 at 2:15am
Bromley wrote:

My old laptop was dead for two and a half years.  I took the 3x3 cell 18650 Lithium-ion battery pack (i.e. 3P3S) opened it up and measured a respectable 3.5 V on batteries 1, 2, 3, 7, 8, 9.  My Lion charger shows they can hold about 2 Ah, which is down from probably 2.6 Ah.  But still respectable.  Batteries 4, 5, 6 show only 0.5 V each.  I suspect the issue was with the power controller on the pack or in the laptop, and not a self-draining cell.  This is what I am doing.  I am applying a minor constant current of about 30 mA to each cell and raising it over time to 3.1 V.  Lo and behold, they actually store the charge and seem to maintain the 3.1 volts when they reach there.  Below 2.0 V, they do not seem to maintain the voltage, probably because it takes very little charge to get to 2.0 V.  The next step is to put these through the Lion charger and measure their capacity.  I expect them to be less than the other six cells, but t is possible that they may still have decent capacity for a flashlight.  This contradicts many reports here and elsewhere that when a Lion fully discharges, it should head to the trash bin.

On March 16, 2017 at 4:26pm
Bromley wrote:

Well, mea culpa.  I think I spoke too soon in my previous post.  Cells 4, 5, 6 were at 0.5 V for at least a couple of years.  So upon charging they showed an increase in voltage and maintained that voltage.  However there were a couple of problems.  The cells could not reach 4.2 volts.  #4 did not go above 3.85 V.  The other two stopped at 4.1 V.  The Lion cell charger was thus unable to trigger a stop, as it never reached 4.2.  Had to put a 0.5 Ohm resistor in series to make it trigger.  The cells became moderately warm at the limit which was about 0.125 mA of charge.  After triggering a stop and starting the discharge cycle, the two better ones displayed a capacity of 0.7 Ah and 0.3 Ah - much lower than their rating of 2.4 Ah to 2.6 Ah.

Thus we conclude that indeed the batteries are headed to the trash bin.

On March 25, 2017 at 12:42am
Older than Dirt wrote:

I bought a cordless trimmer and blower with 56 v battery.  The battery is supposed to recharge in 90 minutes.  The charger flashes a green LED while charging and goes steady when charged.  Trouble is the charger LED stops flashing after 8 to 15 minutes. 

There are three LED indicator lights on the battery. when fully charged, all three should light up when the indicator switch is depressed.  After 8 to 15 minutes, I might get one light.  I have two batteries (new) and both respond this way.  If I remove the battery from the charger and wait 10 to 15 minutes or longer, I can return the battery to the charger for another 8 to 15 minutes of charging. After about 6 to 8 cycles of charging, the battery seems fully charged.  This seems quite odd to me.  What’s up?

On March 30, 2017 at 8:42pm
Magyver wrote:

@ Older than Dirt:

I just happened to see your 5 day old post and got interested. This thread is over 6 years old so my answer may be the only one you get, lol… (BTW, I’m older than most of the dirt in my town too)

I’m a troubleshooter from waaaaay back, so here goes:

It’s most likely the charger, not the batteries. (2 batteries act identically, 1 charger acts nuts) 2 to 1 odds…

Here’s where it gets wacky as I psychoanalyze your charger… A thermistor / thermocouple may be overheating and stopping the charging - each and every time…

1)  Try putting the charger in the freezer for 5 minutes after the first few charges; see if it will start recharging the battery again. Yes, THIS MAY actually work.

2)  If it does you just cut 60 minutes off your recharge time. and can tell the manufacturer your KNOW they gave you a defective charger.

3)  Leave me an update if you try this and tell me what happened. (I’ll come back and check)

If the charger is out of warranty I’ll have another idea to prolong your device life and speed up the charge.

And to “Battery University”, this is a fine informational site. I plan to ‘camp out” in here again, lol. If a guy wasn’t careful he could learn a lot from you guys.

On March 31, 2017 at 10:14am
Magyver wrote:

@ Geoffrey Mason

You said you don’t know how to test the battery - I read in a related thread that the inner 2 terminals aren’t used, it’s the outer pair that connect to the voltage.

Have a buddy put a voltmeter on the outer 2 terminals to read the voltage - most likely it is almost dead.

Then Google this article:  How to Revive a Cell Phone Battery (with Pictures) - wikiHow

It will tell you how you can “boost” the voltage with a 9 volt battery so it will take a charge again - good luck, and get a nerd buddy to help, lol.

On March 31, 2017 at 11:26am
Older than Dirt wrote:

@ magyver
Thanks for the confirmation of my theory and suspicions. I surmised that there was a heat problem with either the battery or the charger or both that was shutting down the charge.  I had not thought of the freezer/refrigerator method of restoring charger’s function.  It is logical and I will try it out.  I do remember the last time I drained the battery, I put it on the charger soon after and it would not charge.  However, I waited a while and retried with success and with enough of the cycles of charging, I got a full charge.  My thought is that the charger sensed the elevated battery temperature right after use.

On March 31, 2017 at 12:03pm
Magyver wrote:

@ Older than Dirt:        Had another idea….....

How soon do you anticipate running/running down your blower? I had a related overheating problem with a laptop.

Until the new laptop fan came in I made do by sitting the laptop on a makeshift platform with a plastic freezable ice replacement thingy right under the warmest part. I also wiped the upper side occasionally with a softer frozen gel bead thingy from the Dollar Tree.

The frozen things dissipated the heat very quickly and saved my laptop.

Might you have something like that to set the charger on to try to get it to stay cooler & stay on longer?

The overtemp sensor might very well indeed be near the battery, but an overheated charger will raise the battery temp as well.

New prognosis: A combination of overheating charger with a over-sensitive battery temp sensor.

Now I’m eager to hear the results, lol.

(BTW, I’m reading up on the Cadex C7200 battery analyzer, and I feel tingles of lust, LMAO)

On April 18, 2017 at 3:07am
Nick Kruger wrote:

I charged my Sony Camera li-ion battery with one of these new adjustable pin universal chargers and now the camera does not recognize it, it’s giving me a message “for lithium battery only” and switches off.

Can the problem be fixed?

On April 18, 2017 at 10:47am
Magyver wrote:

@Nick Kruger - Sorry mate, not ‘enuf data. First, what is the model/type of the batteries and the number of batteries?

I assume they’re ordinary L-ion cells?

What’s the voltage of each one after the charge?

On April 20, 2017 at 11:48am
Nick Kruger wrote:

The battery is a Sony camera battery NP-FR1. 3.6V 4.4Wh. Li-ion

Thank you

On May 18, 2017 at 4:06pm
Eric K. wrote:

Porter Cable multi-tool 18V batteries, 2 of them,  (Model PC 18BL) batteries left in storage for over 2 years.  Battery voltage, measured at the battery terminals was 1.8V and 2.1V.  Connected two 9-volt batteries in series to the + and - terminals of the battery for 2 seconds.  Both charge normally in the PCXMV1 charger afterwards.  May have been a risk, but saved alot versus replacement.

On May 24, 2017 at 7:48am
AlexA wrote:

I am working on a battery pack for a SeaBob, underwater scooter type thing.

The battery pack was left on charge for an extended period of time (3 months, says the owner) and now, irrespective of how long the charger is left on, the pack output voltage remains at 0v

The normal pack output should be 48V as the pack contains 12 x Saft VL41M single cell batteries (41 Ah each) wired in series.

The replacement cost of the pack is around AU$10K so I am looking at way of getting the batteries back to life, cognisant, of course, that he who gives can also take away!

Using one battery as a test, I am charging it with a 4v 1A power pack which is powered through a temperature controller whose sensor is sitting on top of the battery. Current battery temp is 21.5c and it hasn’t moved since I put the charger on it about an hour ago. In any case, if it gets to 24.5 it will be switched off.

The battery is very slowly coming up from 0v and is now sitting at 1.8v and slowly climbing.

My intention is to try and wake the battery from its slumber and then once the voltage is back over 3v, put it on a normal single cell LiFeO4 charger.

Mindful of the consequences of foolhardiness, but also aware that replacement cells are not only extremely expensive, but Saft is not being very forthcoming in selling the individual cells, and having the temperature cutoff in the charging circuit should mitigate any runaway and in any case, the current being supplied is so minimal, I would like to ask this learned group their opinion as to best course of action from here?

Thanks in advance,

On May 31, 2017 at 4:10am
Wayne wrote:

Something mentioned here.  I’ve put lithium batteries in the freezer to get them to charge again. But maybe that was devices and the thermistor / thermocouple in the tablet etc.  Can’t remember if I used it successfully on batteries on their own.

But a few questions are needed.  Lithium batteries used to die after a few years (I think oxygenation) even if never used.  Would this be recoverable by the voltage method?  Another question is, this short circuits bridge forming over time in unused batteries.  Does that happen in only certain battery formulations (and which?) and is it reversible by any method?  I’ve got a long spent li drill battery (or charger) and I would like to restore it but don’t want it blowing up while using it or charging it, or just sitting around or being jostled doing an imitation of an old iPhone battery.


On June 4, 2017 at 12:51am
Alex Apostolou wrote:

Just following on from my earlier post, On May 24, 2017 at 7:48am, just thought I’d let it be known that the technique worked for 6 out of the 12 cells. They are now fully charged and seemingly restored, and without incident. Of the other six, 5 were clearly not interested, and one, was the only one where the temperature actually rose. The cutoff had been set to 22.5 c but this one managed to get itself up to 28.5 on its own. So the very low temp cutoff worked well. Now to find replacements for the other 6.

On June 12, 2017 at 3:45am
karma ella wrote:

I have an iphone 4, the battery was dying even without use, I was going to change the battery until i bought a charger from the pound shop, which obviously did some boosting to the battery and now we’re good but now i think i need to buy another charger that won’t over do it, can someone explain why this happened and to what extent should I be using the charger, if its good to continue to use it or not.

On October 18, 2017 at 4:33am
phil wrote:

I am a business I have some stock of RC helicopters and cameras which have been sat there for about 18 months. New - never used.  I recently sold a few and the customers said that they failed to charge. Is there anything I can do in this case. Is there a way of recharging them or replacing the internal batteries or will I have topdispose of them. If disposal is the only option then how can I do this safely and where ??


On October 18, 2017 at 1:48pm
Stephen Pirie wrote:

please read all the replies to “how to recharge sleeping li ion batteries ” these replies go back a few years but the principle is the same . The battery is most likely good just dropped below the minimum charge level / voltage .

On October 26, 2017 at 6:41am
sanjay wrote:

i have a sony vaio laptop and 2010 model and the batteries don’t even hold the charge for 10 minutes. The laptop bottom portion gets very hot with or without the battery, when i charge the batteries in the laptop they charge slowly but drains very quickly.
so do i have to buy new battery pack or is there any way to reactivate the same battery?

Pls advise, thanks. sanjay.

On October 26, 2017 at 10:44am
Stephen Pirie wrote:

I also have a Sony vaio laptop is the heat of the laptop on the rear left of the laptop as this seams normaly hot on mine after some use , re battery - I have had to replace the transformer as it was working on reduced power , so I suggest you check the operation of this first . Hope this is of help to you .

On October 27, 2017 at 9:47am
JimFLorida wrote:

To answer sanjay’s question, it sounds like your older laptop battery won’t hold a charge because it is at “end of life” from frequent use which is different from this article’s topic, which is what to do with a good battery that has been allowed to drain down in storage so low that the battery’s built-in protection circuit won’t let it be charged any more, and possiby can be brought back to life with a boost from a special charger. Search online for new or good used batteries or a local computer repair shop.

On November 13, 2017 at 6:20am
Jerry wrote:

I have a Nikon EN-ELxx battery which the camera showed as unusable. Charger seemed to charge (light flashing normally, etc) but after many days of trying, no change.
So having read this and other articles I thought I would check the voltage and try to boost the battery to revive it.  Unfortunately could not find my multimeter leads! So, having read that the cleverer chargers start by pulsing the battery to test its condition, I started to think maybe doing this many times might just tip the battery over the threshold.  Assuming Nikon’s charger is a clever one!
I inserted and removed the battery from the standard Nikon charger about 20 times in quick succession, each time leaving it in for about 10 secs before removing it. Then I put it back in the camera - and guess what - the battery was recognised as working again. I put it back on charge again to completion, and I now have a good battery again!

On November 16, 2017 at 1:04pm
Adam Bryant wrote:

I have a li-ion pack that holds 18.4 volts when not in use, drops to 12.6 volts under load but jumps back up to 18.4 when the load is removed.
each battery is reading 3.6v off load.
is there a way to diagnose the issue and fix the pack?

On November 21, 2017 at 7:58am
Philip wrote:

Some use here really wrong words! like “high current” or “high voltage”.

This is most stupid and dangerous.

To boost a battery you use a healthy battery of the same sort to “wake up” a dead cell. This process takes only seconds or perhaps 20 seconds or a few more. Very rapidly the voltage of the dead/sleeping cell will go up. (it is like emptying a bucket of water very rapidly and you only need a few drops to get some wetness) It takes NEVER minutes or longer.

Waking up cells should only be done by people who know what they do. Or perhaps with fresh instructions. Because when done wrong it IS EXTREMELY DANGEROUS. Potential fire hazard, explosion or HOT venting of the battery cell.

If you do this. It’s advisable not to use fully charged good cell to wake up a bad cell. But use a cell with 30% load. It’s even more safe to wake up more then one cell with one not fully charged healthy cell.
If you do this procedure wake up it is VERY important that the sleeping cell and also the power-donor cell is NOT warming up. Stop immediately the procedure and measure the voltages of both cells. Lithium-ions can deliver massive amounts of Amps. Both cells are in danger of damage or even fire or explosive like venting also with fire!

On January 1, 2018 at 4:19am
Johnathan wrote:

I just had two 18650 cells that would not charge.  I am just using them for an e-cigarette and using the vape to charge them.

When measured with a good quality volt meter one cell read 1 volt and the other read 1.2 volts.

I tried giving them a boost from other cells that were fully charged according to the e-cigarette. This is really my only method of charging them seeing as I have not yet bought a $30 charger for them.  It did not work.  I then could not find any plugs for a nine volt battery as I heard that can work.  At a last ditch attempt I have a bench top power supply that I made from a salvaged computer power supply.  I held them against the 5 volt leads for about 10 seconds.

While holding the leads against one of the cells the leads started to get warm to the touch.  The leads are just made from wire salvaged from another dead computer power supply with some pins soldered on to plug them into a breadboard.  On the second cell they stayed cool.

I then put them back into the vape and they began charging.

I left them to charge for a couple minutes.  Did not time it so I’m not sure how long.  I then pulled them out and measured them with the meter and they measured above 2 volts.

After about 20 minutes in the vape it started to show 1 bar that meant they are charging.  I pulled them out and measured again with the meter and they now read 3.2 volts each.

The vape said check battery for quite awhile but after that except after about 20 minutes the vape now works.  It’s still charging but does work and this is just working off a e-cigarette plugged into a wall wort.  The batteries are a no name brand as there is nothing but a sticker on them where as the ones that came with the vape are Samsung 25R’s.  The no name batteries also have dents in the caps on the positive a negative where they plug into the vape.  The originals don’t.  The originals are rated at 3.7 volts. 2500mAh.  The no name ones are rated at 3.7 volts. 3000mAh.

Another 20 minutes and still at one bar.  The vape said check battery.  I unplugged for less than a second and plugged back in.  The vape works.  Still charging at 1 bar showing on the display.

Another 20 min’s and still only at one bar on the display but removed the batteries and tested with meter and am now at 3.6 volts each.

Another 40 mins’s and I removed the batteries and tested with a meter and I have 3.7 volts on each battery. The display shows 2 bars.  Plugged it in and it’s showing that it’s charged to one bar.  Still charging.

10 more mins and I now have 2 bars.

Still charging.

I think the point of this is that yes boosting worked for me.  How I did it was to use a computer power supply and use the 5 volt power rail.  Now I’m still not sure if I would have just left them in the e-cigarette charging these batteries would have worked in the first place without boosting.  I have four of these 18650’s period.  I still would not recommend just leaving them hooked up to a five volt constant current supply as I have heard of them catching fire.

On February 18, 2018 at 4:42pm
Frankie wrote:

I left my HP pro book 440 G2 on hibernation for few days out of town and came to meet it drained and won’t charge.
Anyone know how to revive this one?
Please I’d appreciate

On April 1, 2018 at 10:39am
MadMonty wrote:

Cautionary Tale:  I sought to wake up and recharge a LiPo battery back sole as combo USB power supply and Jump Starter.  Came with its own 9” long jumper cables and 15V 1A charger that no longer charged it after a deep discharge.  Tried applying ~12VDC limited to about 1.5A from lab power supply, to jumper cables which bypass protective circuitry.  Took charge nicely,  10 minutes later, burst into flames, melted nearby equipment, burning plastic released toxic fumes and 4’ flames with nasty black sooty smoke.  Put out with bicarb fire extinguisher.  See damage in photo “LiPo Mistake 3-18.jpg” at https://drive.google.com/open?id=1QGciGkR0g-4jExRH3sGd24RgiEHg_G62
There is a second lesson if you ever use one of these to jumpstart a car:  remove it within 30 seconds after car starts because the alternator will current will flow into the battery without even less protection than my lab supply.  Car fires may be dramatic, but still no fun.

On June 7, 2018 at 8:08am
borja wrote:

Hi @AlexA, did you have any luck finding a solution for your SeaBob? Apparently SAFT has an exclusivity contract with SeaBob so that’s defenitely a no-go. At 6500€ a pop, I am looking for another suppliers that may have compatible li-ion cells as the VL41M format is just too rare.

On June 8, 2018 at 8:05pm
Dean Fletcher wrote:

I just fixed an 18V Eionhell battery…it was dead and plugging into the charger did nothing…took the case apart and it measured the volage at about 5V across all 5 x 18650 in series…I connect a 12V trickle charger across the 18650 terminals (+ to +, 1 to -”) for about 1 minute…voltage came up to about 12V…I then plugged into the standard charger and now its charging:)

On August 6, 2018 at 8:27am
Alin Stefan Hiemesch wrote:

Hello , i have a 36v chainsaw battery , i didnt charge it for a very long time , after deciding to charge it , the charger had 0v output , after some soldering , i got 40v feom the charger , the battery li-ion , had rised the voltage from 33.0v to 34.4 in 2 days , is it possible that the charger would allow full charge after it gets charged enaugh ? Before the diode is 35.1v ,before the regulators i get 40v , it charging but very slow ,would get it self back to life even in this very slow charge? Or it doesnt get enaugh juice from the charger to keep it at the 36-37v range ? Thank you in advance

On August 8, 2018 at 6:16am
Philip wrote:

Best to do with these kind of battery / accupack is: connect to charger and plug and unplug the charger several times. This can awake your battery. The battery receives a bit of peak current pulse and can wake up with after receiving some of these peaks.

But reading your problem description, I think your pack is broken, because one of the cells is going out of line with the rest of the cells. Voltage of that cell, or even cells, can be too low/ too high or cell is (almost) dead. Often this happens with heavy discharge use.

For example too much firewood cutting without any resting for many minutes. Cells can become hot and SDI protection kicks in and disconnects + pole of the battery permanente.

Battery packs hate it to go low in voltage. Battery pack hate HEAVY continues use too, even if the machine is build and designed for it. :(

I think you need most likely a new battery-pack for your chainsaw. Good luck!

On August 8, 2018 at 11:20am
Alin Stefan Hiemesch wrote:

Thank you very much , i charged every row of cells at 7.2 v 7.2/5 =36 v , it is at 36v +- but id , or com is at 34.8 , with the charger plugged in and the battery attached i found that there is a pin on the battery witch grounded , connecting only - (black lid )from the multimeter has an intressting effect , the voltage from com (id ) gets higher , so its just 1 pin from the battery to get grounded and sometimes the led from the charger goes green when touching that pin repeatedly as if it would charge, akward anyway i am gonna keep messing with it untill i get it sorted

On August 20, 2018 at 11:21pm
Leny wrote:

Does anyone know the resistance to be put between the minus contact and the central contact of the power cordless tools of different makers?
I want to use power tools with external batteries, but the three contact tools are designed not to work without input to the central contact.
Heard about 1500 ohm for Bosch, 8250 ohm for Worx/Rockwell/JCB/Erbauer/Ozito/Titan etc. but this isn’t verifyed.

On September 7, 2018 at 2:13am
Sandy wrote:

Hi, I need some help regarding a torch. My friend said it got bad after his charger shorted. He tried charging with a different one but the torch gave a flash and stopped. With a different charger, I tried charging. After some time, I tried putting the torch on with the charger on, the torch is lighting up, however when I remove the charger, the torch does not light. There are two 3.7V lithium ion batteries. Have the batteries gone bad?

Please help.

On September 20, 2018 at 6:11am
halflife2000 wrote:

Hello , i do have troubles with one of my laptop batteries, Acer 4820tg 11.1 V battery type which i dont use it anymore, but i forgot to charge it for a bout 2 months and now the battery dont last for neither 1 sec with the laptop turned on. I checked the voltages with hw monitor and is dropping by day ..now after a week since monitoring is ~6,123 V, with the multimiter shows 0,3 v bettween the first and the last pin( as shown + /-)  . I knew the battery already had a 43% wear (HWmonitor) and now shows (HWmonitor) 15% wear and 31 % charge but ii dont charge and dont last turned on for 1 sec.  I still keep it with the charger plugged in the laptop for a few days but no changes just voltage dropping (hwmonitor)

And ...i do have another laptop dell n5110 that also have a 11.1 v battery but when fully charging on battery report /hw monitor showing 140% charge and 29% wear (i bought this chinese battery 2 months ago, the numbers were normal for a time…

Quite a few anomalies but will i be able to solve any with your help , Thanks

On October 15, 2018 at 9:12am
Nishanth wrote:

Can awake LI-ION battery in smartphones and how

On October 30, 2018 at 5:38am
Chris wrote:

To SANDY above, try switch?? OR use a single battery to operate the led OUT of the torch. Will be one or the other! MORE likely is the switch, but easy repair IF you can take it apart.

On November 8, 2018 at 5:40pm
victor cadillac wrote:

i have a Droid Turbo i changed the USB port and still wont charge my battery new what can i do ???

On January 27, 2019 at 6:05am
Phub dema wrote:

After knowing that my battery doesn’t last long I was horrified and without consulting experts or searching in internet I have kept my laptop battery(li-ion) in freezer for 4 hours. Later my friend told me that li-ion battery should not keep in freezer. After hearing this I took out my battery and now I am terrified as well as horrified. Please suggest what should i do now

On February 6, 2019 at 10:59pm
Jack Fletcher wrote:

I have a Chinese made leaf blower.  84 volt Li ion battery pack.  Is there any way of estimating the shut off voltage?  The charger fails to recognize them.  I have 2 battery packs and both are asleep.  One at 0 volts.