# 18650 won't charge?



## NB68 (Apr 22, 2010)

Ok, I have a relatively new set of 4 Tenergy 18650 batteries I bought in December from all-battery.com

Per Tenergy it is ok and a good thing to discharge them all of the way.
I did this with two batteries and now they will not recharge at all.
I've left them in the charger over night but no charge. The charger shows the green light right from the start.
What's going on?

I tried them in another charger and same thing. Green light. Does that not always indicate they are seen as fully charged? But they do nothing in my Fenix tk-11.

Was it a bad idea to fully discharge them?

I do not know much about these types of batteries yet other than what I'm starting to read on this forum. I don't even know how to test for voltage and such like I'm reading to do here.
Thoughts?

Thanks,
Nick


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## old4570 (Apr 23, 2010)

Protected or unprotected ...?

If there protected , it could be the PC is not re-setting ...
If you discharged them to where the over discharge protection kicked in , then the PC may not be allowing the battery to recharge ..

This seem to happen often enough : 
And I dont remember the fix from the top of my head , hopefully some one else will chime in ... 

If there unprotected cells , oh oh ! :mecry:


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## garden (Apr 23, 2010)

If you over-discharge an unprotected li-ion cell to a certain voltage, they will either lose alot of capacity or die.

If it is protected, the PTC may have shut it down forever.


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## march.brown (Apr 23, 2010)

When you say that you fully discharged the cells , was that to the 3.6 volt point ? ... A 18650 cell that measures 3.6 volts is virtually fully discharged ... Did you measure the open circuit voltage or did you discharge to the point where the torch/battery stopped working ?

Also are the cells protected ? ... If so , the protection circuit should have disconnected the cell to prevent damage to it ... It will need to be reset ... If the cell was unprotected then it has probably died ... There are ways to try to revive it , but I (personally) wouldn't trust it now.

Do you live near to the Fire Station ? ... You will find that most people strongly suggest that you don't leave Li-Ions on charge unsupervised and certainly not overnight ... Even with the best charger in the world , it is strongly recommended that the cell is taken off charge as soon as the "green" LED comes on.

I hope your cells are the protected type as there is a much better chance that they are not ruined.
.


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## NB68 (Apr 23, 2010)

Sorry, they are the 3.7v 2600mah protected cells from Tenergy here:
http://www.all-battery.com/4tenergyli-ion1865037v2600mahrechargeablebatterieswithinternalpcb.aspx


Unfortunately I do not know if they were discharged to "the 3.6 volt point" nor how to measure the "open circuit voltage" etc. 

Tenergy told me directly it was a good thing to run them all the way down. To do this I just left the flashlight on until it quit working, (Fenix TK-11).

So if the "protection kicked in" is there any way to reset the batteries to make them work again?
Why would Tenergy have told me to do it if it's actually not good for the battery?
Is it then a bad thing to actually ever run them all the way down?
I've always heard about rechargables in general to run them down and do full charge for best life but what is the general concensus for these Li- ion 18650 batteries then?

I was recharging them once my flashlight kicked down to the 50% power level.

Thanks for any direction and advice.
As I said I'm just learning about all of this.


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## Igor Porto (Apr 23, 2010)

Probably it overdischarged and the PC kicked in, not allowing it to be recharged. What I did last week and worked, was to get a 9 volt battery, touch the positives and negatives to the 18650 for 3 to 5 seconds. It should charge after that. Try and let me know if it works.


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## NB68 (Apr 23, 2010)

Touch it with a 9 volt battery for 3-5 sec.? 
Sounds interesting but what is the concept behind that?
Also, I see so many posts concerning these batteries blowing up if mistreated I'd like to be assured doing that is perfectly safe.


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## Igor Porto (Apr 23, 2010)

The slightly higher voltage of the 9V battery triggers the PC and releases it from the blocking state, thus allowing the battery to work normally. It will not blow up with a 9V tension and a very low current for a few seconds.


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## NB68 (Apr 23, 2010)

Thanks for the reply.
I'll try that out tonight!


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## yellow (Apr 23, 2010)

the charger should do that
(and I would not do it with such a high voltage)

other idea:
is it possible that the flat top does not make contact with the positive part from the charger?



PS: a "fully discharged" Li-Ion (which is about 2.6 Volts) is ok, when it happens during use.
But there is no need to discharge a half-used cell for charging.
On the contrary, that adds to the already limited lifetime.
It is better to leave them as is, recharge them before use and use them then.

(in short: do not discharge them with cause before recharging, do not keep them stored when fully charged)


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## Igor Porto (Apr 23, 2010)

The charger should do it, but it doesn't. It was either throwing the cell away or trying to apply higher voltage. The higher voltage worked


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## NB68 (Apr 23, 2010)

I have 2 different chargers and both were immediately throwing the green light as if the batteries were already charged. So in this case, the charger is not solving the problem.

Interesting note about not storing a fully charged battery. 
Why? And how do I avoid it?
For example, my charger will only charge 2 batteries, not 1 at a time.
I have 4 batteries and I use 1 at a time. That one will last 4-5 hours in my flashlight which actually means it is good for several weeks or more based upon my typical usage.

So by default I'm going to have at least one fully charged battery sitting around all the time.

Is it not also bad to leave an uncharged battery sitting around for weeks or longer?


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## jasonck08 (Apr 23, 2010)

Keep in mind that the low voltage IC in most 18650's will only kick in if the discharge current is about 500mA and higher. So if you had the light on a very low setting, it is possible that the battery was way over discharged...


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## Igor Porto (Apr 23, 2010)

NB68 said:


> I have 2 different chargers and both were immediately throwing the green light as if the batteries were already charged. So in this case, the charger is not solving the problem.
> 
> Interesting note about not storing a fully charged battery.
> Why? And how do I avoid it?
> ...



Same here, both chargers wouldn't turn the red light.

Storing them charged for a few weeks is OK. Storing for long periods, like months is not good. Your batteries should be fine.


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## arek98 (Apr 23, 2010)

You should not store Li-Ion's completely discharged for a long time. It will damage battery. Recommended charge for prolonged storage is 40% of charge which is about 3.8V open circuit. Also you can put them in refrigerator (but don’t freeze them).
You don’t need to discharge it completely. It is ok with Li-Ions to use them partially and then top them off. I believe that number of cycles specified by manufacturer applies to full discharge-charge situation (or almost). Charging and discharging battery causes it to “breathe”. Internal crystalic structure expands and shrinks damaging itself over time. Avoiding full discharge somehow lessens this effect.
 
See some useful info here and here.


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## NB68 (Apr 23, 2010)

So neither full charge or full discharge is good.
Interesting.
Thanks for the battery U. links good information.
Taking another direction here, how to I test the real voltage of my battery and what tool is needed?

Also I've read a lot of comments about good / bad chargers. I thought they were all the same. Mine are supposedly is made by Tenergy but I've since seen the exact same wall plug type with different or no brand label on them so I'm sure it's pretty generic.
When I search for chargers there's not much info from the retailer so how do you know if the one you get is good or bad performing?

I'm going to try the 9 volt kick start tonight and report back.


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## march.brown (Apr 23, 2010)

yellow said:


> PS: a "fully discharged" Li-Ion (which is about 2.6 Volts) is ok, when it happens during use.


 
Do you mean 3.6 Volts ?
.


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## march.brown (Apr 23, 2010)

NB68 said:


> Sorry, they are the 3.7v 2600mah protected cells from Tenergy here:
> http://www.all-battery.com/4tenergyli-ion1865037v2600mahrechargeablebatterieswithinternalpcb.aspx
> 
> 
> Unfortunately I do not know if they were discharged to "the 3.6 volt point" nor how to measure the "open circuit voltage" etc.


 You really need a Digital Voltmeter to check the state of the cells ... For example a 3.6 volts reading means that the cell is empty whereas 4.2 volts is 100% fully charged ... 4.0 volts is 80% left and 3.8 volts is 40% left ... To check the open circuit voltage , all you have to do is remove the cell from the charger and measure the voltage with your meter ... If the voltage is below 4.2 volts , put the cell back on charge for a while and try a little later ... It's really easy but you will need a meter ... Open circuit voltage just means that nothing is connected to the battery , except of course the voltmeter ... I personally prefer to charge my cells when they get to about 3.8 Volts though you can top up the cells on the charger whenever you want as long as you remember to keep them over the 3.6 volt lower limit.



> So if the "protection kicked in" is there any way to reset the batteries to make them work again?


 To reset the protection you first need a fully charged (4.2 volt) cell ... With a paper clip or similar , connect the two bottoms (-) of the good cell and the bad cell together ... Then with another paper clip do the same with the two tops (+) of the cells for just a couple of seconds ... If the bad cell has reset OK you will be able to measure a voltage across it ... You should then be OK to charge it ... Unfortunately if the bad cell has been discharged at a low current , the protection might not have tripped and the cell might be over discharged ... It then needs to be disposed of properly.

I hope that everything works for you ... By the way , a cheap digital meter is OK , so there is no need to spend more than a few dollars (or pounds).
.


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## arek98 (Apr 23, 2010)

You can buy multimeter at HomeDepot, Sears, Radio Shack and many other places. It does not have to be digital  but digital is certainly easier to read. Analog will be probably cheaper though, you may be able to find one below $10. Depends how much you like to spend.


Once you have it, it is like march.brown wrote: take a battery and measure its voltage. Here is a great tutorial written by HKJ.

“Real” voltage will depend on load. Voltage will always drop under load. You don’t need this information to charge batteries. The information you may be looking for is that your charger does not overcharge batteries meaning that when it goes green and you measure open circuit voltage of fresh battery it is 4.2V or little lower. On the other end you may want to check voltage of discharged cell taken out of flashlight. This way you may learn to estimate when to change batteries.


Personally I tend to replace Li-Ions pretty often. For some devices with fuel gauge it may be necessary to discharge battery fully from time to time to keep it calibrated but for most flashlights I don’t think it is important. I would run Li-Ion to the end only in emergency.

Tanergy protection circuit kicks in at 2.5V but it is possible that flashlight stopped working before that. Did it die suddenly or it was dimming for very long time (like few hours). If it died quickly then probably your voltage is higher that 2.5V because driver in your TK-11 was not able to supply enough voltage to power LED. But if it was running long time dimming gradually then it would mean that driver went into direct drive and was passing directly to the led whatever was left in battery and 2.5V is enough to be higher than Vf of LED at very low current.


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## Igor Porto (Apr 23, 2010)

march.brown said:


> To reset the protection you first need a fully charged (4.2 volt) cell ... With a paper clip or similar , connect the two bottoms (-) of the good cell and the bad cell together ... Then with another paper clip do the same with the two tops (+) of the cells for just a couple of seconds ... If the bad cell has reset OK you will be able to measure a voltage across it ... You should then be OK to charge it ... Unfortunately if the bad cell has been discharged at a low current , the protection might not have tripped and the cell might be over discharged ... It then needs to be disposed of properly.



*march.brown*, that's a great idea, I haven't thought of that. I used a 9V battery, but what you said makes total sense. Using another 18650 is OK because the tension is equal but the current is much higher than a charger.

*NB68*, you should try that and see if it works. If it doesn't work, then try the 9V battery. Good luck! :twothumbs


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## NB68 (Apr 23, 2010)

I searched for voltage meter and multimeter at the HW stores and the shack. Nothing for under $10 in fact everything analog or digital was in the $30-100 range! Guess prices have gone up since you bought yours ha-ha!
I think the neighbor has one.
Thatnks for the tutorial link. I have no idea what setting to put that big dial on but I'm guessing it will be explained on that link when I read it tonight.

One more maybe dumb question on the whole paper clip to the terminals of a good battery thing to "jump" it. If I'm holding both clips as described will I not be shocked or something?! It kind of sounds like I'd be part of the electircal loop.


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## Igor Porto (Apr 23, 2010)

You won't be shocked, don't worry, the current is too low for that. Otherwise we would get shocked each time we touched both poles with our hands, imagine that, getting shocked every time we changed batteries?


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## old4570 (Apr 23, 2010)

Well , push come to shove , you can always remove the protection circuit , and then run it as a unprotected cell .... 

If you wanted too ... And it doesn't hurt the Li-ion to throw it back in the charger a little earlier than complete depletion ...
Its nicads that are supposed to be completely depleted , Li-ions dont have memory , so it doesn't hurt to throw them in the charger for a top up ..
If you know how much you use the light , it might be an idea to cycle the batteries around 50 - 70% use . Its over depletion and over charge that hurt Li-ions , so who ever advised you ? There still thinking Nicad in a Li-ion age ...

[ Li-ion Age ]  

Storage , was it 3.8 to 4 v if your planning on not using them ...


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## Dioni (Apr 23, 2010)

Igor Porto said:


> Probably it overdischarged and the PC kicked in, not allowing it to be recharged. What I did last week and worked, was to get a 9 volt battery, touch the positives and negatives to the 18650 for 3 to 5 seconds. It should charge after that. Try and let me know if it works.


 


march.brown said:


> To reset the protection you first need a fully charged (4.2 volt) cell ... With a paper clip or similar , connect the two bottoms (-) of the good cell and the bad cell together ... Then with another paper clip do the same with the two tops (+) of the cells for just a couple of seconds ... If the bad cell has reset OK you will be able to measure a voltage across it ... You should then be OK to charge it ... Unfortunately if the bad cell has been discharged at a low current , the protection might not have tripped and the cell might be over discharged ... It then needs to be disposed of properly.


 
+1 on both

I have used this technique many times and it is usually successful, worked fine.
Try it out NB68! :thumbsup:


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## ronkar (Apr 24, 2010)

NB68,

Not meant as a recommendation for any of these, but here are some inexpensive digital multi-meters found in stores:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90899

http://www.kmart.com/shc/s/p_10151_...tal+multimeter&prdNo=2&blockNo=2&blockType=G2

http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053

http://www.frys.com/product/4108273?site=sr:SEARCH:MAIN_RSLT_PG

http://www.sears.com/shc/s/p_10153_12605_03482141000P?vName=Tools&keyword=digital+multimeter


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## march.brown (Apr 24, 2010)

ronkar said:


> NB68,
> 
> Not meant as a recommendation for any of these, but here are some inexpensive digital multi-meters found in stores:
> 
> ...


.
The Harbor Freight seems to be used by a lot of CPF'ers and with no complaints ... I use a virtually identical one sold in the UK.
.


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## Dioni (Apr 24, 2010)

march.brown said:


> The Harbor Freight seems to be used by a lot of CPF'ers and with no complaints


 
I also have one of this. No problems so far!


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## NB68 (Apr 24, 2010)

Update.
Jumping it with another good battery worked!
The charger was then able to charge them and they seem to work fine!
I'm pretty excited. This forum just saved me another $20-30 bucks. 
I won't know exactly what they're doing until I get the volt meter and check it out but they seem fine now.

Oddly enough, trying to be cautious before I did it, I had called Tenergy directly and they were the ones who told me it was ok and they even said it was actually a good thing to discharge them all the way in the first place!

Thanks for all the feedback and info/tutorial links. I'm a much smarter man that a few days ago battery-wise.

One last concern. My battery charger. Someone mentioned the charger should have been able to kick start it too maybe but it did not.
I have the waal-plug type charger that was supposedly from Tenergy but there is no branding on it. How do I know if it is decent or junk?
Any recommendations on where to get a good reliable charger? Preferably one that holds two batteries but would let me charge 1 at a time.


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## digitalerik (Sep 1, 2011)

I put my 18650 in the charger wrong, then the battery would no longer charge. I did the 9v battery trick and it worked. THANK YOU!


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## Glock27 (Sep 1, 2011)

I don't believe anyone should be using Li-Ion batteries without owning a Volt Meter. 
4.2V – 100%
4.1V – 87%
4.0V – 75%
3.9V – 55%
3.8V – 30%
3.5V – 0%

G27


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## march.brown (Sep 2, 2011)

Glock27 said:


> I don't believe anyone should be using Li-Ion batteries without owning a Volt Meter.
> 4.2V – 100%
> 4.1V – 87%
> 4.0V – 75%
> ...


Totally agree about the Voltmeter.

The figures that I use are....
4.2V - 100%
4.1V - 90%
4.0V - 80%
3.9V - 60%
3.8V - 40%
3.7V - 20%
3.6V - 0%

I always try to guestimate when the battery gets to 3.8V then I top it up.

I have got pretty good now at guessing the amount of use the battery gets and it's usually slightly over the 3.8V ... If I need to use the torch longer then there will be about another 60 minutes left (on high) on my Solarforces ... I tend not to use the high setting though , so there would be even more time left ... There again , I always have my two EDC ITP-A3s attatched to keyrings and my ITP-A2 clipped in my inside pocket.

There's safety in numbers.
.


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## Bacano (Dec 26, 2011)

Well I have a 18650 battery that has shorted in my battery pack somehow I don't know yet because everything seems fine... in one moment it's shorted in the other everything is ok. need more investigation...

There was just one battery that went down to 0.22V probably because of the short-circuit protection. The battery wouldn't charge so have tried connecting it in parallel with another almost fully charged 18650 battery at around 4V.

* The big question is why did the non shorted battery voltage start to raise!*  right now it's at *5.70V AND RAISING*!! :huh: what a weck?  Is this normal? I am just expecting this to explode at any moment. lol Teh batteries are just connected in parallel (+)(+) with (-)(-)


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## HKJ (Dec 26, 2011)

Bacano said:


> *The big question is why did the non shorted battery voltage start to raise!*  right now it's at *5.70V AND RAISING*!! :huh: what a weck?  Is this normal? I am just expecting this to explode at any moment. lol Teh batteries are just connected in parallel (+)(+) with (-)(-)



Try a new battery in your DMM.


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## Bacano (Dec 26, 2011)

Well they didn't explode, the voltages went back to 0.22V for one and 4V to the other.

I removed the plastic wrapping of the bad cell to check the protection circuit and I can measure directly in the cell 3.8V. The cell seems to be ok! So how can I reset the P.C.? Or is it damaged?


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## SilverFox (Dec 27, 2011)

Hello Bacano,

Welcome to CPF.

You now have a bare cell. The protection circuit is toast.

Tom


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## Bacano (Dec 27, 2011)

Well. thanks I guess.
that's what you get to buy from DX. 4 orders and 5 defective items! way to go china!


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## jjj333 (Mar 15, 2013)

Last year I bought a Li-Ion battery pack with 3 cased batteries + a charger. It recharged various times OK. Yet today, when I tried to recharge the pack, my IC controlled charger reported a connection failure. I then opened the case and measured each battery separately. 
Result: One battery had no voltage at all! I just couldn't understand what happened?
Solution: My investigative mind led me (not to throw the battery into the rubbish, but...) to go a step further and opening up this battery. I then carefully pealed off the metal case from the battery and discovered that the + contact metal tape/lug delivered a voltage of 2V7, yet the top cap of the + contact this plus voltage had no contact (!!!) I then taped the battery safely and now charges happily.
Conclusion: To me it seems to be the "old, rotten tale" of almost all Chinese consumer products, purposely designed with "obsolescence timers", as to encourage the Asian style of "trow-away and buy sheep-me-me-mentality".
I write that, because it's become too obvious with the time I have been forced to buy and use China-made consumer goods.
Only last week, I encountered the same mentality problem with a new vacuum cleaner (with 6 month guarantee), yet this time I was smarter, in that I used it quite often and ran it for at least 10 minutes in one go. Result: the motor burned out; I returned it to the store and received my money back. That way consumers are able to teach shoddy manufacturers a lesson. The same problem I encountered with electric blankets of a great Australian brand name (Sunbeam): near where the cable entered the blanket, the perfect looking cable started to smolder away. Luckily I noticed it, before the house went up in flames. I wonder how many consumers lost their houses or lives?? These tactics are downright criminal...


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## toastyghost (Sep 23, 2013)

I'm an e-cig mod user and I stumbled across this thread via Google. Thank you for the 9v trick! Worked like a charm!


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## InfinityExperience (Mar 4, 2014)

I just want to thank everyone on here for posting tips, information, and how to's.

The 9v battery trick got my batteries up and going again and I literally signed up just to say thank you. I'll have to stick around and see what other treasures are buried within the forum now, thanks again!

:bow::bow::bow:


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## R3dN3ck (Jul 22, 2014)

digitalerik said:


> I put my 18650 in the charger wrong, then the battery would no longer charge. I did the 9v battery trick and it worked. THANK YOU!



Same cause. Put it in the wrong way.
Same symptom. Charge light is green from the start even though the battery is half full.
Same solution. Used a 9v battery and a coat hanger. (a little tricky aligning the batteries and the coat hanger).

It fixed it, but not straight away.
Initially was still green.
Went out to the garage to get the multimeter. When I came back the red light was on - charging.

Thanks everyone.


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## stryfox (Sep 20, 2014)

9v worked on all 4 of my aw 18350 batteries. 
Thanks


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