# Low voltage on 18650 cell



## Black Rose (Apr 21, 2009)

I received a Solarforce L2 package today that included an unprotected 18650 cell.

The battery is a 3.7V 2800 mAh ICR 18650 cell. 
It has TX21G033111 printed on it. No other markings on it to indicate who the manufacturer might be.

I figure it spent about 5 hours in the mailbox today and was quite cool when I brought it in the house. I let the battery come up to room temperature for about 5 hours.

I just checked the voltage of the cell and it appears to not be in good shape - it only registers 2.8V 

Is this cell permanently damaged? Can it be salvaged?


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## csshih (Apr 21, 2009)

the solarforce cells included with their lights usually aren't the highest quality..

I'd say just toss it.

edit.. .the authentic ones seeem to be very good! I just obtained some!


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## 325addict (Apr 22, 2009)

Replace it with either an AW 18650 protected one or a BLUE Trustfire 2500mAh protected one (DX SKU5790, two for just $10,-)
You'd better avoid those Ultrafire ones, these aren't the best either...

Li-ion cells with too low a voltage aren't trustworthy anymore. Discard of that cell, before "venting with flame" problems arise. It just isn't worth it, to set the house on fire because you want to save this cell... just get rid of it, and quickly, is my advice.

Timmo.


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## kramer5150 (Apr 22, 2009)

IMHO its not worth the risk and your personal safety... when new trustfires are ~$10.

play it safe and do the right thing.


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## Black Rose (Apr 22, 2009)

If that's the case, I'll contact the seller and get a replacement cell.

I have one AW 18650 already and will probably get another. 
I am also looking at getting some of SKU 20392 from DX as well.


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## old4570 (Apr 22, 2009)

Throw it in the charger , the two I have are just fine .... + Of the two I have one has the best discharge rate of all my 18650's .. 

I think the limit is 2.7v is it not , so if it drops bellow 2.5 it might be cactus . 

Throw it in the charger , and watch the temp , if it stays cool all should be sweet .... If it gets warm/hot it could be damaged and resistance to charging has increased ... 

Matt


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## Black Rose (Apr 22, 2009)

This is an unprotected cell....

I had it on the charger for a couple of hours. It stayed cool and was up to 3.92 volts when I took it off.


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## old4570 (Apr 22, 2009)

Black Rose said:


> This is an unprotected cell....
> 
> I had it on the charger for a couple of hours. It stayed cool and was up to 3.92 volts when I took it off.



Yeah , Unprotected cell :thumbsup: 

Protection kicks in at 2.7v for protected cells if me remembers correct , your's was sitting on 2.8v so it should be good , and from what you say , it is good .




If anyone wants to throw away there AW's when they hit 2.8 , send them to me ...


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## linterno (Apr 22, 2009)

old4570 said:


> I think the limit is 2.7v is it not , so if it drops bellow 2.5 it might be cactus.


This limit is under load. If you tested the battery without load then it is definitively over-discharged.


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## 325addict (Apr 22, 2009)

exactly. If you measure 2.8V under no-load circumstances, this is not OK. Period. If you discharge a cell to 2.8V the voltage will rise to well over 3V when you remove the load from it. I just measured this, I hit the protection of my Ultrafire 17500s today, after a short while, voltage had bumped up to more than 3.5V in no load conditions.

Timmo.


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## Mjolnir (Apr 22, 2009)

So then what is the minimum voltage without load that an unprotected cell should be allowed to reach? I have at least a dozen cells from laptop batteries, but I'm not really sure what voltage is considered to not be worth the risk.


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## kramer5150 (Apr 23, 2009)

Mjolnir said:


> So then what is the minimum voltage without load that an unprotected cell should be allowed to reach? I have at least a dozen cells from laptop batteries, but I'm not really sure what voltage is considered to not be worth the risk.



I have pulled dozens of laptop cells as well... any one that meters above 3.0V is a keeper. So far this rule has not let me down (knock on wood).


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## mdocod (Apr 23, 2009)

You can hit 0V without doing *much* harm if the cell is recovered in short order. The intensity of the damage has to do with how far away from ideal the voltage the cell is at is combined with how long it has been that way. Unfortunately, when you order a cell and it comes out of the package at a particular voltage you know only half the story. More than likely many of these chinese flashlight oriented li-ion cells are actually pretty old cells bought from factory buy-outs and things of this nature. 

-Eric


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## Mjolnir (Apr 23, 2009)

So if I recharge the batteries when the hit 3V (without load, after using them in a light), they should be relatively fine?


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## csshih (Apr 23, 2009)

It'd be best if you didn't constantly do that.


usage life will suffer


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## bigchelis (Apr 23, 2009)

Mjolnir said:


> So if I recharge the batteries when the hit 3V (without load, after using them in a light), they should be relatively fine?


 

I been using for around 2 months now 2 sets of laptop batteries whose initial voltage was under 3.7v, but not lower than 3v and so far they been holding up. My WF139 charger wouldn't charge them at 3v, but would charge the ones with 3.5v and up. I had to use a cheap unregulated DX 18650 charger to charge the lower voltage cells.


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## Mjolnir (Apr 23, 2009)

csshih said:


> It'd be best if you didn't constantly do that.
> 
> 
> usage life will suffer



So 3 volts is too low? 
Basically, I am trying to determine what the minimum safe voltage for these cells should be (what they would cut off at if they had protection). I have a digital multimeter, so I won't be measuring the cells at load. At what voltage (minimum to preserve battery life) should I cease to use the battery in the light and recharge it? I have enough of these so I don't mind if a few go bad, but I would like to get as much use out of them as I can.


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## csshih (Apr 25, 2009)

be best to read this guide 

https://www.candlepowerforums.com/threads/201375

your batteries are LiCo..

but.. to the lazy:


> LiCo02 cells should not be discharged below ~3.0V under a load, (varies by manufacture). A good rule of thumb is that when the cell reaches ~3.5V open circuit, it is dead and should be recharged. Over-discharging a cell will increase the rate of internal oxidation leading to reduced capacity, reduced cycle life, and increased likelihood of explosion/fire. Different cells are rated for different maximum discharge rates, usually specified between 1.5 and 2C. (C ratings are having to do with time, a 2C rating, means 30 minutes, 1C means 1 hour, 4C means 15 minutes, 0.5C means 2 hours, etc etc, bigger C). Check to see what your cells are rated at and use them in an application that is within the bounds of the maximum discharge rate.



sorry for the delayed response.


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## Bullzeyebill (Apr 25, 2009)

Black Rose said:


> This is an unprotected cell....
> 
> I had it on the charger for a couple of hours. It stayed cool and was up to 3.92 volts when I took it off.



Was 3.92 volts at full charge or did you take it off before the charger indicated full charge? If full charge is only 3.92 volts then it is not a keeper.

Bill


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## Black Rose (Apr 25, 2009)

I took it off before the charger indicated a full charge.

It has now settled down to 3.84v from the initial 3.92v.

I haven't had a chance to finish charging that battery yet. When I do complete the charge, I'll be doing it outdoors.

The big question is how long did that cell sit at 2.8v before I got it.


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## Bullzeyebill (Apr 26, 2009)

I think that the question is will the cell charge up to 4.2 volts, or very close to that. Then see what the drop in voltage is. A healthy LiIon will hold its voltage when fully charged, and if there is a drop it will be very minimal. If there is a severe drop in voltage then yes the LiIon stayed at a low voltage too long.

Bill


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## Black Rose (Apr 26, 2009)

I charged it up this afternoon.

After charge completion, it registered 4.15v (all my cells come off the WF-139 around 4.15 - 4.17v).

Several hours later it has settled to 4.12v.

How long do you normally have to wait to see if a cell is damaged?


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## Bullzeyebill (Apr 26, 2009)

When my good LiIon's charge up to 4.18 (one charger), or 4.2 (other charger) they do not drop more than 0.01 volt. Some of them don't drop voltage at all when fully charged. I try to make it a point to start using them shortly after being charged so they do not start self discharging, however I have had some cells maintain full charge for weeks, or only use about 0.01 volt. 

With your problem cell, see if it self discharges any further. If it does then it is not a good candidate for heavy duty use. 

Bill


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## Black Rose (Apr 27, 2009)

The cell has lost an additional 0.02v in 24 hours.

I'll continue monitoring it for the rest of the week, but it appears to be wounded.


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## Black Rose (May 6, 2009)

The cell continues to self discharge...it's down to 3.97 volts now.

How do you properly dispose of these cells?


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## seaside (May 7, 2009)

My good cells are holding voltage quite well. They are like 4.2V off the charger, 4.19V after a week.

Some of my cheap cells act like what you said. 4.16V off the charger, settled down at 4.14V, then the next day it's 4.08V and they seem to hold the voltage at that level. 

Holding voltage at certain level is good, but they shouldn't loose that much voltage in a day or two. I do not consider them as complete crap as long as they still are usable. But if they go down below 4V like yours? Hmmm.... 

I guess there must be a reason why they are so cheap.


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## Black Rose (May 21, 2009)

After almost 4 weeks, the cell has self-discharged to 3.82 volts.


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## old4570 (May 21, 2009)

If you had a battery cycler , id say cycle it a few times ...

Since you dont , throw it in a flashlight and run it on Hi for 5 minutes , let it cool and do it again till you hit sub 3.5v , charge it up , and then run it down , repeat a few times , then charge it up and see what happens ..

self discharge is a common problem for Li-ions , some do it some dont . 

I have lots of CR123A rechargeables , some discharge more than others , I think its the trustfires , and they dont seem to discharge at all .


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## mdocod (May 23, 2009)

Black Rose said:


> After almost 4 weeks, the cell has self-discharged to 3.82 volts.



IMO, it's done. Hang that cell up.


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## Black Rose (May 23, 2009)

Yep. I'm going to check the city's recycling program site and see who takes back lithium based cells and drop it off.

I'm not going to risk playing with a wonky unprotected cell.


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## DM51 (May 25, 2009)

Li-Ion (LiCo) cells should be shipped/stored at 3.8V – 4.0V. Any cell left sitting at <3.0V for any length of time will suffer permanent damage. The lower the voltage and the longer it has been left there, the worse the damage. 

Over-discharged cells can sometimes be recovered. The correct procedure involves slow charging (at ~1/10C) until the cell is safely >3.0V, then charging normally to full, monitoring it constantly for over-heating. 

A fully charged Li-Ion cell should charge to 4.2V. If it subsequently loses some of the charge, this indicates a degree of damage or aging. If it cannot hold above 4.0V (~80% charge) it is no longer worth keeping.


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## AlexLED (May 25, 2009)

mdocod said:


> You can hit 0V without doing *much* harm if the cell is recovered in short order. The intensity of the damage has to do with how far away from ideal the voltage the cell is at is combined with how long it has been that way. ...
> 
> -Eric





DM51 said:


> Li-Ion (LiCo) cells should be shipped/stored at 3.8V – 4.0V. Any cell left sitting at <3.0V for any length of time will suffer permanent damage. The lower the voltage and the longer it has been left there, the worse the damage.
> 
> Over-discharged cells can sometimes be recovered. The correct procedure involves slow charging (at ~1/10C) until the cell is safely >3.0V, then charging normally to full, monitoring it constantly for over-heating.
> 
> A fully charged Li-Ion cell should charge to 4.2V. If it subsequently loses some of the charge, this indicates a degree of damage or aging. If it cannot hold above 4.0V (~80% charge) it is no longer worth keeping.



Ah, very good tips (although have been repeated for some times now...), thanks to you two !

So, I just unwrapped some 18650 from old Laptop packs. Their voltages were somewhere between 0 and 3.8 Volts. I didn't fuss with those below 2 volts, yet, and will probably dispose them of. Those with 2.2 volts and above I charged, starting with 0.1 amps, under close supervision. Didn't get hot and did accept quite Ah till 4.1 volts. They lit up some of my lights fine.  

I'll check the self-discharge in the next days. 

So, can I assume, after a slow-recharge of 2.2 volt cells, they are still fine ? I have no idea how long they have been below 3.5 volt....


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## SilverFox (May 25, 2009)

Hello Alex,

When dealing with Li-Ion cells that have been over discharged, I think it would be better not to assume anything...

When you have a few charge/discharge cycles on them, find that they don't have a rapid self discharge rate, and verify that they have at least 80% of their initial capacity, you can then feel more comfortable using them.

Tom


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## Black Rose (Jun 27, 2009)

Black Rose said:


> After almost 4 weeks, the cell has self-discharged to 3.82 volts.


That was posted on May 21, 2009.

It is now June 27, 2009 and the cell is now down to 2.76 volts.

I still haven't gotten around to checking out how to dispose of this cell 
Is there any danger of this cell doing anything nasty on its own?


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## Bullzeyebill (Jun 27, 2009)

That is truly a damaged cell. Most counties have a depot for hazardous materials that is open most of the time. Check you phone book for an appropriate agency.

Bill

Just noted that you are in Canada. Check your local province?

Bill


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