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?

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!

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.

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.

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.

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

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.

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 .

:popcorn:

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

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.

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.

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.

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).

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

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?

csshih · Apr 23, 2009

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

usage life will suffer

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.

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.

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.

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

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.

Low voltage on 18650 cell

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