how hot does a cell have to be a heater?

just starting to test capacitys, what is temp is concidered a heater? any reccomendation for a thermal heat gun?
thanks

About 45C, or about 113F. If it reaches that temps in the last few milliVolts (4.18 or so), it's possible it could just need a few cycles and it'll be fine afterwards. But if it still is around 4.1V and getting hot, toss it.

Korishan said:

About 45C, or about 113F. If it reaches that temps in the last few milliVolts (4.18 or so), it's possible it could just need a few cycles and it'll be fine afterwards. But if it still is around 4.1V and getting hot, toss it.

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ok thanks,

If it feels warm to the touch and makes you think "that feels warm" then it's too hot and you should throw it out.

@Average Joe suggested (when I asked the same question) that heaters can self-correct if you set them aside for a few days and retry a charge/discharge.
I am processing a large batch of Panasonic NCR18650As and found that maybe 10 out of 30 seemed to self-correct a week later - but I don't understand why.

OffGridInTheCity said:

10 out of 30 seemed to self-correct a week later - but I don't understand why.

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Battery University had an article on it, but I don't remember which article it was.

Basically what happens is that unused cells the electrolyte begins to separate. During the charge/discharge cycle, it forces the electrolyte to begin to become uniform again. It doesn't have anything to do with dendrites (similar to sulfating in lead acid). That's why sometimes after a few cycles the heaters no longer get hot. Though, they may have diminished capacity.

Jonisingt35r said:

just starting to test capacitys, what is temp is concidered a heater? any reccomendation for a thermal heat gun?
thanks

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Jonisingt35r

Any cell that gets "hot" has a internal physical orchemical problem.
The physical as in dendrites and other issues can influence the SOH of the battery.
IR is a good first indicator of suchissuesas high IR will indicate the SOH of the battery as being poor.
Seehttps://secondlifestorage.com/showthread.php?tid=6575&pid=50728#pid50728.
The chemical problems seem to be confined to certain manufactures and may or may not correct themselves.
Further study is needed but I can say for certain that if the IR is "good" onANY cell it will most likely (99% of the time) not create excessive temperatures. >35C or >10C from Ambient.
Unfortunately most standard testers opus, liitokala, zanflare , etc. use an internal resistor bank and woefully inadequate cooling to test the discharge capacity of the cells. This woeful cooling capacity generally shows up during a heavy discharge cycle and will heat the cell.

Any thermal heat gun will be better than none but to really see a proper picture you need a thermal camera.
They are expensive but I found that perfect primehas some very reasonable prices and the quality is good.

Wolf

I recommend getting a Seek Thermal secondhand, prices are reasonable if you wait for one to show up for sale below $120 or so. You need an Android or iPhone to work with it, depending on the version. For heaters, they may recover, but that doesn't mean they'll be any good after a few cycles. I tested a "typical" Sanyo heater, UR18650F, and it only lasted a few cycles before it hit 80% of original tested capacity. Lots of good info about this phenomenon including the tests I did here: https://secondlifestorage.com/showthread.php?tid=303&pid=41737#pid41737