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how hot does a cell have to be a heater?
#1
just starting to test capacitys, what is temp is concidered a heater? any reccomendation for a thermal heat gun?
thanks
Battery is li iron using 18650s, 14s, 0p, and growing cell so far 1000ish, untesteded.
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#2
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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#3
(09-16-2019, 10:21 PM)Korishan Wrote: 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.

ok thanks,
Battery is li iron using 18650s, 14s, 0p, and growing cell so far 1000ish, untesteded.
Bms chinese bluetooth
No solar yet, very soon, looking to buy panels if anyone has any?
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#4
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.
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#5
@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.
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#6
(09-16-2019, 11:44 PM)OffGridInTheCity Wrote: 10 out of 30 seemed to self-correct a week later - but I don't understand why.

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.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

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#7
(09-16-2019, 09:40 PM)Jonisingt35r Wrote: just starting to test capacitys, what is temp is concidered a heater? any reccomendation for a thermal heat gun?
thanks
Jonisingt35r

Any cell that gets "hot" has a internal physical or chemical problem.
The physical as in dendrites and other issues can influence the SOH of the battery.
IR is a good first indicator of such issues as high IR will indicate the SOH of the battery as being poor.
See https://secondlifestorage.com/showthread...8#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" on ANY cell it will most likely (99% of the time) not create excessive temperatures. >35°C or >10°C 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 prime has some very reasonable prices and the quality is good.

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#8
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...7#pid41737
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