Detecting heaters and other cell testing questions

Dr. Dickie

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With HBs thread scaring the ap out of me.
I have tested or are in the process of testing about 2 thousand cells.
Of course I did many things wrong, but am getting up to speed and trying to rectify things. I have gone back and determined IR on all the cells that I capacity tested before knowing to do that.
My process has been:
1) Charge up (only cells with voltage above 1 V--slow charge and then up)--probably 95% above 2V
2) Capacity test through discharge (Opus),
3) RE-charge and measure IR.
4) Let them sit for about 25 days and toss any that are below 4.15 V
5) Hold for building

I have not, nor do I have a method of testing to see if they are heaters
So, I have several questions.

Will IR testing and self-discharge pick up any bad cells that would be potential heaters? My though is, the heat is result of high internal resistance with either self-discharge of just a short.
If not, I am getting two MegaCellChargers, which I understand monitors and records temperature during test.
So, would it be wise to just go ahead and re-test all the cells with the MegaCellChanrger? And if I do, how high of a temp constitutes a heater?

And, after you test your cells for self-discharge, do you discharge them to 3.6V for storage until you build your packs?

Thanks to all here as I have learned a lot. In fact, I have learned enough to have the questions above.:devilish:
 
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daromer

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You can easily spot them later with IR camera. The important thing that you should make sure is that you dont have the cells in your house. Preferable in a containment away from he houses. And second best in an off shed. NEVER EVER in a house where you live.

Heaters are generally sorted out if you test at 1A during charge and discharge Heaters will never get full and will get warm during that standard charge time.
 

Korishan

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Swap #3 and #1. Test IR first. This will weed out any unnecessary charging. By doing an IR test first, you will also weed out the majority of possible heaters.
It won't grab 100% of them, though. This is in part due to things outside control, like dendrite growth.

However, this is where further monitoring comes into play here. If you monitor each pack for capacity in/out, you can detect if there's a self discharger in that pack. You will notice this if a particular pack requires "less" balancing than the others. This is because it doesn't reach 100% full as fast as the others, so the other packs are brought down to match that one.

Another is to bring out the thermal laser/gun to check the packs for abnormalities. This is especially for bms systems that do *not* have temperature sensors on the packs, or only rely on "1" sensor on a larger pack.
 

Dr. Dickie

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Swap #3 and #1. Test IR first. This will weed out any unnecessary charging. By doing an IR test first, you will also weed out the majority of possible heaters.
It won't grab 100% of them, though. This is in part due to things outside control, like dendrite growth.

However, this is where further monitoring comes into play here. If you monitor each pack for capacity in/out, you can detect if there's a self discharger in that pack. You will notice this if a particular pack requires "less" balancing than the others. This is because it doesn't reach 100% full as fast as the others, so the other packs are brought down to match that one.

Another is to bring out the thermal laser/gun to check the packs for abnormalities. This is especially for bms systems that do *not* have temperature sensors on the packs, or only rely on "1" sensor on a larger pack.
Thanks Korishan.
Oh, I plan to monitor my packs better than the NSA on Assange.
In checking IR after charging, I have not found a single on that was 39 mOhms (my high end cut off). Only have had a couple that were either 37 and maybe one or two that were 38.
I will start checking the IR before charging, though I will have to establish a new value use as cut off.
 

Dr. Dickie

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You can easily spot them later with IR camera. The important thing that you should make sure is that you dont have the cells in your house. Preferable in a containment away from he houses. And second best in an off shed. NEVER EVER in a house where you live.
Thanks, daromer. Yeah, I have thermal vision, and plan to use it. Of course, I would prefer to get them out before making the pack. I am going to put my battery in the garage in a steel cabinet (vented of course). Best I can do, no possibility of a shed at current location. But will be doing that in a few years when I retire and move.
Heaters are generally sorted out if you test at 1A during charge and discharge Heaters will never get full and will get warm during that standard charge time.
Right now, I do my discharge at 0.5 Amp (close to 0.2 C which the manufacture uses), trouble is, I cannot monitor. They do get warm, but I think a lot of that is the Opus getting warm (discharge heat)--when I check with a IR gun, it is warmer between the cells, than on the cells/ Also, the cells do not seem to get warm when charging at 1Amp (or sometimes 0.8 amp) in the other chargers I use, but of course, no monitor.
 

daromer

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If you use 1A you weed out heaters alot easier. I also recommend atleat 1A.
Note that if you test 0.5A only you can/should never go above that later on!.

Most of the time heaters fail that check early and if you do proper IR test you get rid of many as well
 

Korishan

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Check out Wolf's thread on IR/Ohm readings. I think he has a full chart for various different cells.

There are different values because different class cells with different IR readings. For example, a laptop cell may have a higher IR, 40-Ohm, or maybe a little higher. But a power tool cell will have a much lower IR, maybe around 25-Ohm (just a guess). The higher discharge current, the lower the IR will be, generally.
So check out his threads on these topics.
 

OffGridInTheCity

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I find heaters by
- touching the cells as they charge, especially after the discharge test, and especially as they near full charge
- some will just get hot during charge
- and some never reach full charge and get hot as they try to fully charge from 4.15 to 4.2.

In my case, I tend to buy 'batches' of higher quality cells - and the batches have characteristics. For example, I just finished processing 1250 RING packs (2500 cells) and all except 6 were 2.5v+ and tested 100%. Not a single one got anywhere near warm much less hot or self-discharged for that matter. So my worry was quite low for this batch and I settled on a quick touch of each cell during charge.

Another batch I processed was raw NCR18650A medical packs - and about 10% got hot to the touch at various points of charging... so I took pains to test every single one using touch and then based a keep/toss decision on temp readings to keep myself honest. I think I tossed anything over 90F/32C.

In conclusion, you might have a more or less rigorous process depending on the source of cells your processing.
 
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floydR

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I too use the touch method to see if they are heaters.
Most of my LG M26 cells have been 39 mOhms or lower when tested before charging. After a charge test cycle @1A The few I have IR tested have been in the 35-36 mOhm range. The Lishen Cells I have are 18.7 mOhm (hoverboard cells) only have 60 of them. The LG M26 cells I have 2300+ cells. I have my 3 opus's over a fan sucking air from the bottom of the opus's. The cells rarely get warm especially now that it is winter. Ambient temp 65f 18c in room where I test the cells now, summer 75-80f 24-27c

Later floyd
 

Dr. Dickie

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Check out Wolf's thread on IR/Ohm readings. I think he has a full chart for various different cells.

There are different values because different class cells with different IR readings. For example, a laptop cell may have a higher IR, 40-Ohm, or maybe a little higher. But a power tool cell will have a much lower IR, maybe around 25-Ohm (just a guess). The higher discharge current, the lower the IR will be, generally.
So check out his threads on these topics.
Yeah, sorry, I should have said I have only LGM26 cells all from same year in same situation, and the 39m Ohms is based on what Wolf said to use as a max.
 

Dr. Dickie

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I find heaters by
- touching the cells as they charge, especially after the discharge test, and especially as they near full charge
- some will just get hot during charge
- and some never reach full charge and get hot as they try to fully charge from 4.15 to 4.2.

In my case, I tend to buy 'batches' of higher quality cells - and the batches have characteristics. For example, I just finished processing 1250 RING packs (2500 cells) and all except 6 were 2.5v+ and tested 100%. Not a single one got anywhere near warm much less hot or self-discharged for that matter. So my worry was quite low for this batch and I settled on a quick touch of each cell during charge.

Another batch I processed was raw NCR18650A medical packs - and about 10% got hot to the touch at various points of charging... so I took pains to test every single one using touch and then based a keep/toss decision on temp readings to keep myself honest. I think I tossed anything over 90F/32C.

In conclusion, you might have a more or less rigorous process depending on the source of cells your processing.
Yeah, I hit them with the IR as well as touch. For charging they are room temp of a few degrees above.
During discharge in the Opus they might get up around 100oF, but again, I think a lot of that is Opus blowing off heat.
 

Dr. Dickie

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Messages
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I too use the touch method to see if they are heaters.
Most of my LG M26 cells have been 39 mOhms or lower when tested before charging. After a charge test cycle @1A The few I have IR tested have been in the 35-36 mOhm range. The Lishen Cells I have are 18.7 mOhm (hoverboard cells) only have 60 of them. The LG M26 cells I have 2300+ cells. I have my 3 opus's over a fan sucking air from the bottom of the opus's. The cells rarely get warm especially now that it is winter. Ambient temp 65f 18c in room where I test the cells now, summer 75-80f 24-27c

Later floyd
Yeah, all of mine are LG M26 and almost all are 34-36 mOhms. When i touch them during charging after discharge capacity testing (generally 0.8 to 1 Amp charging), they are pretty much room temp or a few degrees above, especially when getting near full charge.
I feel a bit better now.
Thanks
 
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