Why is a cellgroup decarge to 0,0 volt

Eastcoast71

100 µW
Joined
Jun 8, 2022
Messages
8
Hey

I have this two year old pack, 17s8p 18650 battery
I do not know how its been treatet by its previus owner. But one cell group is 0,0 the rest is 4,05 volt.
Why do the bms do that? Or is it because i have a bad cell with High ir after two year? Then it will decharge the whole parallel group. Or is it this stuck bms thing, where do i mesure this? Is it on the big transistors that is mounted on the aluminium heatsink?
https://m.alibaba.com/product/1600124283920/BesTech-12-6V-11-1V-3S.html
 

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Here's some ways,
1. The cell group was the one that was powering the BMS and after a long period of no recharge, it ran down to zero. You've got two IC's on that BMS. They don't need much power, but they still take a little.
2. The BMS had a failure, and the circuits on that cell short circuited.
3. One of the 8 cells in the group started to have self discharge issues. and it drained itself and all of its parallel friends to zero.

Any cell group that has gone to zero is toast and should not be re-used.
 
To docw009 maybe your answer nr 3 is correct. I capacity testes the Cells from the group. Its the 8 first cell in the pic. Cell nr 1 drained it selves after a week to 0,0 again.
 

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To 999zip999 this stuck thing! How do measure it. I have the bms dismantled now. You say its a balance or drain resistor, so it could be to places on the board
 
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