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lithium cells over voltage

terrango

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Joined
Mar 28, 2020
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I have 2 cells in a 16s configuration that are 3.86V. The remaining cells are all perfectly fine, all in a normal range.
I reached out to the supplier of JK bms and they believe that the welding in the cells are faulty.
These cells have worked fine for 4 months. They have been charged to 100% and discharged a few times.
Last full charge was March 3, after that 2 cells started to shut down the charging.
I thought maybe giving it a few days to balance out might solve the problem, but the 2 cells continue to charge up to 3.8V.
This causes the Bms to shut down the charging.

Now i did look into my settings and OVP is at 3.65.
Temp where the batteries are is about 10-14C, nothing has changed in the last 4 months since these batteries have come online.
I attached a photo. Cells 14 and 15 are the issue
Any ideas what i can do??
Or should i reach out to the battery supplier for warranty?
 

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It is possible you have a couple of runners. Have you tried changing the top end to 3.45? Sometimes cells can take off after this.
 
I have 2 cells in a 16s configuration that are 3.86V.
Have you measured the voltage of the cells at the cell terminals?

Also unplug the balance wires from BMS and test voltage at the connector.
Pin 1 is negative.
Pin 1 vs pin 2 = ~ 3.2V
Pin 1 vs pin 3 = ~6.4V

...
 
The cells didn't create their own voltage to get to 3.8 volts. So seems like either the BMS is faulty and not cutting charge(allowing charge past the 3.65 volts), the BMS is faulty and not reading cell voltages correctly and the actual cells are not at that high of voltage, or your voltage sense leads have an issue and are causing incorrect BMS readings.

Have you measured the voltage on all 16 cells?
 
I havent had a chance to measure everything yet. I just shut down the charging on the bms yesterday and i will start testing the leads and the individual cells tomorrow. ill test and let you know what i find
 
Looks like this was a few bad wire leeds. #15,14,6,5,4,1 and the main neg all tested bad. Replaced the wire leeds and everything is back up and running.
After replacing the wires all voltages were within normal range.
The 2 individual cells that were over voltage before, were actually only 3.3v.
Anyway, thanks for the tips and advice.
 
Just stumbled across this vid:


? That thumbnail.... I would not leave them at high voltage for long.
 
So my issue turned out to be a loose connection in the main connector for the leeds that plugs into the bms. The voltage of the cells were actually 3.4v. I guess there must have been voltage leaking the other 2 leeds. The bms seller will send me a new cable.

Thanks everyone for the advice.
 
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