Briefly shorted a cell, but it seems to be the strongest?

[patrickza]

3 months ago I put together a 16S pack made up of EVE280K cells for my electric boat. My JDB 300A BMS has two power leads going in and out, and while connecting the leads to the negative most cell, the other lead briefly touched the positive of that cell. Now it was a split second and my reactions pulled it away, but the terminal did lose a tiny bit of material.

Weirdly, that specific cell has always been 0.003-0.004v higher than all the others while in the flat part of the charge curve, while at the top of the charge curve it's usually in the middle of all the pack voltages with the max difference between high and low being just 0.003v. That same cell also seems to sag much less than the rest. Under a 5.6kw load that cell was at 3.285v, with the average being 3.25v-ish and the lowest at 3.236v.

So that has me wondering, did the brief short actually do some good, or is it showing higher because it's directly connected to the negative most with balance leads and the two fat cables.

It's not causing any issues, the pack has run perfectly for the last 3 months. I typically charge to 3.42v, and then let it go to 3.41v for float, and whenever it's anywhere over 3.4 it's perfectly in balance.

Any thoughts?

 

[timselectric]

The brief short didn't hurt anything. It wasn't long enough to create damage from heating.
But if you never charge above 3.42, you are still in the flat. So, there's no way to know if the cells are balanced.