Bad Cell?


New Member
Hi, so my new prismatic battery I built is exhibiting a behaviour where at rest or low discharge current cell 3 is operating at nominal voltage compared to the other cells. However when under load (see second photo) the cell exhibits a voltage drop that is not nominal compared to the other cells. I top balanced the cells to 3.65v while in parallel, then connected in series before discharging to 2.5v before final assembly of the pack.
The positive terminal of cell 3 does appear to get warmer compared to the other cells when under load.

do I have a bad cell? Or maybe going through the top balance again to see if this behaviour gets corrected is the way to go?



Bob B

Photon Sorcerer
Did you thoroughly clean the bus bar and terminal pad? Many of the terminals have residue on them.
I used goo gone followed by alcohol .... then burnished with emery cloth and then alcohol again. I would just clean the bus bars with alcohol since they are tinned.

One guy just had a hair under a bus bar that was totally messing things up .... you want that terminal pad to be pristine and flat .... also make sure the bus bars are perfectly flat.


Dumb Dumb
In addition the holes in the busbars are stamped out and there might be a slight burr there. I would check for that also.


New Member
You guys are correct. It was bad connections. I made the cable lugs out of copper pipe and they are not entirely flat.