Watch out for bus bar shorts to battery case

[Quattrohead]

I made up a new battery pack using EVE 280ah cells and used the supplied bus bars. However, I like to attach the BMS leads directly to the bus bar with a screw.
The bus bars I got were flat and my self tapping screws slightly too long, I noticed a small spark when screwing down a lead from the bottom of the screw and found this.
It wasn't a 280amp short, more from the floating voltage the cells seem to have on their case.

 

[Hedges]

I think the terminals and metal electrodes are isolated from case, but electrolyte between them forms an electrochemical cell.
I would imagine one gets corroded when current flows, possibly eating through the case.

Is that an insulated separator you have between them, protection beyond the blue plastic? It seems curved, not filling the entire area (which would only matter if compressed.)

 

[Quattrohead]

No compression and no separator, 2x wrap should be good enough.
And yes these latest cells were not the flattest but are well matched....for now.

 

[Ampster]

Yes I found the same thing when tapping the bus bar for screws. Exactly in the center is the spot where the can sides are the spot where they are least protected. The wrap does not extend around the top of the can I offset the location of the tap slightly because the back plastic on the top is thicker. I also used shorter screws, or a washer above the BMS stud to give a margin of safety.

 

[Bluedog225]

No offense intended. Those are a bit more than slightly too long.

 

[featherlite]

I am now forewarned ... thank you!