BMS shutting off randomly

[veloman]

Or sometimes when I hit a bump, ridden on my full suspension ebike. It's a 16s lifepo4 BMS (cellman pack). The cells are fine, I've checked each individually. SOC doesn't matter. Current being pulled from the pack doesn't matter. I've had it shut down when I was not pulling any power.

So I thought it might be a poor connection where the balance lead plugs into the BMS. I applied dielectric grease. Test rode went good for a few minutes, then it shut off again under moderate power and nothing too bumpy.

Could it still be a bad connection at the plug? Maybe somewhere else? I have about 350 cycles on the pack (or 700 half cycles to be more accurate). Still delivers 95% of what it did when it was at it's best.

Or maybe an issue inside the BMS?

 

[amberwolf]

Could be anything connection-wise, including pooor solder at pcb or comoponents, bad crimps on wires, wire borken inside insluation, spread connetor pins/shells, misalinged pins, broken traces or vias on the pcb, etc.

depnding on bms ddesign could even be balance wire broken at cell connection inside pack.

 

[dnmun]

check the sense wire connection to the cells. a bad B- connection will turn it off too. does it turn off the output mosfet's gate voltage when you wiggle the sense wires?

 

[veloman]

I seemed to have fixed the problem. I took out all 17 female pin contacts for the balance wires, tightened them and applied dielectric grease on the male pins. The first two female pins on the negative side were a little corroded. I suspect a poor connection just compounded itself to the point where it would have very poor contact.

On the bright side, all cells were within .01v of each other.

If the problem comes back, I will replaced the female pins.