Huge sparks when turning in battery at controller connection


New member
Local time
4:28 PM
Jan 23, 2023
I have a bbshd with a 52v 17.5ah battery. The other night I plugged it in to charge. The next morning I came out and the charger was blinking between green and red and the display wouldn't turn on. The battery is reading a full charge from the bms and everywhere else. I put new xt90 connector on the battery and the controller. When I plug into the controller and turn the battery on I get a huge spark that melts the metal on the positive of the connection. All connections from the controller to other source e.g. the display, throttle and whatnot are all fine. What would cause this and where should I start. Thank you for your time.
Oh that doesn't sound good.

"turn the battery on I get a huge spark that melts the metal on the positive of the connection."

Sounds like you have a dead short somewhere. Are ya sure ya put the XT90 connectors on correctly? Has the battery been dropped?
I hook up a 52v 40ah battery to my bbshd and get a crazy spark all the time, but nothing melts.

Welcome to the forums by the way :cool:
Positive I put it in right. Haven't dropped it or had any significant damage to it. It stays on my downtube and the bike hasn't fallen over wither
Question, why did you replace the battery connector? Was it melted or damaged in any way that required you to change it??And is this motor rated for 48 volts or 52??
The very first thing I would do is get that pack the hell away from your house or any flammable structure. Maybe put it inside of a barbecue in the back yard in the middle of the lawn.

Sparks are normal on connection unless you are using an XT90S vs. an XT90. But even then they are just annoying little pops and nothing like this. If you have to ask where to start on diagnosis, I'm thinking this is going to end up being a write-off.