Step one of rebuilding the e-bike my co-worker gave me is grafting a different battery management board onto the battery pack.
Transplant complete!

I still need to figure out how to wire up the charger plug. They used an XLR connector with four pins, and the charger doesn't turn the power on until it senses something (maybe a temperature sensor?)

Edit: i just needed to check the back of the charger for the pinout

@MLE_online "50V can bite really badly please be careful"

what did the old circuit have? Disability scooters have a pin on the charger to disable the controller so people dont drive away with the charger plugged in.

@RueNahcMohr Pin 3 on the XLR plug is typically jumpered inside the plug to pin2 to pull the inhibit line down while the charger is plugged in to the chair/scooter. It is this way on PGDrives controllers and a couple other minor ones. Generally, chargers do not communicate with the controller. There is no sensors or ground/earth connection.

@MLE_online

@hotarubiko @RueNahcMohr It's a temperature sensor. I've just figured it out.
@MLE_online That makes sense. Such is not typically needed on most chairs/scooters. @RueNahcMohr