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 I'm going to ignore your first sentence

It's not clear what the old circuit had. The wiring for that plug is somewhat confusing. And it's not to keep the bike from turning on while charging. It's to keep the charger from outputting 52V unless it's plugged into the battery

@MLE_online

I would guess that 'T' is the temperature of the battery pack for two reasons, one it doesn't want to charge batteries that are 'hot' (fire hazard) and batteries start heating "faster" when they are fully charged. (I had a NiMh charger that used this to trigger the 'full/float' state). You might be able drive it with a voltage (start from zero and go up slowly) LM35 worked that way.

@RueNahcMohr