11P - Burnt connector

Symptom

The connection between the battery and motor popped and smoked.

Reason

Controller short circuit

Checklist

Troubleshoot

Solution

Replace controller

Symptom

There will be a spark every timethey connect the controller and battery together

Reason

This is to charge up the capacitor. Even if the antispark connector is fitted. i.e. X90s, usually the resistor inside the connector could fail after multiple uses. And spark will appear again. 

Troubleshoot

 To fix it simply ignore it, or replace the battery side connector with an antispark XT90s connector.

Solution

Meanwhile, a controller short circuit can be verified by connecting to the motor and rotating the wheel/ chainring backward. If there is high resistance it is most likely the mosfet shorted. Usually, controller burnt is obvious, just take a photo to verify is fine.