It definitely wouldn't be caused by any differences in the MP4s, so it must be the batteries that are different
(or the way they are wired up).
Some batteries actually state that the power switch must be in the "ON" position in order for the battery to charge, so unless you physically disconnect the battery supply wire from the controller, it will obviously be supplied with battery voltage, and this may be why the throttle LEDs are lighting up while on charge.
If the charger supply has been wired to the output side of the power switch instead of the battery side
(either deliberately or accidentally) this would also send the charging current/voltage to the controller as well as
(or instead of) the battery.
This may have been done intentionally by the battery manufacturer so that any regen current from the motor can still pass through the charging circuit of the battery's
BMS while the battery power switch is turned off, although a suitable diode soldered across the switch connections would have been a much better solution.
It is difficult to understand why your batteries/chargers might be wired like this without knowing exactly how they are wired internally and how the
BMS is designed to operate.
- Exactly what batteries are you using?
- Do they have separate cables for the power outlet and charging input?
I would also check that the batteries are actually being charged while the power switch is in the "OFF" position by measuring the battery voltage both before and after a full charge.
Alan
