The 200A rating of the VEC-200 is for the Phase current not the Battery current, and is the maximum permissible
pulsed current allowed to pass through the phase wires and motor windings, as the Phase current is not constant it is typically a lot higher than the Battery current.
On the Magic Pie hubmotors, the controller has a maximum "Battery drawn current" setting of 30 Amps, but the "Rated phase current (A)" has a maximum setting of 70 Amps.
I seem to recall that the VEC-300 only has a maximum "Battery drawn current" setting of 110 Amps, in which case, I would expect the VEC-200 to have a maximum Battery drawn current of around 2/3 of that, which equates to just under 75 Amps.
I am wondering whether the 50A continuous limit of the
BMS could have been responsible for the failure.
If the
BMS suddenly disconnects the battery under high load, it could result in a brief high voltage spike from the motor windings which goes straight into the controller. This sudden high voltage spike could result in damage to some of the components within the controller.
Take a look at
this thread for further information regarding a similar problem.
There can be a big difference between the recommended continuous current rating of a battery cell and the amount of current that it can actually supply under extreme load. The
BMS should always ensure that the the individual cells within the battery are not overloaded beyond their acceptable limits.
I accidentally directly short circuited a 5Ah LiPo pack
(without any BMS or fuse to protect it) while trying to demonstrate the spark caused by the inrush current when you first connect a controller to the battery. The pack was rated at 20C continuous and 30C peak, but one of the copper contacts instantly disappeared in a big flash within a fraction of a second, accompanied by an enormously loud bang:
I was very lucky to get away with nothing worse than some minor burns on my fingers. Never underestimate
the power stored within a lithium battery pack.
Alan