Yeah, This image is a decent depiction of what is probably tripping your BMS protection. Inrush_current Basically inrush current is a the sudden current draw that occurs when first applying voltage to the motor coils which act as a dead short to the battery. There is also a ton a current required to get your moving on your board from a dead stop but once you’re at speed all your motor is doing is overcoming friction so the current draw is less.
When you toss in that capacitor it holds enough energy that it can “smooth” out that sudden current draw(if it’s big enough).
EDIT: if you want to learn more about EE stuff than I would take a look at allaboutcircuits it has some good noncalculus based resources.
