Motor braking.

[BrianG]

Aragon, do you think this stiffness is enough to stop a vehicle as fast as it does? I figured the ESC would basically energize all phases at once effectively locking the rotor. Of course, this can be controlled via PWM.

If it's just the motor braking by shorting (more or less) the phases, then the motor is taking the majority of the abuse except whatever voltage is dropped across the FETs. This is the only way I can see any energy being fed back to the batteries, but the induced voltage has to be higher than the battery voltage for them to be charged. Maybe this is what Griffin explained above, but I seem to be too dense to understand it.

If the ESC locks the rotor by PWM energizing all phases at once, then the ESC seems like it would be taking the abuse.