5 Amps through car
The standard is 7.2 (6 cells) so eveything is designed around that. You can push it more by adding a extra cell or even two but the motor will wear much faster.
But as most motors (except the ones for planes of drag racing) everything is supposed to worl to 7.2 volts.
The reason you can get away with more in motor is that a motor wont be destoyed instantly by push it above it limit make it wear fast.