[scottyb]

If by size you mean amperage draw then yes, the motor can pull too much amperage for the controller to manage. By manage I mean that everything in the drive system must be matched up (engineered) correctly. If the motor is drawing more amperage than the controller can comfortably pass it will get too hot and the heat will cause failure, then same holds true for the other components in the system. If you get out of balance then something will fail.
And generally, no a battery charger will not run the system.