[Patrick]

I think car batteries are usually ~40 to 50 Amp hours, maybe a bit more or a bit less depending on the size of the car.
10 nimh cells will give you 12 volts and 3.3 to 5 amp hours capacity depending on which cells you use.
A 10p setup (100 cells) will have similar capacity though. The nimh batteries would be a lot lighter, but probably 5 + times the cost.
Will a 12 amp controller be enough for a 200 watt motor? 12 amps at 12 volts will only be 144 watts.