Found this Home Built Dual 50A H-Bridge Circuit http://www.ianjohnston.com/content/index.php?option=com_content&view=article&id=63 wich is quite nice.
- Dual Channel (able to control each output independently).
- ~50A continous per channel @ 24vdc.
- Beefy design in terms of terminals, cooling etc.
- Output stage containing both N-type & P-type Mosfet for push/pull operation.
- PWM controlled with added logic for motor direction control input.
- Logic for protection against turning both left or right side push & pull mosfets on at the same time (a sure recipe for smoke!).
Design Specifications:
DC supply / Motor drive output = 10 - 30vdc.
PWM / Direction control logic = 5vdc TTL.
PWM frequency = Tested at 488Hz (standard Arduino PWM) & 1.95kHz (should also work a lot higher).
Main output max. load (Amps) = T.B.A. (theoretically = 50A).
+5vdc supply (onboard logic & external)= 0.5 Amp max (1.0A if you upgrade the inductor).
IMPORTANT NOTE: This design offers no real over-current or over-temperature protection. You will also need a suitable heatsink.