2Cell 1200-1500mah Li-Po should give you 15-20 min.

Always give the heli a rest for 8 - 20 min so the electics can cool down. I don't try to charge the LiPo's straight after a flight as they are still quite warm. Quite often I'll pop the warm cells into the fridge for 30 min.

Only use 3C if the electrics can handle 11-12 volts (brushless motor and high freq. tail ESC) .