I'd try around a 3 cell 1300mah 45c as a safe starting place . You could try 4 cell similar specs too, but that might be too much voltage depending on the motor and esc you have. If you have too few cells (voltage) the motors won't spin fast enough to fly. To many cells and they let the smoke out the esc. Too few mah and the flight is just shorter (or longer with extra - but this add weight which can cause poor flying performance). A 'c' rating lower than about 25ish will probably leave the motors starved for pixies, and diminish performance. Higher the C rating, the faster the amps leave the battery without heating up too terribly, which reduces battery life and the amount of energy that can be drawn - sort of a downward spiral of bad performance there.
