I see.
Ok, if you connect two battery Packs in parallel, you should get a longer runtime, since you increase the amount of mAh. Is this correct? If you connect two battery packs in series, you have a higher voltage; why? Higher speed/torque of the engine? If so, my next question is... would the engine be too slow if I make it run on 7.2 volts, in parallel, to increase the runtime?