My uncle just bought a Trex 550E Pro DFC. It has a 730MX 850 KV motor and a 1:7 gear ratio. What kind of battery should he get for it? He's new to flying and is still in the hovering stage with a blade 450. This is obviously a very hot heli, what can we do to keep it tame?


I was thinking it needed a 6S 5000 mah lipo, but I did a quick calculation which doesn't seem to make sense to me.
4 volts * 6 cells * 850 KV = 20400 RPM / 7 = 2914 RPM... I can't imagine a 550 turning at that kind of head speed. I was thinking 1800 - 2000 was a lot more reasonable. I haven't been into helis since 2008 (Getting back in shortly) so maybe my calculations are missing something.