VESC hybrid drone generator

Hello everybody,

currently I'm working on a hybrid propulsion system for a fixed wing drone. The idea is to use a smaller battery to power the electronics and continuously charge it using a bldc motor attached to the shaft of a 2 stroke engine which will also be used for propulsion. I've seen a lot of post about this but they don't often go into detail about it. I have made a test bench with two bldc motors and I did some test to see which kinds of efficiencies I could get out of the bldc generator and VESC setup, and the efficiency results where kind of surprising. Peak efficiency was around 85%. that is power sent to the battery / mechanical input power. 

I'll attach the graphs down bellow, If anybody has any thoughts on this I'd really like to hear them. 

(I did expiriments at 4 different max regen currents)