Run motor with hobby BLDC-controller

[Deere John]

Today I had to do some advanced fault finding. And since I haven't got my diagnostic unit yet I had to improvise a little. Only to see if it was the motor or the controller that didn't work.

So.... as a R/C flyer I thought on of these BLDC-controllers should work as well. So I just took my helicopter, disconnected the little (3.3kW) motor and connected straight to the motor cables. Connected a 6S LiPo (24V). And just tried! I have standard helicopter settings in the speed controller, governered (by the power output and control input). Worked really good, I had the wheel of the ground to make it go easy.



Here is a photo of the speed controller. This is one of good quality, a cheaper one for testing purposes will be bought, this one can handle 90A continous power also, quite overkill for most ebikes (this unit is like 5cm long, can't understand why these ebike controllers are so big).

 

[trex]

there are several reasons, technology: RC motors have high KV number, cost: e-bike controllers tend to cost less because the market is more cost sensitive, voltage: e-bike controllers are optimized to operate at higher voltage 6S to 13S, number of MOSFETs, e-bike controllers have 6/9/12 FETs to handle low speed motors. RC ESCs are just about suitable for crank drive motors, not for geared hubs or direct drives.

 

[Deere John]

I think it's mostly the kv (the high RPM) that makes it so powerful, and the controllers might be that small because they are optimized on a small range of use (70-100% pwm duty cycle only as one example), and also like you say, more exponsive, and also engineered to be light/small.

There are many cases with direct drive, fixed wings have that and I have seen helicopters with direct drive also, they just need a low kv motor.

 

[trex]

direct drive e-bike motors have KV in the region of 7 to 10, helicopter motors have KV in the region of 1000 to 1500.
At low speed, motors are naturally less efficient. The design of e-bike motors needs to be very much more advanced to minimize loss of efficiency.