My 2018 summer project was a prototype electric bike. I converted an inexpensive mountain-bike to electric by adding a relatively small brush-less motor, a VESC controller, a 111Wh battery pack, and a BMS and throttle. The result was a bike that could go up to 44km/h on flat ground, with an assist range of about 10km, and a charge-time of about 2.5 hours.
The motor was a Turnigy SK3 (same model as was used on my electric skateboard project). It was fastened to the rear wheel by replacing the brake disk with a water-jet-cut #25 sprocket, and connected via chain. The motor itself was fastened via aluminum bracket to the same mounting holes as the brake. The brake itself had to be removed.
The 111Wh 6S battery pack was made out two 3S 5Ah packs placed in series, and connected to a suitable BMS. The main output of the battery pack was run through one of my high-power switches to the VESC. Since the VESC and switch don’t heat up that much, I felt it was safe to insulate the battery pack with some foam and place them in close proximity.
The VESC was connected to an inexpensive thumb-throttle, and programmed to control the current going to the motor. (more throttle = more current).
The casing of the electronics was quickly prototyped out of high-density foam. I would like to change this casing for a commercial off-the-shelf one, after which I would feel safe riding this bike in the rain. It’s probably the only thing keeping this bike being a prototype.