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.

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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.

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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).

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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.