Design and Development of a Prototype Super-Capacitor Powered Electric Bicycle

The design and development of a prototype super-capacitor powered electric bicycle (E-bike) is presented. An existing general-purpose bicycle was retro-fitted with a brushed DC motor driving the front wheel, a super-cap bank capable of storing 74 kJ, and a bi-directional motor driver for acceleration and regenerative braking. It was envisaged that the designed E-bike would fulfil the role of a campus commuter, whereby members of the university's community could utilise such E-bikes to traverse a large campus. Consequently, the range of the E-bike was not as important as the rapid and frequent charge cycling requirements, hence the benefits of using super-capacitors as an energy storage medium was exploited. For the design of the E-bike, an 80 kg cyclist was assumed. However, the developed prototype was tested with a 55 kg cyclist and demonstrated a satisfactory range (pedalling-free) and top speed of approximately 1100 m and 23 km/h respectively. Two weaknesses of the design that need future consideration are the unbalanced charging of the series-connected super-capacitors and the inadequate response time of passive thermal fuses under short-circuit conditions of the super-cap bank.