There are two main ways to power an electric bicycle. Both have their advantages, but there's a clear winner in terms of efficiency, safety, ease of use and reliability.
- Twist & Go aka Full Power aka Hub motor The easy way to build a powered bike is to put the motor in one of the wheels, hook it up to a battery and control power via a throttle. The big advantage is there is often no need to pedal but you will need a bigger battery to cover the same distance. There are often noise and other ergonomic issues to consider.
- Pedal Assist aka Power Assist aka Pedelec aka Centre Motor aka Crank drive This is the best way to power an electric bike within the limitations imposed by physics and the law. A centre motor (as used in motorcycles) will efficiently multiply your own pedal power giving you total control over the motor at all times, a wider choice of gears and brakes plus far greater reliability and range, superior efficiency and hill-climbing. That's the theory - in practice it's a bike you'll want to ride every day.