Electric bikes are similar to standard bikes, but have the leg-saving bonus of an electric motor to aid pedalling if needed, for as long as the onboard battery lasts.
The motor powers the bike via a belt onto the rear wheel, or a roller in contact with the wheel. It is mostly built into the hub to allow a low centre of gravity and the re-use of existing bike components elsewhere.
Batteries are usually re-chargeable from the mains, or sometimes also by pedalling or regenerative braking. Battery life can range from 5 to 50 miles, depending on the incline of the terrain and whether you are assisting it with pedal power.
UK the law states that electric bikes must cease providing power above 15mph and that the motor cannot continuously output more than 250W. The motor must stop providing assistance if the cyclist stops pedalling.
