Anyone who’s ever ridden a bicycle with a dynamo light should get an idea of how electric bikes work. With a dynamo light the kinetic energy of the spinning tyres turns the dynamo, transferring energy and ultimately powering the light. Electric bikes work oppositely. A ‘dynamo’ of sorts, in this case a battery, produces energy that transfers to kinetic energy in the tyres and moves them forwards.
A typical battery in an electric bike will have approximately a quarter of the power of a toaster, 350-500W. The batteries need to be able to store as much power as possible, and for this reason lithium-ion batteries (like the ones in your mobile phone and computer) are most commonly used. They can often be taken out of the bike and recharged by being plugged into a standard mains plug socket, and most bikes will give upwards of 80km (50-miles) of battery-assisted riding. The battery powers the motor, which will can increase the speed by about double what the rider is pedalling, up to a top speed of 32kph (although the legal limit for an electric powered bicycle is about 25kph, or 15mph). The motor can either assist the pedalling of the cyclist or provide separate power controlled by a throttle on the handlebars.