Two types of electric bike motors
Author: Source: Release time: 2015-12-15 20:05:12
There are two main kinds of electric cycle, broadly known as full-power and power-assist, and they differ in the way they're powered by the electric motor:
- Full-power: These bikes are designed for minimal pedaling over relatively short distances. They have large batteries and powerful hub motors and they tend to be big, sturdy, and heavy. Bikes like this are for people who love cycling but hate pedaling! Since you're using power all the time, the range is limited (typically 16–30km or 10–20 miles).
- Power-assist: Also known as pedal-assist bikes, these are the bicycle equivalents of hybrid cars: they're designed to be pedaled quite a lot of the time and electrically powered either when you're tired or when you feel like a bit of electric help (when you're going up hill, for example). Unlike full-power bikes, they don't have hub motors; instead, there's a separate electric motor mounted near the rear wheel and driving it either through the gear sprocket or simply by pressing against the rear tire. Where a hub motor is difficult or impossible to pedal without any power (because you're effectively turning it into a generator), power-assist motors turn easily with little or no resistance when you pedal. That gives power-assist bikes much greater range than hub-motor ones (as much as 80–145km or 50–90 miles).
Photo: Zap Electric's power-assist kit turns a conventional bike into an electric one. There's a bolt-on DC electric motor (weighing just over 3kg or 7lb) just above the back wheel, behind the police officer's foot, pressing against the tire and driving it by simple friction. The motor's powered by a compact lead-acid battery (weighing about 5.5 kg or 12 lb) inside a protective nylon bag. This kit adds quite bit of weight to the bike, but gives extra range and speed when needed. Photo taken in Santa Rosa, California courtesy of US DOE/NREL.