The "GreenWheel" lets you turn a bike into an electric simply by swapping the rear wheel. The batteries and motor sit inside the plate at the axle, while the throttle control operates wirelessly through Bluetooth. At full charge, the GreenWheel has a range of around 25 miles, extended by the pedaling of the rider.
A GreenWheel equipped bike is a smooth ride, as Discovery News found out during a recent afternoon test ride around MIT's campus. Turning the handle mounted throttle, like any motorcycle, just a few small degrees produces a noticeable increase in power and a light electric hum.
The inventors estimate a life of nearly 40,000 miles, which is pretty incredible. They're trying out different sizes and power ratios and hope to have a product on the market very soon.