They can be driven by pedals, battery power, or both. Schwinn claims a 40 mile range on a 4 hour charge. Top speed is about 14 MPH. The battery is located in the rack over the back wheel, and its removable so you can still pedal the bike while it charges. The electric drive adds 10 pounds.
2007 Schwinn World GSE Electric Bike for Adults
Schwinn Sting Ray 20″ Boy’s Electric Bike ($400)
Why don’t they charge the battery using pedal power also?
Also see the Revopower Gas Powered Bike Wheel.
