Batteries are heavy, and consequently so are many electric bikes. Alex Coulombe demonstrates the BionX, a conversion system that you can add to any bike, that tops out at fifteen pounds.
Image credit Emma Alter
A seven pound, 350 watt gearless and brushless motor replaces the rear hub and the battery pack is fastened to the frame. The lithium-manganese battery charges in three hours and go for seventy miles, helped along by regenerative braking. Use up a lot of juice going up a hill? It will charge itself going down the other side. Looks like a great option if you need a boost to your ride or have a long way to go to get to work. The ability to put it on the bike of your choice is an interesting option as well; they show it on tandems and recumbents as well as conventional bikes. ::Bionx