Found an EV site which you may find of interest.. http://www.evalbum.com/build#buyparts

Quote from the 'Building an EV' section

"Is there anyway to make it recharge itself while driving?

In a word, NO. Driving generators off the wheels, adding a windmill on top and similar ideas are often suggested. The problem is the increased drag from such items would be several times greater than the added power they would generate. It is a nice idea, but it won't work. There have been some folks working with pusher trailers to allow the EV to become a hybrid for highway use. You can find some info on one on JB's webpage - http://www.jstraubel.com/EVpusher/EVpusher2.htm "

This would explain why a lot of the current hybrid cars only recharge themselves using re-generative braking.