I've actually considered this, and done a little research on the idea.
A small gas generator should work (and having compatible voltages). This is the thing that puts me off. There is NO reason that you cannot substitute some kind of small gas generator instead of all those batteries.
Probably a 3500-5000 watt generator (Even honda sells them), and the same for the electric motor(s). Of course you'll need a converter/step up, or step down transformer, and some other electrical workings. but it should weigh less then all those freaking batteries.
The other thing that puts me off, is the fact 90% of the fuel burnt is wasted in heat. 10% is propulsion. Now, a few years ago, I saw an article in Discover mag, and someone had invented a diode (transister, whatever) that when heated, produces electricity (a voltage, whatever). Now, why can't someone mass produce these suckers, and have a backup electric motor, and
cover any components that produce heat (the generator) with these diodes?
Regardless, the stuff is out there to have a car that will go hundreds of miles to the gallon (considering that, for example, those honda generators will run for like 10-11.5 hours on a tiny tank of gas.
I remember watching on tv, back during the first oil crisis (late 70's) that these university students had taken something like a british MG, (or something like that), and made it run 100 mpg. Now where is that?
It's the car companies that are in bed with the oil companies that won't allow it... or offer it.
If any of you ever do this, best thing to do is to keep quiet about it. Someone will try to shut you down. back in the 80's, there was a guy who had an old 79 volvo, and made his own moonshine, and ran the car on it. The govt gave him such a hard time (all the redtape and such) that they tied him down in legal costs, permits, and bylaw infractions, that he was forced to give up. (Harrowsmith article - The New Moonshiners)
http://evhelp.com/index.htm