In a follow-up to my previous journal entry titled "Multiple Stages," I'd like to add the following link:
I mentioned the fact that you'd be best served by batteries AND supercapacitors. Well, these guys are producing something they call the "powerpak," which is a lithium battery with an integrated supercap. The result is something which is part main store and L1 power cache. It can dump high power until the supercap is drained, then dump a more normal amount of power from the battery. The result: high energy density AND high power density. A few of these, and I could probably make a freeway-capable electric motorcycle.
Oh, and let's not forget these guys. Want a hub-motor for your vehicle, so you can do away with the transmission, differential and drive shaft? No problem; the largest one the make, at the moment, is about 14 kW (about 19 hp), but if you put one in each wheel, you've got nearly 80 hp STRAIGHT TO THE WHEELS! That should sufficient to make some little two-door putt-putt get up and hustle. And, since you eliminate a large part of the complexity (and friction), you improve the miles-per-kilowatt-hour, which mean 20 kWh of batteries will take you even further.
Getting VERY close to being able to make my own, practical, BEV.