Nice writeup, Azimov! I've got a couple questions for ya:
1) Would a car with the mosfet mod be able to use fewer solar cells to get the wheels turning? Perhaps 3 instead of 4?
2) I'm thinking of doing a "hybrid" bit
I'd like it to run off a battery while the battery is getting charged by one or two solar cells mounted on a stock body's hood and/or roof. I'd need a diode for that I guess, but what kind? Would it still be safe to charge up the battery with DC current with the diode and solar array attached, or would I always have to charge with sunlight? Depending on current draw, using just a couple cells to charge probably wouldn't last indefinitely, but it would greatly extend runtimes, and you could just let it idle for a few minutes to recharge some. The only problem I see is that you need enough voltage to charge the 1.2v battery, and these cells are only 0.5v each. Looks like you'd need three of them; I'd like to get that number down to two. Gotta find another cell with at least 0.75v and hopefully still have sufficient current.
BTW, can you edit that link in your first post? It's not working for me.