Regarding battery technology, if I'm not mistaken, that's already a solved problem: Lithium-Ion batteries have great capacity and are quite light. Their only problem is "venting with flame" if you don't charge/discharge them within their limits, but electronic control can mostly eliminate that.

Now we just need a battery company to start making car-battery-sized Li-Ion's and sell them for a reasonable price. When that happens, I think you'll see some serious action.