- Batteries are still pretty sucky. Not everyone is open to the idea of laying down a few grand every xx miles when their battery pack starts dying. And they still ALL do die, even without being used.

- Batteries require a lot of energy to produce, the mining process for the raw materials is horribly polluting, as is the disposal of used batteries.

- simply charging and discharging a battery reduces overall efficiency, on top of energy costs to produce and replacement and maintenance costs

The fact is, even if you COULD get solar up to 100% efficiency cheaply, the battery problem significantly degrades that efficiency. If we did run out of fossil fuels, the smartest way to charge a car battery that WAS efficient would probably be with a nuclear plant, not a solar plant.

I think that synthetic fuel from an organic renewable feedstock (but NOT fricken corn) is the most promising since it won't require a complete infrastructure and/or engine technology change, burns cleaner than fossil fuel (plus the better photosynthesizers eat more CO2 as they're being grown), and does not have reduced efficiency because of the "on demand" problem.