Even with a 6X reduction in capacity, that gives me a ~40 mile range (assuming the Tesla Roadster's 241 mile range), which is enough to get from from the house to the coffee shop to the office to the cafe and back home.
At "only" 6x reduction in capacity, you're still looking at $10,000 of battery if you get a Li-Ion battery. I'm not sure of the costs of a lead-acid, but expect 2x the weight of an equivalent Li-Ion, up to 10x the volume, and much less flexibility in shape.
Sure, if you only travel a handful of miles and you don't mind dropping $20k+ on a car with that kind of range, it works. But it isn't a panacea.
