Two digit range in a dirt-cheap super-fast roadster? Yes, please.

* very low two digit. If you use, for example, a bunch of lead-acid or something like that, you'll see much more than 2-3x reduction in capacity.

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.

In a decade batteries should cost quite a bit less than they do now.

And why would that be? Are raw materials getting cheaper?

If you're banking on battery technology improving, don't. Battery tech marches very slowly.

Well, from the horse's mouth but Musk would disagree:

http://takingpitches.com/2012/09/22/elon-musk-the-role-of-an...

He makes it sound as though the raw material cost is not the problem.

Also, Deutsche Bank in Dec 2010:

http://bioage.typepad.com/files/1223fm-05.pdf

Relevant bit:

"Based on discussions with industry experts and several automakers, the DB Auto team has lowered its advanced lithium ion battery cost projection by about 30% for 2012. Current prices have fallen from $650/kWh+ in 2009 to about $450/kWh now, and DB’s forecast is the price to fall at about a 7.5% CAGR from 2012 through 2020 to about $250/kWh."

And lots others on Google. I don't know enough about it to judge who is credible but I do believe that laptop batteries don't cost as much as they used to. It's not like Moore's Law, but I think prices have been falling pretty steadily.