Lithium ion batteries are pretty good and getting better - already, products like cameras and mp3 players that a few years ago were working on throwaway batteries are now switching to rechargeable lithium ion batteries. We've seen progress as well in the recharge times. The Prius with its Nickel Metal Hydride batteries seems just so yesterday. But we're not looking at an exponential improvement in battery technology, akin to Moore's law and computing power - as said in this interview 18 months ago, with MIT materials scientist and battery expert Yet-Ming Chiang, who cofounded the battery startup A123 Systems;

"One thing we have to keep in mind is you can't really conceive of anything like Moore's Law for electrochemical energy storage. Moore's Law was based on being able to perform similar functions [for computing] using either fewer electrons or, more recently, fewer photons. But energy is constrained by chemistry and the periodic table. Expecting Moore's Law from battery chemistry is like expecting steel next year to weigh half as much and be twice as stron