This sounds kinda cool:

AUSTIN, Texas (AP) -- Millions of inventions pass quietly through the U.S. patent office each year. Patent No. 7,033,406 did, too, until energy insiders spotted six words in the filing that sounded like a death knell for the internal combustion engine.

An Austin-based startup called EEStor promised "technologies for replacement of electrochemical batteries," meaning a motorist could plug in a car for five minutes and drive 500 miles roundtrip between Dallas and Houston without gasoline.

Ah...but not so fast:

Joseph Perry and the other researchers he oversees at Georgia Tech have used the same material to double the amount of energy a capacitor can hold. Perry says EEstor seems to be claiming an improvement of more than 400-fold, yet increasing a capacitor's retention ability often results in decreased strength of the materials.

"They're not saying a lot about how they're making these things," Perry said. "With these materials (described in the patent), that is a challenging process to carry out in a defect-free fashion."

Perry is not alone in his doubts. An ultracapacitor industry leader, Maxwell Technologies Inc., has kept a wary eye on EEStor's claims and offers a laundry list of things that could go wrong.

Among other things, the ultracapacitors described in EEStor's patent operate at extremely high voltage, 10 times greater than those Maxwell manufactures, and won't work with regular wall outlets, said Maxwell spokesman Mike Sund. He said capacitors could crack while bouncing down the road, or slowly discharge after a dayslong stint in the airport parking lot, leaving the driver stranded.

Until EEStor produces a final product, Perry said he joins energy professionals and enthusiasts alike in waiting to see if the company can own up to its six-word promise and banish the battery to recycling bins around the world.

"I am skeptical but I'd be very happy to be proved wrong," Perry said.

The other thing I'd be worried about is sudden discharge if you touch the wrong thing in the engine compartment. I knew folks in high school who thought the funniest thing in electronics class was to charge up a capacitor and then throw it to someone, and laugh when it discharged on contact. At the voltage levels these things would need, I'm betting an accidental discharge would almost certainly be more than a laughing matter.

Still...would be very cool if they can do it. Probably lots of other applications as well.

Wired News - AP News