lightweight battery

Has anyone used one of these in their car (or, dare I say, in a monster mod)?

http://www.voltphreaks.com

It doesn's say, but from the description sounds like they're using Saft or A123 type cells.

That's very cool, but no way am I spending that kind of money.

I've seen those before, and while I am a little nuts about weight reduction on some of my cars, but I'm not crazy enough to spend $350+ on a battery to save just a couple of pounds. The stock battery in my Miata weighed 20 lbs, the Odyssey dry-cell battery I have in there now weighs 11 lbs, and I have a 6 lb AGM battery that we put in a friend's Miata that was designed for a jetski. The 6lb battery worked fine in his car for about a year, and it will soon be going in mine. That 6 lb battery only cost $55, so that extra 3 lbs worth of weight reduction would cost $300. No thanks, but it is nice to have that alternative.........maybe someday.

The cheapest is $359 O_O

No way in hell, I'm sticking with my heavy flooded lead-acid antiques.