For those loking for a lighter weight battery that don't want to spend the $$$ on a dyna batt, I came across somethign that might do the job at Autozone today.

It's a group 51 battery. It's only 5" deep, 9.25" wide and 8" tall. Roughly 1/2 to 2/3rd the size of a normal battery (depending on what group battery you are comparing).

There are three levels of it:
500CCA: $75 (8yr warranty, 3 year non-prorated)
425CCA: $50 (7yr/2yr)
410CCA: $45 (6yr all prorated)

Also found a 8AM1U (I think that's the group size) from a Mazda Miata that's pretty small. It's Miata specific in fact. A little smaller than the group 51, but it's $80

 

Here is a battery you my be interested in :

http://www.gotbatteries.com/Productp...06S1P&AddOn05=

 

I am thinking of getting something similar just to run at the track.