Kind of ghetto, but I run a lawnmower battery. Same size as a half size battery and has the same CCA's. I researched it for a while and bought one from Napa. Fits nicely even with intercooler piping running where the battery tray used to be. You have to modify your cables to mount to the different style terminals, but that's easy. I've had it on my car for a little less than a year and never had any problems with it.