there is a good reason batteries are never mounted in passenger areas, lead acid batteries give off hydrogen gas and are an explosion hazard in closed spaces
Bill
Ahh, but they do put batteries inside the passenger compartment. It's actually becoming very common. VWs used to run them under the back seat for years, as do some BMWs. Buick and Cadillac are currently running the under the back seat, too. These batteries are vented to outside the passenger compartment, and are sealed otherwise.
If you were to mount the batteries behind the seat, I would suggest using a sealed battery box with venting to the outside. You may also want to consider using an AGM type battery, which does not gas as much as a flooded battery. I don't know if you'll be able to find any listings or info on it online, but 4 Wheel & Off Road did a '57 Chevy 4x4 conversion back in the late '80s called Project Early Iron. It was built with dual batteries mounted behind the seat, originally flooded type, but later changed to Optima batteries when they first came out.
