[Bill]

Yes, the battery is located in the compartment at the back. The stock battery sits in a plastic battery box, which in turn sits in a rather crude cutout in the floor so it doesn't slide around. The cover of the box has a short length of mini-dryer-hose running from it to a small outside vent, to keep any fumes from accumulating in the compartment. There is plenty of space for a second battery in the compartment. I would think that it, too, should be in a spill-proof box, and certainly it should be tied down so it doesn't move around. My personal opinion is that the venting is superfluous - this is by no means an airtight compartment - but others may disagree. If you decide to vent the second box, it should be easy to put a tee in the mini-dryer-hose.

This tends to be a busy compartment, as it is one of only two that are accessible from the outside. In this compartment, we carry our water hose, pressure regulator, sediment filter, toolbox, electrical spares and tools box, small vacuum cleaner, bag of charcoal, and a bunch of other stuff. So make sure the new battery is well tied down, and that the battery posts cannot be inadvertently contacted by any of the other stuff that gets tossed in there. With that in mind, it sounds like a great idea. When my stock battery goes bad, I will probably follow the advice of another poster, and put in two 6-volt batteries.

Bill