How many do you have now? Our 2015 Agile has two under the hood and a second pair in a rack under the rear, I'm assuming where the spare tire would normally be. (Our spare's mounted vertically on that trailer hitch set-up.) Those 4 batteries plus the 300W of solar on the roof work very well for us; we essentially never have to plug in.
Is that above and beyond the 12v sprinter engine battery or does your RV run on four 6v batteries instead of two 6v and a 12v? The two under your hood are where my single automotive battery is.Well-- if you already have the wo under the floor in the rear, perhaps you could put two more in under the hood... I'd think the ones in the back would be more difficult.
Here's what ours looks like; they sit directly in front of the driver:
Sorry, should have been clearer. It's a 2007 titled Roadtrek, built on a 2006 Sprinter as I understand it. Last of the 5 cylinders...It sounds like your 2007 Agile was built on the "first generation" Sprinter chassis, built by MB before mid-2006. The engine battery was under the hood in that model. There was no battery under the driver's floor. MB provided space for an auxiliary battery under the passenger seat for the first generation, but Roadtrek used that space for the fresh water tank. So Roadtrek put the auxiliary/coach battery under the rear seat. I thought RT started using the 2nd generation Sprinter chassis, with the engine battery under the driver's floor, in 2007 but apparently not.