I like Jaksbak's solution. I have installed a 100ah AGM battery on its side (they say they don't leak and so far they are right) in the 3rd row foot well along with a CTEK DC to DC charger and suitable cabling to starter this then runs all my auxillary electrics and out to an Andersen plug for the trailer. I find having the battery in the car practical and with it in the 3rd row foot well out of sight and relatively secure and low in the vehicle which is good. It could also be removed quickly oif travelling light. I have trimmed some carpet to go over the battery and wiring and the kids can still sit comfortably in the rear row. I also have enough space for another 100ah