Ditto. We run with two 110a/h batteries (and solar panels). Makes us fairly self sufficient as pump, HWS ignition, and lighting is all 12v anyway. Much cheaper to get wired up at time of manufacture, the weight of battery(ies) up to 30kg each needs to be considered and location (depending on size of your van). Decent AGM or gel batteries are required and get the best charger you can afford.