Just as an aside, I also fitted a B2B (battery to battery charger) on my current motorhome which I've never done before. It's a Renogy 40A charger that connects from the vehicle battery to the battery bank switcher. I've also fitted a physical led switch which means I can start the vehicle, switch the Renogy ON and it will then put up to 40A as required per hour into whichever bank I want. I think the standard alternator on a 2006 Ducato is a 95A (which I can't presume would ever kick out that much) but I have measured the output from the Renogy and it does indeed put out 40A. If the banks ever needed a quick top-up a couple of hours driving would achieve this. This will be invaluable in autumn, winter and even spring when the solar just isn't enough to get a full charge back into my batteries. Lead acid batteries function much better (and longer) if you can keep them at maximum and not have them sitting around at 70% for days on end.