The problem is that standard Eriba Touring spec didn't, maybe still doesn't, include the facility to fit a battery. That means that many, especially older vans, have had systems installed by a caravan workshops and DIYers with varying wiring, charger and control gear, so without fully eyeballing an installation it's v hard to advise. That's why I suggested KC who could look at what you have and advise what you need to do to achieve what you want.