I've got two vans with the hot water Grippa tank systems and I don't use the froststat because it's too noisy in the dead of night! Used to wake me up so god knows what the neighbours were thinking. I bet they were looking out of their windows for a low flying jet! On the plus side, I've never had to charge the batteries as they're always charged up from the split relay charger fitted by Grippa. When I had an Ionics system (years ago) I was always charging the batteries from the mains.