Most caravans domestic batteries are 12v with the batteries charged by the towing vehicle’s alternator. Installing solar panels (probably flexible) on the roof, will need a solar controller to use that solar energy. Alternatively we warmly recommend the alternative of a small hybrid inverter that as well as charging the batteries also provides 220v electricity up to 1200w

Do consider the use of a portable power station that has its own solar controller. It may seem a bit more expensive than the sum of its component parts but the absence of installation costs, its versatility, and the ease with which it can be connected to portable solar panels are major advantages to those living on the move.