I originally bought one of the 18v5w solar chargers for my 2002 Ford Ranger. Unfortunately it wasn’t powerful enough to hold the charge from all of my residual loads even when everything was turned off. I intend to use this one to trickle charge the camper in the bed of the Ranger. That battery gets completely disconnected so I think it will work ok. I just need a water proof transparent cover for it. So I bought two more and have connected them in parallel for the Ranger battery. I’m hoping that 10w will cover all of the residual loads. We’ll see.