I have a landscape trailer with a break-away battery that looks like it is currently getting charged from my 7 pin plug. I've recently added a 12v deep-cycle battery to power an electric jack on the trailer. I'm having trouble figuring out how to also charge this additional 12v deep-cycle battery. Do I hook them both in parallel and will that charge both? With the batteries being different sizes I wasn't sure if that was problematic or not. Appreciate any help.