I am assuming that you will just haul the panel outside when you need it? If not, why not put more panel watts on the roof? That controller will handle 45amps, you could put a half dozen of those 100w panels up.......
There's some very knowledgeable folks here with install advice, and a permanent install, or even a temp/haul out one should have some circuit protection. If you get the temp sensor for the controller, your charge will be right on for the temp your battery is seeing. And.........the remote panel is really cool to put inside to monitor the charge and voltage, etc.
Yes, 1 panel over 4-7 days will charge the batteries after a trip, and a good charge controller like that one will be better than most plug in chargers at keeping the battery happy. But, if you want faster, you could always add more panels. BTW, you need to get a '12v' panel for that controller, I think.
