I"m not sure what the...
... size of your solar panel is (i.e., output) nor what the demands are on your batteries so it's hard to provide specific advice. On my boat, for example, I have two Group 24 batteries (I like and use Group 24's because they are light, cheap, and typically last 5-7 yrs if I take care of them...). Although I have an onboard charger, I do not connect my boat to shore power for a variety of reasons, mostly have to do with my fear of ambient electricity in the water and so do not want to ground my boat. I have an ICP 5-watt solar panel for years and it seems to do what I want it to do quite well: maintain my two batteries. Since this is a small output panel, I only connect it directly to one battery at a time. I'm typically at the boat once or twice a week. Whenever I'm there, I switch the panel to the other battery. My demands for DC power, however, are minimal. I only use it to start the engine, run some basic electronics while sailing, and for a cabin light now and then. I typically use candles and oil lamps when at anchor. This system has worked for me, perhaps it will for you too. Good luck with your new inboard.
