Keep in mind, there’s a limiting factor beyond the generator: The output of your battery charger.
If you’ve got an 8-10 amp on-board charger, you’re going to have to run that generator for about 6-8 hours if you run a 120 AHR battery (or batteries) down to nearly dead in order to charge the batteries.
I don’t care how quiet the generator is, running it outside a motel or hotel or in a campground all night isn’t going to win you any friends. Also, there’s the possibility of theft, so you’ll need to lock it up.
BTW, Don’t even think of chaining your generator to the boat trailer or to the back bumper of your truck as a way to prevent theft. I’ve seen this go very, very wrong for one Honda generator. Sadly, as you might expect, driving away with a Honda generator dragging behind your RV is going to be tough on equipment.
Obviously, if you have a higher amp output charger, you could cut that down. But high charge rates have possible implications for the service life of the battery. Also, most likely you’re going to have to buy and carry a stand-alone charger. I’ve never seen a 30 or more AHR on-board, maybe they exist, but I’m guessing that size and cost would then bring other issues into play.
Would it be more feasable to wire an A/B/Both switch in to your boat so that you can switch over and charge the deep cycle battery from the outboard alternator when running?
This has a handy side benefit of being able to use your deep cycle battery as a starting battery in case the starting battery goes dead.
Grouse
