For close to home sailing, two grp 27 for a bank and one for starting are more than I need. For daysails and overnights, there's never a need to consider running the engine to charge. The in and out from harbors is more than enough with all the sailing between I want to do. I think I'm mostly supporting the AP which can run all day but that's the biggest AH user.

I like to anchor which means using the windlass and salt water wash. 40' of chain gets thick with mud in Maine and that can take some time. Rather than running the diesel the entire time, I take most of it up and hose the mud off casually. Then start the engine to break it loose and get going. The engine battery is may than ample for that and is usually the highest resting voltage after a week of resting before testing.

But then go off for a few weeks and the storage quickly becomes an issue. After a couple of days at anchor or just sailing between destinations, and AH storage begins to be inadequate. Then charging becomes part of destination "planning" and effects how we may or may not sail.

The solutions are to go to a bigger storage bank, add a solar panel, cut usage. I can't see the first one for our usage. It's just more space, wiring, weight and as is proven, more cost per season in regular battery replacement. I'm still looking for the right solar panel for our boat(not many spots that make sense unless you want be playing with it all day) , that would be a good help. It's not needed though for regular use.

So I'm inclined these days to go to the third solution while off for a few weeks. I've gone to a low watt battery light, learned the boat will more often sail itself if I give it a chance. Plus the kids are not onboard as much on long trips so there are no laptops to charge.

I'm shooting for having the same freedom from charging and complication I have for close to home sailing even off for a few weeks.