I can't tell you the number of times I have started to write about the simple, efficient and inexpensive (relatively) DC electrical system that I designed and have recently finished (just about) installing in our new-to-us J/109, only to find that there's a major issue I need to cover first.
Today it happened again. I was going along fine only to get dragged down the rabbit hole of how to choose battery master switches and install them.
And that lead to charging both engine and house banks at the same time.
Which was all complex enough five years ago, but now we have lithium to deal with.
If I could just say, "This is the best way, now do it", it would be easy. But I can't. Like most things around cruising boats, there is no best way, just the best way for each of us, which depends on our usage profile, and how techie we are or wish to be.
So, after thinking about all of the above, I realize that my design is a lot less useful than I thought it would be. Better to spend my time, and yours, exploring the options, so we can all come up with our individual best, rather than jamming a design that works for Phyllis and me down your throat—YouTube presenters take note. That said, I will publish said design eventually, since it will be useful to some of you as is, and to more of you as a starting point for your own system.
I will cover battery switches in this chapter of our Online Book Electrical Systems for Cruising Boats and cross-bank charging in the next.
There are three usable battery switch options and one that, though very common, no one should go near.