Many thanks for this. It's early here and I haven't had any coffee yet but this sounds like a very promising lead... I am not beyond an elec pun. Seems like a case for having the clamp on ammeter. And I gather you're saying while the "drain" was real it wasn't causing an actual drain to the system as a whole.
I had hoped my starting bank was really and truly isolated from the house but we shall see by following Zanshin's suggestion of measuring and remeasuring the banks to see if there is a difference over a couple of hours
I ran into the elec guy yesterday afternoon and the meeting went downhill pretty fast but he expressed some surprise that the AirX toggle had two 6 ga Negs coming off it where the diagram shows just one. My project for the day is to see what is what about that and to lengthen the AirX cables, and correctly transitioning from 6 to 8 gauge (per factory specs) and mounting the toggle on the panel rather than down where it lives now. It's that ol' when ya want it done right ...
I knew I'd have to learn this stuff someday, and that day has dawned.
The (now) ex-elec guy claimed that the use of too large of wire contributed to his screwdriver hitting two terminals and providing the fireworks
. I have to agree but only wish he'd mentioned the need for smaller gauge before we took the AirX out. I also pointed out that he's the local boatyard elec guru but a lowly worm of a boatowner (me) owned an insulated elec screwdriver set. As noted, though, I didn't think of that in time either.
On the good news front, a brief little squall blew through last night, and after a ($4.73) 50 amp fuse, the AirX's LED was working again so it seems likely the sacrificial fuse worked correctly, saving the system.