Some may recall my $500 jump start from Boat US last year. Okay, I've already admitted the batteries were old and I got what I deserved, but after replacing all 8 GC bats, I was still puzzled that both old banks died overnight, when the "start" bank was switched off as soon as we anchored.
I now believe that the inverter was installed to draw from both banks irrespective of the position of the two rotary switches. "Inverter - OFF" is now on my shutdown list.
(Also bought one of those nifty jumper packs, just like boat US.
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Brian, good hint about Windlass breaker. Just turned mine off.