Here's another thing I just discovered last week while dry camping in the Interstate. My Goal Zero 3000 had already provided me with three nights of running fridge and freezer only by turning off the 12v
switch at the sliding door so that the GZ would not attempt to charge the house batteries. The GZ reserves go down 30% with each 10 hour evening. I still had 76% house battery life which is not enough to last all night (220Ah, and I don't go below 50%).
Since I have the Blue Sea ML-ACR 9622, I can use its switch to override and manually connect or disconnect the house batteries from the chassis battery. If I manually connect them with that switch, I've increased the total Ah available. Has anybody else done this?
When running this way, my Victron BMV-712 battery monitor reveals that I'm drawing only about 5.5A, not 8A, when both fridge and freezer are running. So my house batteries are contributing 2/3 of what the fridge and freezer needs and the chassis battery must be providing the rest.
Result: I can extend the usable Ah range of the house batteries to cover 50% longer time periods.
Of course, one must be careful not to let the total voltage get below 12v
(like you normally do already) because now you are lowering your engine battery's reserves too.