[Carl n Susan]

13.5V when the converter is running (either shore or gennie power) is normal charge level. 12.6V is normal full charge for a battery that is not being charged by an external source.

You really need to measure what your amperage draw is when running off the gennie with no external charging going on.

The 230 amp capacity of the dual battery setup only allows for about 110 amp hours of consumption before you are down to 50% discharge. You don't really want to discharge a FLA battery more than 50%.

I don't remember what the fan on the furnace takes to run, but I know it is a power hog. I am pretty sure more battery power is required if you want to depend on it for heat when boondocking.