Well I'm doing this the lazy way and figured someone on these forums might find my boneheaded method useful for their build out or might be able to help out along the way.
The first step today was to simply swap out the marine house batteries and replace with lithium and see what happens. I bought 2 12v
battleborn 100 amp GC2 batteries that are supposed to be drop in replacements for marine batteries.
Like I said, this is the boneheaded way, I'm sure there are better ways, but it's interesting to see what happens with the most basic methods.
Removed the house batteries and plopped in the lithium. First thing to note is that the lithium "drop in" have these little tabs on the sides and with those, the batteries are about a quarter of an inch too wide. Because the tabs are symmetrical, the batteries still seat level, but don't go that far down. Also the batteries are a few inches taller than the original, so even if i sawed off those tabs, I'm not sure the battery case would close.
Anyway, I used the battery cables that were already in there for the house batteries and literally just replaced the house batteries with those lithium ones... Almost everything works right out of the box. All lights, gas etc detectors, water pump, etc. The only things that are currently a problem are:
1 the circuit breaker for the furnace-water heater
2 the circuit breaker for the "din-gal-refer-end table outside recepts"
both of these flipped and won't flip back. I tried hitting that test button and nothing.
3 The truma display is showing complete jibberish. Not sure what kind of display that is, but it's show more signs and symbols than it's supposed to. The knob can move across the options, but with random things being highlighted i'm not sure what's going on. I removed the display and plugged back in and no effect.
The battery monitor shows a little over 13v and 100 percent, but I doubt that's going to be reliable, so I bought a victron battery meter (BMV-712). (I don't work for, get paid from, or have any relationship with any of these products/brands).
I also bought a victron multiplus compact 12v
2000va 80amp 120vac that I'll be connecting.
So I guess the next step is to find my manual and start looking through the wiring diagrams to see if I can figure out what's the problem.