Thanks...but it's really not an original idea... Rather than use traditional RV industry ways of doing things, I research and borrow from aircraft, trucking, and boating component suppliers.
A lot of info is already on the Expedition Portal link above, so I'll just expand on a few items here.
I started out using a Battery Brain automatic low voltage disconnect but it stop working
They are no longer manufactured so switched to Cooper Bussman LVD.
With our Rig the house has a separate central positive terminal so the LVD is wired there.
All other cab electric functions are turn off by the ignition key and aren't protect with a LVD.
The LVD is rated 100 amps and disconnects at 12.1 volts. Last winter tested it at about zero degrees.
Powered house electrics until LVD switched off, still had plenty of reserve power to start the Diesel engine.
Have 3 frame mounted Odyssey AGM 75 amp hour batteries (225 amp hour Bank), these are replacement size batteries for the Ford OEM batteries. The extra third battery is also mounted in a OEM frame rail battery box behind the other two batteries.
With the 3 AGM battery bank fully charged we can power the 900 watt microwave for about 10 minutes.
With only 2 of the batteries wired to the house the microwave would barely run... Peukert effect.
For efficient charging of all 3 batteries, they are all the same size and age. They are all balanced wired too, ie all cables to the 3 batteries are of the same length and gauge. There are two Blue Sea terminal blocks (+ & -) on the frame rail and the main OEM cables runs to the terminal blocks. Each of the 3 battery cables are cut to same length and also run to the same terminal blocks.
The inverter and on board UPS/charger are also wired to the frame rail terminals
Because powering appliances using a 120 volt inverter is less efficient that 12 volts, I try to run everything possible directly from 12 volts. Any 120 volt appliance with a power block (laptop, ruko, wireless router, tv, DVD player etc) I convert to 12 volts with Radio Shack adapters.
Another feature that is very helpful to monitor the battery bank state of charge are the separate large Blue Sea amp and voltage gauges. While camping a glance at the two gauges tells the batteries SOC.
With a little practice, look at the amp draw and voltage, factor in non resting voltage reading and can pretty much estimate amp hours left in bank.