Me neither. This is big on the Escape forum as well. Folks will have two battery banks with a switch between them to switch from one bank to the other. Seems to be a thing in the boating world, but I'm not a boater so I guess I am missing it.

  I would like that.  Seriously though, it has had an impressive run.  I last charged in November 1, it received a 2 amp trickle charge for 24 hours.  Since then it has been sitting directly on the concrete floor in our unheated garage in northern Michigan.  Checked it just a few minutes ago, so it has been about 140 days since getting the charge - reading is 12.39v with ambient temp of 36.  So it doesn't have the oomph it used to have, but last year it would still last 2 days when we ran the furnace in 40 degree weather.  The more robust Trojan T-1275 reads 12.63v but it is nearly new at 4.5 years of age.

jato, if that battery gets any older it's going to be eligible for Social Security.

Since this setup worked well on your boat, it should work equally well on your rpod.  As long as your  vehicle and 7 pin Bargman plug is setup for charging, you will be good to go.  I have batteries of different ages so I use one at a time, changing out when the voltage drops to 12.2.  I carry two 12v, they are: 14 year old Interstate deep cycle and a 4.5 year old Trojan T-1275.  Without using solar or generator I can go off-grid for 6 days when night temps are in the 40's with day temps in the 50's or better.

Having both batteries of the same age is critically important and you will have that setup - good to go.