Battery capacity

FWIW  i have an 80watt zamp panel that has served me well.  The zamps are more expensive than doing it yourself or other products.  But for most needs, an 80-100 watt panel should serve you well given normal loads and decent sunlight.  As you said, the pod is prewired for solar and the zamp is plug and play, nothing to figure out other than point at the sun.  All of this electrical, battery and solar talk only matters if you boondock(no shore power for extended period, say 3 days to equal extended) If you plan to boondock, you want a dual battery setup (either 6 or 12volt) and a solar panel. 

Again, i have an 80 watt and don't even drain my batteries to 75% when boondocking.  The electrical part of all of this is the biggest learning curve for me.  Generators also negate the need for all this discussion and planning as well, but then there is the noise.  But if you want the a/c while boondocking, you have to have a generator.  Hope this helps.  Also, while the dual 6 setup is of no use in the car, they should still boost the car to start given the pickle discussed above. 

Probably 1 step behind marwayne as we are commencing year 8 with our original 2 - 12 v set up.  We do monitor water levels a couple times a year, as I am sure marwayne does as well.

Dennis, here's where I sit.

Another option is to get two 12 v. deep cycle marine batteries and switch from one to another as you drain them, there are plenty of switches available that allow you to switch back and forth.  In the long run it'll probably be more expensive than the $170 +/- for the Costco 6 v. pair.

It isn't quite so simple. I don't think you are going to find a 12V 210AH battery. For example, the Duracell Ultra Deep Cycle for Deep Cycle 12V RV SI78AGM which is the highest capacity battery I saw on Batteries + Bulbs has a 20 hour rate of 105AH. That doubled is 210AH which is less than the 215AH of the 6V GC2 GLIGC110 batteries I have. While it is true that one of these is less than the two 6V batteries I have, two of them is significantly more, even with the current 10% off for ordering online and picking up in store. Even with the current $10 rebate on the 12V batteries, it would cost significantly more than the GC2 batteries.