I can't believe some of you experienced guys can make battery capacity so dam difficult.
First of all, basically there in no difference in amp hour capacity between 6v & 12v. The physical size and weight of a battery determines it's AH capacity.
Therefore, if you figure that each typical RV deep cycle battery, whether 6 or 12v, contains approx. 100 AHs capacity, then it is all very simple, correct ??
But we know that the skimpy group 24 12v batteries are smaller, therefore have some less capacity. But they are not the typical RV battery either, so just forget them, ok !!
All gp 27 12v batts contain between 90 and 115 amp hours.
All typical 6v GC batts contain between 200 and 220 amp hours.
So any way you slice it, 4 typical deep cycle RV batts, 6v or 12v, are going to give you on average of about 400 amp hours, excluding those skimpy little 24's
Now if we want to get all teckie over each single amp hour, then lets start a different thread, and really get down to the nitty gritty,......but really, who cares,.....is it worth haggling over ?
I'd like to think this clarifies the subject of AH capacity just a little.