On other RV forums, there is some discussion of the advantages in having two 6v batteries in series, instead of the typical 12v in parallel. Flashlights are setup the same way, partially for the same reasons.
On my 2007 2350, one of my original 12v batteries was diagnosed as a failer after two years of service. I decided to stay with 12v batteries and replaced them both with two larger 12v from Walmart. They were the largest ones Walmart stocks.....they have a yellow label, though I forgot the brand name. The two larger batteries fit in the slide-out battery tray perfectly without the need to add my little wood shims used with the original batteries to keep them close to eachother so the little white wire with square tip temp sensor could measure the battery temperature more accurately.
At Walmart, I went through their stash of batteries, selected the ones that were manufactured most recently, and having the same manufacturing month/year. They cost around $70 each, but they have a lot more power than the original ones ever had. I do wonder if one of my original batteries had issues from the start or shortly thereafter because right from day-one I struggled to maintain battery reserves much more than I do with the Walmarts now. The larger size will make a difference, but I did not think so much.
One other thing I like about the Walmart batteries are the tops & caps. If there is any boil-over, the top & caps don't purge it so quickly. It seems there is a tiny top reservoir design to handle the occasion which would surely save my battery tray and connections.
