As long as they are "TRUE deep cycle" there seems to be little difference anymore. 6 volt seem to still carry more weight and the lead in the battery is what give the # of amp hours. $$ wise T105's, Trojan batteries still are what others a measured by, Amp hours to cost, and will last IF taken care of. But for the cost one can get 4 of the Costco or Sams club batteries and have more Amp hours than the T-105's . Just look on the batteries and if they have cranking amps "they are not true deep cycle". As to how much battery you need only you know you camping style. If you use hookups a lot then less battery and inverse if you boondock a lot then more battery storage power.
I run 4 T-105's in the HM and do quite a bit of boondocking and would like 2 more but am out of room.
In my sons last TH, he ran 6 cheaper deep cycles and seemed to do fine, but did boondock at the dunes alot.
Hi Newjo and welcome to the RVUSA Forum. Like Len said - if you boondock (no hookups) camp alot, go with two deep cycle batteries. You can use either two 6 volt battteries wire in series or two 12 volt batteries wired in parallel. If you stay in established campgrounds with hookups, you can get by with one 12 volt battery.
Personally I have two 6 volt golf cart batteries that I bought at Costco for about $80.00 each and they have held up fine for the past three years.
Thanks guys, but the clincher came when I was asked "what if one cell goes bad in the 6v system'' SOL ! w/ 12v you still have power....that seems good enough for me, plus I COULD use my truck battery if necessary,
ANY THOUGHTS ???
If a cell goes bad in the 12 volt you got the same thing. I have 2 6 volt interstate workhorse batteries that have served us well. We can camp a week with no problem boondocking. We will run the generator each night for a hour or so. This will not fully charge the batteries. Like others say it just depends on how you plan on camping. Just a weekend a 12 volt deep cycle will be fine. You will have to learn how to conserve with electricy same as water. We have no inverter to run tvs and such. If you plan on invertering you will need a big battery pack of 6 volt. JMO