Originally Posted by monkey
So are two 6volt batteries better than two 12 volt batteries ??? We have one 12 volt in our new rv,, no real room to add a second battery but I bet I could... We don't "dry camp" but you never know when you might need it....
No, not really. a group 27 usually has about 105 amp hours. A 6 volt about 110 amp hours. so you are talking about 210 amp hours for (2) 12 v and 220 amp hours for a (2) 6 volt batteries. An 8D battery is equal to about 3 12 volt batts and has about 200 amp hours but the plates are all in the same box so they charge and discharge at exactly the same rate. I replaced the last one after 7 years.
12 volt batteries come in different sizes, 6 volt batteries are pretty much one size. You are going to have to measure your battery box, measure the different battery group dimensions and then figure out how many of what you can fit into your compartment.
So, the goal is to get as much battery in your battery box as you can fit. Older coaches sometimes could fit (2) 12volt group 24 deep cycle's in them, while only 90 amp hours (180 amp hours) instead of just one group 27 (a slightly larger battery).
If you can afford it then go with the newer technology, AGM's. AGM batteries are usually at least twice as much and can run up to 3 times the cost of a flooded cell battery. The jury is still out if they will last longer than a flooded cell. There is less cell maintenance on AGM's, but you still have to clean the terminals. It comes down to how much cheese you have!!!
Like I mentioned before, some manufacturers make their battery box's so that they will fit (4) 6 volt batts but you can only get (2) 12 volt units in the same compartment.
Lastly, golf carts have electric motors that put huge loads (drain) on the batts for short periods of time with periods of rest. A coach puts a constant lower load/drain on the batts over a long period of time with no rest. I think the 12 volt units work better in this situation.