Two 6 volt batteries or two 12 volt batteries ??

marcsbigfoot20b27 wrote:

Huntindog wrote:
A catastrophic battery failure, one that will basically stop one from having 12 volt power is usually caused by a shorted cell. Sometimes called a dead cell. This commonly occurs when the sediment from the lead plates that is constantly being attacked by the acid accumulates enough under the plates to touch them. When it does, the battery dies really fast. It makes no difference whether it is a 6 volt or a 12, the result is the same. What is different about them is that the 6 volts have a lot more room under the plates for the sediment to collect before touching the plates. So much room that the owner usually replaces the battery due to reduced capacity long before a cell shorts out.

During the 60s,70s, 80s, and 90s cell shorting in 12 volt batteries was very common. I had many batteries replaced in my autos during that time frame. Lately that seems to have declined.

Most people that prefer two 12s for RV use will state that fear of catastrophic faliure leaving them without power as the reason they prefer two 12s. They likely remember how many batteries they have had fail in their cars over the years.
So common sense tells them that a backup is a good thing.

What they fail to understand is the fundamental difference I just explained. If sixes leave you stranded, you have likely been ignoring the warning signs for a long time.

Regardless, choosing two 12s and doing nothing else will not give one the redundancy they are seeking. When two 12s are wired together and a cell shorts in either one of them, both 12s will go dead very quickly. The result is most always two dead 12 volts. If one wants redundancy, then the 12s need to be isolated from each other. There are different ways to do this from manually connecting and disconnecting them all the way to automatic switching systems.
It all depends on how one wants to do it and how much they want to spend.

You may notice that I have not said which is better yet sixes or twelves. The answer is it depends. For higher powered inverter use, 12s win. I have a 600 watt whole house inverter with two 6s. This system has been in use for about 7 years. My TT has 3 TVs. we use everything excepting the high amp loads as we wish and the batteries hold up fine.

So for low powered or no inverter usage, I think the sixes get the nod.

Certainly other personal factors may come into play, but the redundancy issue alone is moot.

In fact under common applications where one does not isolate the 12s, they will fare worse than the sixes.

I pretty much agree.
A few more points on catastrophic battery failure 6 or 12 volt.......
If one 6 volt dies, it’s dead and you are out of business until you replace it and better yet BOTH.
If one of two 12 volt dies it may drag the good one down, but you can remove the dead one and recharge the good battery and you are still in the game.

Best in either case 6 or 12 is AGM if sediment killing the battery is a worry.

I wish my TT was big enough to accommodate 2-4 six volt AGM and a switch to 2-3 AGM 12 volt batteries...... 6 volt CG2 for normal use and flip the switch to 12 volt if I need to run my inverter.