12V or 6V

[joelc]

I have a 5er that came with a single 12V RV battery. I am thinking of replacing it. What I don't know, given the same amperage, would I get better service from 2 12V batteries in parallel or 6 6 V batteries in series? Once I know whether a 6V system or 12V system is better I can choose the battery.

[joelc]

Most of the time we are at our pad. When we do camp, the batteries would be used just as a BU in the event power fails. This way we can still keep the fridge going and if needed water heater.

Thanks for all your input.

[theoldwizard1]

rlw999 wrote:
Why is that? What's the difference between 2 6V batteries in series and 2 12v batteries in parallel for running an inverter?

6V batteries are usually "golf cart" batteries. They are designed specifically to provide power for a longer period of time compared to an "engine starting" battery which just has to give a burst of power for a short time.

You will have a hard time finding this data but, 12V batteries, even one that are labeled "RV/Marine deep charge" have a shorter life than 6V "true" deep discharge batteries when you repeatedly discharge them to <80% and then re-charge them. It is worse, if you discharge them to <60%.


There are "true" deep deep discharge 12V batteries, but they are difficult to find and expensive. You will likely only find them at a golf cart store or at a solar power store.

[theoldwizard1]

time2roll wrote:
I recommend the 6v GC2 if you are spending money to have two batteries.
Most Costco and Sams club have good value GC2 batteries.

Don't be surprised if two 6V golf cart batteries actually COST less than two 12V "dual purpose" RV/marine batteries !

They will likely last longer.

[valhalla360]

bucky wrote:
Bob213 is the only one that mentioned weight. Six 6 volt batteries will weigh 375 lbs or so. Something to consider.
Mounting them safely also deserves some thought.

I'm pretty sure that was a typo. It makes no sense to compare Six 6v batteries to two 12v batteries. It's a massively different battery bank size.

[bucky]

Bob213 is the only one that mentioned weight. Six 6 volt batteries will weigh 375 lbs or so. Something to consider.
Mounting them safely also deserves some thought.

[valhalla360]

time2roll wrote:
Either way I recommend 4 batteries minimum if running a 2000 watt inverter anywhere close to capacity.

Agreed, maybe even more if you plan to do more than a couple minutes with the microwave.

2000w translates to around 170amps @ 12v. A pair of 6v can provide the amperage as can a 12v starting battery. The problem is if you have 220 amp-hr @ 12v (supplied by 6v or 12v bank), you will be lucky to get 25-30min before you hit 50% charge pulling that kind of amperage (keep in mind Mr. Peurket will ding you hard with those kinds of draws)

Now if you start talking about exotic battery types, it's a totally different discussion from what the OP is asking about.

[valhalla360]

Old-Biscuit wrote:
If one 6v battery fails you have NO DC for RV
If one 12V battery fails you still have 12V DC for RV

If a cell fails, a cell fails and you have no DC. 2 6v vs 1 12v and you have the same number of cells.

Of course, deep cycle battery cell failure is less likely as they have thicker stronger plates.

[bob213]

I think the first question should be "Do you need the extra amp hours that 2 6 volt batteries will give you?" Do you plan to boondock often or have an inverter to run or do you usually camp with hook ups? If the need is truly there then 6V has the advantage. We very seldom if ever camp without hookups, don't use an inverter, so I have no need for the extra amp hours or weight.

[time2roll]

Yes Lithium or SiO2 with 200 amp rating is typically two batteries and is fine. I don't think these are on the radar.
For what the Op is looking at I recommend 4+ batteries to properly drive 2000 watts.

[azdryheat]

If you boondock a lot I'd get four 6 volt batteries. If you go to RV parks then a single 12 volt will do. We mostly go to RV parks but I've boondocked with a single 12 volt but do run the genny.

[pianotuna]

time2roll,

Either 4 lead acid--or 2 SiO2

[time2roll]

Either way I recommend 4 batteries minimum if running a 2000 watt inverter anywhere close to capacity.

[pianotuna]

Rlw999,

thicker "plates" in 6 volt = higher resistance

Lower internal voltage in the 12 volt

double the number of cells, in 12 volt, so each cell has to produce only 1/2 as much of the current.

6v = 3 cells; 12v= 6 cells

x 2

6v pair = 6 cells; 12v pair = 12 cells.

My microwave draws 150 amps.

6 volt in series--each cell has to do 150 amps

12 volt in parallel--each cell has to do 75 amps

[rlw999]

pianotuna wrote:
It depends what you wish to run. If you plan on a large inverter then 12 volt may be better.

Why is that? What's the difference between 2 6V batteries in series and 2 12v batteries in parallel for running an inverter? (I understand why putting the 12V batteries in series to get 24V would make it easier to feed a big inverter, but that's a much bigger project)