12v vs 6v for house batteries

[mikeylikesit]

we just go into a newer Class A. I am surprised to find that the house batteries are 2 - 12v deep cycle/marine batteries.

Our older (1996) Class A used 2 - 6v batteries..which worked really well for us.

I might be overthinking it, but I am wondering which is better? These original 12v batteries still have a "winnebago" label, so I am sure that they are original to the unit. I hesitate to switch out from what the OEM specifies, but my experience with batteries tells me that the 6v are better suited for motorhome use. Am I wrong?

any thoughts or advice appreciated.

 

[Lou Schneider]

Overall, two 6 volt batteries give better performance than two 12 volt batteries.

For any given amperage, since there are half as many cells in two 6 volt batteries each cell is twice as large as the 12 volt cells. Bigger is better in deep cycle use.

With two 6 volt batteries in series, there's only one path through the batteries. All of the charging current and load current flows equally through all of the cells.

With two 12 volt batteries in parallel, the currents are free to divide between the batteries. This means if the batteries get even slightly out of balance or develop a slightly corroded connection one battery will wind up working harder than the other, shortening it's life.

All of the above applies only to lead acid batteries. Lithium (LiFeP04) batteries have internal battery management systems making them much more tolerant of parallel connections and IMO for several other reasons are vastly superior to use in an RV.

 

[DonTom]

Overall, two 6 volt batteries give better performance than two 12 volt batteries.

I think you mean one 12V battery.

-Don- Tucson, AZ

 

[rvlifer]

Trojan t105 6v batteries weigh 62lbs each

12v wet cells typically weigh 40 - 60lbs each

Battleborn lithiums weigh 31lbs

Any benefit to using 6v vs 12v is probably lost from having to carry around the extra weight.

If the oem batteries dont have recommended charging specs then you can probably get better results from replacing them. No reason you need to keep the oem batteries.

 

[1blue78]

I think you mean one 12V battery.

-Don- Tucson, AZ

No - two 6 volts are better then two 12 volts for the reasons Lou explained. The other major difference is that 12 volt 'deep cycle' batteries are 'marine' batteries which means they must also be able to deliver a starting amperage so they try to be a staring battery and a deep cycle and as with everything where you try to please both sides of the equation, they are not great at either one. For a true deep cycle battery you 'need' 2 x 6 volts, or 4 x if you want the extra capacity...

 

[mikeylikesit]

thank you Lou, your answer leads to another question...should I change them out to Lithiums?

as a point of reference, we rarely boon-dock anymore.....we used to camp out in the desert alot, not so much anymore. We mostly use full hook ups.

 

[DonTom]

two 6 volts are better then two 12 volts

I guess I didn't understand what was meant by Lou's post. I still do not see how two 6-volt batteries can compare to two 12-volt batteries.

But if it is a comparison between two six-volts in series to two 12-volts in parallel, more info is needed on the capacity of each battery. But I understand series is less critical if not perfectly matched.

-Don- Tucson, AZ

 

[rvlifer]

Lithiums are great but still a lot more than lead acids. Not sure i would do it in your case unless you want the weight savings or you plan for not having full hookups

No matter what batteries you have make sure you have a good battery monitor such as a trimetric and that your converter or inverter/charger properly charge them. Ideally you would have a programmable charger that you set to the battery manufacturer's charging recommendations

 

[DonTom]

We mostly use full hook ups.

Sounds to me like you have no reason to change anything.

I do have a 300-AH lith in this Class C RV for the main house battery. In my Class A, I have the same but in addition to the stock LA batteries. Not much of the 12V electrical stuff is stock in this Class C.

I often want to make my coffee (Keurigs draw a lot of current), or use a hair dryer or the MW oven without running the genny when on the road or boondocked. The higher voltage is also good for my ham gear and other things.

But it sounds like you do not have a reason to change anything if you're mostly at places that have electricity.

-Don- Tucson, AZ

 

[mikeylikesit]

thank you Don. That will save me a few bucks.

 

[DonTom]

That will save me a few bucks.

If you do decide to change to lith batteries, only consider it when your LA batteries crap out.

The lith batteries last a lot longer, do not cause cables to corrode are lighter for the same capacity, release no gasses (need no venting) and by then they will probably be the same price as LA batteries.

So there are some advantages even to you. But wait until your LA batteries crap out and then decide.

-Don- Tucson, AZ

 

[Larry N.]

he other major difference is that 12 volt 'deep cycle' batteries are 'marine' batteries which means they must also be able to deliver a starting amperage so they try to be a staring battery and a deep cycle and as with everything where you try to please both sides of the equation, they are not great at either one. For a true deep cycle battery you 'need' 2 x 6 volts, or 4 x if you want the extra capacity...

While that is often the case, it's not always the case. The 4 12V house batteries I had in my Beaver were true deep cycle batteries, not marine batteries. They were about as large as the usual pair of 6 volt deep cycles combined (very, very heavy).

Of course the 12V ones I had were more expensive than a typical pair of 6V.

 

[Lou Schneider]

I guess I didn't understand what was meant by Lou's post. I still do not see how two 6-volt batteries can compare to two 12-volt batteries.

But if it is a comparison between two six-volts in series to two 12-volts in parallel, more info is needed on the capacity of each battery. But I understand series is less critical if not perfectly matched.

-Don- Tucson, AZ

<sigh> Two six volt batteries in series deliver about 200 amp-hours at 12 volts. Voltage adds, current stays the same.

12 volt batteries are about 100 amp-hours at 12 volts. Voltage stays the same while the currents add. So you need two in parallel to get the same capacity as two 6 volt batteries in series.

 

[rvlifer]

Arent there different ah 6v batteries like there are with 12volts?

 

[DonTom]

<sigh> Two six volt batteries in series deliver about 200 amp-hours at 12 volts. Voltage adds, current stays the same.

12 volt batteries are about 100 amp-hours at 12 volts. Voltage stays the same while the currents add. So you need two in parallel to get the same capacity as two 6 volt batteries in series.

Of course, I don't now remember what I was thinking when I read your other post, but something there confused me.

-Don- Tucson, AZ

 

[John From Detroit]

I think you mean one 12V battery.

-Don- Tucson, AZ

For the same number of amp hours an 8D DEEP CYCLE is the same as a pair of GC2 in series
Same voltage. Same amp hours. Same usable amp hours. SAME WEIGHT (As the two combined)

But 200 Amp hours of MARINE/Deep cycle is not the same as 200 Amp Hours of DEEP CYCLE.

The common GC-2 (Golf Car 2 are needed to get 12 volts is one way to think of that) are DEEP CYCLE.designed to be run down and recharged... But also designed for Slower discharge (Relative to full capacity)

MARINE/deep cycle are designed to provide a lot of AMPS (Fast discharge) For a brief spurt to fire up the Mercury.. but if run them down they age faster (Age is how long in years the battery lasts)

There are also some other concerns but a pair of GC-2 inseries.. Is the better choce

or LiFePO4's Ijust went from 300 amp hours of Lead Acide (MARINE/Deep cycle) for my apartment's main Emeregency back up to LiFePO4. also 300 Amp hours about 4 times the usable amp hours or if you like watt hours or if you like hours before I'm w/o power.

 

[Gary RV_Wizard]

The other major difference is that 12 volt 'deep cycle' batteries are 'marine' batteries

Not universally true - there are true 12v deep cycles available from brands such as Trojan, Concorde (aka Lifeline), and Crown.
Marine deep cycles are cheaper and widely available wherever batteries are sold, but they are not the only 12v type available.

 

[Mark_K5LXP]

I understand series is less critical if not perfectly matched.

Capacity for series strings is very critical, as the bank discharges any difference in cell capacity results in a greater depth of discharge for the weaker cells. So those cells get exercised harder and their capacity diminishes more quickly than healthier cells creating a snowball effect.

To the OP, if all you're doing is travelling pedestal to pedestal then any nominal 12V battery will be fine. You may discover you can get by with even just one. I ran my class A off one wounded wally world marine battery the first few months I had it before installing GC2's.

Mark B.
Albuquerque, NM

 

[DonTom]

For the same number of amp hours an 8D DEEP CYCLE is the same as a pair of GC2 in series
Same voltage. Same amp hours. Same usable amp hours. SAME WEIGHT (As the two combined)

But 200 Amp hours of MARINE/Deep cycle is not the same as 200 Amp Hours of DEEP CYCLE.

The common GC-2 (Golf Car 2 are needed to get 12 volts is one way to think of that) are DEEP CYCLE.designed to be run down and recharged... But also designed for Slower discharge (Relative to full capacity)

MARINE/deep cycle are designed to provide a lot of AMPS (Fast discharge) For a brief spurt to fire up the Mercury.. but if run them down they age faster (Age is how long in years the battery lasts)

There are also some other concerns but a pair of GC-2 inseries.. Is the better choce

or LiFePO4's Ijust went from 300 amp hours of Lead Acide (MARINE/Deep cycle) for my apartment's main Emeregency back up to LiFePO4. also 300 Amp hours about 4 times the usable amp hours or if you like watt hours or if you like hours before I'm w/o power.

Yeah, I know all that stuff. I think of "Marine Deep Cycle Batteries" as being between a true deep-cycle battery and an engine-starting battery. I have never used those "marine deep cycle" batteries in any of my RVs ever. I only used the Trojans True Deep Cycles until I went with LIFEpo4 batteries.

But I have kinda done the opposite, on a suggestion from others. I use a "deep cycle" battery on my BMW motorcycle for engine starting. I cannot say why, but this battery has lasted longer than the stock battery--used for engine starting--as others have told me would happen. I think it is now about seven years old and still working well. I get this battery at Battery Plus and they told me it was a big seller for old BMW motorcycles--often asked for, but NOT designed for engines . . .but does a much better job of it than the stock battery!

-Don- Tucson, AZ

 

[Kirk]

.should I change them out to Lithiums?

I would not unless the present batteries are in need of replacement but when that time comes, at least compare the two. Lithium batteries have the advantage of not needing electrolyte added and they are longer lived. The price of lithium batteries is dropping so keep that in mind even though they may not be needed today.

Arent there different ah 6v batteries like there are with 12volts?

Absolutely. You do need to compare batteries of the same capacity.

Not universally true - there are true 12v deep cycles available from brands such as Trojan, Concorde (aka Lifeline), and Crown.

If you want the best deep cycle, wet cell batteries then those listed as golf cart batteries are best but also cost more and are not as readily available.