Parallel or series battery run

[Jamesiam]

Would it be better to have 2 six volt in series or two 12 volt parallel? I believe two, six volts hold more amps. Any other Pros or cons?

 

[pods8]

Batteries of the same size are going to be the same once you get to your desired voltage. For example the 6V 210ahbatteries batteries I have are the same size/weight a that manufactures 12V 105ahthere battery. So battery size /weight is a wash comparing the 6V in series and 12V in parallel.

That said the 6V may have thicker plates. But in one battery fails you are definitely out of luck. Pros and cons on both. As usual I advise buy what is locally affordable. I got into my 6Vaccount batteries for cheap so it was a no brainer.

 

[White Dog]

I've used a pair of 6 VDC batteries in my travel trailer for a while now. Width is about the same, length a bit less but they are definitely taller. The amp rating for these paired to give 12 VDC is definitely greater and in fact this has been my experience. The 6 VDC batteries are also quite a bit heavier because they have more lead in them. The ones I use are for golf carts which seems to be the norm in larger RVs. They are designed to charge faster and take more discharge/recharge cycles. So in the end, I think it's a decision of size and weight vs amp capacity and long life. By the way, my local battery supplier recommends charging the 2 - 6 VDC as a pair with a 12 VDC charger, never independently.

I've also heard some good things about the AGM batteries but I don't have any personal experience. My new Grandby will come with 2 of these so I guess I'll figure it out soon enough.

 

[pods8]

White dog you're not comparing apples to apples in your statements. Sure a 6V battery in a golf cart sized casing is going to have more juice than many 12V but they aren't the same thing. You can't make broad 6V battery statements based on it. They make 6V batteries in the same size cases as corresponding 12V batteries as well. My 210ah 6V batteries are in a 12.05"x6.65"x8.65" case weight 64lb, that manufacture makes a 12V battery in a 12"x6.6"x8.15" case weighing 68lb and it's 100ah. So as you can see for the same case size it's basically a wash.

I do run/charge my batteries as a pair.

 

[White Dog]

White dog you're not comparing apples to apples in your statements. Sure a 6V battery in a golf cart sized casing is going to have more juice than many 12V but they aren't the same thing. You can't make broad 6V battery statements based on it. They make 6V batteries in the same size cases as corresponding 12V batteries as well. My 210ah 6V batteries are in a 12.05"x6.65"x8.65" case weight 64lb, that manufacture makes a 12V battery in a 12"x6.6"x8.15" case weighing 68lb and it's 100ah. So as you can see for the same case size it's basically a wash.

I do run/charge my batteries as a pair.


What you say is true enough. But . . .

In the RV industry, manufactures usually install clamps and cases for 12 VDC Group 27 batteries, occasionally the smaller Group 24. The battery industry has standardized case sizes in these groups so they are interchangeable. Using the measurements from Trojan's website (Trojan just happens to be the brand I use), the Group 27 is 12 3/4" X 6 3/4" X 9 3/4". Similarly, their T105 6 VDC, is 10 3/8" X 6 3/4" X 10 3/4, 2" shorter and 1" taller than the 12 VDC Group 27. The Group 27 weighs 55 lbs and the T105 62 lbs. Using the 20 hr. rating, the Group 27 has 105 and the T105 225. Using two Group 27s would give 210 amp compared to the 225 for the T105 - 7% higher for the T105.

Perhaps the point I should have made clearer was whether James was simply replacing factory installed Group 27 batteries with 6 VDC. Sure it is possible to get a less common size of 12 VDC that would mimic the performance of the 6 VDC but it too would likely require a modification of the mount assuming the space is tall enough for the larger T105 or its 12 VDC equivalent. I suppose it all comes down to volume of the battery case and weight of lead. I did talk to a technical rep at Trojan before I switched to the T105s and he said to expect more low voltage discharge cycles from the T105s than their equivalent Group 27 batteries because that is what they were designed to do. I can only take him at his word.

I'm not sure this discussion helps much. I do know from experience that it pays to buy brand name batteries and to follow the manufactures maintenance recommendations if you expect long life.

 

[AK Nomad]

James,
2 6V in series give you 12V.
2 12V in parallel give you 12V.
Like was said, it's a wash. No one way is better.
You can't generally say 2 6V batteries hold more amps. (I assume you mean amp-hour capacity) When shopping for batteries you need to consider the amp-hour ratings and other specifications whether it be a 6V or a 12V battery. Like was said, it will boil down to price and availability. Good luck.

 

[Nimbl Vehicles]

For me it depends on space.
I can fit a 4 x 6 V Battery pack in my camper which gives you 600 amp 12V
In a slightly larger footprint I can fit 2x 210 amp @12V which gives you 420 amp 12V.

Amp/h per Lbs is about the same.

 

[White Dog]

One advantage to having 2 12 volt batteries is if one dies or gets weak, it can always be disconnected and you can limp along on the single remaining 12 volt. If one of the 6 volts dies, you're hooped. Similarly, if your vehicle battery dies, you could likely jury rig one of the 12 volts into the engine compartment to get you back to civilization. Hard to do with the 6 volts.

 

[Mark W. Ingalls]

One advantage to having 2 12 volt batteries is if one dies or gets weak, it can always be disconnected and you can limp along on the single remaining 12 volt. If one of the 6 volts dies, you're hooped. Similarly, if your vehicle battery dies, you could likely jury rig one of the 12 volts into the engine compartment to get you back to civilization. Hard to do with the 6 volts.


Nice...

 

[Mark W. Ingalls]

For me it depends on space.
I can fit a 4 x 6 V Battery pack in my camper which gives you 600 amp 12V
In a slightly larger footprint I can fit 2x 210 amp @12V which gives you 420 amp 12V.

Amp/h per Lbs is about the same.


Not sure I follow the accounting procedure here... to what does "slightly larger" refer?

I always assumed, unencumbered by analysis, that golf carts had 6 volt batteries because of higher available current-hours.

 

[pods8]

One advantage to having 2 12 volt batteries is if one dies or gets weak, it can always be disconnected and you can limp along on the single remaining 12 volt. If one of the 6 volts dies, you're hooped. Similarly, if your vehicle battery dies, you could likely jury rig one of the 12 volts into the engine compartment to get you back to civilization. Hard to do with the 6 volts.


I mentioned that above.


Not sure I follow the accounting procedure here... to what does "slightly larger" refer?

I always assumed, unencumbered by analysis, that golf carts had 6 volt batteries because of higher available current-hours.


Golf cart batteries are thick plate deep cycles. As far as I know all "golf cart" are 6v but you can't say the reverse. The thread asked about 6v so I have talked that and not specifically golf cart. They usually have a smaller footprint for the amp hours but are taller. So it goes to what fits and what is cost effective for your goals.

 

[White Dog]

Here is pretty good general discussion on deep-cycle batteries. Seems to bring together a lot of useful information in a format understandable to those of us without an engineering degree.Battery Information

 

[Jamesiam]

Thanks everyone for your valuable input! I was actually a bit tipsy and camping at Clearlake when I typed that message, the next day when I woke up I hoped it made a bit of sense.

This was actually for a friend of mine who I was camping with who recently purchased a used Hallmark camper. It came with two 6 volt batteries which were mostly depleted of water when he received the camper and weren't holding a charge. He ended up calling Cabelas and getting two group 24, 12 volt batteries on sale with a saving of around 35 off each battery. The price was better and the size will work with his battery compartment.