6v or 12v house batteries?

[StevL]

I’ve read where some people when changing house batteries opt for 6v in series vs. 12v in parallel. Why? Seems this would reduce your capacity.

Steve

[twinboat]

It will, in most cases, increase capacity.
A 6 volt battery, the same size as a 12 volt battery, will have more then twice the capacity. It will be a few inches taller.

About 75 AH for a gp24 12 volt battery and 200 or more AH for a gc2, 6 volt battery.

2, 12 volt batteries in parallel = 150 AH
2, 6 volt batteries in series = 200 AH.

You can get larger 12 volt batteries but that takes up more space.

The second reason is that most 6 volt batteries are spicificicly designed and built for electric golf cars ( The GC designation ).

They are made to be drawn down and recharged many times, it to the thousands, if cared for.

Most 12 volt Marine, RV, Deep cycle batteries are a mix of deep cyclinging and starting design.
They do both OK, but not as good as real deep cycle or just starting batteries.

There are 12 volt " true " deep cycle batteries but they cost a whole lot more money then the 6 volt ones.

Last but not least is cost. Because golf cars use 8 batteries, there is a large market for them. That keeps the price down.

[Crasher]

Originally Posted by StevL

I’ve read where some people when changing house batteries opt for 6v in series vs. 12v in parallel. Why? Seems this would reduce your capacity.

Steve

Just the opposite. It increases your capacity. Plus, I have read that two deep cycle 6 volt batteries in series will give better service than two 12 volt batteries in parallel.

https://www.youtube.com/watch?v=tGNMenyNqwU

[Old-Biscuit]

Well...


Two 12V batteries in parallel = same voltage BUT DOUBLE AMP HOURS
Two 6v batteries in series = Double Voltage with SAME AMP HOURS


BUT
6V batteries typically have higher AMP HOURS vs 12V battery


6V golf cart batteries are made for true 'deep cycle'
12V 'deep cycle' batteries are not really deep cycle


Two 6V give you good 12V as long as BOTH are good batteries....one go bad/no 12V
Two 12V give you good 12V even should 1 go bad


????

[Mr_D]

Originally Posted by Old-Biscuit

12V 'deep cycle' batteries are not really deep cycle

I think Lifeline would argue that point!

[BCam]

Originally Posted by Mr_D

I think Lifeline would argue that point!

I'm pretty sure that Mr_D knows this but, for those that don't, there are "true deep cycle" 12V batteries like Lifeline makes and then there are the so-called 12V "marine" batteries, that are commonly referred to as "deep cycle" batteries. In reality, they're really a less than optimal hybrid with both starting and deep cycle capabilities. These marine "hybrid" batteries are commonly found in RVs.

Personally, I use 6V golf cart batteries in series but I've read some recent posts that maintain that "true deep cycle" 12V batteries are a better solution.

[StevL]

Okay so lets forget cost.... I can't even image that if you need capacity and you own a 100K+++ motorcoach you're really worried about another few hundred dollars.

With the new AGM batteries (and other battery chemistry, with less maintenance) the amp hour between 6v and 12v has been greatly reduced. Thus the 12v parallel does have way more capacity.

In my coach using 4 house batteries I'm thinking about 6v having x2 the amp hour capacity vs. 12v having 4x capacity.

Steve

[Sbrownstein]

Originally Posted by StevL

...With the new AGM batteries (and other battery chemistry, with less maintenance) the amp hour between 6v and 12v has been greatly reduced. Thus the 12v parallel does have way more capacity.

Hmmm, disagree, don't see it! Trojan spec sheet for 6 and 12 volt batteries of the same weight still show 6 volt with an advantage... (GC2 vs 31). Size is always different but energy is in lead, hence weight.

For the same volume, 6 volt batteries have fewer cells, hence less plastic and at the same weight, more capacity.

[twinboat]

Originally Posted by StevL

Okay so lets forget cost.... I can't even image that if you need capacity and you own a 100K+++ motorcoach you're really worried about another few hundred dollars.

With the new AGM batteries (and other battery chemistry, with less maintenance) the amp hour between 6v and 12v has been greatly reduced. Thus the 12v parallel does have way more capacity.

In my coach using 4 house batteries I'm thinking about 6v having x2 the amp hour capacity vs. 12v having 4x capacity.

Steve

Do you have some specs on these 12 volt batteries with " way more " capacity ?

[Scottybdivin]

Assuming both are deep cycle, the cost / Ah will be higher with 12V. As mentioned, it is a matter of prodution quantities and availability. Another factor is weight / Ah, If you look at the chart above;

2 GC2 130 lbs 230 Ah
2 Gr31 134 lbs 204 Ah

[Sbrownstein]

Besides, the more batteries you have in parallel the poorer your charge control is. 2x6 has completely balanced charging. 2x12 not so. Gets worse as you add more batteries.

I have also continually read about the plan that with 12 volt batteries you can "lose one and still have 12 volts in the other." Lose one to a shorted cell...and you lose two since they are in parallel.

[Sbrownstein]

Finally, on another thread that I have been involved with, I believe that if you have a TT, you will get far better charging performance from your TV charge line with 2-6 volt batteries than with 2-12 volt batteries.

Just a theory, but it does make sense.

[StevL]

Originally Posted by twinboat

Do you have some specs on these 12 volt batteries with " way more " capacity ?

I actually took some time to look at what is available battery wise. It seems the gold standard for 6v is the Trojan, depending which one the 25amp capacity is from 447 to 530 minutes, thus equaling a bank of four from 894 to 1060 total capacity in minutes. Lifeline has a 12v battery that will fit my compartment (may not fit all) that has a 25amp capacity of 315, this equals in parallel 1,260 minutes. It is also AGM which requires no maintenance. The issue would be size to some and cost to some. I will agree there are few choices that work out this way, the simple solution may very well be 6v batteries for most. We do not boondock, my solution will be AGM in the future.

BTW: the 12v solution I would gain about 200lbs which we can afford.

Steve

[StevL]

Originally Posted by Crasher

Just the opposite. It increases your capacity. Plus, I have read that two deep cycle 6 volt batteries in series will give better service than two 12 volt batteries in parallel.

This is correct if using 105 minutes of capacity at in 12v (which he states over and over).... what happens if you use two 12v with 230 or 315 minutes at 25amp (Lifeline batteries)? Now the 12v will give 460 or 630 minutes vs. his number of 225 (not sure where he got the 225, the 25 minute rating as used in my 12v example for a T105 is 447 minutes per Trojan). Lifeline wins by 13 or 183 minutes.

Now say you have four batteries like I do: Trojans=894 minutes Lifeline=920 or 1,260 (if you can put the little larger Lifeline in which I could, you now have over 6 hours of additional use at 25amp). And, without the maintenance!


Steve