6volt or 12volt batteries?!

[Willywalderbeast]

So when I picked up my camper and started heading back it seemed like my batteries were finally giving out and not holding a charge. Although I had plans to revamp the electrical system when I got home I stopped at a Interstate Battery shop to see if they could test the 12v interstates I had. Sure enough they were toast and I picked up two new ones to make the trip more enjoyable.

While there, the sales person was advising me to buy two 6v batteries and run them in series to make them 12v but with a lot more amp hours stored. I have looked into it more and can't really find a reason why you wouldn't want to do this. On the positive side the batteries should have a longer lifespan as the plates are much thicker and more stored amp hours. Only negatives I see are that I would have to remove my side out battery tray to fit them so topping them off would be more difficult but I'm not to worried about that.

I know a lot of you guys have gone the way of AGM batteries but for sake of argument, if I was to stay with flooded batteries is there any reasons not to go with two 6v run in series? If not I plan on returning the two 12v ones I got in exchange for two 6v now that I'm home and can remove the battery tray.

[ltg]

My 2 cents worth. Keeping the two 12 volt batteries have three advantages. You keep the slide out tray, no rewiring of battery wiring, and if one battery goes bad you simply remove it and go on until it can be replaced.

[Willywalderbeast]

Itg, Removing the tray and rewiring (one new cable) don't bother me, but you make a good point on being dead in the water if one battery was to go bad. Although it wouldn't be the end of the world to me to be out of power till I could get new one and the reality of that happening randomly I don't believe would be high.

[Scott]

Willy,
I agree with your analysis. I feel that flooded 6V batteries give you the most value for the money. The advantages of AGMs are well documented, but they still didn't pencil out for me personally. My pair of US Battery 6V flooded golf cells have 232ah for $280 and 126 pounds. If you get flooded batteries, and space is tight, a battery irrigation system makes the chore a 2 minute job. On that subject, I've used my batteries consistently since June and I've added water once, and it was very little.

[A Rooney]

Not sure it's recommended to replace just one battery,if one fails...both should be equal as to brand and manufacture date....Most marine batteries are not "true deep cycle" (golf cart 6volt) are,and designed to cycle more deep discaharges without damage.....I truly don't know and can't say if you draw down your batteries as I do very little before recharging whether this is an advantage or not.The remote watering system is a great idea if you remove the tray IMO,as is an item in your electrical system that allows you a short high voltage charge that "equalizes" the battery bank as needed.I have heard negative hearsay on Interstate quality control.....and I believe as far as 6 volt fla golf cart/forklift deep cycle batteries....Trojan and Crown both have sterling reputations....Rooney

[Blue~Go]

Just as a general note, there isn't anything "magical" about 6 volt batteries as compared to 12 volt, in terms of amp hours. I have seen where sometimes people (not saying you) accidentally think (or are told) they are getting twice as many amp hours, but because you have to wire two of the batteries in series (to get 12 volts), that's not true. In other words if one 12 volt battery has 120 amp hours, and two 6 volt batteries have 120 amp hours EACH, both arrangements will have the same 120 amp hours once the two 6 volt batteries are wired in series to make 12 volts (you don't get 240 amp hours with the two 6 volt batteries, in other words).

Sometimes it's possible to get a few more amp hours just due to case dimensions and how they fit a given space, but that's not due to the voltage, but rather just due to the variations in case size and your available space. In general, 6 volt batteries tend to be taller than their 12 volt brethren, which can make it a challenge to fit them in a space that was designed for typical 12-volt case sizes (especially if they are flooded cells, which have to be installed right side up).

Either 6- or 12-volt batteries can be flooded cells, AGM, or etc. Either can be true deep cycle, "fake" deep cycle, or starting batteries. Just depends on the battery spec. Traditionally, in flooded cell batteries, 6 volt "golf cart" batteries were known to be tough, deep cycle batteries (T-105, etc.). But you can get good and less good batteries of any type.

There is an advantage to 6 volt batteries if you are going to be running a larger bank of say, four batteries or more. That's because in a set of four parallel 12 volt batteries the two middle ones don't get the same "use" as the outer two. With the same four batteries in series it's like two batteries and they both get equal use (presuming you wire them in balanced fashion of course). But in reality, I don't know how much this matters unless you have a larger bank (number of batteries) than most of us are likely to.

A possible advantage to 12-volt batteries in our Chinooks is that you can fit three batteries in the stock space. You can't run three 6 volt batteries because you can't get 12 volts out of odd numbers of them. So in that case amp hour advantage goes to 12 volt batteries. Three 12-volt GPL 31XT Lifelines will give you 375 amp hours, for example.

As usual, there is no one best answer and I don't see a blanket statement that "6 volt batteries will give you more amp hours" holding true. It all depends.

[Scott]

Just as a general note, there isn't anything "magical" about 6 volt batteries as compared to 12 volt, in terms of amp hours. I have seen where sometimes people (not saying you) accidentally think (or are told) they are getting twice as many amp hours, but because you have to wire two of the batteries in series (to get 12 volts), that's not true.

Good point, and thanks for mentioning it. It never occurred to me that people might get misled regarding capacity with 6V vs. 12V. I can see how it might happen though.

[Blue~Go]

Yeah, I've read a number of posts (RV forums, boat forums, etc.) where people say how many amp hours they have in their battery bank, but they use the 6 volt figure (even though they have them wired in series pairs to make 12 volts so should be dividing the figure by 2). So they think they have twice as many amp hours as they actually do. Oopsie.

I can see how that would happen though; just figured I'd note it here since the two voltages are being compared. Not sure if that's what was happening in the quote below, but maybe, because using the stock compartment I don't see how you could fit "a lot more" amp hours in by using 6 volt batteries. If anything, I think the advantage would go to 12-volters, as you can fit three and add them together (parallel).

I stopped at a Interstate Battery shop ...While there, the sales person was advising me to buy two 6v batteries and run them in series to make them 12v but with a lot more amp hours stored.

[Willywalderbeast]

I know I won't be getting double the amp hours. In the grand scheme of things, with the configuration I would be going with I would only be getting 30amp hours more. Although many people claim to notice a big difference in run time when switching to 6v. I guess the big positives for me are that the lifespan if properly maintained should be a lot longer and true deep cycle 6v cart batteries can handle being draw down low, although I guess the same can be said about a true deep cycle 12v.

I was original planing on running 3x12v since it would fit nicely in the battery compartment but I have realized I don't need that much amp hours. We don't use much electricity and tend to move around a lot so between the solar and alternator charge I don't ever see myself running the batteries down much at all.

I guess it just comes down to longevity, in which it seems that everyone agrees that the 6v are superior.

[Willywalderbeast]

Old post I found on another forum(so the prices my be off) that I found interesting.

"The Trojan 6V T105 has much thicker plates than the 12V Trojan SCS200 of almost equal weight.

A pair of T105s weighs 124 lbs and provides 225 amps at a cost of $168

A pair of SCS200s weighs 120 lbs and provides 230 amps at a cost of $230.

The T105 can be cycled deeper due to its thicker plates and will have a greater cycle life.

So, in an apples-to-apples comparison, or at least equal weight and amps of the same manufacturer's deep cycle batteries, the 6 volters can be cycled deeper, last longer and cost less than the 12 volters..

In my conversation with an engineer at Trojan today, we went over these numbers, and I asked why on earth people bought the 12 volt batteries. His reply was that many RVs came that way and they just continued, and many RVs (mine, for example) did not accommodate the taller 6V golf cart batteries well. And, many RVers are happy and well served with just one battery, since they do little or no dry camping. So, they are meeting the market, like every other business.

EDIT: In a later conversation, he confirmed by suspicion that the thicker plates in a T105 do allow a higher charging rate than the thinner plate 12 volt batteries. They can take about 25 percent of rated capacity instead of the 10 to 13 percent rate quoted on their site. This is useful if you have a big enough charger, and can minimize generator run time, saving a little fuel, noise and CO production."