Two 6 volt batteries or two 12 volt batteries ??

skipro3 wrote:
The reason I bought 6 volt batteries is because each plate is much thicker than the 12 volt batteries.

Which is why their internal resistance is significantly higher than those in 12 volt jugs, which in turn results in greater voltage drop under heavy load from an inverter. 12 volt AGMs in particular offer significantly lower internal resistance and for those running an inverter can be the "best" choice. ;)

If you can find TRUE deep cycle 12v batteries, they are an option but most you see at walmart or other non-specialty stores with the "deep cycle" label are not real deep cycle batteries but a cross between starting and deep cycle.

6v batteries are almost always deep cycle and easy to find as every golf course will burn thru dozens per year, so just about anywhere in the USA there is a market for them.

The net result is if you have a failure, it's far easier to find a replacement for 6v batteries.

SoundGuy wrote:

RasMouSein wrote:
People go for the 6v because (story goes) of the footprint, they tend to be taller and fit in the same rack. Therefore more amp/hour in the same place.

Closer to the truth ... many go for two 6 volt GC-2s because pundits here on the forum tell them that's the "better" way to go. :S In reality there's much more to the story and a pair of properly selected G31 12 volts in parallel, some of which are in fact true deep cycle despite what the "experts" here will tell you, could serve some just as well or better. Aside from the obvious advantage that if one 12 volt fails you can still "fly", another is that 12 volt jugs usually have less internal resistance, which in turn means if you're using those batts to power an inverter chances are voltage drop under heavy load is going to be less. So too do more expensive AGM batts have less internal resistance. OTOH, a pair of GC-2s will have a smaller footprint and therefore may be easier to mount than a pair of G31s. They generally also offer the biggest bang for the buck, especially flooded, as so many are sold for so many different uses, not just in RVs. So which is "better"? - you be the judge, for your own reasons, not for someone else's. ;)

FWIW, this spring I'm replacing my pooched 10 yr old flooded G27 that's been sitting on the tongue with a single G31 AGM that will be mounted in the front pass through storage compartment where the run to my 1000 watt PSW inverter will be much shorter. I'm installing only one because we most often camp with shore power available, only occasionally without it, but if we dry camped more often I'd run 2 in parallel ... personal choice. :B Keep in mind though that what batteries, how many you install, their AH rating, and charging requirements must be properly matched to the charger you intend to use to maintain those batteries ... don't get that right and you'll be replacing those batteries sooner rather than later regardless of whether they're 6 volt or 12 volt jugs. ;)

yup, if you intend to run heavy loads, like an inverter to run a microwave, 12V wins. First lower internal resistance, second, if you have two in parallel, each sees 1/2 the load further reducing voltage drop.

A typical pair of GC will run a 1000W inverter load till the batteries are down to around 8085% SOC, not down much, while 12V will run till they are down to 50% or more.

In our case, we compromised. we do lots of dry camping so GC gives more cycles and capability to discharge to 75%DOD with 500 cycles or more, but still want to run a microwave. Solution 4 GC for capacity and ability to run the inverter with batteries near 50%.

Now, if we seldom dry camped, or predominately used high inverter loads, IMHO GC would make no sense. a pair of 12V would way less expensive and do a better job.

I bought 6v because they were a good price at Costco and I could get a single battery box to hold all four :B

The reason I bought 6 volt batteries is because each plate is much thicker than the 12 volt batteries. Think about it; in roughly the same size package there are only 3 cells so the plates are thicker. Thicker plates are less likely to experience mechanical damage. A physically stronger battery. I also like a wet cell battery where I can test the electrolyte specific gravity, which is a better way to determine battery capacity.

FrankShore wrote:
One 6v goes out and you're in trouble... snip

snip...I didn't have a "theory"

Umm.. by stating that "one 6V goes out and you are in trouble" you HAVE stated YOUR "THEORY".

Using one PAIR of 6V GC batts in series is no worse than folks using ONE single 12V battery as which MANY folks do.

My previous TT only had provision for one single 12V group 27 RV/marine battery and in the 5 yrs of use it never got me "in trouble".

Not to mention unless you have ventured several thousand miles away from human civilization you can EASILY just go drive to a store and buy replacement batteries and continue on camping.

Minor inconvenience, yes, trouble, not hardly.

The "redundancy" theory that you have posted is really a silly argument that holds no weight.

You drive a vehicle which unless it is a Diesel has but ONE SINGLE 12V STARTING BATTERY.. How many times have you personally been left down by that one single starting battery?

Myself ZERO times and that includes sub zero freezing weather.

I would be more concerned about having a starting battery go dead out in the middle of nowhere.. Walking out of wilderness is often not an option.

lawrosa wrote:

FrankShore wrote:
One 6v goes out and you're in trouble.

Yes. In that instance your options are.

1. Go out and buy another battery. You can find 6 volts without much trouble locally.
2. Disconnect the batteries and run the RV off the tow vehicles battery temporarily to get you through the weekend.
3. disconnect batts and Run off generator to get you through.

When I'm on the boat, it isn't just a "run off the tv or run off the generator" situation. That's why I always use Lifeline AGM's in both.

Gdetrailer wrote:

FrankShore wrote:
One 6v goes out and you're in trouble.

One CELL of a "12V" shorts and you are in trouble..

One shorted cell of one 12V battery when in parallel will discharge the "good" battery and will also prevent the "good" battery from recharging properly.

One 12V battery gets "weak" and the OTHER 12V battery takes a beating until BOTH no longer work.

The problem with your "theory" is the mere fact that MOST CONSUMER "12V" batteries are actually COMBINATION "starting/deep cycle" batteries which are marketed as "RV/Marine" batteries.

RV/Marine batteries are a COMPROMISE, they are designed to take the demands of high current for a short time (starting) and the demands of deep discharge (trolling motors) for a longer time than just a starting battery.

As a compromise they HAVE some drawbacks.. They do NEITHER "job" well.

They don't function as well under "starting" or a deep cycle.

IE, they don't last as long as a standard car battery in starting mode or can be deeply discharged as a real deep cycle.

A group 27 RV/marine battery has about 70 Ahr of capacity, of that you only want to use no more than 20% (14 Ahr) of that capacity for longest battery life but can be discharged to 50% (35 Ahr) at a REDUCED LIFE.

Granted, you can find true 12V deep cycle batteries (group 31), the draw back to those is not every battery shop carries them (special order) and since they are not in super high demand they ARE considerably MORE EXPENSIVE.

Hence the reason as to why 6V Golf Cart batteries are a great alternative..

6V GC batteries ARE a true deep cycle, ready available and extremely low cost per Ahr.

Typically 6V GC batts give you about 210 Ahr of capacity per pair and you will need two of these wire in series (pos of on to the neg of the other).

6V GC batteries ARE designed to be able to withstand up to 80% (168 Ahr) discharges but for max life should be limited to %50 (105 Ahr).

It would take THREE group 27 RV/marine discharged to 50% to equal one pair of 6V GC batteries at the same 50% discharge.. However the life of the group 27 12V RV/marine batteries WILL be considerably LESS and you end up spending MORE on the THREE RV/Marine batteries over the life of your RV.

If you don't boondock, then no reason to buy GC batts, but if you do boondock, you WILL get much more capacity and it WILL cost you less in the long run.

I don't boondock but I did convert my TT to a residential fridge so one pair of 6V GC batteries can easily run my fridge, some lights and even the furnace for 24 hrs before needing to recharge. It would take at least three if not four group 27 RV/marine batteries to do the same job and the service life will be much shorter..

I just replaced my first set of GC batteries this spring, the first set gave me 9 years of service and they were still working OK but I did notice that they had lost some capacity so I replaced them.. Not bad service and the replacements cost $80 each at Sam's.

I didn't have a "theory"

We prefer boondocking and have done so extensively since getting our current rig over a decade ago. Upon purchase we had the dealer install a pair of 12 volt rv/marine batteries that appeared to do a decent job of providing power when we were RVing off the power grid, after a couple of years they were not bouncing back like they had before, we went to Samsclub and picked up a pair of 6 volt GC2 batteries for $60 a piece.

Same smart converter charger, same built-in genny, didn't notice a drop off in performance for 7 years. Gave them another year of use and just replaced them last season for another set of GC2 batteries where we paid $80 each. I guess 8 or so years from now when I need batteries again they may cost nearly $100 each, without a doubt the best bang for your buck if you plan to run them hard like we do.

KD4UPL wrote:
This gets discussed to death about every couple weeks. If you search the topic you could find enough reading material for years.

Done.

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