Two 6 volt batteries or two 12 volt batteries ??

I asked this same question back in the summer. We don't boondock, but we do have a residential fridge. I got a similar reply, and I read a bunch of threads.

In the end I went with 2 6 volt GC2's from Sams Club. They were about the same price as the RV/Marine batteries. I really think for my use, it really probably doesn't make much of a difference, I went 6v just to see how well it worked, and figured with price being the same, I didn't have much to lose, but there did seem to be alot of people talking about getting longer life from the 6v.

Unless you boondock just pick one and go camping and enjoy!

SoundGuy wrote:

lawrosa wrote:
OK.. So I am able to run say my toaster oven now. Even @ 12.5 volts the drop dont go much below 12v..

So your saying if I went 6 volt and had the batts @ 12.5 and put a 800 watt load on the voltage would drop below my 11.5 inverter cut off?

You're trying to apply specific numbers to a situation chock full of variables so no one can give you a definitive answer. A better way to look at it is this - one scenario you have two 6 volt GG-2s connected in series and 20 Hr rated @ 220 AH as a pair, under a second scenario you have two G31 12 volt batteries connected in parallel and 20 Hr rated @ the same 220 AH as a pair AND in both scenarios these batts are connected with the same gauge & length of cable. Compare the two setups and you'll find the 12 volts will suffer noticeably less voltage drop under the same load than will the 6 volts because internal resistance of the 12 volts is much less than the thicker plate 6 volts. Likewise if you use 12 volt AGMs instead of 12 volt flooded the results will be even better. Voltage drop isn't only about running the batts themselves down but shutting down the inverter when input voltage drops below it's operating limit which is determined by the manufacturer and will vary somewhat from one inverter to another.

I have 3 75 ah duracells in parrelel.. Actually one is a 70 ah... so 220 ah's. But the batts are getting old and I will probably replace this summer..

was thinking 6 volts but I dont want my inverter to suffer..

Oh im sorry its

Under Voltage Shutdown Under 10 VDC
Low Voltage Alarm Audible at 10.6 VDC

LOL last year I had the alarm going off in morning when wife making coffee. But I had challenged charging abilities then.

lawrosa wrote:
OK.. So I am able to run say my toaster oven now. Even @ 12.5 volts the drop dont go much below 12v..

So your saying if I went 6 volt and had the batts @ 12.5 and put a 800 watt load on the voltage would drop below my 11.5 inverter cut off?

You're trying to apply specific numbers to a situation chock full of variables so no one can give you a definitive answer. A better way to look at it is this - one scenario you have two 6 volt GG-2s connected in series and 20 Hr rated @ 220 AH as a pair, under a second scenario you have two G31 12 volt batteries connected in parallel and 20 Hr rated @ the same 220 AH as a pair AND in both scenarios these batts are connected with the same gauge & length of cable. Compare the two setups and you'll find the 12 volts will suffer noticeably less voltage drop under the same load than will the 6 volts because internal resistance of the 12 volts is much less than the thicker plate 6 volts. Likewise if you use 12 volt AGMs instead of 12 volt flooded the results will be even better. Voltage drop isn't only about running the batts themselves down but shutting down the inverter when input voltage drops below it's operating limit which is determined by the manufacturer and will vary somewhat from one inverter to another.

lawrosa wrote:

ktmrfs wrote:

lawrosa wrote:

SoundGuy wrote:

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. ;)

I never read anywhere about this voltage drop... How much are we talking about? I run an 1100 watt inverter. I have 3 24 group batts @ 75 ah..

I run 800 watt toater oven and coffee maker.

I ran #2 wire 5 feet maybe..

How much worse will the voltage drop be with 6 volts?

I been meaning to go 6 volt but now this threw a wrench in the works...

I have 2/0 cable of 2 ft from my two GC to the inverter. with a pair of GC, anything below 80% SOC or so will kick out the inverter with a 800W load on the inverter. For your application I'd say stay with 12V.

12V has two big advantages for you. One, significantly lower internal resistance on each battery. Two, you are sharing the load between two parallel batteries so each battery is supplying roughly 1/3 the total current draw. 12V wins' hands down.

you would need at least 4 GC to run what you want on the inverter at reasonable DOD on the batteries.

OK.. So I am able to run say my toaster oven now. Even @ 12.5 volts the drop dont go much below 12v..

So your saying if I went 6 volt and had the batts @ 12.5 and put a 800 watt load on the voltage would drop below my 11.5 inverter cut off?

If so thats is good info..

my experience and also BFL, going through similar use, if the pair of GC drops below about 75-80% SOC, you can hit the inverter shutoff limit pretty easy with loads of 800-1000 W. Some may depend on the specific inverter and what it's lower limit is.

Now if the batteriesa are above 80% or so, you in good shape. but that means keeping them near full charge when you want the inverter. So.... run the furnace at night then get up and turn on the toaster.... likely be a nope! low temps= higher internal resistance, lower capacity, coupled with partial discharge.

IMHO if your happy with your current 12V setup, don't mess with it. Or, get GC for most of the stuff and run the inverter off 1 or 2 12V AGM's or similar.

ktmrfs wrote:

lawrosa wrote:

SoundGuy wrote:

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. ;)

I never read anywhere about this voltage drop... How much are we talking about? I run an 1100 watt inverter. I have 3 24 group batts @ 75 ah..

I run 800 watt toater oven and coffee maker.

I ran #2 wire 5 feet maybe..

How much worse will the voltage drop be with 6 volts?

I been meaning to go 6 volt but now this threw a wrench in the works...

I have 2/0 cable of 2 ft from my two GC to the inverter. with a pair of GC, anything below 80% SOC or so will kick out the inverter with a 800W load on the inverter. For your application I'd say stay with 12V.

12V has two big advantages for you. One, significantly lower internal resistance on each battery. Two, you are sharing the load between two parallel batteries so each battery is supplying roughly 1/3 the total current draw. 12V wins' hands down.

you would need at least 4 GC to run what you want on the inverter at reasonable DOD on the batteries.

OK.. So I am able to run say my toaster oven now. Even @ 12.5 volts the drop dont go much below 12v..

So your saying if I went 6 volt and had the batts @ 12.5 and put a 800 watt load on the voltage would drop below my 11.5 inverter cut off?

If so thats is good info..

lawrosa wrote:

SoundGuy wrote:

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. ;)

I never read anywhere about this voltage drop... How much are we talking about? I run an 1100 watt inverter. I have 3 24 group batts @ 75 ah..

I run 800 watt toater oven and coffee maker.

I ran #2 wire 5 feet maybe..

How much worse will the voltage drop be with 6 volts?

I been meaning to go 6 volt but now this threw a wrench in the works...

I have 2/0 cable of 2 ft from my two GC to the inverter. with a pair of GC, anything below 80% SOC or so will kick out the inverter with a 800W load on the inverter. For your application I'd say stay with 12V.

12V has two big advantages for you. One, significantly lower internal resistance on each battery. Two, you are sharing the load between two parallel batteries so each battery is supplying roughly 1/3 the total current draw. 12V wins' hands down.

you would need at least 4 GC to run what you want on the inverter at reasonable DOD on the batteries.

valhalla360 wrote:
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.

Even TRUE 12V deep discharge seldom have the cycle life of a comparable GC. Look at trojan's spec's for cycle life vs. DOD for GC and 12V Deep discharge. GC still wins. Now, for many or most campers, the trojan 12V deep discharge will likely give plenty of cycle life. and they win for high current discharge.

However, it's much easier to find a GC battery somewhere than a true 12V deep discharge like the Trojans.

so, like so many things, each has advantages and disadvantages. pick and choose based on what is BEST suited for YOUR application.

lawrosa wrote:

SoundGuy wrote:

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. ;)

I never read anywhere about this voltage drop... How much are we talking about? I run an 1100 watt inverter. I have 3 24 group batts @ 75 ah..

I run 800 watt toater oven and coffee maker.

I ran #2 wire 5 feet maybe..

How much worse will the voltage drop be with 6 volts?

I been meaning to go 6 volt but now this threw a wrench in the works...

You will be fine with 6 volt batteries. Remember voltage in batteries is dependent on draw. I = V/R. Your 1100W inverter will be fine with a pair of 6V batteries or even better with 4.
FWIW, I run a 1000W inverter to power a small 120V fridge and the entertainment gear. Voltage may temporarily drop into the high 11's with use but that is OK. With your recent abundance of solar power, I'd suggest to size your battery bank to the amount of solar charging available. A guy can't have too much free power. :B

BTW, I have both 12V and 6V batteries, three 12V AGM's inside near the axles and 2 6V's inside near the axles in a vented box. The two banks can be switched but I typically keep them drawing/charging together.
Since I now have a big piece of a planned 12V upgrade (inverter), I'll be looking for more solar charging and more batteries. A guy can't have too much power. ;):B

Well we all have our reasons. My choice is 3 of the Wal Mart Marine 12V batteries. For me three 12's are easier to take out and store in winter with a maintainer. I hated to lift out and carry the 6V Golf Cart Batteries I had for about 5 years.

PLUS the big bonus for me, is I use two of the batteries in the boat when I get to the lake. I can troll all day with the electric motor and crank the 115hp Evenrude engine when I need it.

I almost never boondock but if I do those three last all night and still power the slide in and out with no problems.

Almost forgot to mention I also use the batteries out of the RV to run the tractor. Three batteries and three uses.

SoundGuy wrote:

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. ;)

I never read anywhere about this voltage drop... How much are we talking about? I run an 1100 watt inverter. I have 3 24 group batts @ 75 ah..

I run 800 watt toater oven and coffee maker.

I ran #2 wire 5 feet maybe..

How much worse will the voltage drop be with 6 volts?

I been meaning to go 6 volt but now this threw a wrench in the works...