12v to 6v review?

jaycocreek wrote:

how many cycles will the 12V give at 50%? unknown but probably enough to be adequate for many users

Lifeline are rated at 1000 cycles at 50% and Vmax are rated at 900 for the same..

similar to a GC2 at 50%. True deep discharge can take way more cycles than a "marine" or similar battery.

I'd say for the vast majority of users, this kind of cycle life is such that the batteries will go bad from age than cycles.

how many cycles will the 12V give at 50%? unknown but probably enough to be adequate for many users

Lifeline are rated at 1000 cycles at 50% and Vmax are rated at 900 for the same..

JimK-NY wrote:

mr_andyj wrote:
.....
Nonsense? No. Good advice, but go do an easy forum search as there are many post on this same topic and easy easy to find with a few keystrokes....

I am still trying to locate some facts and studies, not just opinions. Forum searches have not been any better. Instead I have seen even more myths, fallacies and unfounded opinions.

Yup that is true you would have only 235ah in a two 6-sixer set up. But you'd only have 200ah in two-12er set up and they both have the same "safe draw down to 50%". The weight is about the same, the sixers being about 2 pounds heavier. The 12's will take up more space as their foot print is a little larger. There is some talk that 12's are better with heavy draw from an inverter, but I don't really care about that as I don't use an inverter. The other thing about using 6's vs 12's is, if the average person went "down town" to buy batteries the chances of getting true deep cycle 12's aren't nearly as good as getting true deep cycle 6's. For me, 6's are the way to go. For others, maybe not.........

pianotuna wrote:

Vintage465 wrote:
I think if you went for a comparison chart that showed pounds of battery per amp/hour you'd find that 6v golf cart batteries have the advantage. If I added up 4 100ah 12v batteries vs 4 235ah 6v batteries you'll be ahead with the 6's and also use less space and right at the same weight.

And if you have 4 125 amp-hour 12 volt batteries the end result would be more amp-hours than the 6 volt format. Or if there is room for an odd number of batteries, 12 volt may have the edge.

The best battery bank would consist of 2 volt cells--say 1000 amp-hours each connected in series to yield 12 volts. on my beer budget, I can't afford them.

four 125A twelve volt batteries =470AH.
Four 250 AH 6V GC2's = 500AH

now lets talk useable AH with decent cycle life
four GC2's 470AH x 0.75= 350 AH
four 12Vs 500AH x 0.4 = 250 AH

GC2 has a 100AH (40% or so advantage)

from the trojan website four GC2's will give approx 500 cycles discharged to 25% SOC (75% DOD) before dropping below 80% of initial capacity. over 1000 cycles at 50% DOD. More than most of us will ever see.

how many cycles will the 12V give at 50%? IIRC Trojan true deep discharge 12V are rated for about 500 cycles at 50%. It drops rapidly for DOD > 50% unlike the GC2

how many at 75% DOD ??? who want to try??

Vintage465 wrote:
I think if you went for a comparison chart that showed pounds of battery per amp/hour you'd find that 6v golf cart batteries have the advantage. If I added up 4 100ah 12v batteries vs 4 235ah 6v batteries you'll be ahead with the 6's and also use less space and right at the same weight.

And if you have 4 125 amp-hour 12 volt batteries the end result would be more amp-hours than the 6 volt format. Or if there is room for an odd number of batteries, 12 volt may have the edge.

The best battery bank would consist of 2 volt cells--say 1000 amp-hours each connected in series to yield 12 volts. on my beer budget, I can't afford them.

JimK-NY,

Pretty much all batteries are tested at 77 F and 25 amps. Iirc that is how the "reserve capacity" number is created.

Most of the makers have that data available.

One good source is Battery University, and another is the smart gauge site.

mr_andyj wrote:
.....
Nonsense? No. Good advice, but go do an easy forum search as there are many post on this same topic and easy easy to find with a few keystrokes....

I am still trying to locate some facts and studies, not just opinions. Forum searches have not been any better. Instead I have seen even more myths, fallacies and unfounded opinions.

Vintage465 wrote:


I think if you went for a comparison chart that showed pounds of battery per amp/hour you'd find that 6v golf cart batteries have the advantage. If I added up 4 100ah 12v batteries vs 4 235ah 6v batteries you'll be ahead with the 6's and also use less space and right at the same weight.

Sorry but that is a common fallacy. Looking at specs it seems that for batteries of roughly the same size and weight, the 6 v seems much better. That is because the amp draw is based on 6 v, not 12v. If in your example you have 2 235 AH 6 volt batteries, you only get 235 AH total for both batteries wired for 12 volts.

If you compare size of batteries, typically 6 v batteries will take up much more space than the equivalent 12 v batteries. The weight will be about the same.

Gdetrailer wrote:

ktmrfs wrote:


actually most 12V batteries have lower internal resistance than a comparable AH 6V because they have more and thinner plates per 2V cell than 6V. But the thinner cells and associated tradeoffs means lower cycle life and not likeing deep discharges.

But yes, using four 6 volt will give about 500AH capacity and suitability for reasonably high current draw. But four 12V in parallel will still give lower voltage drop due to lower internal resistance and load sharing amongst four batteries instead of two.

4 "12V" batteries will net you considerably less Ahr capacity when comparing similar square inches of space in comparable battery size.

For instance group 27 has foot print of one 6V GC2 and Ahr capacity of 80Ahr. Of that 80Ahr it is rated for only half of the capacity for the cycle life. Cycle life improves drastically if you only use 20% of the capacity.

GC2s cycle life are rated at 80% of the capacity, don't try that with group 27, you will degrade a group 27 very quickly if you try..

So, in reality, if you want max life, max draw with max capacity the GC2s are the better choice even with high current draw.

I don't know what folks are doing to bother an inverter with high current draw on GC2s, so far I have not had any issue. I know for a fact that my home fridge conversion does indeed spike 100A draw on the compressor startup surge. Even draining my GC2s down to 50% discharge I have never had any issue with my inverter low voltage alarm or shut down.

I do know this, I can easily go 24hrs without recharging my one pair of GC2s. In fact, I typically will travel 800 miles over two days, overnighting one night without power to get to my camping spot all without any commercial power or stopping for generator. As you know, vehicle charge lines provide very minimal charge support.

To get that kind of run time with group 27s I would need better than 4 of them, most likely 8 and then I would be replacing batteries every few yrs because I would be discharging very deeply..

So far the first set of GC2 batteries lasted me 9 yrs, could have gone 10, maybe 11 yrs but I did notice they didn't have as much capacity as they did when new and they were using twice the water as new.

You can continue using group24/27 in parallel, myself I am more than satisfied with the long, long battery life I am getting with GC2s in series..

I'll agree with GC2 for cycle life, ability to do hundreds of really deep discharges, and long life. And even 100A or so spikes in current draw from GC2's. That's why I like them.

where I had trouble with a pair of GC2's was running my panasonic true inverter variable output microwave for long periods (5-10 minutes) . it doesn't cycle between 0 and 100% but stays at a fixed %. On my 1000VA inverter with very short (18 inches) of 4/0 cable between the batteries and inverter it would run the microwave just fine at 50% input (90A 12V draw) as long as the battery bank was at 80% or more. much below that and it would shut down due to low input voltage after 30-60 seconds.

Keep current draw below 30A-40A or so and they perform wonderfully.

On one trailer I have a pair of GC2's running a small fridge on a MSW inverter. Like you mentioned current can spike, in my case in the 75A range, but then settles down to 15A or less. A pair of GC2's will do this all the way down to 50% SOC or less no problem.

I think BL13 and some others experienced the same thing at very high continous current draw (100A or so). I since switched to a bank of 4 GC2's, and no issues down to 50% SOC.

And I've run two sets of batteries on different trailers for 10 years on a bank of GC2, often averaging 60 days or so off grid so the batteries will last a decade if properly cared for.

ktmrfs wrote:


actually most 12V batteries have lower internal resistance than a comparable AH 6V because they have more and thinner plates per 2V cell than 6V. But the thinner cells and associated tradeoffs means lower cycle life and not likeing deep discharges.

But yes, using four 6 volt will give about 500AH capacity and suitability for reasonably high current draw. But four 12V in parallel will still give lower voltage drop due to lower internal resistance and load sharing amongst four batteries instead of two.

4 "12V" batteries will net you considerably less Ahr capacity when comparing similar square inches of space in comparable battery size.

For instance group 27 has foot print of one 6V GC2 and Ahr capacity of 80Ahr. Of that 80Ahr it is rated for only half of the capacity for the cycle life. Cycle life improves drastically if you only use 20% of the capacity.

GC2s cycle life are rated at 80% of the capacity, don't try that with group 27, you will degrade a group 27 very quickly if you try..

So, in reality, if you want max life, max draw with max capacity the GC2s are the better choice even with high current draw.

I don't know what folks are doing to bother an inverter with high current draw on GC2s, so far I have not had any issue. I know for a fact that my home fridge conversion does indeed spike 100A draw on the compressor startup surge. Even draining my GC2s down to 50% discharge I have never had any issue with my inverter low voltage alarm or shut down.

I do know this, I can easily go 24hrs without recharging my one pair of GC2s. In fact, I typically will travel 800 miles over two days, overnighting one night without power to get to my camping spot all without any commercial power or stopping for generator. As you know, vehicle charge lines provide very minimal charge support.

To get that kind of run time with group 27s I would need better than 4 of them, most likely 8 and then I would be replacing batteries every few yrs because I would be discharging very deeply..

So far the first set of GC2 batteries lasted me 9 yrs, could have gone 10, maybe 11 yrs but I did notice they didn't have as much capacity as they did when new and they were using twice the water as new.

You can continue using group24/27 in parallel, myself I am more than satisfied with the long, long battery life I am getting with GC2s in series..