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 > 12v to 6v review?

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pianotuna

Regina, SK, Canada

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Posted: 05/03/21 09:37pm Link  |  Quote  |  Print  |  Notify Moderator

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.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, soon to have SiO2 batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

pianotuna

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Posted: 05/03/21 09:45pm Link  |  Quote  |  Print  |  Notify Moderator

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.

ktmrfs

Portland, Oregon

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Posted: 05/03/21 10:00pm Link  |  Quote  |  Print  |  Notify Moderator

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??

* This post was edited 05/04/21 09:36am by ktmrfs *


2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
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2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!


Vintage465

Prunedale CA.

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Posted: 05/04/21 08:15am Link  |  Quote  |  Print  |  Notify Moderator

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.........


V-465
2013 GMC 2500HD Duramax Denali. 2015 CreekSide 20fq w/450 watts solar and 465 amp/hour of batteries. Retiring in 2021, then look-out road, here we come!

jaycocreek

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Posted: 05/04/21 09:34am Link  |  Quote  |  Print  |  Notify Moderator

Quote:

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..

ktmrfs

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Posted: 05/04/21 09:43am Link  |  Quote  |  Print  |  Notify Moderator

jaycocreek wrote:

Quote:

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.

JimK-NY

NY

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Posted: 05/04/21 11:42am Link  |  Quote  |  Print  |  Notify Moderator

Vintage465 wrote:




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.
......


I found 2 batteries that compared closely for AH ratings. The first was a 6 v Duracell @235/2=117 and the second was an Apex 12 v with 115 AH. Two of each would be comparable. The weight for each was identical @ 68#. The 6 v took 794 cu in of space and the 12 v tool less at 729 cu in. The biggest difference is in height of the batteries. Typically 6 volt batteries are higher, in this case by almost 3". My battery box will not accommodate the extra height so for me there is no choice but to stick with a pair of 12v batteries. At least I found a pair totally 300 AH that will just fit.

ktmrfs

Portland, Oregon

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Posted: 05/04/21 12:29pm Link  |  Quote  |  Print  |  Notify Moderator

JimK-NY wrote:

Vintage465 wrote:




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.
......


I found 2 batteries that compared closely for AH ratings. The first was a 6 v Duracell @235/2=117 and the second was an Apex 12 v with 115 AH. Two of each would be comparable. The weight for each was identical @ 68#. The 6 v took 794 cu in of space and the 12 v tool less at 729 cu in. The biggest difference is in height of the batteries. Typically 6 volt batteries are higher, in this case by almost 3". My battery box will not accommodate the extra height so for me there is no choice but to stick with a pair of 12v batteries. At least I found a pair totally 300 AH that will just fit.


the height increase with GC2 is an issue with a fair number of applications. And couple that with few vented boxes for GC2 use in 5th wheels.

However for tongue storage there are many nice boxes made for two GC2's either end to end or side to side configuration if you have enough clearance to get to batteries in. But that assumes the TT battery location on the tongue has enough height, and on many new trailers that can be an issue.

pianotuna

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Posted: 05/04/21 12:33pm Link  |  Quote  |  Print  |  Notify Moderator

ktmrfs,

Your math perhaps contains a typo? 125 x 4 = 500 amp-hours x 50% = 250 amp-hours and will run a microwave far longer than a similar bank of 6 volt jars.

Why, because the 1556 watt load (number from my Dometic) is divided by twice the number of cells--so each cell only has to do 788 watts. Voltage drop is going to be smaller.

mr_andyj

Georgia

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Posted: 05/04/21 03:53pm Link  |  Quote  |  Print  |  Notify Moderator

My real-world experience over 20 years, always using multiple batts, is two 6's are better than two 12's. For reasons I stated, mostly because that you do not need to magically pair the 6's as you do parallel 12's.
Resistance and inner workings? What? Really? No. Im not running a carpentry shop here, just lights, fans, fridges and normal RV stuff that runs fine off of any 12 volt supply I have ever had.
Science and theory aside, two 6's have been far superior for me and my use than paired 12's.

IF you want science I think Trojan battery has a lot of info on their site, and any high-end battery site will have similar details, but you come to a forum to get real-world non-commercialized feedback. Sort through all the post I guess.

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