6 volt versus 12 volt HELP

ken white wrote:

...
If you A-HR numbers are correct, 2 - 31's in parallel would produce 420 A-HR while the 2 - GC2's would produce 190 A-HR...

Ah, no. I was taking the lotal Ah of two AGM batteries, 6 or 12V.
So 210 Ah Total for the two 31's, 105Ah ea. 12 cells total.
And 190Ah for ea 6V and 190Ah for two in series. 6 cell total.

Hi,

The Duracell AGM group 31 is 105 amp-hours at the 20 hour rate.

A nice table here:

http://www.samsclub.com/sams/duracell-agm-deep-cycle-marine-and-rv-battery-group-size-31dtmagm/prod3590232.ip

Being a 12 volt aficionado I'd probably go 12 volt (since I can't afford 2 volt).

ken white wrote:

If you A-HR numbers are correct, 2 - 31's in parallel would produce 420 A-HR while the 2 - GC2's would produce 190 A-HR...

This. I would not worry about number of cells with RV usage. Plenty of people here with 6+ years on paralleled 12V batteries. I would go for the amp-hours and the twin 31's get my vote.

brulaz wrote:
Interesting. Perhaps it's best to store AGMs on end with the lead plates horizontal to the ground. Shedded material would tend to stay in place more.

I see that Sam's Club is selling Duracell AGM's (East Penn is the manufacturer, I think). The 12V 31 (210Ah) and 6V GC2 (190Ah) are going for exactly the same price (US$180 ea) down in Fort Myers FL. Buying two of each you would end up with about the same weight but the 31s would have 20Ah more. But there would be twice as many cells with the 31s.

So, buy the AGM GC2 or 31? I'm leaning toward the golf carts and with the fewer, bigger cells despite the lesser Ah.

I could put them inside, closer to the trailer axle, helping my tongue weight issue; and run them as a separate/switchable battery bank.

If you A-HR numbers are correct, 2 - 31's in parallel would produce 420 A-HR while the 2 - GC2's would produce 190 A-HR...

Interesting. Perhaps it's best to store AGMs on end with the lead plates horizontal to the ground. Shedded material would tend to stay in place more.

I see that Sam's Club is selling Duracell AGM's (East Penn is the manufacturer, I think). The 12V 31 (210Ah (EDIT:for two)) and 6V GC2 (190Ah) are going for exactly the same price (US$180 ea) down in Fort Myers FL. Buying two of each you would end up with about the same weight but the 31s would have 20Ah more. But there would be twice as many cells with the 31s.

So, buy the AGM GC2 or 31? I'm leaning toward the golf carts and with the fewer, bigger cells despite the lesser Ah.

I could put them inside, closer to the trailer axle, helping my tongue weight issue; and run them as a separate/switchable battery bank.

Optima's are small amp-hour batteries though. Of course they have less space. No comparison. I'm talking about LARGE amp-hour batts like Fullriver 415Ah 6V's. There's absolutely no reason they need to be that size if there's no reason to have that amount of space below the plates. That's just asinine! Also, that link states that loss of compression is MITIGATED not eliminated and plate shedding is DELAYED not eliminated. Which stands to reason that the space below the plates is still required just not used as quickly.

Mena661;

By that logic, there must be air space all around the case as AGM can be installed on a side or end. IDK if air space is required for AGM battery operation.

I believe any air space is there so that the case can conform to GRP size specs. Look at the Optima. Where is the air space for shedding? There is a top and bottom to give the battery its GRP designation.

Your link goes on to discuss the compressions's role in trapping any shedding because if material escapes then the compression is lessened. This compression is critical to keeping the mat in contact with active material. A wet fills in the space left from shedding with liquid to keep the electrolyte in contact with active material.

HTH;
John

Hi mena,

That would leave you with the same cell count--but some slightly higher resistance connections.

pianotuna wrote:
Hi Mena,

I'm saying that a 400 amp-hour single twelve volt battery would be better than 8 100 amp-hour six volt batteries.

Oh ok. Well, I wouldn't do that, I'd get two 400Ah 6V's.

full_mosey wrote:

Menna661;
Great link!

Thanks! Large amp-hour AGM 6V's still have similar amounts of space below the plates as similar amp-hour wet cells though. If that space wasn't needed, I doubt manufacturers would waste money including that space. The plate shedding must reach the bottom of the jar.

Per Deka's pdf, A pair of 31M is 210AH and a pair of GC2 is 190AH. The 31M gives more AH.

However, the GC2 has less CCA which may indicate thicker plates and possibly deeper discharge with the possibility of more cycles. Tradeoffs?

Either pair's run time would exceed the wet GC2 pair for inverter use due to holding Volts better.

Menna661;
Great link!

AGM's mats/plates are compressed. There is shedding, but it is trapped. A wet drops shedding and there is a reservoir under the plates to collect it. Both extend the life of the battery.

HTH;
John