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Old 13-07-2017, 06:06   #16
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

GC2 batteries have more liquid over the plates than any 12 volt marine battery. GC2 batteries have thicker plates than any marine 12 volt battery. GC2 batteries handle deep discharges better than any 12 volt marine battery. Oh shat! GC2 batteries need that extra wire to form the series connection.
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Old 13-07-2017, 06:56   #17
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

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And half the cost. As long as the 12 volt batteries meet your capacity requirement what is the point of using 6 volt GC's. All this assumes that the individual 6 volt and 12 volt batteries have about the same watt-hour capacity. Thanks.
But, you have to take into account the basic quality of the battery. Golf cart batteries are made to resist frequent discharge-recharge cycles, and therefore are built tough, much stronger than lets say regular batteries.
By the way, mysailboat is equiped with Duracell 31 batteries in 3 banks, for the last 3 years. Up to now nothing to complain about. Costwise, quite cheaper than the Trojan 6 volts that it replaced.
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Old 13-07-2017, 07:00   #18
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

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Does anyone have experience with the Duracell Deep Cycle Group 31 size lead-acid battery? 105 AH. $94 ea. at Sam's Club. Components made in US and assembled in US.
$376 for 4 batteries (+core charge).
House bank total: 420 AH. at $376. at Sam's Club
Sounds like a deal. No? Experience?
Hi Rob,

We're running those exact batteries in the same configuration for our house bank. Four of them provide a nice deep cycle bank. They're a great deal. We've been very satisfied and would happily buy the same again.
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Old 13-07-2017, 07:02   #19
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

I have 5 of the Duracell group 31's from Sam's in a parallel bank for a 3000w inverter. I deep discharge them and they have held up for 6 months so far, granted I'm not using them daily. They have about 25 deep cycles on them so far. I have no complaints
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Old 13-07-2017, 07:11   #20
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

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And half the cost. As long as the 12 volt batteries meet your capacity requirement what is the point of using 6 volt GC's. All this assumes that the individual 6 volt and 12 volt batteries have about the same watt-hour capacity. Thanks.
Smaller batteries cost less? Really! Who would have guessed? Smaller batteries are... wait for it... SMALLER? What an earthshaking revelation! Certainly, if 105ah is plenty, then no need to go bigger. The OP obviously needs more capacity, because he was contemplating 4 gp31s for a 12v bank. That is the main reason I suggested 6v in series. If you only ever draw lets say 3a, for no more than say 4hrs, a 220ah bank is probably overkill and a 105ah bank is more than plenty. If you want to be able to draw 10a for 6 or 8 hours, 105ah just won't cut it. As I have said, golf cart batteries are not the ideal solution for everybody or every boat. They are ideal for me, and for many others.

A battery, as the very word suggests, is a group of cells. No matter how you look at it, it is all about the cells. Bigger cells have higher capacity. More cells in series gives you higher voltage. With lead batteries a cell's voltage is a bit over 2v, and so 6 cells is 12v. Doesn't matter if it is 6 single cells, 2 6v 3 cell batteries, or a single 12v 6 cell battery. How you achieve a total of 12v is not particularly important. But that is only half the problem. You need to have the necessary capacity in amp hours, and you get that by either using bigger cells, or cells in parallel. gp31 = not very big. gc2 = kinda big. L16 = BIG. IND33 2v = REALLY BIG. Your capacity requirements determine which size groups are and are not practical for your application. Not everyone is well served by gp31 batteries. And also, as Zil points out, the gc2 type is a very robust battery. You really do get a lot for your $85.

The fact of the matter is, the 12v battery and the 6v battery being discussed do NOT have the same capacity. A pair of gc2 batts in series has about twice the capacity of a gp31. They are NOT equal. If they were, then 12v worth of 6v batteries would occupy roughly the same space and weigh roughly the same as 12v worth of 12v batteries. Or maybe slightly more due to heavier construction. So overall you gain pretty much nothing by going with gp31 over gc2, unless the gp31 happens to meet YOUR specific requirements more closely than gc2.
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Old 13-07-2017, 08:04   #21
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

Thanks for all the replies and informative opinions. I'll continue my research before pulling the trigger on purchasing batteries. But based on this thread I'm now leaning towards two 6V GC2 batteries wired in series. Duracell (East Penn) makes a 6V FLA battery with 215ah.
https://www.samsclub.com/sams/durace...ll-description
If I'm understanding this correctly, two 6V batteries wired in series gives me the 12V I need and the combined 430ah capacity for my house bank. This would be more than enough capacity for our lower energy demands. And they're only $85 each.
We'll be heading through the Caribbean after storm season this year, then to Panama, Galapagos, South Pacific, etc. Probably no Sam's Club down there. Ramblin Rod made a good point though re: losing one 6V battery wired in series renders your system useless. So I'll probably buy a back-up to my back-ups. Thanks in advance for any continued input.
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Old 13-07-2017, 08:16   #22
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

Rob, in series amp hours doesn't add. Two 6v 215ah in series will still be 215ah.

You will need two pairs in series/parallel connection to get 430ah.

Still the best approach if you have room for them. In my opinion.
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Old 13-07-2017, 08:44   #23
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

Gotcha. So wiring two 6V batteries in series creates 12V. I would need two of these banks wired together in parallel to double the ah capacity. So they're wired in both Series and Parallel. https://www.batterystuff.com/kb/arti...-tutorial.html
Seems like a better deal for the capacity.
(4) 6V=$340 for 430ah VS. (4) 12V=$376 for 420ah
Not a huge difference but a difference nonetheless.
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Old 13-07-2017, 08:52   #24
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

Rob:
That is why I spent more to get the 255AH Duracell 6V, just a bit more robust. I think you will find the 6v to be far more hearty than the 31. The price you have is fair. My local Costco has Interstate 215 AH 6V GC batts for under $100 each as well.
Chuck them in and go have fun.
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Old 13-07-2017, 08:53   #25
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

Correct. You're on the right track. The six volts will serve you well as you venture far away.

I'm using 2 East Penn 31s, but intend to switch to four gc2s when I can get my act together.
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Old 13-07-2017, 09:21   #26
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

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Originally Posted by RobMinton View Post
Thanks for all the replies and informative opinions. I'll continue my research before pulling the trigger on purchasing batteries. But based on this thread I'm now leaning towards two 6V GC2 batteries wired in series. Duracell (East Penn) makes a 6V FLA battery with 215ah.
https://www.samsclub.com/sams/durace...ll-description
If I'm understanding this correctly, two 6V batteries wired in series gives me the 12V I need and the combined 430ah capacity for my house bank. This would be more than enough capacity for our lower energy demands. And they're only $85 each.
We'll be heading through the Caribbean after storm season this year, then to Panama, Galapagos, South Pacific, etc. Probably no Sam's Club down there. Ramblin Rod made a good point though re: losing one 6V battery wired in series renders your system useless. So I'll probably buy a back-up to my back-ups. Thanks in advance for any continued input.
Losing one 12v battery in series makes the bank useless, too.

Two separate banks, each made up of two 6v in series, gives you plenty of redundancy. You can lose two batteries and still have two remaining for 12v. I myself would not parallel them but there are folks who will tell you to do so.

Apologies if the following is kinda duh, and you already know all this stuff, which you probably do, but:

Don't be cheap with the cable and connection hardware. A bad connection can cripple you. Before a serious charge cycle, make sure that there is water covering the plates but do not add more if the plates are submerged. AFTER bringing them up to full charge, you can top off the water. The electrolyte level will rise slightly during charging. Carry plenty of distilled water with you. Even if you have a watermaker. Maybe RO water is just fine for batteries. Maybe not, expecially if it is not operating properly. Be sure to secure your batteries properly. The cruiser's rule of thumb is to install them as if the boat might turn upside down. At the very least you want to be able to take a full knockdown and not have to round up your batteries. Get a good temperature compensating hydrometer too. Keep your battery tops clean and covered. Petroleum jelly on all terminal connections. An IR thermometer is great for finding hot connections.
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Old 13-07-2017, 23:23   #27
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

If you told your local fisherman with a flats boat that he needed four 6 volt
GC's to provide 24 volts for his trolling motor instead of two 12 volt batteries his response would be quite colorful. In his case weight is important when the 6 volt GC's would be twice the weight of the 12 volt. Thanks.
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Old 13-07-2017, 23:41   #28
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

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If you told your local fisherman with a flats boat that he needed four 6 volt
GC's to provide 24 volts for his trolling motor instead of two 12 volt batteries his response would be quite colorful. In his case weight is important when the 6 volt GC's would be twice the weight of the 12 volt. Thanks.
He'd be happier when told he would have more than twice the range though.
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Old 14-07-2017, 00:10   #29
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

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If you told your local fisherman with a flats boat that he needed four 6 volt
GC's to provide 24 volts for his trolling motor instead of two 12 volt batteries his response would be quite colorful. In his case weight is important when the 6 volt GC's would be twice the weight of the 12 volt. Thanks.
Depends on how much capacity he needs or wants. If he only needs 105ah at 24v then there is no need for the gc2 batteries. In fact maybe he would even be better served by gp27 or gp24 batteries if his needs were even more modest. If he actually needs 200ah+ then to get it, he would need no two, but four batteries if he wanted to use gp31s. Same weight. Same number of monobloc batteries. But he now has to wire in parallel. No advantage. One major disadvantage. Open and shut case.

Stop assuming that we are recommending folks to use 220ah batteries when they have no need for them. Nobody has said that. But if you need higher capacity than what you can get from a GP31, then GC2s make a lot more sense than wiring GP31s in parallel. This was the case with the OP which is why I presented it as an alternative. I honestly dont understand how you cannot see that. You seem to think that we are forcing bigger batteries down people's throats or something.
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Old 14-07-2017, 03:25   #30
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Re: Duracell Deep Cycle Group 31 Lead-Acid - 105 AH

There is nothing wrong with batteries in parallel. It all depends on having proper connecting cables.
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