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Old 07-20-2018, 04:56 PM   #21
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Not sure if I ever head of wiring 6V batteries that way....

Any battery gurus know if 3 pairs in parallel are better worse than 2 series sets of 3 in parallel?
If you had only enough space to place an odd number of batteries per side it might be a more efficient way to run the wiring. Itís never been the simplest most efficient way on any boat I have done.

I agree with bacchus, 6v gcb are the most amp hr per $. Doesnít mean itís the only way or the right way for everyone but itís what I would try to start with.

Didnít understand the comment about using 12v batteries cause if you lost a 6v battery nothing would work. Batteries are made up of 2 volt cells. Loose a cell and you have issues. Doesnít matter if you use one box of 6 cells or two boxes of 3 cells.
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Old 07-20-2018, 05:13 PM   #22
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Ron,

Check out these wiring diagrams. There's a difference between what you're describing (2 paralleled 6V sets wired in series) and what is recommended by industry experts (multiple 12V series sets wired in parallel).



94 Battery Wiring Diagrams

I don't believe you understood what I was describing, and possibly I did not do the best job of describing the house battery bank. At the bottom left of your diagrams you will see "3 Parallel 12V" batteries. What I had was that same exact bank, but only 6 volt GC batteries, each rated at 225 AH. So with the ONE BANK you have 3 X 225 AH = 675 AH AT 6 VOLTS !!!
You take two (2) of these banks, and hook the minus (-) of one bank to the (+) of the second bank. Now you have a SERIES of 2 banks, each bank has 6 volts at 675 AH. When connected in SERIES, the total of the two banks is 12 VOLTS and the 675 AH remains the same.


Sorry if I did not make my self clear. If you refer to your 3 parallel diagram, but with only 6 volt batteries, not 12 volt, you will have the combined AH but the same voltage. When you take the two banks of 3 each 6 volt batteries in parallel, AND hook those 2 banks in series, the voltage is 6 + 6 = 12 volts at the 675 AH. Again, sorry if I did not do the best job of explaining myself in my prior text. Captain Ron D. Sandy Eggo.
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Old 07-20-2018, 05:19 PM   #23
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Sure you can figure out ways to get 12 v from two 6 v.
But why worry about it when 12 v already have 12v.

If for some reason you cant run the gen, then you need a big bank you can deplete for a longer time. All that energy has to go back into the batteries that you took out, eventually, by running the gen, or plugging into shore!

I got 6 years from the batteries that just failed, so I must be doing something right. I think I will keep on doing it. Those were not deep cycle marine, they were all starting batteries. This time I bought 2 Duracell marine that have a 'deep cycle' label on the side.

The fridge has to run almost constantly, just draws about 1 amp of 120vac, but more during a defrost cycle. That is the only constant drain I have I think.

Even 'deep cycle', if you take them below 50%, it wears on them quicker.
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Old 07-20-2018, 05:35 PM   #24
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Not sure if I ever head of wiring 6V batteries that way....

Any battery gurus know if 3 pairs in parallel are better worse than 2 series sets of 3 in parallel?


That was my thought. Iíve always approached it with creating 12v batteries and then connecting them in parallel instead of creating large 6v batteries and connecting them in series.

Iíd love to hear from some of the electrical guys if there is any difference.
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Old 07-20-2018, 05:45 PM   #25
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I just replaced all the boat batteries over the last 2 months.
All are 12vdc, I had wondered about using golf cart cg2 batteries, but nixed the idea. Costs a lot more, and if one goes out, then I dont have 12 vdc and nothing will work.

Nothing wrong with the Group 27. However, those batteries have a 20 hour Amp Hr rating of 90 amps. A cheap GC2 will typically have 20hr Amp Hr. Of >200 Amp hours and cost the same as those Group 27. So you get more Amp Hrs for the same cost and you get a true deep cycle battery that will likely perform better and last longer.

However, if one of those batteries craps out, then yes, you would be in trouble. With your 2 Group 27s you do have better redundancy.
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Old 07-20-2018, 05:49 PM   #26
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Sure you can figure out ways to get 12 v from two 6 v.
But why worry about it when 12 v already have 12v.

If for some reason you cant run the gen, then you need a big bank you can deplete for a longer time. All that energy has to go back into the batteries that you took out, eventually, by running the gen, or plugging into shore!

I got 6 years from the batteries that just failed, so I must be doing something right. I think I will keep on doing it. Those were not deep cycle marine, they were all starting batteries. This time I bought 2 Duracell marine that have a 'deep cycle' label on the side.

The fridge has to run almost constantly, just draws about 1 amp of 120vac, but more during a defrost cycle. That is the only constant drain I have I think.

Even 'deep cycle', if you take them below 50%, it wears on them quicker.
The reason for pairing up golf cart batteries over using 12v batteries is lead and economics. By the time you get enough lead in a 12v battery it weighs 300lbs. With the golf industry consuming so many 6v batteries they have become the best value through mass production.

Battery life is a function of cycles, % of discharge, thickness of lead plates and maintenance. 6v gc batteries excel in the first 3, the last one is up to the owner.
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Old 07-20-2018, 05:56 PM   #27
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Didnít understand the comment about using 12v batteries cause if you lost a 6v battery nothing would work. Batteries are made up of 2 volt cells. Loose a cell and you have issues. Doesnít matter if you use one box of 6 cells or two boxes of 3 cells.

He will only have 2 batteries. If one of those batteries dies and both are 12v batteries, he will still have 12v. If both batteries are 6v and one dies, then he is left with only 6v.

Using 2 12v batteries, he will have 12 - 2v cells. Using 2 6v batteries he will have 6 - 2v cells. I would suggest that the odds of one of his 12v batteries failing is 2x the odds of one of his 6v batteries failing. The reason is that there are twice the number of 2v cells that can fail with the 12v batteries. However, a single 2v cell failure in the 12v battery is merely an inconvenience. A single 2v cell failing in a 6v battery means he doesnít have a house bank.

I would still go with the GCs, but I understand the OPs argument for the Group 27s.
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Old 07-20-2018, 06:29 PM   #28
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Absolutely agree rhat thete are many waus to do a house bank.
None be c essarilt right or wrong it deprnds on your objectives and priorities but GCs are a economical starting point. If AH is a priority there are ways to get more but at at higher cost.
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Old 07-21-2018, 06:10 AM   #29
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Didnít understand the comment about using 12v batteries cause if you lost a 6v battery nothing would work. Batteries are made up of 2 volt cells. Loose a cell and you have issues. Doesnít matter if you use one box of 6 cells or two boxes of 3 cells.

That was about if you only have two batteries, in a 12V system...

Lose one cell in one 12V battery, you can take that battery off line and still have one usable 12V battery.

Lose one cell in one 6V battery, you no longer have a 12V capability.

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Old 07-21-2018, 06:19 AM   #30
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Not sure if I ever head of wiring 6V batteries that way....

Any battery gurus know if 3 pairs in parallel are better worse than 2 series sets of 3 in parallel?
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That was my thought. Iíve always approached it with creating 12v batteries and then connecting them in parallel instead of creating large 6v batteries and connecting them in series.

Iíd love to hear from some of the electrical guys if there is any difference.

Mostly I've read about 6V batteries in 12V pairs, and then those pairs being paralleled to make a larger 12V system.

But...

I've also read about 48V systems made up of eight 6V batteries in series, so I'd guess stringing a boatload of 6V batteries together is common.

But...

I've also read that it's not great to parallel more than 3-4 batteries at a time. Dunno if that's gospel, or if so, why...

But that might lead to why I've more commonly read about 6V series pairs being paralleled. In Ron's situation, that'd be three pairs of 125-Ah 6V batteries series wired to 12V, those three pairs being paralleled to a 675-Ah bank.

If it's better that way, I dunno why...

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Old 07-21-2018, 06:28 AM   #31
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Ron,

Check out these wiring diagrams. There's a difference between what you're describing (2 paralleled 6V sets wired in series) and what is recommended by industry experts (multiple 12V series sets wired in parallel).



94 Battery Wiring Diagrams


This could be a worthwhile read when considering battery wiring:

https://www.impactbattery.com/blog/t...s-in-parallel/
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Old 07-21-2018, 07:22 AM   #32
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I don't believe you understood what I was describing, and possibly I did not do the best job of describing the house battery bank. At the bottom left of your diagrams you will see "3 Parallel 12V" batteries. What I had was that same exact bank, but only 6 volt GC batteries, each rated at 225 AH. So with the ONE BANK you have 3 X 225 AH = 675 AH AT 6 VOLTS !!!
You take two (2) of these banks, and hook the minus (-) of one bank to the (+) of the second bank. Now you have a SERIES of 2 banks, each bank has 6 volts at 675 AH. When connected in SERIES, the total of the two banks is 12 VOLTS and the 675 AH remains the same.


Sorry if I did not make my self clear. If you refer to your 3 parallel diagram, but with only 6 volt batteries, not 12 volt, you will have the combined AH but the same voltage. When you take the two banks of 3 each 6 volt batteries in parallel, AND hook those 2 banks in series, the voltage is 6 + 6 = 12 volts at the 675 AH. Again, sorry if I did not do the best job of explaining myself in my prior text. Captain Ron D. Sandy Eggo.
You get the same amp hours either way......

The question is how they compare in charging and discharging
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Old 07-21-2018, 02:55 PM   #33
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You get the same amp hours either way......

The question is how they compare in charging and discharging


Yep - I agree, but maybe worth considering. I changed my battery set up to balance the charging when I replaced the batteries a few years ago. The hope is that they will last longer and it would be kinder on them. The old batteries had loads taken from part way along the bank and were treated pretty bad and still lasted 8 years so maybe not worth the effort other than peace of mind. The water use now seems to be similar across the bank so who knows, maybe I will get 8 years and 3 days out of this set. (Probably more likely 7 years will tick over and Iíll change them as a matter of course and it would of been a waste of time)
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Old 07-21-2018, 04:02 PM   #34
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Yep - I agree, but maybe worth considering. I changed my battery set up to balance the charging when I replaced the batteries a few years ago. The hope is that they will last longer and it would be kinder on them. The old batteries had loads taken from part way along the bank and were treated pretty bad and still lasted 8 years so maybe not worth the effort other than peace of mind. The water use now seems to be similar across the bank so who knows, maybe I will get 8 years and 3 days out of this set. (Probably more likely 7 years will tick over and Iíll change them as a matter of course and it would of been a waste of time)
Were yours in pairs or groups then in series?
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Old 07-21-2018, 04:58 PM   #35
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When I got my boat, PO had four 6v golf cart type. 2 linked for 2 banks. They did not crank well the engines. When they failed, were about 5 yrs old. I just was not impressed. Bought an 8D, terrible choice. Huge heavy. Got 2 yrs out of it. Then bought used starting batteries for 25 dollars. They lasted 4 to 6yrs. Just as good as the others and cranked well. Recently decided since used where up to $45, got the Duracells. The 31 farm was used 1 yr old for $45. Tested like new. Seeing I have generator not been worried much. I had a Motorcraft battery . It was in boat used before about 4yrs. I used it for 4 more yrs. Then I put in car. It is now 11 yrs old and like new. That Motorcraft was ford dealer and somehow has survived.
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Old 07-21-2018, 05:50 PM   #36
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When I got my boat, PO had four 6v golf cart type. 2 linked for 2 banks. They did not crank well the engines. When they failed, were about 5 yrs old. I just was not impressed. Bought an 8D, terrible choice. Huge heavy. Got 2 yrs out of it. Then bought used starting batteries for 25 dollars. They lasted 4 to 6yrs. Just as good as the others and cranked well. Recently decided since used where up to $45, got the Duracells. The 31 farm was used 1 yr old for $45. Tested like new. Seeing I have generator not been worried much. I had a Motorcraft battery . It was in boat used before about 4yrs. I used it for 4 more yrs. Then I put in car. It is now 11 yrs old and like new. That Motorcraft was ford dealer and somehow has survived.
GC batteries do not make good starting batteries. They make great deep cycle battery banks. Like wise if you want to kill a starting battery use it as a house battery. 8D batteries come in many forms, there are starting versions and deep cycle versions. Their are also huge differences in cranking amps with 8Dís. Iíve seen as little as 650 cc and as much as 1350cc.

It is very hard to have battery bank discussions due to the Apple vs Orange comparisons. Battery quality varies greatly, no two people cycle batteries at the same %. Poor chargers can shorten battery life, poor maintenance, bad wiring, all kinds of things have an effect on battery life.

Some practices are better than others.
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Old 07-21-2018, 06:25 PM   #37
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I bought a boat that came with 3 8D batts - 2 8Ds as a house bank and the other for start. I was replacing the whole shebang and wanted to pack the most bang into the solid 8D boxes. The GC-2 fit the bill perfectly with 3 GCs per 8D box. They sat a little higher but I had room to work with. I ended up increasing my house from ~440-660AH in the same footprint giving me a ~50% increase. (I sure don't miss lifting those 8Ds in and out.) As a GC-2 from Costco, I can return one anytime within 40 or 48 months (?) for a free replacement. It's about the best battery support I can afford on my budget.

I like having a larger bank from the 6 GCs but the larger the bank, the better the charging needs to be. In my case, I also had to upgrade cables, switches, combiner, charger, SOC meter, inverter, alternator and external regulator. In the end, it was worth it.
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Old 07-22-2018, 11:24 AM   #38
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Good idea on upgrading the charger . Mine maxs at 30 amps on the gauge. It does 3 banks. It has lasted since 1970. I did replace couple output diodes. Charger made by Raritan. Bigger banks might be an issue for me. Yrs ago called and talked to Vic. When I gave him model and serial, he was surprised and pleased it was still working. Said he probably hand built mine.. It was based on a popular mechanics article from 1960's. It is not ferroresonant. Has some fancy feedback circuitry. I could even improve it adding in an equilization cycle by modifying the circuit. He sent me the schematic. I am just too busy to do that. And it works as is.
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Old 07-22-2018, 03:55 PM   #39
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Hi psneeld,


Mine are in series.

I only mentioned that it could be worth thinking about the effect the wiring may have on how they are charged to try and draw a comment.

I don't know enough about batteries to give any valid advice myself.


I think it really depends on how they are used and we a varied lot in that regard.


Although balanced charging makes good sense to me, it could be that if the charge isn't balanced across the bank, but you regularly charge the bank fully, that the battery or batteries receiving the lower charge get everything they need anyway so may make little difference.

There are some pretty smart people here (I suspect yourself included) that I hope will be able to comment if balanced charging is just a nicety or something worth considering when making changers to the banks.
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Old 07-22-2018, 04:02 PM   #40
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The more things you do right the longer life you will see out of your batteries. What is hard to say is how significant balanced charge would be as there are so many variables in the whole system.
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