Another battery question

Hi to all,
Hopefully soon we will be building a new battery bank using 6 volt golf cart batteries. The question arouse as to the advantages and disadvantages there are using 4 lower AH batteries or two higher AH batteries.
I could not answer it. Any insights ?
Thanks

Space/weight savings if only 2 batteries. Less cables also.
These are the one I can obviously see as advantage.

L

Different Ah, like 8D verses 2GC?


Smaller battery pros: Easier to carry. Availability.
Smaller battery cons: More connections to clean and check, more holes to water.


Large batteries: opposite of above.

I don't quite understand your question. GC batteries come in two varieties: GC1 and GC2. The GC2s have slightly more AH capacity but only about 5-10% more The dimensions are the same and the weight of the GC2 is slightly more due to more lead.

You can get much bigger (and taller) 6V batteries like L16s which are used in floor polishers which have about double the AHs and double the weight. But I suspect that simple GC1 or GC2s give you the most AHs for the buck.

Finally very few 12V 8Ds are true deep cycle batteries like golf carts. And they are back breakers.

David

I would go with 4 GC batteries over 2 L16’s. I have 8 L16’s because I have only enough foot print for 8 batteries but no height limitations.

I have 4 L16 AGM batteries. Each has a claimed Ah capacity of 390 Ah for a total bank size of 780 Ah.

One of the reasons I went with this combination was the desire to get as much capacity in the available footprint. The other reason was I found a great price on the L16 batteries.

I would go with the combination that will give you the most battery capacity for the best cost. Often, that is the GC batteries.

One advantage of GC2’s is ready availability. If one goes bad, you can replace it as fast as you can get to a Sam’s Club. When I was deciding on redoing my battery banks, Rolls quoted me 8 weeks for delivery of an 8D; I went with GC2’s again for the house bank, and 3 Group 34’s instead of 2 8D’s for the start bank.

Gordon B said:

Hi to all,
Hopefully soon we will be building a new battery bank using 6 volt golf cart batteries. The question arouse as to the advantages and disadvantages there are using 4 lower AH batteries or two higher AH batteries.
I could not answer it. Any insights ?
Thanks

Click to expand...

I'd offer that when building a bank, bigger IS better. Refer to information on the peukert effect. Simplified, for a constant amp draw, a larger bank will yield a disproportionately higher capacity than a smaller bank. Then there's the DOD (depth of discharge) to factor in. Battery life is not measured in time, but in cycles, each discharge/recharge being a cycle. If you look at the manufacturers' ratings, you'll see that the same battery is rated for more cycles at a lower DOD. For example, a battery may be rated for 1500 cycles at 50% DOD, and 2000 cycles at 35% DOD. Each manufacturers' spec will vary, but all will follow that basic profile. So for a given load, a larger bank will result in lower DOD, with the end net that it will deliver more cycles, ergo, a longer lifespan.

So it's good to know with some degree of accuracy your daily energy use in order to build the bank that will provide that with the lowest manageable DOD. Remember, with lead acid you're only utilizing half of the rated capacity.
You'll rarely hear the complaint that "my battery bank is just too big...." The bank is part of the system, assess the SYSTEM of which the battery is just one piece.

Post #8: +1

Gordon B said:

Hi to all,
Hopefully soon we will be building a new battery bank using 6 volt golf cart batteries. The question arouse as to the advantages and disadvantages there are using 4 lower AH batteries or two higher AH batteries.
I could not answer it. Any insights ?
Thanks

Click to expand...

If you have only two 6Vs wired in series to a 12V bank... and one goes bad... you've got squat.

If you have 4 or more 6Vs wired in series/parallel for a bank, if one battery goes bad, you may still have a relatively easy get-home option.

Given druthers, think I'd rather combine your choices: four or more batteries, higher AH each to the extent possible, space permitting, etc.

-Chris

ranger42c Post #10

+1

Bigger is always better when it comes to battery bank AH. I think GC batteries make an excellent house bank. If you have the room, go for the most AH you can fit. No one ever said "this battery bank lasts too long."

Ken

Thanks everyone

6 volt Golf Cart Batteries

Gordon B said:

Hi to all,
Hopefully soon we will be building a new battery bank using 6 volt golf cart batteries. The question arouse as to the advantages and disadvantages there are using 4 lower AH batteries or two higher AH batteries.
I could not answer it. Any insights ?
Thanks

Click to expand...

In my prior boat, a 38' Sportfisher with twin Diesels, I had 2 8-D wet cells to start the motors, but had a 'house bank' of 6 Trojan 105 Golf Cart Batteries to run the inverter which kept mama's microwave, hair dryer and most important coffee maker going in the AM when she wanted coffee prior to 0800hrs.


I had the trojans wired with 3 batteries in parallel, for two sets. This gives you two banks of 6 volts at 675 AH each. Then I took the two banks and put them in series to get 12 volts at 675 AH total. It worked like a champ. I also installed a hefty charger which ran from my 6 KW Genset.
I was very happy with that set-up and keep in mind the Trojan 105's are meant to slam charges at them, and drain them under heavy loads as they do at golf courses for the electric carts. I had this set-up for 10 years and never replaced the batteries, then sold the boat. ****KEEP IN MIND to religiously check the distilled water in the wet cells monthly at a minimum. Hope this helps. 'Captain Ron D'

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?

psneeld said:

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?

Click to expand...

If you own one of those bright LED flashlights that use 4 AA cells, you will find 2 AA in Parallel and the two sets in series giving you 3 volts at double the current. Same wiring concept except using 3 Trojan 105's in parallel giving you 675 AH at 6 volts, then the two banks in series giving you 12 volts

at 675AH.
Captain Ron D

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.

I now have a Commercial Farm group 31 CarQuest for starting both engines.
https://shop.advanceautoparts.com/p...battery-group-size-31-950-cca-31p30/2100010-P

I now have two group 27 Duracell Deep Cycle from Sam's Club. At $82 each seems worth it.https://www.samsclub.com/sams/durac...sel:people-who-viewed-this-item-also-viewed:9

The gen has its own start battery. As long as the gen starts it is never a problem, can use as much electricity as anyone could want out there.

I have no need for a larger bank of batteries. No gen, then that's a different story for me.

One weekend, all was fine, go out to boat midweek and 2 batteries went out with shorted cells, they were from 2012, so 6 years old.

I noticed the problem when checking the volt gauges, one bank was trying to charge at 15.6 vdc. And some gassing could be heard, batteries were warm. And when I pulled them out, some acid had leaked.

With the new batteries back to 13.6vdc.
My old Raritan 3 bank charger tries to compensate with failing batteries by raising the charge volts on whatever bank is going out. I had also noticed last use of boat, the house bank had run down a lot sooner than usual, I dont always run the gen.

sdowney717 said:

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.

I now have a Commercial Farm group 31 CarQuest for starting both engines.
https://shop.advanceautoparts.com/p...battery-group-size-31-950-cca-31p30/2100010-P

I now have two group 27 Duracell Deep Cycle from Sam's Club. At $82 each seems worth it.https://www.samsclub.com/sams/durac...sel:people-who-viewed-this-item-also-viewed:9

The gen has its own start battery. As long as the gen starts it is never a problem, can use as much electricity as anyone could want out there.

I have no need for a larger bank of batteries. No gen, then that's a different story for me.

One weekend, all was fine, go out to boat midweek and 2 batteries went out with shorted cells, they were from 2012, so 6 years old.

I noticed the problem when checking the volt gauges, one bank was trying to charge at 15.6 vdc. And some gassing could be heard, batteries were warm. And when I pulled them out, some acid had leaked.

With the new batteries back to 13.6vdc.
My old Raritan 3 bank charger tries to compensate with failing batteries by raising the charge volts on whatever bank is going out. I had also noticed last use of boat, the house bank had run down a lot sooner than usual, I dont always run the gen.

Click to expand...

A pair of GCs at Sams will be about the lowest $/AH/ cycles.
They are usually $85 ea and sometimes onsale.
Just make sure house battys are True Deep Cycle. If they list CCA they are dusl purpose at best and not true deep cycle
See below for goid info on GCs

http://www.pbase.com/mainecruising/deep_cycle_battery

sdowney717 said:

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.

I now have a Commercial Farm group 31 CarQuest for starting both engines.
https://shop.advanceautoparts.com/p...battery-group-size-31-950-cca-31p30/2100010-P

I now have two group 27 Duracell Deep Cycle from Sam's Club. At $82 each seems worth it.https://www.samsclub.com/sams/durac...sel:people-who-viewed-this-item-also-viewed:9

The gen has its own start battery. As long as the gen starts it is never a problem, can use as much electricity as anyone could want out there.

I have no need for a larger bank of batteries. No gen, then that's a different story for me.

One weekend, all was fine, go out to boat midweek and 2 batteries went out with shorted cells, they were from 2012, so 6 years old.

I noticed the problem when checking the volt gauges, one bank was trying to charge at 15.6 vdc. And some gassing could be heard, batteries were warm. And when I pulled them out, some acid had leaked.

With the new batteries back to 13.6vdc.
My old Raritan 3 bank charger tries to compensate with failing batteries by raising the charge volts on whatever bank is going out. I had also noticed last use of boat, the house bank had run down a lot sooner than usual, I dont always run the gen.

Click to expand...

Not quite: You said " 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." My system used 6 each 6 volt GC Batteries.
2 clusters of 3 each 6 volts in PARALLEL. This gives you 675 AH at 6 volts (225 AH each) NOW yuu take the two clusters and hook them in SERIES, + to - and you will have 12 volts across the OTHER + and - TERMINALS.


With me so far? Say one of the 6 volt batteries craps out. You simple pull that one from its bank of 3, and reduce the OTHER BANK by pulling one from that bank. Now you have 12 volts, but only 450 AH.



If one more craps out you pull one more from each bank (pull the bad one) and hook up the banks and you will have 12 volts but only 225 AH, still enough to crank over your engine.


Maybe I am missing something, but I ran my 38' Cheoy Lee Sportfisher for 15 years using that system as the HOUSE bank, albeit I could have also used it to start the diesels.


However, if you are happy with the Group 27 Deep Cycles Duracell's from

Sam's club, then go for it. Keep in mind, in my application I was on the hook often for for two weeks in Catalina Island Harbor off California, where you cannot run your genset until 0800 and Mama had to have her coffee at 0730 when she arose !! Remember, If Mama's not happy, NO BODY is happy. Captain Ron has spoken !!

Captain Ron D

psneeld said:

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?

Click to expand...

Captain Ron D said:

If you own one of those bright LED flashlights that use 4 AA cells, you will find 2 AA in Parallel and the two sets in series giving you 3 volts at double the current. Same wiring concept except using 3 Trojan 105's in parallel giving you 675 AH at 6 volts, then the two banks in series giving you 12 volts

at 675AH.
Captain Ron D

Click to expand...

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

psneeld said:

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?

Click to expand...

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. It’s 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 $. Doesn’t mean it’s the only way or the right way for everyone but it’s what I would try to start with.

Didn’t 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. Doesn’t matter if you use one box of 6 cells or two boxes of 3 cells.

FlyWright said:

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

Click to expand...

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.

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.

psneeld said:

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?

Click to expand...

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

I’d love to hear from some of the electrical guys if there is any difference.

sdowney717 said:

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.

Click to expand...

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.

sdowney717 said:

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.

Click to expand...

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.

tiltrider1 said:

Didn’t 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. Doesn’t matter if you use one box of 6 cells or two boxes of 3 cells.

Click to expand...

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 doesn’t have a house bank.

I would still go with the GCs, but I understand the OPs argument for the Group 27s.

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.

tiltrider1 said:

Didn’t 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. Doesn’t matter if you use one box of 6 cells or two boxes of 3 cells.

Click to expand...

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.

-Chris

psneeld said:

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?

Click to expand...

dhays said:

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

I’d love to hear from some of the electrical guys if there is any difference.

Click to expand...

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...

-Chris