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Old 07-11-2018, 12:47 PM   #1
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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
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Old 07-11-2018, 12:52 PM   #2
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Space/weight savings if only 2 batteries. Less cables also.
These are the one I can obviously see as advantage.

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Old 07-11-2018, 01:06 PM   #3
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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.
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Old 07-11-2018, 02:38 PM   #4
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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.

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Old 07-11-2018, 06:32 PM   #5
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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.
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Old 07-11-2018, 09:51 PM   #6
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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.
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Old 07-12-2018, 05:55 AM   #7
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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.
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Old 07-12-2018, 07:57 AM   #8
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Quote:
Originally Posted by Gordon B View Post
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
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.
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Old 07-12-2018, 08:00 AM   #9
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Post #8: +1
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Old 07-12-2018, 10:05 AM   #10
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Quote:
Originally Posted by Gordon B View Post
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

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
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Old 07-12-2018, 10:41 AM   #11
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ranger42c Post #10

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Old 07-12-2018, 12:19 PM   #12
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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
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Old 07-12-2018, 02:10 PM   #13
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Thanks everyone
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Old 07-20-2018, 01:20 PM   #14
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6 volt Golf Cart Batteries

Quote:
Originally Posted by Gordon B View Post
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

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'
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Old 07-20-2018, 01:30 PM   #15
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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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Old 07-20-2018, 01:44 PM   #16
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Originally Posted by psneeld View Post
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 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.
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Old 07-20-2018, 03:58 PM   #17
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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.

I now have a Commercial Farm group 31 CarQuest for starting both engines.
https://shop.advanceautoparts.com/p/...1p30/2100010-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/durace...-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.
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Old 07-20-2018, 04:12 PM   #18
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Quote:
Originally Posted by sdowney717 View Post
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/...1p30/2100010-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/durace...-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.
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
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Old 07-20-2018, 04:45 PM   #19
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Quote:
Originally Posted by sdowney717 View Post
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/...1p30/2100010-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/durace...-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.

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 !!

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Old 07-20-2018, 04:54 PM   #20
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Quote:
Originally Posted by psneeld View Post
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?

Quote:
Originally Posted by Captain Ron D View Post
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
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
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