Two 6-V vs. Two 12 V Batteries

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Johnboy777
Johnboy777 Registered Users Posts: 19 ✭
in Solar Beginners Corner #1
Two 6-V vs. Two 12 V Batteries

I think I have my small system pretty well sorted out - I'll post it up once i assemble all the parts.

One question i have though, is all things being equal (price, Ah, weight), should I buy two 6 volt or two 12 volt.

I plan to get AGM batteries, mainly due to shipping and lower maintenance. The price is higher than flooded, but the lower maintenace makes up for it for me.

Any thoughts? Does a series vs. parallel configuration really matter?

Thanks. John
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Two 6-V vs. Two 12 V Batteries

    Yes it does.
    The two 6 Volts in series gets my vote because there is less wiring (one link between the two batteries instead of two) and no problem with keeping the current shared between the two (always a problem with parallel batteries).

    Beware that AGM's have disadvantages other than high price: you can't check the SG and they are picky about Voltage. If you do something wrong they aren't as tolerant of mistakes as FLA's.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #3
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    Re: Two 6-V vs. Two 12 V Batteries

    6V batteries in series wins.

    It avoids the mystery's of cells in parallel, and when something goes wrong, it's easy to find.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #4
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    Re: Two 6-V vs. Two 12 V Batteries

    Particularly with a first set of batteries, if you have problems it limits what could be wrong. Even if you don't go with FLA batteries, I'd vote for 2 6v.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #5
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    Re: Two 6-V vs. Two 12 V Batteries

    +1 on everything said - go with the 6 V in series, and start with flooded lead-acid unless you have a good reason for AGM. Like a battery installed in an unvented compartment.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • Johnboy777
    Johnboy777 Registered Users Posts: 19 ✭
    #6
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    Re: Two 6-V vs. Two 12 V Batteries

    Got it, thanks for the replies - 6V it is.

    Is the service life different between AGM and FLA's? Does one last longer, is service, than the other?

    Thanks, John
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Two 6-V vs. Two 12 V Batteries

    All other factors being equal (and they never are) FLA's have a slight lifetime advantage over AGM's.
    But it's so easy to ruin either that most people never see the 7-8 years expected of either anyway. :p
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  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    #8
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    Re: Two 6-V vs. Two 12 V Batteries

    I bought my last set of 6V golf cart batteries at Sam's Club:

    photo2-1.jpg

    That was a couple of years ago. Checked the prices two weeks ago, the Duracell GC2 batteries are now priced $78.83 each. I have a total of 8 of these batteries. Each pair connected in series to make 12V, then tied to a bus bar. Total of 4 pairs. About 900AH worth of batteries. The oldest batteries are now a tad over 5 years old. They are kept clean, and the water is checked/added every month.

    I purposely put them on a 36" tall dedicated workbench, making maintenance very easy. Takes me about 5 minutes to water all the batteries. I use a small funnel, and a gallon jug of distilled water. Done this enough that it's very quick, and very little splash.

    You could go the easy route, and get a battery watering system. These are not cheap, but simplify this necessary task. Multiples of these can be tied together, so all batteries, and all cells, are watered at the same time:

    Attachment not found.

    More info here: http://www.flow-rite.com/battery-watering/qwik-fill

    FWIW, Sam's also sells 6V AGMs. These were $159.73 each.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
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    Re: Two 6-V vs. Two 12 V Batteries

    I envy you guys with your warehouse bargains. It's almost twice that money for economy GC batteries around here! :grr
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  • Johnboy777
    Johnboy777 Registered Users Posts: 19 ✭
    #10
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    Re: Two 6-V vs. Two 12 V Batteries

    Good advice - thanks

    As luck would have it, I have a Sam’s, Costco and Bj's all within an hour of me. There's a large golf cart distributor near me (New Castle, PA), as well

    Getting the batteries for under 200 bucks total, sounds good. I'll start looking this weekend.

    John
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #11
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    Re: Two 6-V vs. Two 12 V Batteries

    I live a little more than 50 miles north of New Castle pa. There is a battery distributore called Battery Giant, They are located on route 18 going north 724 658 5501. It is located at the old NEW CASTLE BATTERY location. They have a few brands, US BATTERY, FULL RIVER AND A COUPLE OTHER BRANDS. They don,t charge core charges and don,t even want them. :Dsolarvic:D
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  • Johnboy777
    Johnboy777 Registered Users Posts: 19 ✭
    #12
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    Re: Two 6-V vs. Two 12 V Batteries
    solarvic wrote: »
    I live a little more than 50 miles north of New Castle pa. There is a battery distributore called Battery Giant, They are located on route 18 going north 724 658 5501. It is located at the old NEW CASTLE BATTERY location. They have a few brands, US BATTERY, FULL RIVER AND A COUPLE OTHER BRANDS. They don,t charge core charges and don,t even want them. :Dsolarvic:D

    I think that's the one I was thinking of. It's just north of the PA State Police barracks on a side road. There's a large colf cart distributor next door. I pass it when i take my wife to Grove City outlets. She shops while I chill out at Primanti Brothers (not quite as good as the Strip District though)......best sandwiches on the planet. John
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #13
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    Re: Two 6-V vs. Two 12 V Batteries

    The outlet mall is in southern Mercer county, I live in north Mercer county. s the sandwich place at the outlet mall? The battery mart is On rt 18 north out of New castle. and if you stay on 18 north about 15 miles you can connect to I-80 interstate. at sharon Pa. interchange. :Dsolarvic:D
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #14
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    Re: Two 6-V vs. Two 12 V Batteries
    Johnboy777 wrote: »
    Good advice - thanks

    As luck would have it, I have a Sam’s, Costco and Bj's all within an hour of me. There's a large golf cart distributor near me (New Castle, PA), as well

    Getting the batteries for under 200 bucks total, sounds good. I'll start looking this weekend.

    John

    heck, you've got pittsburgh and cleveland within about an hour of you. that gives you plenty of options.;)
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  • Johnboy777
    Johnboy777 Registered Users Posts: 19 ✭
    #15
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    Re: Two 6-V vs. Two 12 V Batteries

    Bingo!!

    Thanks 2manytoyz - I just came from Sam's club, they are $78 for 215 Ah GC2 Energizer 6V batteries. I'll get two this weekend. John
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  • JimMariner
    JimMariner Registered Users Posts: 13 ✭
    #16
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    Re: Two 6-V vs. Two 12 V Batteries
    Johnboy777 wrote: »
    Bingo!!

    Thanks 2manytoyz - I just came from Sam's club, they are $78 for 215 Ah GC2 Energizer 6V batteries. I'll get two this weekend. John

    Right next to the batteries 2manytoyz talked about are these
    Attachment not found.

    for just a few bucks more, I choose these @ Sams Club
    (This was the price in March of 2012)
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #17
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    Re: Two 6-V vs. Two 12 V Batteries

    Late to this thread, but I have some O2 on GC-2 Batteries. I bought 10 GC-2's from a guy last week for a $9.00 core charge each. They were a year old and failing according to him. It was kind of dark and I looked down in the cells with a flashlight. I was like , this isn't right. He had used a automatic water filling bottle and pushed it down into the plates and bent the plates over and the separators, some touching, some not. I took a wooden paddle and straightened the plates and separators up. After doing a EQ on them for 4 hours they everyone came up to 1.26 SG.


    I noticed something that I'v never seen before. These were Interstate HD GC-2 The plates were very thin and there was twice the number of plates in them as a normal GC-2. I am still trying to work out in my mind if having many thinner plates is better than having half as many plates, but twice the thickness. I weighed one of them and it was about 67 lb, thats in line with most GC-2's. I am guessing that filling them that the spout was to long and that the thin plates didn't have enough strength to push the spring in on the waterier, so they just bent over..

    Batteries: Interstate Workaholic Extreme HD , Model : GC-2 - XHD - UTL , Green Tops with Black bottoms

    Any thoughts ??
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,446 admin
    #18
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    Re: Two 6-V vs. Two 12 V Batteries

    In theory, lots of thin plates point more towards a automotive battery design (short bursts of high current, not cycling very deep).

    Thick plates tend to be for deep cycling batteries.

    Others here have argued that thin plates do not affect cycling life...

    -Bill :confused:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #19
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    Re: Two 6-V vs. Two 12 V Batteries

    thoughts? At that price, even if they only last 1 year, I think you should run back and get 6 more to make 2 - 48V batteries.
     
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  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    #20
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    Re: Two 6-V vs. Two 12 V Batteries

    Current prices/choices at my local Sam's Club (Cocoa, FL):

    a.jpg

    b.jpg

    d.jpg

    c.jpg
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  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    #21
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    Re: Two 6-V vs. Two 12 V Batteries

    Couldn't put 6 pics on one post, here's the other battery:

    f.jpg

    e.jpg
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