Four Trojan GC12 12V AGM 140ah in a 24 volt system?

Skyko
Skyko Solar Expert Posts: 121 ✭✭✭✭✭
in Off Grid Solar & Battery Systems #1
Making some measurements, I think I could manage to fit four of the GC12 class model 12-AGM Trojan batteries inside our truck camper. It would have to be two side by side with two on a shelf above that (already have the shelf in place, 1 1/8" plywood). Since we are going to go with a 24V system this would still require some series and parallel configurations. It would give me 24V at 280ah, which I could probably get 200ah with an average drawdown of 70%. I would guess I could get at least 400 cycles out of that. 4800 watt-hr would be enough for our needs if we are conservative, along with the 1000 watt solar system.

Any cons with these particular batteries? Would it be best to wire two in series then parallel those or wire two in parallel then series them?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Four Trojan GC12 12V AGM 140ah in a 24 volt system?

    "Average draw down of 70%" = kiss them goodbye.

    Have you got room for these: http://www.solar-electric.com/catalog/product/view/id/207/

    Always wire batteries as series strings first to get the required Voltage, then parallel the strings.
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  • Skyko
    Skyko Solar Expert Posts: 121 ✭✭✭✭✭
    #3
    Re: Four Trojan GC12 12V AGM 140ah in a 24 volt system?

    I have a space on the floor that is 16W x 16L x 11H and a identical space right above that (except could be taller on that shelf).

    I actually could now fit four of the Lifeline 6V 220ah AGM part GPL-4C This would of course give me 24V at 220ah and a useable 24V at 110ah and 1000 cycle life according to the lifeline charts. Three years would be totally fine for $1300. If I ran a Honda eu2000i for an hour a day every day for 3 years I would probably use it up also (I do have a new eu2000i which is what I plan to charge the batteries with on rainy days).

    I wish there were a slightly better fit battery for my space. I can go 16 inches long and 8 inches wide, but only 11 inches tall. The GPL-6C 300ah 6 volts are over 12 inches tall.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Four Trojan GC12 12V AGM 140ah in a 24 volt system?

    This is always an issue with batteries: they don't come in exactly the capacity and dimensions you need. So it's the first part of the design you have to 'fudge' with, followed by adapting the charging to suit.

    This is probably the largest AGM you could fit in there (but there are thousands of batteries out there and I'm not going to go through the dimensions on every one): http://www.solar-electric.com/catalog/product/view/id/210/
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  • Skyko
    Skyko Solar Expert Posts: 121 ✭✭✭✭✭
    #5
    Re: Four Trojan GC12 12V AGM 140ah in a 24 volt system?

    Can you mount the Sun-Xtender 6V AGMs on their short side? If so, then I could fit four of the 305AH 6V in my allocated space. An advantage would be easy access to all of the battery terminals as they would be facing the (non-conductive) door of the compartment.

    http://www.solar-electric.com/catalog/product/view/id/217/

    24V at 305ah all contained in my camper as one series bank would be nice.

    Attachment not found.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: Four Trojan GC12 12V AGM 140ah in a 24 volt system?

    That's a question that has come up before. Wish I could remember the answer. :blush:
    I went looking at their web site http://www.sunxtender.com/xtender_main.php but the answer wasn't readily apparent there either.
    On the one hand you have the fact that AGM's are "spill proof" but that is "for transport". On the other we know they have a vent somewhere on them and that vent mustn't be blocked. Then again some batteries of this type are in fact designed to be usable "on their sides".

    To be absolutely certain contact Sun and tell them exactly which model you want to be used mounted which way. Can't do better than the manufacturer for information about "non standard" use.
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  • Skyko
    Skyko Solar Expert Posts: 121 ✭✭✭✭✭
    #7
    Re: Four Trojan GC12 12V AGM 140ah in a 24 volt system?

    A quick call to lifeline (who I think makes the sun-xtender too) said zero problems mounting on the short side down. He said people do that all the time.

    This is the best solution at the best price point for AGM. I get one series bank, so no parallel issues. I get a 24V system at 300ah. I should get around 1000 cycles if I keep the DoD at 50%, which will be easier to maintain with a 300ah bank.

    There may never be a need to go with extra batteries under the truck, which would sure make things easier.
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