How to configure my battery bank

BajaGringo
BajaGringo Solar Expert Posts: 40 ✭✭
in Solar Beginners Corner #1
I have ten, 200ah 12 volt batteries (8D). I would like to wire them up in a series-parallel configuration to give me 24 volts out. I am curious as to what some of you experts out there would suggest to keep my bank balanced as best as possible. Somebody suggested this to me and I was curious as to what you all think of it...

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  • BajaGringo
    BajaGringo Solar Expert Posts: 40 ✭✭
    #2
    Re: How to configure my battery bank

    The only way I knew to do it was this:

    attachment.php?attachmentid=1874&stc=1&thumb=1&d=1276801894
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: How to configure my battery bank

    There's only one way to do it. For 24 Volts you need to put two 12 V in series, so your ten batteries end up being divided into five banks of two each. The parallel connections are the tricky part. For that many parallel banks I'd recommend you use bus bars (one + and one -), and run separate, equal length cables from each battery bank to the bus bars. Each ban should have its own fuse too.
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  • BajaGringo
    BajaGringo Solar Expert Posts: 40 ✭✭
    #4
    Re: How to configure my battery bank

    Do the inter connect cables connecting each pair of 12v batteries together need to be the same length as the connecting cables to the buss bars???
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: How to configure my battery bank
    BajaGringo wrote: »
    Do the inter connect cables connecting each pair of 12v batteries together need to be the same length as the connecting cables to the buss bars???

    No. They should be as short as possible but the same length on each battery bank. The idea is to get the resistance in the different battery circuits as close as possible so that each bank charges & discharges relatively the same.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: How to configure my battery bank

    actually that should be a yes for the reasons cariboocoot stated. try to make everything identical going to each buss from the batteries and oversize the current ratings of the busses and the wires to help keep losses and inequalities down to a minimum.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: How to configure my battery bank

    Niel;

    I thought he was referring to the series connections between any two batteries in the 24 V string; i.e. the connections that turn two 12V into one 24V battery. Those should be kept short as possible. Length of all battery to bus bar wires should be equal and whatever length necessary - within reason.

    Maybe I've got the wrong end of the stick.:confused:
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #8
    Re: How to configure my battery bank

    Good description of parallel connecting bats here: http://www.smartgauge.co.uk/batt_con.html
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  • BajaGringo
    BajaGringo Solar Expert Posts: 40 ✭✭
    #9
    Re: How to configure my battery bank

    I was asking about the wires that run between positive and negative that makes the two 12v batteries a 24v.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: How to configure my battery bank
    BajaGringo wrote: »
    I was asking about the wires that run between positive and negative that makes the two 12v batteries a 24v.

    Short and thick and all the same. Like politicians. :p
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #11
    Re: How to configure my battery bank

    yes, what i said before applies to battery series interconnections as well. all identical and large thickness.
    edited to add the word thickness so that you do not think long wires.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #12
    Re: How to configure my battery bank

    Short and think (i.e., low/balanced resistance among the strings) is all relative too...

    If you are going to take 30 amps average peak for 12 hours a day--that is a lot different than 300 amps for 1.2 hours per day....

    And the series fuse per string--that should be rated to protect the wiring (i.e., a 14 gauge wire would be fused at 15 amps; a 0000 wire may be fused at ~300 amps or so.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BajaGringo
    BajaGringo Solar Expert Posts: 40 ✭✭
    #13
    Re: How to configure my battery bank
    stephendv wrote: »
    Good description of parallel connecting bats here: http://www.smartgauge.co.uk/batt_con.html

    If you look at the example number four on that page it looks a lot like my friends suggestion except adapted for 24v:

    attachment.php?attachmentid=1873&stc=1&thumb=1&d=1276801340
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  • rplarry
    rplarry Solar Expert Posts: 203 ✭✭
    #14
    Re: How to configure my battery bank

    Bajagringo
    If your battery configuration allows, think about using either solid copper or brass bar stock to use as battery interconnects. Much cheaper than heavy battery cable with crimped lugs on each end, which will eventually get corroded away.
    Larry
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