24v Battery Configuration

Discussion in 'Electrical Systems' started by SeaJay, Mar 29, 2011.

  1. SeaJay
    Joined: Jun 2007
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    SeaJay Senior Member

    Attached (hopefully) is a diagram of how I think I should connect four 12v batteries in a parallel / series configuration to A) get 24v to the boat circuits, and B) provide cross connections to enhance battery life and performance.

    This cross connection configuration is discussed on page 22 of Calder's most recent edition of Boatowner's Mechanical and Electrical. I need to modify/simplify what he has shown in order to accomodate the post positions of the four 8D batteries, as well as the layout of my battery box. I have numbered the batteries in my sketch so that they correspond to Calder's Fig. 1-21 in the following manner. Battery 1 is in the lower left corner (Fig.1-21). Battery 2 is in the upper left corner. Battery 3 is in the lower right corner. Battery 4 is in the upper right corner.

    I know this is pretty basic stuff, and I completely get how to wire batteries in series or parallel. I can follow Calder's logic, but want to be sure that my cross connections accomplish the same thing.

    Can someone knowledgeable please take a look at this and confirm that I have it correct (or all screwed up for that matter ;))?

    Best Regards,


    Attached Files:

  2. SeaJay
    Joined: Jun 2007
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    SeaJay Senior Member

    Balancing Battery Banks

    OK you brainiacs...you're lookin' but not talkin'. Maybe you don't have the Calder book for reference. Not to worry, here is another take on the topic of balancing batteries. Note the author is only discussing 12v systems, but it isn't a stretch to extend it to 24v.

  3. CDK
    Joined: Aug 2007
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    CDK retired engineer

    As you yourself wrote, this is pretty basic.
    You have only two choices: two parallel circuits in series or two series circuits parallel.
    Both have the same result, I cannot think of any argument to prefer either circuit.
  4. tazmann
    Joined: Aug 2005
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    tazmann Senior Member

    Hello Seajay
    I cant see any benafit wiring them up like you show.
    The only drawback I can think of and it is probably because I was a mechanic in the service working with 24 volt setups. Is you only have 1 ground and 1 hot with the power of 4 batteries. loose or dirty connection and a heavy draw will melt/ fry off the battery post. Myself for safety I would run the 4 as 2 banks to a switch in a 24 volt setup
  5. SeaJay
    Joined: Jun 2007
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    SeaJay Senior Member

    CDK, Tazmann,

    I was hoping you two would weigh in. The issue is balancing charge/discharge of the individual batteries. Take a look that the excellent article I posted before:


    I haven't had a chance to check my configuration against his preferred models but he explains why they should be connected in this manner. The problem I'm facing relative to either my proposed layout or the other options shown in the article (and Calder) is that a) the 8D battery posts are all on one end, and b) there is a lot of structure to work around in my "battery box".

    Anyway, I think I'm starting to have a better feel for how a multiple battery bank should be connected in order to balance the loads. I suggest that anyone interested in the subject read the article as it is the best explaination I've been able to find.

    Best Regards,


  6. Mark Cat
    Joined: Jun 2011
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    Mark Cat Senior Member

    Wow, I am very confused.

    On every ground up project I have worked on this combo series parallel configuration stuff never ever makes it to the design option meetings. Not to say that there might be merit to this. I have never heard a manufacturer recommend it. Please if someone has been recommended this form the more popular manufacturers, like Rolls or Lifeline AGM please give me their name.

    In doing research with the battery manufacturers it is never discussed as an option.

    For me the procedure is more like this:

    How large does the battery have to be?

    Is it starting or house?

    Do you need redundant banks? Equal CCA for starting redundancy.

    How will the batteries be moved? That is handling, how heavy.

    Then we work with the manufacturer to put together the best serial string for the terminal voltage needed (24V).

    So a very high power 24V bank may be based on 12 2V cells. A medium may use 4 6V cells. A low 2 12V cells.

    Then purchase all the cells new at the same time, and install and put into operation at the same time. If wet, install, then add electrolyte, charge and equalize, test, then put into service.

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