Question on Battery Bank Wiring

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williaty
williaty Solar Expert Posts: 60 ✭✭
in Solar Beginners Corner #1
Early on, I found a thread on here linking to an outside site showing just how terrible the results can be when you parallel a bunch of batteries ladder-style, so I'm aware of some of the issues with bank wiring. However, I was reading on a marine forum about their DC power systems and a couple of people who generally seem to know their stuff were adamant that you needed to wire the batteries into parallel groups to get your desired storage capacity, then wire the groups into series to get your desired voltage. This is exactly opposite to what seems intuitive to me, which is to string batteries in series to get your desired voltage and then parallel the strings if you want more capacity. I've created two wiring diagrams to depict the two different theories. The first one shows building strings and paralleling them, the second shows building groups and stringing them. Is one really better than the other?

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Question on Battery Bank Wiring

    The first design will work better.

    Assume all wire sizes are equal. Compare current flow between the first and second design. See the 'bottleneck' in the second one?
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  • williaty
    williaty Solar Expert Posts: 60 ✭✭
    #3
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    Re: Question on Battery Bank Wiring

    Yeah, I wondered about that. The first design just makes more intuitive sense to me. But when I see a bunch of people who know more than I do all claiming something weird is the One True Way, I figure it's at least worth asking a second group of people if I'm missing something that makes it smart, not weird.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: Question on Battery Bank Wiring

    It could be worse: they could be connected both ways (parallel and series connections between the batteries). That creates alternate current paths that can lead to some serious battery depletion.
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