Cable length

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Joe94
Joe94 Solar Expert Posts: 42 ✭
in Off Grid Solar & Battery Systems #1
I'm redoing my battery box next weekend and have a question. When making the connections between batteries do all the cables need to be the same length. In my case it would make for a cleaner install to use shorter cables for the series connections then the parallel connections. I know it is very important to keep the parallel connections the same length but I don't see why the series cables cant be shorter.

Thanks
Joe
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Cable length

    It's a matter of having the total length in all battery strings the same, not the individual cables.

    Example: two strings of two batteries;

    ---BATT--BATT----
    --BATT----BATT---

    That's 3 + 2 + 4 on one string and 2 + 4 + 3 on the other but the lengths both work out to 9 total (arbitrary length units).

    This can get tricky to figure out with the standard 'diagonal' wiring
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #3
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    Re: Cable length

    Which brings up another question. Do the wires all need to be the same size?

    Meaning, if someone needed 1/0 for current requirements, could they use some 1/0 and some 2/0 in the same string if they were all the same total length?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: Cable length
    jcheil wrote: »
    Which brings up another question. Do the wires all need to be the same size?

    Meaning, if someone needed 1/0 for current requirements, could they use some 1/0 and some 2/0 in the same string if they were all the same total length?

    The wires should all be the same size. A length of 0 AWG and an equal length of 4 AWG have two different resistances.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
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    Re: Cable length
    jcheil wrote: »
    Which brings up another question. Do the wires all need to be the same size?

    Meaning, if someone needed 1/0 for current requirements, could they use some 1/0 and some 2/0 in the same string if they were all the same total length?

    in some cases you could, but let's not complicate things here. remember that the idea is to present the same total resistance as would be presented by other strings to keep equality among the strings. if you don't know what you're doing in those resistive calculations then stay with the basics.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
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    Re: Cable length
    niel wrote: »
    in some cases you could, but let's not complicate things here. remember that the idea is to present the same total resistance as would be presented by other strings to keep equality among the strings. if you don't know what you're doing in those resistive calculations then stay with the basics.

    I presume he meant wire sizes connecting the batteries. These would not necessarily have to be the same size as the wires going to the inverter which may be 'over sized' to reduce Voltage drop. And we won't get in to current division between strings as you don't want to depend on that being 50/50 even though it's what you're trying to achieve.
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