Length of cable for series connected batteries

rgk1
rgk1 Solar Expert Posts: 135 ✭✭✭
in Off Grid Solar & Battery Systems #1
I have 2 rows of 4 6-volt batteries (8 total) to be wired in series for 48 volt.  If all eight were in a straight line, cable length would not be an issue as I have same length inter-connect cables for each battery.  However, I have to make 2 rows of 4.  Is it OK to have a longer (15" vs 12") inter-connect cable to series row 1 to row 2?  I can use same length to connect the two rows, but would have to go over battery caps to reach.  Really don't want to have to make all new, slightly longer cables or disconnect 1 cable every time water has to be added.  I guess what I am really asking is do series connected batteries have to have equal length inter-connects?
4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • mike_s
    mike_s Registered Users Posts: 156 ✭✭
    #2
    It doesn't matter. If they're in series the exact same current will flow through all of them.
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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #3
    Thanks Mike_s.  That is what I felt was correct, but a search turned up varying opinions.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #4
    With two rows of batteries,  if you connect then in a U  --  series four going away from the inverter,   a jumper between row 1 to row 2,  and return jumpering  batteries of the second row of four,  toward the inverter the total length of interconnects should be about as short as one could make it.

    If you understand that too-long description   ...   FWIW,   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #5
    I do understand.  I could make the leads to the inverter about 3 1/2' shorter but reluctant to cut the current leads.  You can always make them shorter, but hard to make them longer if things change.  I figure 1/0 at 15' and 48 volts is acceptable for my current 1100 watt inverter. Thanks for mentioning that as i really didn't think about it at the time.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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