Connecting batteries in Parallel

n1st
n1st Solar Expert Posts: 77 ✭✭✭✭
in Solar Beginners Corner #1
I have four 6v 220ah batteries. I've split them into pairs. Each pair is made of 2 batteries connected in serial. One pair is 12.96v, the other is 13.01v. When I attempt to connect the two pairs to each other in parallel to double current, with cables that have fuses in them, the fuses are blowing. I started with 5a fuses and moved up to 7.5a. I'm puzzled, I've done this many times before with no issues. :confused:

Is the voltage differential enough to be causing this?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Connecting batteries in Parallel

    in series you place the 1st battery's + to the 2nd battery's -. do this for the other 2 batteries as well. after that tie the 1st string's - connection to the 2nd string's - connection. do the same with the top +s so that the 1st series string parallels the 2nd series string. if fuses are blowing you have it wrong and are creating a short circuit.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #3
    Re: Connecting batteries in Parallel

    It COULD be the difference in voltages, but still the voltage doesn't seem that far off. Are you really sure that by some slip of attention, or error, the two strings might not be connected + to + and - to - ? That is, the + from one of the two strings, connected to the + of the other string, and the same for the two - terminals.
    You might try charging and doing an EQ on each of the two strings separately, then let them sit for a few hours until the voltages settle, hopefully very closely, and try connecting them together again, perhaps with a 30 amp fuse in case there might be some instantaneous surge if the voltages still don't exactly match.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Connecting batteries in Parallel

    A Voltage difference of 0.05 should not blow any fuse.
    Check wiring as per attachment.
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  • n1st
    n1st Solar Expert Posts: 77 ✭✭✭✭
    #5
    Re: Connecting batteries in Parallel

    Thanks for all the input - I see the error of my ways. The parallel connects were coming off of the same battery in one of the pairs. It Looked like this(thanks CC)....
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: Connecting batteries in Parallel

    That would do it. Putting 12 Volts to 6. :roll:
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  • TDSolarguy
    TDSolarguy Solar Expert Posts: 31 ✭✭
    #7
    Re: Connecting batteries in Parallel

    Greetings
    Learning here. Would this mean that n1st would have a 12 volt bank with 440 AMP hours now?

    Regards

    TDSolarguy
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #8
    Re: Connecting batteries in Parallel
    TDSolarguy wrote: »
    Would this mean a 12 volt bank with 440 AMP hours now?

    Regards

    TDSolarguy

    Yes, but only IF all 4 of the batteries are up to scratch. Any single, or more of the batteries that aren't up to specs will drag down the lot.
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