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Battery Bank Voltage Issue

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  • Battery Bank Voltage Issue

    We have a 48 volt (eight six volt batteries in series) battery bank. The batteries are brand new as it's a recently installed system. For some reason the batteries in the 5th and 6th positions in the series always have a lower voltage and eventually drop so low it triggers low voltage shut down. The other six batteries will be fully charged but those two will be at three and four volts. We took those two out and put two new batteries in their place and by that evening they were both one volt and under. What would cause batteries in that particular position in a series to have such an issue?

  • #2
    Position in a series string (unless they are hot from no air circulation) means nothing, in a series circuit, current (amps) is the same. So those batteries are either damaged, or "extra" capacity and have never been fully charged. With random batteries, one will be 90ah, one 85ah, one 95ah. Like PV panels, they are called 205Watt, but can vary 200 - 215w.
    With 3 or 4 volt reading on a 6v battery, one cell in the battery is dead. You might try pulling the batteries out of the circuit and charging them with a 12v charger, but they are likely dead
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A



    • #3
      Mike90250 , they are all the same exact batteries bought at the same place at the same time. I took them out of the circuit and took them to the auto place where they charged them over night. In the meantime I had put two brand new batteries that are exactly the same in their place and they did the same thing. When I picked up the original batteries after being charged and put them back they did the same thing. Before any of that I wanted to test my theory of only that position in the series having problems so I switched them with two other batteries in the series. After switching them they worked fine in the new position but the ones I put in their place did the same thing. It only happens in the 5th and 6th positions in the series. Could the cables connecting those two batteries in the series be faulty? If so how would I test them?
      Last edited by drewola; 03-18-2018, 06:11 PM.


      • #4
        Do you have a 12V feed off that pair ?


        • #5
          We did (a 12v pump) but that was the first thing we did which was take it off and hooked it to a car battery to eliminate it as the cause. Even after taking it off and everything else mentioned above it does the same thing


          • #6
            Are the cables home made?

            Maybe post up a picture of the wiring.


            • #7
              Bala ill post pics tomorrow. Everything is brand new. It's a brand new system. Flex Power One F08D3C38-3FB6-4B70-823C-7F2BD79A3A07.jpeg