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  • 2 weak batteries

    I have 12 Rolls S550's at my cabin. 24v system with 3 banks of 4 installed fall of 2017. I shut down my 3000w inverter about a month ago for in between seasons. For security reasons I connected a small 12v inverter to 2 batteries in one bank so I could leave on 1 light. I went in last week to have a look and do a few battery checks. I discovered that the two batteries with the 12v inverter connected were low. -1v difference in volts and SG was down to 1.165 compared to 1.265+ of the other 10 batteries. All 12 were 1.265+ back in June. Disconnected small inverter and did equalization last week with little results. Set up another auto equal for 2 days ago. Went in today and they seem to be coming back with 1/2 v difference and SG 1.220. Is it possible the 12v inverter caused this, or is it just a coincidence that I have 2 weak batteries?
    NL

  • #2
    Unevenly loading a battery bank, as you did, can quickly ruin the bank, as you are discovering.

    The charger looks at the overall bank, and only knows it's low, so it keeps pumping charge, while the inverter is bleeding it off of a battery in the middle. All the other batteries get overcharged, and the inverter's battery never reaches full. To repair, remove the inverter batteries and charge them separately, reinstall without the inverter in the middle , and then see if the bank can balance itself out.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      Originally posted by Mike90250 View Post
      Unevenly loading a battery bank, as you did, can quickly ruin the bank, as you are discovering.

      The charger looks at the overall bank, and only knows it's low, so it keeps pumping charge, while the inverter is bleeding it off of a battery in the middle. All the other batteries get overcharged, and the inverter's battery never reaches full. To repair, remove the inverter batteries and charge them separately, reinstall without the inverter in the middle , and then see if the bank can balance itself out.
      Thanks Mike. That's the reply I was hoping for. In suspicion, I have already removed inverter. Will work on charging those two separately. Always something to learn with renewable energy.
      NL

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