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Should I Ground or Float my Off-Grid 12V System?

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  • Should I Ground or Float my Off-Grid 12V System?

    Here is my setup:
    295 watt panel (32 Vmp)
    15 amp MPPT charge controller
    12 volt 150 ah FLA battery
    Fuse block with Negative Bus

    The setup will be stationary.
    The house is off-grid so the system is stand-alone.

    All loads will be 12 volt, I only plan on running a couple lights and a low power laptop.
    Though, if possible, a 12 volt freezer to make ice once or twice a week during the sunny days.

    The panel will be about 30 feet from the house.
    If there is the possibility of a storm, the panel will be disconnected from the charge controller.

    I've attached two pictures, one grounded and one floated.
    Would the floated diagram work since the system is 12 volts?

    Thanks for any help

    Grounded.pngFloated.png

  • #2
    Both will work since you do not use an inverter. Your local building code may require a ground on the battery minus terminal
    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

    Comment


    • #3
      Thank you
      I think, however, I may have made an error on the floating diagram.
      I have the ground wire connected to the fuse where the CC meets Battery (Number 1 in picture).
      In order to operate the fuses in case of a fault, should the ground wire be connected to the fuse where the Fuse Block meets Battery (Number 2 in picture)?


      Ground Wire Return Path.png
      Attached Files

      Comment


      • #4
        FUSES are a very different thing than grounding, and I was not attending to fusing.

        Fuses are only to protect the wires from causing a fire

        Transistors and FET's protect cheap parts of circuitry.

        So a fuse has to carry the Normal amps that things use.
        Wires cannot be thinner than what the fuse (or circuit breaker) is designed to protect

        Sunking has some very well drawn sketches in the stickies, of proper wiring and fuse location. (drat, I can't find the posts)
        here's one, but it's not what I was looking for:

        SunKingBatterySolar_rough.jpg
        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

        Comment


        • #5
          Which one are you looking for Mike?
          MSEE, PE

          Comment


          • #6
            Originally posted by Mike90250 View Post
            Sunking has some very well drawn sketches in the stickies, of proper wiring and fuse location. (drat, I can't find the posts)
            These have helped me quite a bit, they might be some of the ones you were looking for.
            Post #23
            https://www.solarpaneltalk.com/forum...s-ground/page2

            Comment


            • #7
              Originally posted by Sunking View Post
              Which one are you looking for Mike?
              ones where you cover the ground, chassis, ungrounded system. But I guess Greta is on the path now
              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

              Comment

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