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DIY Combiner Box

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  • DIY Combiner Box

    Just thought this might be helpful to some of the newer folks on the forum. If you have the money, by all means buy a Midnite Solar or other name brand combiner box. But for those of us on tight budgets, here is another option:


  • #2
    As you stated the QO breakers are rated at 48Vdc so is not suitable for most off grid arrays feeding any modern charge controller that goes up to 150Vdc (or more). It is such an advantage to get the string voltage up as high as the charge controller will allow, that hamstringing your array with a 48Vdc combiner doesn't make sense to me. Going with 200Vdc+ strings for a Midnite Classic200 for example allows you to run as many as 6 panels in a string and up to twelve panels before even needing a combiner.
    BSEE, R11, NABCEP, Chevy BoltEV, >2500kW installed

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    • #3
      @solarix That is true, good point. I probably should have emphasized that more in the video.

      But the majority of off grid solar applications do not go above 48V. I guess I should have posted this in a different sub-forum because you are right, homeowners off the grid will be using higher voltage to power an entire home with long cable runs. This DIY build is for everyone else that is using them for RV's, boats, sheds, workshops, job sites, SCADA, surveillance cameras, and other smaller off grid installations.

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      • #4
        Once someone is using over a 1kw inverter, stepping up to the next voltage (24v) makes more sense then bunches of parallel batteries and super heavy fat cables
        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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        • #5
          I like the video. Have built many of my own combiner boxes. All I would add is that the Midnite or Outback dc breakers are very competitively priced, making the need to use QO or QOU breakers with their relatively low dc rating unnecessary. You may need to use din rails in the enclosure though.
          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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          • #6
            Also, sometimes DC breakers have a "polarity" of which direction the current flow goes, and their internal arc suppression works best in, You may see a + on one of the terminals.
            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


            • #7
              I am wondering if you actually plan to physically open a conducting breaker? That
              is something to only be done in an emergency for my 400VDC grid tie system. If
              not, DIN mounted fuse holders can be used, and can be used to break the circuit
              manually when the sun is down as well.

              The Evil Bay fuse holders I ordered were economical, and I asked them to put in
              the proper size fuse, no extra charge. Bruce Roe

              Comment


              • #8
                As soon as the panels have build in blocking diode and they are fused and grounded appropriately, what else is nessacery for safe use?

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                • #9
                  Most panels, do NOT have a blocking diode, that task is usually handled by modern Charge Controllers.

                  Many panels contain several BYPASS diodes, that allow a partially shaded panel to pass electricity thru it, instead of totally stopping the electricity
                  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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