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  • Marine solar install

    Hi All,
    I have a large boat and have installed a 2kw array and a house bank of 8 x 6 volt Trojan T16 FLA in series for a 48 volt system. I have a xantrex SC and a cheap chinese 6000w inverter. The layout is the SC and inverter on a wall in the stern cabin all hooked to the inverter and then long heavy cables to the battery bank in the bilge about 30ft away. The question is I picked up a new SC as a backup and the instructions state the SC must be run directally to the batteries VS the inverter.

    I can do this but my understanding was the SC can be any point on the 48 volt loop. Am I missing something. ?? Also I am thinking about a new inverter in the 4000 to 6000 w range as a back up to the existing Power Jack unit and I welcome recomindations.

    Thanks Upston

  • #2
    What is an SC ?

    Long cables from battery bank to inverter are generally bad, as the high resistance (even with 4/O cable, 30' / 60' round trip) will limit your inverter and trip it offline from low voltage.

    I would not use a low end inverter in a marine environment like a boat, it's a poor place to not have a well made piece of gear.

    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
      Hi Mike,
      Thanks for the reply SC is Solar controller. Roger on the inverter so what would you advise on a new one. Batteries have to go in the bilge as 1000 lbs of of lead needs to be low. Not wise to have electronics in bilge so not sure how to make them closer.

      Comment


      • #4
        What size wire do you have running from the battery bank to the inverter?

        I tried plugging the numbers into a couple of online wire size calculators and they all choked on:

        48v/125a and a 60' run to the batteries.

        Comment


        • #5
          Hi Steve

          The cable is 0 ort and the run is 30 so do you double it pos and neg ?. My max load is 15 amps at 110 ac so 35 amps or so. How does that look to you ?

          Comment


          • #6
            Originally posted by PNW_Steve View Post
            What size wire do you have running from the battery bank to the inverter?

            I tried plugging the numbers into a couple of online wire size calculators and they all choked on:

            48v/125a and a 60' run to the batteries.
            Doesn't anyone understand Ohms Law anymore? Bruce Roe

            Comment


            • #7
              Memorizing at best, "exposure" at worse, and actually understanding and internalizing a concept are two completely different things (-: I learned and applied Ohm's law in HS. But, to be honest, most of the applications involved calculating the current give a certain voltage DC battery and different sized resistors in various series and parallel configurations.

              Understanding that V=IR, and that V can also equal VD (Voltage Drop) is what they might call "extension" these days (-: Though I believe I do recall a few examples. Most folks get hung up fingering out the typical resistance of the conductor depending on its cross sectional area and material.

              This is a nice calculator that does AC 1-phase, 3-phase, and DC. No "knowledge" required (-:
              https://www.calculator.net/voltage-drop-calculator.html

              Comment


              • #8
                Originally posted by bcroe View Post

                Doesn't anyone understand Ohms Law anymore? Bruce Roe
                Are you referring to OP or me?

                I have a good understanding of Ohm's Law. What I don't have is the resistance per foot of various wire sized committed to memory. I may be a bit lazy as I use a calculator instead.

                Works well for me but I have never installed a 6kw interter with a 60' connection to the batteries. I tend to lean a little more conservative and limit the inverter capacity to match actual needs and keep the inverter much closer to the batteries.

                Just me though....

                Comment


                • #9
                  I do not memorize charts, I just look them up when I need them. Then a couple grade
                  school level calculations will give results. I certainly would not trust some unknown
                  software until I had throughly tested it out for sanity, if needed for frequent use.
                  Bruce Roe

                  Comment


                  • #10
                    Well, I am so conditioned to seeing 12v and giant inverters, I shot this down too early. It still does not feel right, with 30' between batteries and inverter, but 125A & 2/O cable, it would work in theory, if the cable impedance is not too bad.

                    125A_60FT_dROP.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


                    • #11
                      Hi Mike
                      Wow that is a great spread sheet, thanks a bunch. I have 90Volts apx coming from the array to the controller not 48 but that would half the amps right? The panels are flat, it's a boat, so I never get the full 2000w even in summer.

                      The base question I have is is it ok to hook the controller output to the inverter or should it be run all the way to the batteries? Also can you advise a good 48v inverter .
                      Thanks Upston

                      Comment


                      • #12
                        I think that I would be taking a long and hard look at what may be done, practically, as far a moving the inverter closer to the batteries.

                        Just me though..... I tend to try and keep inverter and batteries as close as I am able.

                        Comment


                        • #13
                          I agree. Why not keep the inverter with (or very near) the batteries and just extend the AC side of things? Large diameter copper wire is very expensive per foot.

                          The current coming from the panels to the MPPT/Charge Controller (Xantrex SC), and from the Charge Controller to the batteries will be very small. But the current coming from the batteries to the Inverter can be quite large and the inverter can shutdown if the voltage sags too much under load.

                          Comment


                          • #14
                            Often, I see the inverter mounted low on a bulkhead near the batteries. then 120Vac is run to the main power center.
                            the example I dummied into the spreadsheet, was to minimize all resistance, except for the inverter cables

                            How large of an inverter do you need ? Are you running a 1500w microwave or hair dryers ? Refrigerator ? The size of your inverter is dictated by the size of loads reasonably expected to be run together.
                            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


                            • #15
                              Hi Mike,

                              I got a larger inverter than I need as the chinese over state the numbers. I never run more than 2000 w at a time..

                              Upston

                              Comment

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