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Parallel & Series Solar Panels String Question

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  • Parallel & Series Solar Panels String Question

    Hi again -

    Would a string of eight 100W, 12V panels connected in parallel in 2 groups of 4 using a pair of MFFFF + FMMMM branch connectors then connecting these two pairs in series to 40 ft 8AWG mc4 cables work to make a 24V string? Or should I connect them in series of 2 and then connecting 4 of these series in parallel to my 40 ft run which again, I assume, would give me a 24V (nominal) output? If both would work, is one better then the other?

    Many thanks?

  • #2
    3 or more PARALLEL strings require fusing . Most commonly approached with a combiner box. While a fused combiner is fine you can go 1 step further and use a combiner with dc rated breakers. Look up Outback or Midnite Solar.
    Those 4 into 1 harnesses aren't legal to use without inline fuses for each panel. Then you need larger gauge wire from the harness.You're better off with a combiner box and series wire 2 panels at a time then into the combiner.
    Last edited by Mike90250; 06-30-2019, 10:04 PM. Reason: Mod edit PARALLEL
    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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    • #3
      I'm not sure if we're on the same page. I am using bus bar and fuses but my questions is about how to connect 100W, 12V panels in parallel & series to get one single 24V(nominal) string which then I'm running to bus bar and fuse. BTW, this is off grid setup.

      Right now, I have 8 of these panels divided in two strings, 4 panels in each string wired in parallel run to two separate 12V inputs on Goal Zero Yeti 3000 generator. I am replacing Goal Zero with Victron 150/100 charge controller, adding some more panels etc. So I thought it would be easier to leave the panels connected in parallel as they are and connecting 4 (one to four) branch connectors in series to make one single 24V run to 150/100 controller and use my remaining 40ft run for my other 8 panels. But I am not sure if it's okey to do it this way. My understanding is that it's usually done by connecting two panels in series and then connecting these pairs parallel to have 24V string using 12V panels.

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      • #4
        Unless I'm missing something 4S2P seems to be the better option. Higher voltage and smaller wire can be used with your solar controller.

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        • #5
          I have already run 2 pairs x 40ft of 8AWG mc4 cables which, I've been told, would be able to handle 2 strings; each string: 8 x 100W, 12 V panels at 24V.

          Also I think 24V, that's actually around 40V, would be safer to work with than 48 which would be something like 80V, no?

          So, 1 to 4 branch cables, as sold on Amazon are illegal to use? Interesting! How about 1 to 3 and 1 to 2?

          Sorry, there is a lot I need to learn but not giving up yet.

          Comment


          • #6
            Originally posted by Bozant View Post

            Also I think 24V, that's actually around 40V, would be safer to work with than 48 which would be something like 80V, no?
            No. 48V would be half the amps and generally safer.

            Originally posted by Bozant View Post
            So, 1 to 4 branch cables, as sold on Amazon are illegal to use? Interesting! How about 1 to 3 and 1 to 2?
            1-4 and 1-3 do not meet code when attached to your house so yes illegal to use on your house.
            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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            • #7
              Originally posted by ButchDeal View Post

              No. 48V would be half the amps and generally safer.
              My understanding is that with in series panel connections Volts go up, Amps stay the same.

              40 V may sting you, 80 V would do more than that, I would think.

              Quotes from the web: "Connecting your panels in series will increase the voltage level and keep the amperage the same."

              "If you had 4 solar panels in a series and each was rated at 12 volts and 5 amps, the entire array would be 48 volts at 5 amps."


              1-4 and 1-3 do not meet code when attached to your house so yes illegal to use on your house.
              By "attached" do you mean used in a solar system for the house or physically attached to the house, screwed to the roof of the house, for example? My panels are not attached to the house. Would using 1 to 4 be okey then?


              Comment


              • #8
                Originally posted by Bozant View Post

                My understanding is that with in series panel connections Volts go up, Amps stay the same.

                40 V may sting you, 80 V would do more than that, I would think.

                Quotes from the web: "Connecting your panels in series will increase the voltage level and keep the amperage the same."

                "If you had 4 solar panels in a series and each was rated at 12 volts and 5 amps, the entire array would be 48 volts at 5 amps."
                Generally you rate a PV system on the BATTERY not PV voltage, so when you say 24V vs 48V you are talking about the battery configuration.

                Yes when you put PV modules or Batteries in series the volts go UP and the amps stay the same, Thus my statement about 48V vs 24V, having 48V at half the amps of a 24V system.
                so your choice would by 2S2P or 4S with 2S4P being half the voltage but twice the amps of the the 4S system.

                The concern over a 24V vs 48V battery bank is that the 24V system would have to pull TWICE the amps to do the same work as the 48V system. Those amps get high, fast and hot. melting many metals. actually not just melting but flash vaporizing metal. What do you think a 24V high amp potential system will do to a finger wearing a ring that comes in contact with both terminals....
                The ring and finger go away in an arc flash....
                OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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                • #9
                  Okey, thanks. But my question is about solar panels installatio before I get to the charge controller and the battery bank. Actually, about how to hook up together a group of 8 panels to one run of cables. Voltage of my battery bank is determined by my Inverter which was going to be 24V.

                  Comment


                  • #10
                    Originally posted by Bozant View Post
                    Okey, thanks. But my question is about solar panels installatio before I get to the charge controller and the battery bank. Actually, about how to hook up together a group of 8 panels to one run of cables. Voltage of my battery bank is determined by my Inverter which was going to be 24V.
                    understanding the terminology will help you when talking to others.
                    Also if you have an MPPT charge controller then you can go higher on the voltage with more in series, thus reducing line losses as well as number of wires needed...

                    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                    Comment


                    • #11
                      Originally posted by ButchDeal View Post

                      understanding the terminology will help you when talking to others.
                      Also if you have an MPPT charge controller then you can go higher on the voltage with more in series, thus reducing line losses as well as number of wires needed...
                      Reading the thread. listening to what people are saying may save us some time. I appreciate any help I can get but som of us elderly people get sensitive about wasting of our time. I was asking a very specific question. I have an expert advisor but he is not available all the time. I am in the middle of this, anxious to get it done. I was hoping to get a clear answer to my question.

                      Comment


                      • #12
                        I believe you have an answer with explanations. 4S2P higher voltage is the best way to go. Any more than 2P should be fused, higher voltage will have less loss as well and be more efficient for the MPPT.
                        OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                        Comment


                        • #13
                          Yes, thank you! That's what I'm going to do. Same with my other group of 8 panels. Two pairs of mc4 cables #8 to combiner box with fuses, to circuit breaker, to Victron 150/100 MPPT controller.

                          My next big question is how to ground all of this in the best way?

                          Comment


                          • #14
                            Originally posted by Bozant View Post
                            ........ I was asking a very specific question. I have an expert advisor but he is not available all the time. I am in the middle of this, anxious to get it done. I was hoping to get a clear answer to my question.......
                            Your expert advisor is not worthy of either term, if he provided the recommendation to use 100w panels, MC4 Y or tap cables without fuses.

                            Would a string of eight 100W, 12V panels connected in parallel in 2 groups of 4 using a pair of MFFFF + FMMMM branch connectors then connecting these two pairs in series to 40 ft 8AWG mc4 cables work to make a 24V string? Or should I connect them in series of 2 and then connecting 4 of these series in parallel to my 40 ft run which again, I assume, would give me a 24V (nominal) output? If both would work, is one better then the other?
                            When going 4S with the panels, insure your chosen charge controller can handle the voltage on a cold morning (Voc)

                            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
                              Originally posted by Mike90250 View Post

                              Your expert advisor is not worthy of either term,
                              LOL. That's funny. Can I tell'm that?

                              Actually 100W panels were my choice. Reason, because I can handle them by myself.

                              Mc4 Y connectors were recommended by Goal Zero for their 3000 generator and by Renogy; I bought the panels and 1 to 4 connectors from them.

                              I am going to use Victron 150/100 charge controller. Would it do okey in cold weather?

                              So, how to find a highly qualified expert, experienced with off grid Solar Systems? Don't mind paying for advise by email or phone. I'm aware this is potentially dangerous stuff, not making an apple pie. But, the installation itself, I have to do by myself, otherwise it defeats the purpose. I am doing this because I need to stay active physically and mentally.

                              Any suggestions how to find this solar expert?

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