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  • Do I Understand this Correctly?

    As you may have read in some of my past questions/postings, I'm gathering different sizes of new and used panels, as I find them at low prices, for a future small array. All are 12 volt, but will be charging a 48v battery bank.

    So far, I have four 75 watt (used Siemens), two 90 watt (new China), four 100 watt (new China), and two 120 watt (used American Signal).

    If I add two more 90 watt panels and two more 120 watt panels, then I can have four strings at 48v.

    As I understand it, mixing different wattage panels within a series string will only lower the output. Do I understand THIS correctly: If I parallel four 48 volt strings, a 75 watt string, a 90 watt string, a 100 watt string, and a 120 watt string, then I won't lose any watts?

    I have a new 60amp, Tristar PWM controller. For the money (under $200), will this work with the four strings?

    Also gathered an old stock, but new 1500 watt PSW Aimes inverter designed for 48v input and 120v output. ($175) and a 500' reel for single run #6 multi-strand copper wire ($85)

    I've checked the amps on the 75 watt panels and they range from 4.5-4.8. I would expect the others to perform at their ratings.

    Bill

  • #2
    Originally posted by BilljustBill View Post
    As you may have read in some of my past questions/postings, I'm gathering different sizes of new and used panels, as I find them at low prices, for a future small array. All are 12 volt, but will be charging a 48v battery bank.

    So far, I have four 75 watt (used Siemens), two 90 watt (new China), four 100 watt (new China), and two 120 watt (used American Signal).

    If I add two more 90 watt panels and two more 120 watt panels, then I can have four strings at 48v.

    As I understand it, mixing different wattage panels within a series string will only lower the output. Do I understand THIS correctly: If I parallel four 48 volt strings, a 75 watt string, a 90 watt string, a 100 watt string, and a 120 watt string, then I won't lose any watts?
    Bill
    The electrical law here is thus:

    Panels in SERIES, add the voltage of each panel, but are limited to the lowest amp panel in the string.
    crude example:
    20V.3A - 12V.4A - 22V.6A - 18V.4A = 216W
    would yield 72v at 3A You are wasteing the watts from the higher amp panels


    Panels (or strings of panels) in parallel, will drop to the lowest voltage panel (or string) but the amps will add.
    crude example: (same panels)
    20V.3A
    12V.4A
    22V.6A
    18V.4A = 204W
    yields 12V @ 17A Where you are wasteing the volts of the higher panels.

    throw away the 12v panel and you get:
    20V.3A
    22V.6A
    18V.4A = 234W
    18V @ 13A The higher voltage factors into your wattage

    So i can't look at the strings you describe, and give an answer, you need to break the strings down like i just did, and figure the best way to combine them - maybe even throw away a panel, if it lowers the whole. So I find it easier to just say "don't mix & match" !

    Now you try the first example (series), but delete the 3A panel !

    (PS - I just started typeing #'s, these are all totaly random panel sizes)
    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
      very reasonable!

      Comment


      • #4
        Mike,

        I'm trying to keep it simple and low cost while making sure it is efficient enough to justify the future cost of a 48v battery bank. Mixing panels is my only way of keeping the cost down.... If I can get my money back, or a little more, I may sell the two new 90 watt panels this weekend and order a pair of new 120 watt panels as I continue gather enough panels for a 1kw array.

        All the 12 v panels are operating in the 17v-22v range, and the amps average out to the specs of an average rated panel (ie, 75w, 100 watt, & 120 watt string)

        How would you combine all the strings? To get all the panels to one junction box, the longest #6 panel wire run would be under 15'. What type of box and what type of fuse/breaker would you use to protect each different wattage string? What is used to protect the run between the array and the building to be solar powered?

        From a 5" diameter ground pole with a future tracker system, it is 50' to the controller and battery bank. I have aquired 80' of #2 aluminum wire and gray PVC conduit for this long run.

        Again thanks for the guidance!
        Bill

        Comment


        • #5
          On to another question.... If I have equal voltages of 12v and four panels of same wattage for 48v strings, say there are four strings: 1 string of 75 watt panels, 90 watt, 100 watt, and 120 watt, would a single MPPT controller still be better than the PWM controller?

          Comment


          • #6
            Combining parallel with series

            If I have a variety of panels, why would I limit myself to only series only or only parallel wiring?

            My MPPT should respond best if I set up strings that pair up panels in series with one, + to - connection, and then parallel them to the next panels, - to - on the one panel of the pair, and + to + with the other panel of the pair. Then the MPPT can use the volts and watts from the panels in any way it needs to use them in order to supply the demands of the load--the appliances and the batteries.

            Also, it seems to me that I would not be wasting a panel just because it has a different output than the others if I combine parallel and series wiring.

            Comment


            • #7
              MPPT is terrifically complex. If you mix strings of panels, it may find the best point 10% of the time, none of the time, or 90% of the time. None are tested on mixed panels.

              If you hold your mixed strings to +- 10% of each other, that would be a good start of getting the best out of your system. The more you vary from a straight string of the same, the more you are likely to be unhappy.
              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


              • #8
                Bill is gone, hijacked thread.
                MSEE, PE

                Comment


                • #9
                  Originally posted by Sunking View Post
                  Bill is gone, hijacked thread.
                  No, sunking, I'm not gone, just haven't gotten a notice that shows someone posted to my question....

                  What's a hijacked thread?

                  Bill

                  Comment


                  • #10
                    Originally posted by Mike90250 View Post
                    MPPT is terrifically complex. If you mix strings of panels, it may find the best point 10% of the time, none of the time, or 90% of the time. None are tested on mixed panels.

                    If you hold your mixed strings to +- 10% of each other, that would be a good start of getting the best out of your system. The more you vary from a straight string of the same, the more you are likely to be unhappy.
                    Thanks for the help, Mike.

                    As an update to what I'm still trying to do, because of the Kaneka panels not working very well for a 48v system, I've changed in midstream and am finished collecting equipment for a 24v system with my garage sale jewelry "Fundraising" profits....

                    I have two Outback GVFX3524 inverters. I got a great price at "Solar Biz" as they are a distributor willing to meet anyone's prices, plus 10% of the difference. I may be running a 240v stacked inverter set up to the house from the battery and solar arrays. For the 12 Kyocera panels I have an Outback FM-80, and for the 30 Kaneka panels, I have another FM-80 specific to them. All together, these two arrays combined, it should be approx. 3.5KW...

                    This third array, although very economical on the panel costs, is the Bugger... How does this sound? Since it is a 24v system, wiring the four 75w panels in pairs, the two 90w panels in pairs, the four 100w panels in pairs, and the two 120w panels in pairs. Each pair has its own breaker in the pole mounted combiner box, and I've collected plenty # 6 to do the panels runs and #2 copper for the run from this third array to a smaller MPPT controller. Do you think that this would prevent loss and problems from the layout?

                    Thanks,
                    Bill

                    Comment


                    • #11
                      What's a hijacked thread?
                      griffin87901 jumping in with a non-answer, redirecting the topic.
                      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


                      • #12
                        Originally posted by BilljustBill View Post
                        What's a hijacked thread?
                        Someone else jumping in trying to take over your thread with their questions and toss you aside.
                        MSEE, PE

                        Comment


                        • #13
                          ???????

                          Originally posted by Sunking View Post
                          Someone else jumping in trying to take over your thread with their questions and toss you aside.
                          So who did that?

                          Comment

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