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Need help, mixing panels..?

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  • Need help, mixing panels..?

    So I've been running 6x100w 12v in parellel, I finally upgraded to a Midnite Classic 150 strictly Solar charge controller and love it. I'm ready to expand and I want to change my system over to 24v and I want to order some 24v panels to expand, the question I'm asking is can I take my 6 100w 12v panels and run them in series pairs for 24v and then parallel them with the new 24v panels..?
    Last edited by uscgsapper1; 06-21-2019, 10:22 PM.

  • #2
    it depends on the working voltage ( Vmp) of the new panels and if it's a multiple of the 100 panels.

    Or just mothball the 100w gear and have it on standby if something untoward happens
    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



    • #3
      The "12" volt panels should produce about 18 VMP and two in series would be 36 volts, the 24 volt panels will be about 36 volts..........but.....36 volts is not quite enough to charge a 24 volt battery bank with a MPPT type controller such as the MidNite Kid or MidNite Classic controllers. The minimum voltage would be more like 1.4 times the maximum charge voltage of 28.8 volts or 40-42 volts, so minimum recommended paneling is 2 "24" volt 72 cell panels in series for a 24 volt system charged by a MPPT controller , 4 "12" volt panels should work fine in parallel with 2 "24" volt panels, but do check the total of the rated MPV voltage of each of the panel strings, they should be within 5% of each other

      If your controller is the MidNite Brat controller which is of the PWM type then 2 "12" volt panels in series will work with a 24 volt panel in parallel with it, if the MPV voltage of each string is within 5% of each other


      • #4
        My panels are Windy Nation 100w 12v 17.4 (Vmp) and my CC is a Classic 150 SL. So I would need to series 4 for (48v) and then (2) 24v panels in series for 48v to charge a 24v system..?
        Thats 4x100w panels in series for 48v so actually 100w@48v and 2x 300w 24v in series at 48v for 300w total, that's the best way to charge a 24v system with my CC..?
        Last edited by uscgsapper1; 06-21-2019, 10:56 PM.


        • #5
          If my math is correct that
          Last edited by uscgsapper1; 06-22-2019, 08:44 AM.


          • #6
            Yes, that would work with the classic
            panel strings in parallel need to be within about 5% of each other to work well.

            check the number of cells on any panel you intend to purchase, you have 36 cell "12" volt panels, to add to these you will need 72 cell panels, do be aware that there also 60 cell panels, they will not work well with the 36 cell panels.

            On the purchase of the Classic, great choice, it's the best one out there, it's very versitle and should give you good service. I've had 5-6 flawless years out of my 2 Classic 150 controllers, I bought the full Classic as it has the MNGP Graphic controller and that is very useful for setup and troubleshooting.
            Last edited by Tecnodave; 06-22-2019, 07:43 AM.


            • #7
              That's only 400w@48v, I'm at 600w@12v now. So I would be loosing power..??


              • #8
                Originally posted by uscgsapper1 View Post
                That's only 400w@48v, I'm at 600w@12v now. So I would be loosing power..??
                Your math is incorrect. Watts are watts regardless how you configure them. You are confusing amps with watts. 4 100 watt panels in series will give you 400 watts but at the amperage rating of a single panel and 4 times the voltage.
                2.2kw Suntech mono, Classic 200, NEW Trace SW4024


                • #9
                  4 ea. Of the 100 watt panels will be about 400 watts at 69.6 volts and would be converted to 400 watts at 24 volt battery by the charge controller Add to this the amount of power of the "24" volt panels that you intend to add to the system, for total system output.

                  or use strings of three "12" volt panels in series to produce about 52.3 volts ,600 watts and feed this to the classic which will convert that to 28 volts at 21.4 amps...600 watts at about 95-97% effeciency but if you do that you will have 108 cell strings and will not be able to use any standard panels in parallel with this setup.

                  Or don't use the 12 volt panels and buy the best bang for the buck panels which might be 60 or 72 cell grid tie panels and use 2 in each series string for about 60 or 72 volts into the. Classic which will convert this voltage to the battery voltage at 97-98% or so of effeciency

                  Bottom line, series strings af matched strings that have 72 cells total will work well with other 72 cell strings

                  "12 volt " panels are 36 cells, "24 volt" panels are 72 panels so generally will work well togather