The right mppt cc for me

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  • Floating down here
    Junior Member
    • Nov 2017
    • 14
    #1

    The right mppt cc for me

    hi all, I've checked the threads and can't find an answer so perhaps someone can assist me. I have 4x 190w pv array (760w) total to charge a 24v 150ah battery bank. These are the specs:

    Pmax-190 (24v)
    Vmp-36.6v
    Voc-45.2v
    Imp-5.2a
    Isc-5.62


    i want to configure them in parallel to give me the following:

    760w
    36.6v
    20.8a

    by these calculations (if correct) the total amps (as represented by the Imp of 5.2a x4=20.8a)gives me the output current of the array (+25% =26a for extra light/reflections etc)


    So I determining the right mppt charge controller am I correct in assuming the 26a output is related to the max amp a CC can take? IE: a 30a model like the tristar 30 or MidNite solar the kid?

    The reason I'm confused is because I've read that to find the right amp CC you should take the total watts of the system (760w) and divide by the battery bank voltage (24v)

    760/24=31.6a +25%=39.5a

    significantly higher than the current at Pmax (20.8a) requiring a larger CC.

    any ideas?
    Tags: None
    • Mike90250
      Moderator
      • May 2009
      • 16020
      #2
      Yes, MPPT controllers are rated at output capacity. 30A at whatever the battery charging voltage is.

      But your problem is that 36V is not likely to be enough voltage to allow the controller to work in the MPPT region, and it may simply charge as PWM because a 24v bank, needs to charge at nearly 30V. When panels get hot, you may get 34 or 33 volts from them. I like to run battery charge voltage x 1.5 to get my min PV array Vmp , So wiring your array to 45V would be a better way to insure MPPT activity.

      Also, the major controller manufactures, have a Size Calculator to verify your expensive gear will work right.

      Kid http://www.midnitesolar.com/sizingTool_kid/index.php
      Classic http://www.midnitesolar.com/sizingTool/index.php
      Morningstar http://string-calculator.morningstarcorp.com/
      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

        • Floating down here
          Junior Member
          • Nov 2017
          • 14
          #3
          Thanks Mike90250, I will endeavour to use those calculators at a more acceptable hour here. I'm a little curious, how would I wire the array to 45v?

            Comment

            • Mike90250
              Moderator
              • May 2009
              • 16020
              #4
              Originally posted by Floating down here
              Thanks Mike90250, I will endeavour to use those calculators at a more acceptable hour here. I'm a little curious, how would I wire the array to 45v?
              I don't know what your panel voltages (Vmp) and amps (Imp) are, you may need to wire 3 in series, or only 2 depending on the voltages of the panels. Tell us the Voc also, it's very important too.
              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

                • Floating down here
                  Junior Member
                  • Nov 2017
                  • 14
                  #5
                  Pv info (each)

                  I have 4x

                  pmax-190w
                  output tolerance- 0/+5%
                  Imp-5.2A
                  Vmp-36.6V
                  Isc-5.62A
                  Voc-45.2V
                  TNoct-45

                    Comment

                    • Floating down here
                      Junior Member
                      • Nov 2017
                      • 14
                      #6
                      Perhaps configuring them as 2x series/ 2x parallel? Would this solve the problem?

                      cheers again Mike.

                        Comment

                        • Mike90250
                          Moderator
                          • May 2009
                          • 16020
                          #7
                          2S,2P is the route I'd go, to utilize a MPPT controller. 2S will give you nearly a 100V open circuit, so the small 75v controllers are out. 25A is a reasonable expected output, so a 30A controller would work. Run the thermal on the string sizers, and make sure they don't exceed the controllers specs on a cold day
                          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

                            • Floating down here
                              Junior Member
                              • Nov 2017
                              • 14
                              #8
                              Originally posted by Mike90250
                              2S,2P is the route I'd go, to utilize a MPPT controller. 2S will give you nearly a 100V open circuit, so the small 75v controllers are out. 25A is a reasonable expected output, so a 30A controller would work. Run the thermal on the string sizers, and make sure they don't exceed the controllers specs on a cold day
                              What is meant by "run the thermal on the string sizers"?

                                Comment

                                • neweclipse
                                  Solar Fanatic
                                  • Aug 2015
                                  • 118
                                  #9
                                  Originally posted by Mike90250
                                  2S,2P is the route I'd go, to utilize a MPPT controller. 2S will give you nearly a 100V open circuit, so the small 75v controllers are out. 25A is a reasonable expected output, so a 30A controller would work. Run the thermal on the string sizers, and make sure they don't exceed the controllers specs on a cold day
                                  Originally posted by Floating down here

                                  What is meant by "run the thermal on the string sizers"?
                                  To make sure they don't exceed the controllers specs (for peak voltage) on the coldest day at your location.
                                  That is a temperature that only you would know for your area...input that temp into the calculator(s) with everything else required.
                                  Excess "open circuit voltage' above MAX can destroy a CC.

                                    Comment

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