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Solar Charge Controllers - Multiples

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  • #46
    Originally posted by Mike90250 View Post
    What you have to beware of, is a cold morning, when the panels will be at their coldest, and the sun comes up. The panels, without a load, quickly jump to their max voltage, and a few minutes, later when the charge controller wakes up, the load of the charge controller brings the voltage down. But if is cold enough, and you don't have enough safety margin, you fry your controller as it begins to wake up.

    You can go to the charge controller's mfg page, and check the panel voltage there.

    What is the mfg/ model of your panels ?

    If your 2 panels in series are insufficient for charging, I'm not sure why 4 would be too much. The tristar MPPT has a max of 150V input
    http://www.morningstarcorp.com/en/tristar%20mppt

    string calculator:
    http://www.morningstarcorp.com/en/strings/calc.php
    EMMVEE 230 PS is the panel, Moringstar TriStar 60 Amp MPPT is @ 150 volt max.

    It is the string calculator from the morningstar that which warns me of the High Voc exceeding the CC's Max Voc in the record cold mornings.
    But it maybe that Max Voc Calculation is at 1000 w/m2 irradiation .. And in my tropical climate when the sun is at that level of radiance, it can never be at record low. Its just a catch 22, in my situation. So do not want to spend too much time worrying if its just an unpractical/unattainable Voc in my situation

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    • #47
      Originally posted by billvon View Post
      It likely never will - but it might. Decide what level of risk you want to live with. If that level is "low" then I wouldn't try to make assumptions about temperature without very good data (like actual recorded temperatures during daylight hours taken over years.)

      If you are OK with higher risks you might just go with the series panel arrangement. If you are comfortable with electronic design you could add a clamp, which is a simple circuit that limits voltage by shunting current through a resistance. The simplest sort of clamp is a zener diode; for your power levels you would need a much larger clamp. Example: http://sound.westhost.com/appnotes/an007.htm
      Thanks for the advice, will checkout the zener diode ... and see if I can put it on

      Comment


      • #48
        Originally posted by solarponders View Post
        ...... And in my tropical climate when the sun is at that level of radiance, it can never be at record low. Its just a catch 22, in my situation. So do not want to spend too much time worrying if its just an unpractical/unattainable Voc in my situation
        Sadly, that's not the way it works. It only takes a little light, to bring up a panel to voltage. Till the controller wakes up, and loads the panels down, the high voltage, even at sunrise, will fry it.... The AMOUNT of light will only increase the amps.

        so I wonder if a Zener diode, @ 145 VDC, 100watts, could solve the issue. ??
        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

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        • #49
          Originally posted by solarponders View Post
          But it maybe that Max Voc Calculation is at 1000 w/m2 irradiation ..
          It is. However, voltage is not significantly decreased by reducing the intensity of light, above a certain limit (about 50 w/m2.) So even if you get just a little light during early morning it will be pretty high voltage. And of course (and unfortunately) that's when it is coldest.

          But again, if it never gets to below a certain temperature where you are, and you can back that up with temperature records, that might be a worthwhile risk to take.

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          • #50
            Mixing Controller types

            I have 3 arrays in 3 different locations feeding 1 battery bank. Only 2 arrays run at the same time, ie, 7am-1pm (8 amps), 11am-3pm (6 amps), 2pm - 7pm (8 amps). Two of the arrays have chinese mppt controllers and the third has a MorningStar Sunsaver pwm controller. I don't seem to be getting the amperage I was expecting- I am seeing 6-7 amps instead of 14 . Is this a mismatch between controllers, and if so, should I be running 3 mppt controllers, or is there a way to adjust voltage outputs so they will work together?

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            • #51
              If the other controller have filled up the battery, it just won't take anymore charge by the time the sun gets to the 3rd controller. That's my guess.
              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


              • #52
                Mixing Controller types

                Originally posted by Mike90250 View Post
                If the other controller have filled up the battery, it just won't take anymore charge by the time the sun gets to the 3rd controller. That's my guess.
                The batteries are well below their maximum charge - resting voltage is around 65% charge. The topic I would like to hear about is the effectiveness of mixing controllers with slightly different cutoff voltages. The SunSaver when set for gel batteries is 14.1 V; one of the chinese MPPT's is 13.7 v . I am interested in the effect of those differences.

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