MPPT - Input Voltage

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  • xperthunter
    Junior Member
    • Mar 2013
    • 1

    #1

    MPPT - Input Voltage

    Okay team, reading this forum for a few months but never joined or posted. Now I have a question I have been unable to answer through searching the web or this forum.

    Setup:
    • 6 Solar panels (Thin-film, flex) operating at a maximum of 85v , .36 amps (35w) in maximum sun. Arrayed as 2 sets of 3, in Parallel.

    I was able to acquire these cheep, in great shape, and operating "as new"...they are rated at 30W. I am looking for a MPPT Charge controller, and one that is not expensive. Thus after much searching the


    Looks as though it will fit my needs, and be inexpensive. My concern is the Max 75V input rating. Does this mean that > 75V will cause damage, or that > 75V will simply be unused? As these only produce > 75V in maximum sun the peroid of time in which they will do so will be < 12% of total sun Collection time. Also is there a better, option for my setup in terms of MPPT Charge controllers that will not break my pocket book ($200-250 max)?

    Non Pertinent information:

    The battery setup is a series of (used) industrial batteries in series to provide 12V 800AH bank. Real load will be 20 hrs/week of LED light strips that light my basement/garage; These are separated in 2 arrays of 90w each (high efficiency 5050 LED variable wavelength) that pull a maximum of 90W and a minimum of 30W. Right now these are powered by the AC power of my local POCO. As in the heat, snow, wind...or any adverse condition we tend not to have lights. Once this solar system is UP I will be adding a manual switch to go from one power source to the other, and some sensing electronics to cut over to battery, and turn the lighting on in the case of power loss.

    Thanks mates!
  • ckhorne
    Junior Member
    • Nov 2012
    • 29

    #2
    Try plugging in your values into Morningstar's string calculator - it'll tell you your optimal configuration for a given setup:



    You'll likely need to enter in the specifics for your panels.

    Comment

    • Sunking
      Solar Fanatic
      • Feb 2010
      • 23301

      #3
      Not going to work. Thin Film panels are not good partners fro Off-grid solar because the voltage is too high. In your case a complete no-go. The controlle has a max Voc rating of 75 volts, and a single panel is 85 volts. Not going to work. You would damage the controller if you tried.
      MSEE, PE

      Comment

      • Naptown
        Solar Fanatic
        • Feb 2011
        • 6880

        #4
        The Tristar MPPT is rated at 150V input
        NABCEP certified Technical Sales Professional

        [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

        [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

        [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

        Comment

        • SunEagle
          Super Moderator
          • Oct 2012
          • 15147

          #5
          Originally posted by Naptown
          The Tristar MPPT is rated at 150V input
          At 85v each he can't even put two panels in series because the 170v will exceed the Tristar 150v max input.

          Those panels may be inexpensive but at 85v and 1/3 amp each they seem to not get you much wattage (35w) for what it takes to wire them into a CC.

          Comment

          • Naptown
            Solar Fanatic
            • Feb 2011
            • 6880

            #6
            He would have to wire them in parallel
            NABCEP certified Technical Sales Professional

            [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

            [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

            [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

            Comment

            • Sunking
              Solar Fanatic
              • Feb 2010
              • 23301

              #7
              Originally posted by Naptown
              The Tristar MPPT is rated at 150V input
              Rich he is talking about a Sun Saver with a max of 75 volts right? Not a Tri-Star with 150 input?
              MSEE, PE

              Comment

              • Naptown
                Solar Fanatic
                • Feb 2011
                • 6880

                #8
                Originally posted by Sunking
                Rich he is talking about a Sun Saver with a max of 75 volts right? Not a Tri-Star with 150 input?
                he would have to use a Tristar which is what I meant and did not communicate that very well.
                NABCEP certified Technical Sales Professional

                [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

                Comment

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