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  • Problem with my small 50 W system

    Hello!

    New to the forum, hopes to get some needed help

    I have a small system setup on my balcony, running a 50 W solar panel via a regulator to a 50 Ah deep-cycle AGM battery. I use the system to charge my cell phone and laptop battery mostly (and some xmas lights during winter) and it has been working fine for about one year.

    Then suddenly the panel stopped charging the battery about one week ago. On the panel side of the regulator I get about 8-10 volts only which is not nearly enough to charge the battery.

    I have done the following troubleshooting:

    * Replaced the battery with a smaller one, still not charging - So battery is not the problem
    * Replaced the regulator with a spare one, still not charging - So regulator is OK
    * Replaced the solar panel with a small 10 W unit - Charing, so problem must be with the panel.

    I have googled a bit and then measured the Voc and Isc. Voc is 20.7 V (specs says 21.76 V) and the Isc is 2.84 A (specs says 3.06 A). It's not spot on, but still not so bad I think.

    But as soon as I connect a small DC load to the panel the voltage just dives to 2 Volts, so I guess there is a large internal resistance right?

    Is there anything more to do or test, or just accept that the panel broke already and buy a new panel?

    /Johan

  • #2
    Originally posted by frasse4 View Post
    But as soon as I connect a small DC load to the panel the voltage just dives to 2 Volts, so I guess there is a large internal resistance right?
    No does not mean that at all. A solar panel is a current source, not voltage
    MSEE, PE

    Comment


    • #3
      Originally posted by frasse4 View Post
      Hello!

      New to the forum, hopes to get some needed help

      I have a small system setup on my balcony, running a 50 W solar panel via a regulator to a 50 Ah deep-cycle AGM battery. I use the system to charge my cell phone and laptop battery mostly (and some xmas lights during winter) and it has been working fine for about one year.

      Then suddenly the panel stopped charging the battery about one week ago. On the panel side of the regulator I get about 8-10 volts only which is not nearly enough to charge the battery.

      I have done the following troubleshooting:

      * Replaced the battery with a smaller one, still not charging - So battery is not the problem
      * Replaced the regulator with a spare one, still not charging - So regulator is OK
      * Replaced the solar panel with a small 10 W unit - Charing, so problem must be with the panel.

      I have googled a bit and then measured the Voc and Isc. Voc is 20.7 V (specs says 21.76 V) and the Isc is 2.84 A (specs says 3.06 A). It's not spot on, but still not so bad I think.

      But as soon as I connect a small DC load to the panel the voltage just dives to 2 Volts, so I guess there is a large internal resistance right?

      Is there anything more to do or test, or just accept that the panel broke already and buy a new panel?

      /Johan
      It could be a problem in a few places. It may be a loose connection on one of the wires or a couple of components not working properly.

      What is the Vmp and Imp rating of your panel?

      The Voc (open circuit) and Isc (short circuit) is ok to determine the panel is functioning but not data to be used when the panel is connected to a charge controller and battery.

      Also depending on what that DC load is that you used it can drop the panel output voltage down next to nothing.

      I presume you first connected the charge controller to the battery and then the panels to the charge controller. If not then go try it again and make sure the panel is pointed directly at the sun around Noon time without any clouds.

      Comment


      • #4
        Sounds like you've got a multimeter, can you put it in line with the negative from the solar to the charge controller to see if there is any current flow? Don't put it across plus and minus, just have it black lead to the negative from the solar panel and the red lead to the negative in of the charge controller.
        Solar Queen
        altE Store

        Comment


        • #5
          Hello everyone!

          Thanks for the fast response! Sunny day today in Stockholm so perfect for some more troubleshooting.

          Long story short, I found that there is an internal bad wiring in the panel. When I bend the panel slightly (it a semi-flexible panel) the current comes and goes. I soldered some new wires directly to the panel and got it to work for now. I will look into get a new panel eventually, perhaps go up to 80 W.

          Atleast this panel has given me 14 kWh so far...

          /Johan
          Last edited by frasse4; 06-06-2016, 05:36 AM.

          Comment


          • #6
            Originally posted by frasse4 View Post
            Hello everyone!

            Thanks for the fast response! Sunny day today in Stockholm so perfect for some more troubleshooting.

            Long story short, I found that there is an internal bad wiring in the panel. When I bend the panel slightly (it a semi-flexible panel) the current comes and goes. I soldered some new wires directly to the panel and got it to work for now. I will look into get a new panel eventually, perhaps go up to 80 W.

            Atleast this panel has given me 14 kWh so far...

            /Johan
            Glad you found the problem. Usually a bad electrical circuit is first due to a wiring issue and second a piece of equipment.

            Comment


            • #7
              Originally posted by frasse4 View Post
              Hello everyone!

              Thanks for the fast response! Sunny day today in Stockholm so perfect for some more troubleshooting.

              Long story short, I found that there is an internal bad wiring in the panel. When I bend the panel slightly (it a semi-flexible panel) the current comes and goes. I soldered some new wires directly to the panel and got it to work for now. I will look into get a new panel eventually, perhaps go up to 80 W.

              Atleast this panel has given me 14 kWh so far...

              /Johan
              The reason that you measure full open circuit voltage may be that there are bypass diodes in the panel that allow current to flow from the undamaged section, bypassing (of course) the damaged section. Enough leakage current can flow through the damaged wire or cell to allow you to measure full voltage, but when any significant current is drawn the voltage drops to that of the undamaged group of cells only.
              In a string of panels, that can allow the string to work almost normally. For a single panel it usually means that you do not have enough voltage for your application.
              The apparently normal Voc and Isc from the panel is a limitation on finding that kind of damage just from those measurements. The voltage with the controller connected gives you a third data point.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

              Comment


              • #8
                Thanks for letting us know what the problem was. By any chance did you measure Voc and Isc afterward to see if they went back up to spec?

                Comment

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