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solar panel 18v and very low current

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  • solar panel 18v and very low current

    Hello

    I am new here, so i may have posted in the wrong category.
    Basically i have recently purchased a 20w solar panel and charger from ebay (link below). i am having a problem with the panel, i have measured the short circuit current 30 miliamps and i have measured it in series 60 miliamps, also the panels open circuit voltage is 18volts. The panel its self rarely goes over these values any idea what is a matter with it?

    http://www.ebay.co.uk/itm/2818064630...%3AMEBIDX%3AIT

  • #2
    Welcome, glad you found us.

    Solar panels are rated for noon time sun, any haze in the air, any faint clouds, and the power will be much lower.

    Panels reach their voltage with just a little light, and the brighter light, produces more current (amps)

    A 20W panel, at 18V, would be expected to produce no more than 1.1A under the very best conditions, normal conditions about 20% less would be expected, about 850mA (0.850A)

    The tricky fact about PV panels, is they are "Current Devices", not a Voltage Device. Generally, everybody's life experience has been with voltage sources, and PV panels are current sources, which behave differently when loaded. That's why with larger systems MPPT tracking becomes important.
    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


    • #3
      Originally posted by Mike90250 View Post
      Welcome, glad you found us.
      A 20W panel, at 18V, would be expected to produce no more than 1.1A under the very best conditions, normal conditions about 20% less would be expected, about 850mA (0.850A)
      even on the best days it has never gone over that figure, measured it today on an over cast day an only got 2 milliamps at best

      Comment


      • #4
        Originally posted by ryisnelly View Post
        even on the best days it has never gone over that figure, measured it today on an over cast day an only got 2 milliamps at best
        If I had to bet, you do not know how to measure Isc. Try reading this.
        MSEE, PE

        Comment


        • #5
          Originally posted by Sunking View Post
          If I had to bet, you do not know how to measure Isc. Try reading this.
          seriously do you think i am an idiot, of course i know how to take those readings, i would not of posted them if i didn't have any idea what i was doing.

          Comment


          • #6
            Originally posted by ryisnelly View Post
            seriously do you think i am an idiot, of course i know how to take those readings, i would not of posted them if i didn't have any idea what i was doing.
            Yep most folks who come here are ignorant. Otherwise if thee knew what they were doing, they would not be here asking questions now would they? This is one question that gets asked a lot because people do not know how to use there meters or the test conditions that must be met for a valid test result.

            If you have bright noon sun, panel pointed directly at the sun, your meter set up correctly, and get a low Isc reading: Then you would know the panel is bad and would not be here asking questions. You would be getting a new panel, and not asking questions.

            This statement right here tells us you do not know what you are doing

            i have measured the short circuit current 30 miliamps and i have measured it in series 60 miliamps
            To measure Isc there is only one way to do it. No series circuit involved and will only have one value.

            You can measure Voc with a flashlight as a light source. Isc must be made at noon on a very bright sunny day with your panel facing directly into the sun. So if you aree doing it correctly and only seeing a few milliamps, you rpanel is a POS and needs replaced.

            If your panel Voc is really 18 volts which is way too low for a 36 cell panel, then you already know you have a problem because a 36 cell panel should have a Voc of roughly 22 volts and Vmp of 18 volts. Having said that if the panel Voc is really suppose to be 18 volts tells us you have a very odd panel and not suitable for a 12 volt battery. At 20 watts Isc should be a minimum of 1.3 amps with a Vmp of roughly 14 volts.

            Now get over it and figure it out.
            MSEE, PE

            Comment


            • #7
              Originally posted by Sunking View Post
              Yep most folks who come here are ignorant. Otherwise if thee knew what they were doing, they would not be here asking questions now would they? This is one question that gets asked a lot because people do not know how to use there meters or the test conditions that must be met for a valid test result.

              If you have bright noon sun, panel pointed directly at the sun, your meter set up correctly, and get a low Isc reading: Then you would know the panel is bad and would not be here asking questions. You would be getting a new panel, and not asking questions.

              This statement right here tells us you do not know what you are doing



              To measure Isc there is only one way to do it. No series circuit involved and will only have one value.
              Ok that is understandable why that would annoy you, but why not ask how i tested the panel?
              instead of jumping to conclusions and being so self righteous. i came here to see if there was anything that could be done to the panel before i replace it. As for the information i gave, it was to give the reader (you) an idea of what was going on, rather then just saying 'there is no current', as with any forum people normally flock to them for knowledge and information which is why i am here as i have little knowledge on solar panels ,

              Thanks for your help it is most appreciated

              Comment


              • #8
                Originally posted by Sunking View Post
                Now get over it and figure it out.
                Before i go one more question, there are white marks near the soldered strips, there is quite a few of them and they are no bigger than 3mm is that a sign of damage?

                thanks

                Comment


                • #9
                  Originally posted by ryisnelly View Post
                  Before i go one more question, there are white marks near the soldered strips, there is quite a few of them and they are no bigger than 3mm is that a sign of damage?

                  thanks
                  It could indicate surface damage from water infiltration. Or it might be cosmetic. Can you post a photo or two?
                  SunnyBoy 3000 US, 18 BP Solar 175B panels.

                  Comment


                  • #10
                    Originally posted by inetdog View Post
                    It could indicate surface damage from water infiltration. Or it might be cosmetic. Can you post a photo or two?
                    Yep certainly, please excuse the low light.
                    thank you.

                    1.jpg2.jpg

                    Comment


                    • #11
                      Originally posted by ryisnelly View Post
                      Yep certainly, please excuse the low light.
                      thank you.

                      [ATTACH]8073[/ATTACH][ATTACH]8074[/ATTACH]
                      The two blobs near the center of the photo do not look normal by any means, but they also do not, by themselves, look like evidence of catastrophic damage to the cell(s).

                      Possibly there is a crack in the panel somewhere too. Or a corroded internal lead.
                      SunnyBoy 3000 US, 18 BP Solar 175B panels.

                      Comment


                      • #12
                        Originally posted by ryisnelly View Post
                        Before i go one more question, there are white marks near the soldered strips, there is quite a few of them and they are no bigger than 3mm is that a sign of damage?

                        thanks
                        I concur with Dave (aka inetdog) you have a damaged panel. A ISC test will confirm.
                        MSEE, PE

                        Comment


                        • #13
                          Originally posted by Sunking View Post
                          I concur with Dave (aka inetdog) you have a damaged panel. A ISC test will confirm.
                          ok, thank you for your time and help.

                          Comment

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