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I shorted my Panels ... Are they Dead?

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  • I shorted my Panels ... Are they Dead?

    OK so I know it was a dumb thing to do. I was hot and had been on the roof most of the day and was not thinking clearly.

    I bought 9 285w REC TwinPeak 2 Modules. I also bought 3 30 foot cables with the idea of cutting each of them in 2 to run 3 series strings of 3 panels to a combiner box. Hear is where the "fun" started. I was not thinking ... or more specifically was thinking more about wire length as I knew it would be tight getting everything to the combiner, so I never actually cut the cables (+ and -) in to 2 parts ... but rather, I connected everything to find out where the "center cut point" of each cable would be. I plugged in the series strings, and then plugged in the cables to themselves, BEFORE cutting them in 2. So the series strings were shorted. Probably for about an hour in full mid day sun.

    So now I wonder ... Are the modules now dead? I have not yet installed the charge controller so I have not been able to test them yet. BUT ... The VOC rating for the strings @ STC should be 115.8, and at NOTC should be 107.4. I am getting between 95.6 and 102.7 VOC. I cannot test the ISC because I cannot easily take the panels apart. And I do not yet have the Charge controller, so I cannot simple just "hook it up" and see.

    But will shorting the panels in full sun for an hour or more definitely "kill" them ?

    How bad is it?
    285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

  • #2
    If the panels were robust and healthy, they are fine. Shorted panels produce Isc (amps, short circuit) and if there are some thin or defective traces, they may be damaged long term, but shorting a good PV panel should not hurt it, even for an hour. IMHO
    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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    • #3
      Shorting the panels is fine. It is a normal diagnostic exercise to short them and measure Isc. (The sc stands for short circuit).
      CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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      • #4
        Thanks ... that is what I was thinking too. The modules are new ... so I can only hope they are robust and healthy.

        I also just re-read the spec sheet. And If I am seeing it correctly ... the Nominal Power Current @ STC is 8.95a and the Short Circuit Current @ STC is 9.49 ... a difference of .54 amps between the shorted current and the operating current. So very very close.

        And interestingly, when I read the NOCT numbers for the same (which I assume the NOCT numbers are probably more real world day-to-day expectations for the panel) , The Nominal Power Current @ NOCT is 7.24a and the Short Circuit Current @ NOTC is 7.68a.

        So would I be correct in assuming that my shorted current would have been probably around 7.68a .... which is actually LESS than the Nominal Power Current of 8.95a in the "lab" at STC ?

        So my Short Circuit would have been lower than what would have been being produced in ideal conditions for normal use?
        285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

        Comment


        • #5
          Originally posted by Matrix View Post
          So my Short Circuit would have been lower than what would have been being produced in ideal conditions for normal use?
          Probably. Shorting the leads and measuring current is a normal diagnostic procedure. The panel is fine. The connectors, on the other hand, may not have handled it well. Making and breaking the connection in daylight can cause damaging arcs to the contacts in the connector housing.
          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

          Comment


          • #6
            Originally posted by Matrix View Post
            Thanks ... that is what I was thinking too. The modules are new ... so I can only hope they are robust and healthy.

            I also just re-read the spec sheet. And If I am seeing it correctly ... the Nominal Power Current @ STC is 8.95a and the Short Circuit Current @ STC is 9.49 ... a difference of .54 amps between the shorted current and the operating current. So very very close.

            And interestingly, when I read the NOCT numbers for the same (which I assume the NOCT numbers are probably more real world day-to-day expectations for the panel) , The Nominal Power Current @ NOCT is 7.24a and the Short Circuit Current @ NOTC is 7.68a.

            So would I be correct in assuming that my shorted current would have been probably around 7.68a .... which is actually LESS than the Nominal Power Current of 8.95a in the "lab" at STC ?

            So my Short Circuit would have been lower than what would have been being produced in ideal conditions for normal use?
            FWIW and a small point, real world or not, NOCT conditions are no more real world than any other reasonable set of test conditions with irradiance at 800 W/m^2 irradiance. STC is at 1,000 W/m^2. Other test conditions are different as well.

            Panel current is pretty close to linear with respect to irradiance so your string current was probably about in proportion to the panel irradiance when you were working on them. If it was sunny and the panels were in their operating position, they may have been seeing ~ 800 -900 W/m^2 depending on a few variables like location, time of day, array tilt and azimuth and how sunny it was when you were working on the array.

            Comment


            • #7
              Originally posted by J.P.M. View Post

              FWIW and a small point, real world or not, NOCT conditions are no more real world than any other reasonable set of test conditions with irradiance at 800 W/m^2 irradiance. STC is at 1,000 W/m^2. Other test conditions are different as well.

              Panel current is pretty close to linear with respect to irradiance so your string current was probably about in proportion to the panel irradiance when you were working on them. If it was sunny and the panels were in their operating position, they may have been seeing ~ 800 -900 W/m^2 depending on a few variables like location, time of day, array tilt and azimuth and how sunny it was when you were working on the array.
              So does that mean they were damaged ... ??
              285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

              Comment


              • #8
                I am now a little more concerned. Without any real world experience ... on day one at 11 am in full N. Florida Sun, panels are at a 15.7 degree tilt and facing south ... I am not getting what I would have thought would be very good current or watt out put from the panels. I was expecting about 18 to 20 amps ... it would seem right now in full sun at 11am I am getting 2.2 amps and 200 watts from a 285 watt x 9 panel array. Out side temp is 82* F.

                Would this be correct ... or do I have a problem?
                Attached Files
                285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

                Comment


                • #9
                  Looks like you might be in absorb, with the battery at 28.6 V. At that stage of the charge cycle, the controller dials back the PV power so that the battery only gets as much charge as it can accept.

                  What specific charge controller are you using?
                  CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                  Comment


                  • #10
                    Originally posted by Matrix View Post

                    So does that mean they were damaged ... ??
                    I don't know. I'm not there and experience has taught me that unless there's a no brainer problem, to not attempt to diagnose system problems without being on site. From what it sounds like your trying to do, what you've done, and the types of questions you're asking, I don't know what else you may have done that's possibly causing problems.

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                    • #11
                      Well maybe its just my lack of understanding how a solar system works ... and how it interplay with a charge controller. The amps dropped to 1.2amps .... but the batteries were fully charged. I turn on the inverter ... and immediately, the input amps from the array jumps to 7 amps and now I am producing 600 watts.

                      So does a Classic 150 limit input PV current if it is not needed? I thought that input amps was what was coming in from the array ... all the time as the sun was making power available. So I guess what I am asking, does a classic 150 limit the PV current if not needed to supply charging or load?
                      285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

                      Comment


                      • #12
                        Originally posted by Matrix View Post
                        So I guess what I am asking, does a classic 150 limit the PV current if not needed to supply charging or load?
                        Yes, that is exactly what any charge controller is designed to do.
                        CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                        • #13
                          Thanks ... i did not realize that. I was thinking that the PV current was what the panels were producing ... not what the controller was drawing. Seems I am OK. before I shut down the CC to drain the battery a bit ... It was up to 8 amps.
                          285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

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                          • #14
                            1. If a panel WAS damaged at Isc, it would be a good thing. It should be returned on warranty, the earlier discovered the better.
                            2. A better amperage test would be to put 9x285W = 2565W (plus won't hurt) load on the system during great sun, then it won't matter what the battery SOC is. Round up your vacuum cleaners and such and keep adding them until 'panel amps' levels off.

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                            • #15
                              Solar panels are CURRENT SOURCES and NOT Voltage Sources like a battery. You can short any panel out for a day, week, month, or year with no problems. In fact that is how you test a solar panel. As CURRENT SOURCE current is limited and in a solar panel is Isc. A shorted panel cannot even heat up its own wires.

                              Short out a voltage source like a battery, and you are going to have a very bad day.
                              MSEE, PE

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