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  • SolarEdge optimizer acting funny, or maybe the panel....

    I designed, permitted, and completely installed my own grid tied solar system with P320 SolarEdge optimizers, SE7600 HD Wave inverter and Q-cell Duo G5 310W panels. I have 27 panels in 2 strings all facing the same direction (due west). One string is 14 panels, the other is 13. I'm a huge reader but I rarely post to places. You guys have been very helpful with my journey of learning on solar panels and I've read a significant number of threads on this forum.

    It all works great, except I have one panel (on the first string, panel 1.1.5) that has about 60% of the power output of the others. It's clean, looks fine and does something that I think is really strange. During the low output time (which is always during peak hours and sunny) the optimizer drops the voltage for that panel down to 16V, which is about half of what the other optimizers on the string are doing (about 29V each). I contacted SolarEdge and they shipped me out a replacement optimizer which after replacing does the exact same thing. The logical part of me says at this point it must be the panel but I can't figure out why the optimizer would behave like it's doing. I asked SolarEdge and they brushed me off.

    Normal output for a panel on this string is voltage around 29V when it's putting out 250-270 watts and the optimizers also put out about 29V as well. On the bad optimizer/panel I have a module voltage 2V higher, about 31V and it's only putting out 150W. And the optimizer voltage is of course at 16V.

    Whole inverter runs about 394V. I know it's not clipping because that's when the inverter voltage rises above 400V (usually 440V) and I watch for that with some python scripts I wrote.

    Here are some clues I'm considering

    * My panels are really two half panels in parallel. Maybe half the panel has a temperature related defect and for some reason this causes the optimizer to drop the voltage?
    * Because this is my string of 14 (other string is 13) One of the optimizers has to have reduced voltage output to balance the strings for some reason?
    * I got two bad optimizers in a row?
    * I'm lazy and should just swap the panel position instead of starting this thread?

    I do plan on swapping the panel position but it's no fun moving panels around on the roof and I was hoping maybe someone would have ideas on what could cause the optimizer to behave so strangely.

  • #2
    Originally posted by library View Post
    I have one panel (on the first string, panel 1.1.5) that has about 60% of the power output of the others. It's clean, looks fine and does something that I think is really strange. During the low output time (which is always during peak hours and sunny) the optimizer drops the voltage for that panel down to 16V, which is about half of what the other optimizers on the string are doing (about 29V each). I contacted SolarEdge and they shipped me out a replacement optimizer which after replacing does the exact same thing. The logical part of me says at this point it must be the panel but I can't figure out why the optimizer would behave like it's doing. I asked SolarEdge and they brushed me off.
    It is trying to compensate for the defective PV module.

    Originally posted by library View Post
    Normal output for a panel on this string is voltage around 29V when it's putting out 250-270 watts and the optimizers also put out about 29V as well. On the bad optimizer/panel I have a module voltage 2V higher, about 31V and it's only putting out 150W. And the optimizer voltage is of course at 16V.
    See here is the thing. The PV module is putting out much different so the optimizer has to use different circuits to regulate it
    Other optimizers are seeing 29V in and putting out 29V and about 9a
    This optimizer is seeing 31V in but only 4.8a and putting out 16V and ~9a


    Originally posted by library View Post
    * My panels are really two half panels in parallel. Maybe half the panel has a temperature related defect and for some reason this causes the optimizer to drop the voltage?
    Your PV module has a bad diod cutting the production by ~1/3 or a cross connect of the Duo sub panels either way the PV module is defective.
    To the optimizer it looks like a smaller PV module. The big clue is the output in watts of the optimizer, the voltage difference of the PV module (not the optimizer as it is working normally). It

    Originally posted by library View Post
    * Because this is my string of 14 (other string is 13) One of the optimizers has to have reduced voltage output to balance the strings for some reason?
    Nope, they do not balance the strings.

    Originally posted by library View Post
    * I got two bad optimizers in a row?
    unlikely I am surprised they even sent you a replacement. It looks like a bad PV module not optimizer.


    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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    • #3
      Originally posted by ButchDeal View Post
      Nope, they do not balance the strings.
      I don't believe that is correct. Though, in this case, I do agree, it sounds like he has a bad PV module.

      However, in normal operation, it would seem that the modules from two unbalanced strings would need to adjust voltage output so that the two strings balance. A string of 10 modules would output roughly 39v per optimizer and a string of 9 would output 43v each. I can't say for sure, since my system has 4 strings of 10, so all are equal, but I'm guessing this is what would happen. But, the balancing would be across all optimizers in the string, not just one.
      https://pvoutput.org/list.jsp?sid=54099

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      • #4
        Originally posted by NukeEngineer View Post

        I don't believe that is correct. Though, in this case, I do agree, it sounds like he has a bad PV module.

        Ho
        wever, in normal operation, it would seem that the modules from two unbalanced strings would need to adjust voltage output so that the two strings balance. A string of 10 modules would output roughly 39v per optimizer and a string of 9 would output 43v each. I can't say for sure, since my system has 4 strings of 10, so all are equal, but I'm guessing this is what would happen. But, the balancing would be across all optimizers in the string, not just one.
        They do not balance the wattage or amperage but the Voltage is balance (forced as the strings are tied together).
        The optimizers have buck-boost DC converters in them and one of the primary purposes of the optimizers is to provide consistent voltage to the inverter. But balancing the strings voltage is not a function of the optimizers since this happens mechanically from tying them together.

        but in this case you would not see ONE optimizer dropping the voltage a lot like this, but all a little, since they try to optimize the PV modules output.

        Here is the voltage output from four optimizers on two strings on the same roof face (the third string is facing north west)
        String 2 is in a row below string 1 so shadows effect it differently.

        These four modules are right next to each other but the strings are different lengths,
        string 1 (panel 1.1.14 & 1.1.15) is 18 modules
        string 2 (panel 1.2.1 & 1.2.2 ) is 12 modules
        string 3 (North West ) is 15 modules

        optimizer 1.2.1 is putting out more voltage but not consistently so and the optimizer is not individually trying to balance the strings just do the best production it can while keeping the inverter input at the voltage it wants.
        Optimizer 1.2.2 though puts out only slightly more than the string 1 optimizers and in the afternoon it puts out less voltage.


        Charts.jpg


        When you look at power for the same optimizers at the same time you see that they are fairly consistent (these modules are working correctly unlike the OPs) and indicative of a cloudy day...

        Charts2.jpg
        OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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        • #5
          Originally posted by ButchDeal View Post
          They do not balance the wattage or amperage but the Voltage is balance (forced as the strings are tied together).
          Yes, balance of voltage, not amperage or wattage, is what I was implying.
          https://pvoutput.org/list.jsp?sid=54099

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          • #6
            Originally posted by NukeEngineer View Post

            Yes, balance of voltage, not amperage or wattage, is what I was implying.
            right the voltage is balanced but not by the optimizers as the strings are directly tied together. They don't make any special effort or even have any programming to do this it just happens due to the electrical connection.

            But as OP was implying that ONE optimizer would drop out to balance the two strings, this is not the case. We have seen very imbalanced strings of 8 with two strings of 18, There is no one or two optimizers dropping voltage. Usually what happens is the smaller string ends up boosting the voltage to get to the inverters operating range.

            The optimizers have two main functions, MPPT and then buck/boost voltage to keep the inverter happy (with a third being send data, and 4th being rapid shutdown)
            They have no programming to balance the strings.
            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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            • #7
              I can address a couple things that were brought up.

              1) My bad optimizer/panel is putting out 16V but not 9A like you would think, at least not according to the solaredge monitoring. It only puts out 5A or so. Which makes no sense since solaredge monitoring also says it's putting out 160W and 16V * 5A == 80 watts. Maybe the low optimizer voltage is a red herring or reporting error? Something certainly isn't reporting correctly.

              My understanding of electricity is that each string is a series circuit. So by definition the the current must be equal among all devices but the voltage can vary. That would make sense as to why the voltage on the optimizer is dropping to compensate for the bad panel. It *has* to pump out 9A like the rest of the optimizers but to do that it drops the voltage since the panel cannot put out the same power as the other panels. That also means solaredge has a bug in their reporting/monitoring interface because the graphs clearly do not show that.

              Here's the optimizer voltage for the bad panel (1.1.5) and it's neighbor (1.1.6)

              Screen Shot 2018-05-18 at 9.06.57 AM.png

              And here's the current (amps) for the same pair.

              Screen Shot 2018-05-18 at 9.06.09 AM.png

              Finally the power output

              Screen Shot 2018-05-18 at 9.08.26 AM.png

              2) A bad panel diode is a failure I hadn't considered and I'm guessing it's one of the more common infant mortality problems with solar panels? It just seemed odd that the panel would be half alive but I suppose it makes sense.

              I'll be honest, I'm not looking forward to a panel RMA. I wish I'd just bought an extra panel when I was already paying freight shipping on the rest of them. Qcell seems to want a lot of documentation although this seems like a pretty open/closed case with the panel being faulty.

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              • #8
                Swap the optimizer and panel connections with a neighboring optimizer and panel. See if the lower wattage follows the panel or the optimizer. That will rule out the unlikely event of two bad optimizers.
                https://pvoutput.org/list.jsp?sid=54099

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                • #9

                  Originally posted by library View Post
                  My understanding of electricity is that each string is a series circuit. So by definition the the current must be equal among all devices but the voltage can vary. That would make sense as to why the voltage on the optimizer is dropping to compensate for the bad panel. It *has* to pump out 9A like the rest of the optimizers but to do that it drops the voltage since the panel cannot put out the same power as the other panels. That also means solaredge has a bug in their reporting/monitoring interface because the graphs clearly do not show that.


                  Try looking at the module voltage (module is the solar panel).


                  Originally posted by library View Post
                  2) A bad panel diode is a failure I hadn't considered and I'm guessing it's one of the more common infant mortality problems with solar panels? It just seemed odd that the panel would be half alive but I suppose it makes sense.

                  I'll be honest, I'm not looking forward to a panel RMA. I wish I'd just bought an extra panel when I was already paying freight shipping on the rest of them. Qcell seems to want a lot of documentation although this seems like a pretty open/closed case with the panel being faulty.
                  diode failure is indeed one of the most common failures of PV modules. you should be able to use the SolarEdge information to prove it to the manufacture and this is an early failure which is also common.
                  Last edited by ButchDeal; 05-18-2018, 11:42 AM.
                  OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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                  • #10
                    Agree with the above, swapping leads probably will verify a bad panel. My experience is, this is most likely
                    to show up under best sun and production conditions. On a DIY project, spare parts are a good idea.
                    Bruce Roe

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                    • #11
                      Originally posted by NukeEngineer View Post
                      Swap the optimizer and panel connections with a neighboring optimizer and panel. See if the lower wattage follows the panel or the optimizer. That will rule out the unlikely event of two bad optimizers.
                      This is where a set of 5' extension cables with MC-4 ends would really come in handy.
                      2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                      • #12
                        I will add, very bad to be breaking and making connections on substantial voltage DC circuits
                        under power. Even if you don't electrocute yourself, bad things could happen to the equipment.
                        All that work here is done at night, don't leave MC4s open to the elements. Bruce Roe

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                        • #13
                          Ah, ButchDeal, that makes more sense. So the Solaredge reporting is reporting the *module* amps/volts but just the optimizer voltage. Now all the math makes sense.

                          I submitted for my panel RMA. I'll swap the panel to a good location if I have to. With the optimizer swap I already did it's essentially the same thing.

                          Yes, I know how to work around electrical circuits. I have a thick blanket I throw over panels before connecting/disconnecting.

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                          • #14
                            Originally posted by library View Post
                            Ah, ButchDeal, that makes more sense. So the Solaredge reporting is reporting the *module* amps/volts but just the optimizer voltage. Now all the math makes sense.

                            I submitted for my panel RMA. I'll swap the panel to a good location if I have to. With the optimizer swap I already did it's essentially the same thing.

                            Yes, I know how to work around electrical circuits. I have a thick blanket I throw over panels before connecting/disconnecting.
                            With solaredge you do not need to use the blanket just use the rapid shut down on the inverter. With that you should have nothin over 36 volts.

                            bruce is talking about arcing damaging the connectors as well as potential hazard to you, though if you do the rapid shutdown procedure all should be good.
                            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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