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Grid tie inverter low power output.

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  • Grid tie inverter low power output.

    Hi, I have two free cracked 60 cell panels that were given to me, I've tested them and they seem to work fine, both have an open voltage of around 34V and both give me a short circuit amperage of aroun 8.5A.

    I ordered one of those chinese 600W grid tie inverters (GWV-600W) that has an input range of 22 to 60VDC and I connected the panels in parallel to the inverter. The problem is I've never seen it outputting more than 190ish watts when the sun is at it's highest with clear skies, I was expecting more of around 350W - 400W including losses.

    I thought that maybe there's a bad connection and only one panel is working, but at that moment I turned off the inverter and tested the panels again, there was a 32V open voltage and 14.4A combined short circuit amperage. So I was expecting that the inverter would at least put out 400W but it's producing less than half.

    I don't understand why. What I noticed was that when the inverter is working it reduces the panel voltage to around 24-25V.

    I tried connecting them in series but since the combined voltage is over 60V (around 64V) the inverter turns on the fault light and refuses to produce energy. Tried a boost converter within range but the inverter started cycling in and off as it was trying to find the MPPT.

    Other than replacing with another (and much more expensive inverter) is there anything else I can try? A 200+W difference of what the panels can do and what the inverter is doing seem very wastefull.

  • #2
    Hello t0nito and welcome to Solar Panel Talk

    Well first off those cheep Chinese "grid tie" inverters are illegal to use in the US as well as being of low quality. I expect you are seeing the results of poor workmanship and trashy manufacturing process. Of course the poorest result could be they short out and cause a fire so buyer beware.

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    • #3
      Lost in translation?
      Mandarin 600 Watts
      English 200 Watts

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      • #4
        Originally posted by t0nito View Post
        I ordered one of those chinese 600W grid tie inverters (GWV-600W)
        Is it this one? https://www.youtube.com/watch?v=Nr6U7IbaL-o

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        • #5
          Yes, but mine does not have that issue. Everything seem to work fine except for the lower than expected output, I've seen videos of it putting out more power with a single panel than mine with two of them.

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          • #6
            Perhaps your damaged panels are really bad, and their max power output is lower than nameplate ?
            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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            • #7
              Originally posted by t0nito View Post
              I don't understand why. What I noticed was that when the inverter is working it reduces the panel voltage to around 24-25V.
              Sounds like a bad inverter. I've compared a cheap Chinese inverter to a better one (a used Enphase) and the Enphase produced ~20% more power on the same panel.

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              • #8
                Today we're having cooler temperatures and some overcast, I don't know if it's due to the lower temperatures or if it's cloud edge effect but today I've seen it go upto 260W/270W, weird.
                Last edited by t0nito; 05-16-2019, 08:38 AM.

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                • #9
                  Originally posted by t0nito View Post
                  Today we're having cooler temperatures and some overcast, I don't know if it's due to the lower temperatures or if it's cloud edge effect but today I've seen it go upto 260W/270W, weird.
                  Perhaps it is both.

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                  • #10
                    Open circuit voltage and short circuit current aren't the same as an actual panel under load. Using shattered panels and cheap non UL listed inverters is a recipe for disaster.
                    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                    • #11
                      Originally posted by littleharbor View Post
                      Open circuit voltage and short circuit current aren't the same as an actual panel under load. Using shattered panels and cheap non UL listed inverters is a recipe for disaster.
                      True. You can have a cracked cell which will only deliver 1/2 normal current and the open circuit voltage will still be normal. And the short circuit current can also be normal because of the action of the bypass diodes. If you can measure the DC voltage and current while connected to the inverter you will get more information.
                      SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                      • #12
                        Originally posted by littleharbor View Post
                        Open circuit voltage and short circuit current aren't the same as an actual panel under load. Using shattered panels and cheap non UL listed inverters is a recipe for disaster.
                        Well unfortunately I'm not wealthy enough to buy high end equipement. I'm just trying to make use of those panels.

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                        • #13
                          Originally posted by t0nito View Post

                          Well unfortunately I'm not wealthy enough to buy high end equipement. I'm just trying to make use of those panels.
                          The amount of power you will generate is valued in cents per day, if you get this stuff working properly. Is it really worth it to risk property damage and personal injury/death in the event of a fire? Keep in mind that, in the event of a fire insurance companies will not cover the losses if it is found that this non UL listed, illegal inverter was the cause.
                          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                          • #14
                            As for not getting expected output...Ohms Law will never tell you a lie...or might just use the ole "s hit in equals s hit out "

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                            • #15
                              Originally posted by neweclipse View Post
                              As for not getting expected output...Ohms Law will never tell you a lie...or might just use the ole "s hit in equals s hit out "
                              In other words, if you have X number of Watts going in then if the output is less than X the difference in the output is loss due to poor efficiency (resistance) which probably shows up as heat. I use Watts because it is a calculation that accounts for differences in Voltage and Amperage between input and output.

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