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  • #31
    Originally posted by teknatronik View Post
    Hello, im back
    So I seem to lose about 100 watts from each 255 watt panel

    i have 10 set direct bury wire in a 60ft run. Im 24 volt and have 4 255 watt panels . I caollect about 600 watts on a good day.


    I checked each panel and they watt out roughly the same. 155 watts each is what they show at c.c .

    I run them in series as it seems to work the best. I also do not have a combined box.

    What can i do to get my extra juice?
    It sounds like the panels are not getting the full amount of needed sunlight to produce more wattage.

    It really depends on where you are located and what angle the panels are facing. But even if you are at the Equator with total sunshine those panels may not provide more then 90% of their nameplate wattage. That 255 watts is really Lab results and not true field results.

    Your system may also have wire that is too small to stay below the 2% voltage drop. Your system will lose if it is not properly wired or if you have a inefficient charge controller.
    Last edited by SunEagle; 12-05-2018, 12:37 PM. Reason: added last sentence

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    • #32
      What charge controller are you using? Sounds like a PWM controller from your statement about working better in parallel.
      2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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      • #33
        Originally posted by teknatronik View Post
        Hello, im back
        So I seem to lose about 100 watts from each 255 watt panel

        i have 10 set direct bury wire in a 60ft run. Im 24 volt and have 4 255 watt panels . I caollect about 600 watts on a good day.


        I checked each panel and they watt out roughly the same. 155 watts each is what they show at c.c .

        I run them in series as it seems to work the best. I also do not have a combined box.

        What can i do to get my extra juice?
        How are you figuring how much irradiance is available when you're measuring ~ 155 W/panel ?

        The array's output will always be less than 255 * 4 = 1,020 W. Probably no better than 85 - 90 % or less of that number even under ideal conditions, even with the direct normal incidence angle == zero, that is, when the sun's rays are perpendicular to the plane of the array.

        If the POA irradiance is less than the rated STC irradiance (which is most all of the time) when you are reading 600 W output, the output will be less than STC output.

        You may have problems, but expecting 255 * 4 W output will not happen except maybe on very rare occasions if for no other reasons than the POA irradiance will almost never be 1,000 W/m^2.

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        • #34
          I have the energy mppt40 commander..

          I was expecting about 800 watts tbh.

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          • #35
            Sun Eagle, I am in south carolina, anderson. The sun does move a lot in the sky depending on season. I move my panels to fit that best I can.

            Littleharbor, it is mppt. I actually think the panels collect more in series vs par. I might have worded wrong earlier.

            Jpm, I am not checking irradiance as far as i know. I am hooking the panels up and looking at the info on the cc. The panels are 255, I expected 200 watts from them I figure with distance and all a 55 watt loss is not bad. 100 watts per panel seems a bit much. That is just my own opinion though.

            If wire size is an issue, should I just go to 8 awg?

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            • #36
              Originally posted by teknatronik View Post
              I have the energy mppt40 commander..

              I was expecting about 800 watts tbh.


              You should be wired 2s2p to get the voltage higher for that long wire run. Why do you think it works better wired up in parallel? Incoming amps will look higher in an all parallel configuration but That doesn't mean you're getting the best charging efficiency. The MPPT controller does the voltage conversion and will boost incoming amps when it matches your charging voltage.
              Last edited by littleharbor; 12-05-2018, 01:18 PM.
              2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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              • #37
                I do not think its work better in par.

                From my tests, it works way better in series.

                I would wire in 2s 2p, but no combiner box yet. However, when I tie right into my charge controller with the 2p2s It doesnt seem to charge the battery as fast.
                Last edited by teknatronik; 12-05-2018, 01:15 PM.

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                • #38
                  Originally posted by teknatronik View Post
                  I do not think its work better in par.

                  From my tests, it works way better in series.

                  I would wire in 2s 2p, but no combiner box yet. However, when I tie right into my charge controller with the 2p2s It doesnt seem to charge the battery as fast.
                  Wiring 2s 2p may not produce a voltage high enough for a 24v battery system if the wire run is long and the voltage drop is high. Going all 4 in series gets you the highest voltage to the CC which will convert almost 100% of the panel wattage to charging amps.

                  Something else may be a factor. Batteries that are close to full SOC will not accept more amps then needed. So the CC actually throttles back the amount of amps going to the battery which makes it look like your panels are not producing as much as you expect.

                  One way to test that is to discharge your battery system SOC to 50% and then see what the output of those panels are around Noon time under a clear sky. I expect the output wattage will be higher then that 600w you are currently getting from your 1000w system.

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                  • #39
                    Originally posted by SunEagle View Post

                    Wiring 2s 2p may not produce a voltage high enough for a 24v battery system if the wire run is long and the voltage drop is high. Going all 4 in series gets you the highest voltage to the CC which will convert almost 100% of the panel wattage to charging amps.

                    Something else may be a factor. Batteries that are close to full SOC will not accept more amps then needed. So the CC actually throttles back the amount of amps going to the battery which makes it look like your panels are not producing as much as you expect.

                    One way to test that is to discharge your battery system SOC to 50% and then see what the output of those panels are around Noon time under a clear sky. I expect the output wattage will be higher then that 600w you are currently getting from your 1000w system.


                    His controller has a 100 VOC limit .These panels will come in with over 140 volts, open circuit.
                    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                    • #40
                      Originally posted by littleharbor View Post



                      His controller has a 100 VOC limit .These panels will come in with over 140 volts, open circuit.
                      Shoot. I missed that. Thanks for the info. It looks like 4s will not work for that CC.

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                      • #41
                        Originally posted by teknatronik View Post
                        Jpm, I am not checking irradiance as far as i know. I am hooking the panels up and looking at the info on the cc. The panels are 255, I expected 200 watts from them I figure with distance and all a 55 watt loss is not bad. 100 watts per panel seems a bit much. That is just my own opinion though.
                        You will only measure irradiance with a pyranometer.

                        The point is that you will only get about 85-90 % of the panels' STC output under the best of conditions that rarely occur. Anything less than ideal conditions will reduce output even more, and even less yet if the panels are not aimed directly at the sun.

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                        • #42
                          My c.c. is 150volt. I run 130 into it.

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                          • #43
                            Originally posted by teknatronik View Post
                            My c.c. is 150volt. I run 130 into it.
                            The one I looked up had 100 Voc. limit, various models under that name I think. Anyway 4 in series isn't advisable with 255 watt panels, knowing typical Voc. and Vmp. of this size panel..When you say you run 130 volts into it, is this working voltage, or rated Voc.?
                            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                            • #44
                              I might have given wring name for c.c. its def 150 volt. Its working volts .The rated per panel is 37...

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                              • #45
                                The voltage limit relates to the sum of the Voc. which will be higher than the Voc. number on the panel, in very cold conditions.
                                2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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