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Using 2 panels on one micro inverter (numbers not adding up)

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  • #16
    To get back on topic. The question from the OP is why is the wattage of 2 panels wired to a single micro not adding up to what they expect.

    While the input to the IQ7+ allows up to 440watts why is it only showing less then 300w when over 400watts are being inputted to it?

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    • #17
      Originally posted by SunEagle View Post
      .........
      While the input to the IQ7+ allows up to 440watts why is it only showing less then 300w when over 400watts are being inputted to it?
      We don't know if 400 Watts are being inputted to the IQ7. It could be the two panels in series are the issue like PV Andy asked. Perhaps the voltage is out of the range of the inverter and the MPPT algorithm is not able to optimize the output?
      Someone did suggest putting the panels in parallel but that may put the current out of range.
      Last edited by Ampster; 08-08-2020, 09:54 AM.
      9 kW solar. Driving EVs since 2012

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      • #18
        Originally posted by Ampster View Post
        We don't know if 400 Watts are being inputted to the IQ7. It could be the two panels in series are the issue like PV Andy asked. Perhaps the voltage is out of the range of the inverter and the MPPT algorithm is not able to optimize the output?
        Someone did suggest putting the panels in parallel but that may put the current out of range.
        Agree. The IQ7+ may see the panels wired in series much differently then wired in parallel. I am hoping for someone else that uses the IQ7+ equipment chime in.

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        • #19
          I use some IQ7+ and specifically chose that model because it is designed for the higher voltage of 96 cell panels. However as I reread his post it was a prospective question based on his interpretation of the AC output. He did not compare the voltage of two panels in series to the voltage spec of IQ7s as you suggested earlier.
          In my case I will never approach the max output of the IQ7s because they are powered by used Sunpower 305 Watt panels that are west facing in a sub optimal orientation.





          9 kW solar. Driving EVs since 2012

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          • #20
            I looked up the specs of the IQ-7+ and it clearly states that the maximum continuous power output is 295 Watts. That means a DC to AC ratio of 1.35 to 1 if the OP uses two panels per inverter. I would be curious what the cost benefit would be of using one panel with less expensive reqular IQ-7 versus two panels with more expensive IQ+7+ with clipping.

            My system was designed with a ratio of 1.5 to 1 and it performs to the PV Watts model and installer's estimate.
            Last edited by Ampster; 08-08-2020, 07:18 PM.
            9 kW solar. Driving EVs since 2012

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            • #21
              Originally posted by Ampster View Post
              I looked up the specs of the IQ-7+ and it clearly states that the maximum continuous power output is 295 Watts. That means a DC to AC ratio of 1.35 to 1 if the OP uses two panels per inverter. I would be curious what the cost benefit would be of using one panel with less expensive reqular IQ-7 versus two panels with more expensive IQ+7+ with clipping.

              My system was designed with a ratio of 1.5 to 1 and it performs to the PV Watts model and installer's estimate.
              Thanks for the update. At least that should provide the OP with some data to make a decision to maybe not use 2 panels wired to a single IQ7+.

              Strange that the spec indicate a maximum input of 440watts but only a 295w output. Seems like a waste of panel wattage.

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              • #22
                Originally posted by SunEagle View Post
                ............
                Strange that the spec indicate a maximum input of 440watts but only a 295w output. Seems like a waste of panel wattage.
                At the risk of hijacking this thread into a discussion about clipping, high DC to AC ratios are a more common aspect of system design.They have gone unnoticed in the microinverter environment because the shape of the production curve may be less pronounced than that of a string inverter. High DC to AC ratios don't get that much comment until someone sees the results in term of a "Fez" shaped curve instead of the "somewhat" sinusoidal curve that they expect. They feel gyped, but the result of higher DC to AC ratios result in a steeper ramp up and a longer production period than with less capacity in panels. For sure, just increasing the inverter size would give more overall production but in this case that would double the amount of inverters to get a marginal increase. It may not be cost effective and it is not a simple calculation for many because it reminds them of their calculus teacher in high school.
                Ironically the comment of @gbynum did offer a solution because with two panels on one microinverter with different orientation one could avoid the clipping and possible increase the amount of total production from that inverter. That is essentially what Bruce Roe has done with his multiple orientations. Conceptually it would be harder to do with micro inverters with paired panels but one could imaging them on a ridge contiguous to each other one slightly south east and the other slightly southwest. As the cost of panels has come down these kind of outside the box ideas seem to have a life of their own.
                Last edited by Ampster; 08-09-2020, 12:16 PM.
                9 kW solar. Driving EVs since 2012

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                • #23
                  Originally posted by Ampster View Post
                  I use some IQ7+ and specifically chose that model because it is designed for the higher voltage of 96 cell panels. However as I reread his post it was a prospective question based on his interpretation of the AC output. He did not compare the voltage of two panels in series to the voltage spec of IQ7s as you suggested earlier.
                  In my case I will never approach the max output of the IQ7s because they are powered by used Sunpower 305 Watt panels that are west facing in a sub optimal orientation.




                  I might be wrong but IQ7+ cannot handle voltage of Panasonic panels. The spec has 60V max DC voltage for + and 80V for X. Most 60 cells panels will have more than 60V for 2 connected in series.

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