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  • New to solar

    Hey, I'm Mike and I'm new to solar system design, and understanding specs etc. I am a neon sign maker and glass artist by trade so I understand some things about electricity and I have wired my own buildings and properties for most of my life. I have been studying solar wiring and systems and found there is quite a bit of variation in what there is out there to use. One issue I am having and have not found an answer to is how my 4 new HQST 190watt 12 volt panels are rated at 2xs that voltage and when I hook them up to a volt meter they product 27volts and change...I did search the forum for an answer to this question but did not find an answer.
    Any help to point me to an explaination would be much appreciated.
    Thanks,
    md

  • #2
    Most 36 cell panels put out approx. 21 volts open circuit (voc) and about 18 volts under load (vmp). This has been considered a 12 NOMINAL panel because when crystalline panels get hot the voltage will fall below those numbers. When charging your batteries you need higher voltage to push the current into the battery. When equalizing a 12 volt battery bank you need up to and even above 15 volts. If a panel is real hot you may not get more than 16 vmp out of it . So that is why you see higher voltage when testing your open circuit panel.
    As solar cells have increased in efficiency they have also have put out higher voltages. The highest power 12 volt "nominal" panels have this extra high voltage you are seeing..
    With todays MPPT controllers Voltage isn't as critical in an individual panel any more due to now wiring in series to achieve high voltage for the MPPT controllers to process.
    2 Kw PV Classic 200, Trace SW 4024 460ah,

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    • #3
      Since HQST does not have a contact phone number for customers to ask these questions I was at the mercy of email and their response time. Thank you for your answer. I think that I understand that as long as I am using an MPPT controller the voltage spike or drop should not matter from the perspective of overkill from the panels voltage production. Does that sound correct or did I miss the facts?

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      • #4
        Originally posted by MDanapas View Post
        Since HQST does not have a contact phone number for customers to ask these questions I was at the mercy of email and their response time. Thank you for your answer. I think that I understand that as long as I am using an MPPT controller the voltage spike or drop should not matter from the perspective of overkill from the panels voltage production. Does that sound correct or did I miss the facts?
        You are correct. The beauty of MPPT controllers is they are pretty much Watts in = Watts out. If you were using those panels with a PWM type controller. you would be losing a good percentage of the panels output. You only get the current output 9.6 amps @ the battery voltage 13.6 average, = 130.56 watts.
        2 Kw PV Classic 200, Trace SW 4024 460ah,

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