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  • Charge Controller Upgrade

    I'm in the process of upgrading my 24 volt equipment. I have (9) 20v nominal 255watt panels on the roof currently wired in parallel going to a 80A PWM. I have purchased a MidNite Solar classic 150 controller and plan on wiring my panels 3x3.. A friend is going to help me with the panels and he is gone for 3 weeks. The question until he returns would it benefit me at all to go ahead and hook up the new controller?? Or should I wait until I have my panels reconfigured. Thanks

  • #2
    Originally posted by douglasjett View Post
    I'm in the process of upgrading my 24 volt equipment. I have (9) 20v nominal 255watt panels on the roof currently wired in parallel going to a 80A PWM.
    Huh? That would have never worked with a 24 volt battery. It takes a minimum of 32 volts for a 24 volt system. No need to answer your second question.




    MSEE, PE

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    • #3
      I know... I know.... It didn't work, the batteries failed.. That is why I got a new controller. So, will the MN controller get more watts down to run my appliances during the day? Or should I just wait until I can get the panels reconfigured... Thanks

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      • #4
        Originally posted by douglasjett View Post
        I know... I know.... It didn't work, the batteries failed.. That is why I got a new controller. So, will the MN controller get more watts down to run my appliances during the day? Or should I just wait until I can get the panels reconfigured... Thanks
        As currently wired it will not work with either charge controller.
        OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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        • #5
          Originally posted by douglasjett View Post
          I know... I know.... It didn't work, the batteries failed..
          Wait. There is no way to charge a 24 volt battery with 20 volt panels wired in parallel. Everything you did was wrong.

          MSEE, PE

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          • #6
            I know SunKing..... I didn't do it, it was sold to me like this. I'm fixing it. 1st I now have a MPPT controller. Then I'm going to have the panels wired 3x3... Then I'm going to buy brand new batteries and put it together properly. I currently get about 55-60A to the controller @ 26 Volts or so... Call it 1500W. Will I get more than 1500W If I hooked up the MPPT while I'm waiting for a rewire? The question has nothing to do with charging a battery... I know it's a strange question but I could use a more daytime juice for the next 3 weeks. I'm stuck in the Mexico desert and its HOT!

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            • #7
              Originally posted by douglasjett View Post
              I know SunKing..... I didn't do it, it was sold to me like this. I'm fixing it. 1st I now have a MPPT controller. Then I'm going to have the panels wired 3x3... Then I'm going to buy brand new batteries and put it together properly. I currently get about 55-60A to the controller @ 26 Volts or so... Call it 1500W. Will I get more than 1500W If I hooked up the MPPT while I'm waiting for a rewire? The question has nothing to do with charging a battery... I know it's a strange question but I could use a more daytime juice for the next 3 weeks. I'm stuck in the Mexico desert and its HOT!
              You will have to understand your charger limitations. Usually an MPPT type charger (like the Midnite Solar Classic) can handle up to a maximum panel wattage based on it's rated amp output.

              For a 12volt battery system - 1000 watts = 83 amps
              for a 24 volt battery system - 2000 watts = 83 amps

              So if you are getting about 60 amps out of 9 x 225 watt panels wired in parallel I say each panel has an Imp rating of 7 amps. Which is low for 225 watts because they would need to have a Vmp ~ 32volts (32v x 7a = 224watts). I think you may have a wiring issue.

              So what are the specs of those 225 watt panels and that 80A pwm CC.

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              • #8
                Originally posted by douglasjett View Post
                I know SunKing..... I didn't do it, it was sold to me like this. I'm fixing it. 1st I now have a MPPT controller. Then I'm going to have the panels wired 3x3... Then I'm going to buy brand new batteries and put it together properly. I currently get about 55-60A to the controller @ 26 Volts or so...
                OK here is what is bothering us. How can yxou get 26 volts from a 20 volt panel? You say you have 255 watt panels at 20 volts? That is not possible to my knowledge as that would be a 40 cell panel and there is no such thing. Take a look at your panels, find the nameplate, and look for

                Vmp =
                Voc =
                Imp =
                Isc =
                Pmax =

                With 9 panels you only have one configuration possibility of 3S3P. That is the very first thing you need to do and that should give you around 80 to 85 amps charge current.
                Last edited by Sunking; 06-09-2018, 09:58 AM.
                MSEE, PE

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                • #9
                  Thank You SunKing. Thats all I needed to know. I will wait until have the panels re-wired to install the CC.

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                  • #10
                    For the record these are the panels: http://www.solardesigntool.com/compo...ata-sheet.html

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