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  • Solar for freezer

    I ordered a 24v DC powered freezer along with solar modules, batteries and controller a year ago but I'm just now getting around to installing the panels. I got the freezer with the 120v AC option so it's been humming along just fine but I wanted to make sure I had power to the freezer in case there was an extended power outage. My question is this. When I ordered the system I explained that this was for off-grid use and in fact got a quote for a turn key system for off-grid. Just checked the panels (24v DC 60 cell 255 watt) and they are rated at 30.5v Vmp. Will they charge my batteries? After doing some research it appears that these panels are for grid tie applications and not for off-grid. Did they send me the wrong panels?

    (2) 24v 255 watt solar panels
    (4) 12v Trojan batteries T-1275 150 AH
    Morningstar TS-MPPT-45 charge controller

  • #2
    The terms "Grid Tie" and "off grid" when related to solar modules is not really accurate. It just means that the voltage is higher and you will need an MPPT charge controller which it looks like they sent you.
    Last edited by ButchDeal; 10-13-2016, 11:44 AM.
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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    • #3
      You have an MPPT charge controller so wire the 2 panels in series.

      WWW

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      • #4
        Sounds like a nice little "off grid" system. What was the approximate cost for it?

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        • #5
          Originally posted by Wy_White_Wolf View Post
          You have an MPPT charge controller so wire the 2 panels in series.

          WWW
          So if I wire the 2 panels in series I get 61v Vmp ? The ratings for the charge controller are max 150 volt dc solar power input so that should work ok. Thanks!

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          • Wy_White_Wolf
            Wy_White_Wolf commented
            Editing a comment
            Yes. But for the calculation you should use the VOC of the panel and compensate for high-lite conditions. Usually about 125%. So the calculation should be VOC*2*1.25

            You'll be OK though as they should have run those numbers when they designed the system.

            WWW

        • #6
          Originally posted by SunEagle View Post
          Sounds like a nice little "off grid" system. What was the approximate cost for it?
          I don't recall. I got the Sundanzer 8 cu ft freezer for $1245 plus shipping. I ended up getting the batteries and charge controller locally.

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          • #7
            Wy_White_Wolf

            Yes. But for the calculation you should use the VOC of the panel and compensate for high-lite conditions. Usually about 125%. So the calculation should be VOC*2*1.25

            VOC is 37.6v x 2 x1.25 = 94v Is that correct?

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            • Wy_White_Wolf
              Wy_White_Wolf commented
              Editing a comment
              Yep!
              ......

              WWW

          • #8
            Have the batteries been on at least a maintenance charge up until now?
            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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            • #9
              Yes. But for the calculation you should use the VOC of the panel and compensate for high-lite conditions. Usually about 125%. So the calculation should be VOC*2*1.25
              Actually strong light will produce more current, but not higher voltage.
              It is low temperature that raises the panel voltage.
              If you know in detail the possible ambient temperatures you can do a more exact calculation using the panel data. 125% is a conservative figure if you have no information.
              Last edited by inetdog; 10-13-2016, 12:50 PM.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

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              • #10
                Originally posted by littleharbor View Post
                Have the batteries been on at least a maintenance charge up until now?
                Yes. Battery Tender.

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