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  • What size Controller

    Hi All,

    Long time browser.... Love the site.

    I'm starting to plan the solar setup for our A Class RV

    6 Trojan T105 ( Have 2 in place already )
    2 Kyocera KU265 solar panels. possibly adding another 2 in the future
    Renogy 2000W 12V Pure-Sine Wave Inverter ( Already in place ) Possibly add a 2nd one in the future.


    Solar Panel Spec:
    • Number of Cells: 60
    • Tolerance: +5%/-0%
    • Vmp: 31.0 volts
    • Imp: 8.55 amps
    • Voc: 38.3 volts
    • Isc: 9.26 amps
    • Max system voltage: 1,000 Volts DC
    • 65.43" x 38.98" x 1.8"
    • 41.9 lbs.
    • Amphenol H4 locking connectors
    My question is...
    What size controller would be best, I'm looking at the morning star MPPT controller... but not sure what one... 30 / 45 or 60.

    Any other suggestions are very much welcomed


    Thanks
    Dave

  • #2
    Being an RV and likely remaining a 12 volt system, If you are thinking of adding 2 more 265 watt panels you will have 1060 watts in place. You need a 60 amp controller minimum and that may be pushing it . Probably better with an 80 amp Outback or Midnite Solar Classic 150.
    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

    Comment


    • #3
      Real easy for MPPT Controler. Output Current = Panel Wattage / Nominal Battery Voltage.

      You cannot use a PWM controller with those panels, It must be a MPPT controller, a real one that cost no less than $500. With 1060 watts is a 80 amp @ 12 volt battery $500 to $700 controller.

      Be very careful selecting MPPT controllers. You just went into sticker shock and will start searching for cheap MPPT controllers. Catch is they are Chi-Com fakes and are PWM controllers claiming to be MPPT. You are looking at Midnite Solar Classic 150 for around $600, and Outback FLEXMAX 80 for around $550. Take note they look almost identical because they are. Midnite Solar is just an improved Outback. Outback engineers left Outback and started Midnite Solar.
      Last edited by Sunking; 02-07-2016, 12:58 PM.
      MSEE, PE

      Comment


      • #4
        Originally posted by littleharbor View Post
        Being an RV and likely remaining a 12 volt system, If you are thinking of adding 2 more 265 watt panels you will have 1060 watts in place. You need a 60 amp controller minimum and that may be pushing it .
        BS, minimum is 80 amps with 1060 watts @ 12 volts. Max panel wattage on 65 amps into a 12 volt battery is 800 watts. Read the spec sheets.
        MSEE, PE

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        • #5
          Thanks for all the info !

          If i wired them in series & parallel making the input into the charge controller 24v. could i get a smaller than 80amp MPPT controller ?

          Comment


          • #6
            Originally posted by publin View Post
            Thanks for all the info !

            If i wired them in series & parallel making the input into the charge controller 24v. could i get a smaller than 80amp MPPT controller ?
            Regardless of how you wire the input to the MPPT CC, you cannot escape the fact that 1060 watts at 12V is more than 80A, and a lot more than 60A.

            If you do not care that you cannot use the maximum output of your panels, then you are free to use a smaller MPPT CC without any harm to CC or batteries.
            SunnyBoy 3000 US, 18 BP Solar 175B panels.

            Comment


            • #7
              Originally posted by inetdog View Post
              Regardless of how you wire the input to the MPPT CC, you cannot escape the fact that 1060 watts at 12V is more than 80A,
              Midnite Solar Classic 150 is 96 amps or 1380 watts input into a 12 volt battery running 90 VOC input. . 1060 watts / 12 volts = 88 amps. His panels will never generate more than 900 watts.

              Last edited by Sunking; 02-07-2016, 04:37 PM.
              MSEE, PE

              Comment


              • #8
                Originally posted by publin View Post
                If i wired them in series & parallel making the input into the charge controller 24v. could i get a smaller than 80amp MPPT controller ?
                Yes a 80 amp controller has the following maximum wattage input vs battery voltage.

                1000 watts @ 12 volts
                2000 watt @ 24 volts
                4000 watts @ 48 volts.

                The limit is based on battery voltage, not input voltage to the controller. You want to run input voltage as high as possible without exceeding the controller VOC input.

                The key is the Panels VOC and the controller maximum VOC input. Midnite Solar Classic 150 is 150 VOC plus Battery Voltage or 162 volts maximum input which means you can wire 4 panels all in parallel, 2 x 2 or all 4 in series, Having said that the most efficient and affordable configuration for you is 2 x 2. So wire your first two panels in series which gives you 76.6 VOC, When you get the 2 extra panel wire them in series and put them in parallel with your other 2 for a 2 x 2 config. That still leaves you with 76.6 VOC input into the controller. That will work with any true 80 amp MPPT controller as all of them are at least 150 VOC input. Some go as high as 600 volts. Yes 600 volts for a 12 volt battery.

                MPPT controllers are rated for output current at a specified BATTERY VOLTAGe. You are married to a ball and chain 12 volt system and limited to 1000 to 1380 watt input @ 12 volt battery depending on manufacture of the controller. Midnight Solar Classic 150 is 96 amps if you run 1380 watts with a panel voltage of 90 volts.
                Last edited by Sunking; 02-07-2016, 04:35 PM.
                MSEE, PE

                Comment


                • #9
                  The saving grace is that the panels on a RV roof, will seldom be at optimum angle, and will never generate their full power. A good controller will throttle back and preserve itself, cheap ones will BBQ themselves. The Midnight Classic and Morningstat MPPT-60 are pretty robust and can be overpaneled a bit.
                  Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                  || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                  || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                  solar: http://tinyurl.com/LMR-Solar
                  gen: http://tinyurl.com/LMR-Lister

                  Comment


                  • #10
                    Originally posted by Mike90250 View Post
                    The saving grace is that the panels on a RV roof, will seldom be at optimum angle, and will never generate their full power. A good controller will throttle back and preserve itself, cheap ones will BBQ themselves. The Midnight Classic and Morningstat MPPT-60 are pretty robust and can be overpaneled a bit.


                    Careful what controller you recommend, You might get the BS card thrown at you.
                    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                    Comment


                    • #11
                      Originally posted by littleharbor View Post
                      ​ Careful what controller you recommend, You might get the BS card thrown at you.
                      I own both, no bs
                      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                      solar: http://tinyurl.com/LMR-Solar
                      gen: http://tinyurl.com/LMR-Lister

                      Comment


                      • #12
                        Originally posted by Sunking View Post

                        Yes a 80 amp controller has the following maximum wattage input vs battery voltage.

                        1000 watts @ 12 volts
                        2000 watt @ 24 volts
                        4000 watts @ 48 volts.
                        Quite true, but the way I read the OP's post he wanted to know whether he can keep his 12V battery and still use a smaller than 80A CC just by playing with the panel arrangement.

                        The body of your answer is just fine, but the initial "Yes" is not an answer to his question.
                        SunnyBoy 3000 US, 18 BP Solar 175B panels.

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