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  • Compatibility of a 24V panel with a 12V battery

    I have brought a 245 watt solar panel solar panel the specifications of which can be obtained from http://www.dmegcsolar.com/download/P156-60.pdf The panel no is DM245-P156-60. Now I need a MPPT controller which can charge a 150 Ah Tubular battery. I stay in India. This is a 24 v panel. Can it be used to charge a 12V battery? I am choosing Steca PR 1515, which is attached as an attachment. Another choice is Steca Solarix MPPT 1010. I have attached both the specifications. The company representative is telling me that these cannot be used to charge a 12V battery. You have to upgrade battery to 24 Volt. Is this true ? I am thinking of using a DC to DC voltage convertor that can bring the panel voltage to be compatible with 12 V. Is this OK ? Out of the two options which one shall be O.K. ? I have also attached circuit diagram of a PWM controller. What modifications have to be made to support my panel and my battery ?
    Attached Files

  • #2
    welcome. The panels you mention, produce their max power, at about 29V. You could use them to charge a 12V battery with any common PWM controller, but you would waste about 50% of the panel power. (8 amps x 14V = 112 watts). To get the max power out of them, you need any reliable MPPT controller, which has the built in DC - DC convertor.
    I don't open attachments, so I cannot comment on your controller choice, a link to the Steca site would have been helpfull.
    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


    • #3
      Originally posted by banerjee_saikat View Post
      I have brought a 245 watt solar panel solar panel the specifications of which can be obtained from http://www.dmegcsolar.com/download/P156-60.pdf The panel no is DM245-P156-60. Now I need a MPPT controller which can charge a 150 Ah Tubular battery. I stay in India. This is a 24 v panel. Can it be used to charge a 12V battery? I am choosing Steca PR 1515, which is attached as an attachment. Another choice is Steca Solarix MPPT 1010. I have attached both the specifications. The company representative is telling me that these cannot be used to charge a 12V battery. You have to upgrade battery to 24 Volt. Is this true ? I am thinking of using a DC to DC voltage convertor that can bring the panel voltage to be compatible with 12 V. Is this OK ? Out of the two options which one shall be O.K. ? I have also attached circuit diagram of a PWM controller. What modifications have to be made to support my panel and my battery ?
      The PR1515 will work to charge a 12 volt battery, but as Mike said, you will only get 8 amps of current to the battery, wasting half of your panel power.
      The MPPT 1010 will work better, but will only give you a maximum output of 10 amps, only a 25% increase over the PR.
      If you go with the MPPT 2020, will be able to use the full power of your panel and will give you about 17 amps charging current at maximum.
      (In real life, the output of the panel may be only about 75% of the rated wattage most of the time, so all of the amperages should be scaled back a bit, but the comparison ratios will remain the same.)

      If instead you buy a second matching battery, you will be able to use almost the full panel power with the PR1515, and just a bit closer to full power with the MPPT1010. You would not need to go to the MPPT2020 in that case.

      The Vmp of the panel, at 30 volts, will be a little on the low side for charging a 24 volt battery (it is at the very lower limit for the MPPT1010 and 2020.) And the voltage will be reduced as the panel gets hotter, so I would not be completely comfortable going that route.

      [Mike: The attachments (pdfs) look clean, if that makes any difference to you.]
      SunnyBoy 3000 US, 18 BP Solar 175B panels.

      Comment


      • #4
        Requirement of MPPT 2020

        Where can i get this charge controller in south india ?

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        • #5
          I am using Tracer 1206 for charging my 12V Battery.

          Well for my 12V Tubular battery the charge controller that i am using is http://www.epsolarpv.com/en/uploads/...1761387257.pdf This is china made but relatively cheap. Well my battery is 150 Ah Tubular. Now the problem is the current that i am getting from the charge controller is starting from 1 Amp around 8:00 A.M. in the morning increases to max 5.5 amps from 11:00 A.M. stays upto 1:00 P.M. then again starts decreasing after 5:00 P.M. becomes less than one amps. sun sets at 7:00 P.M. and rises at 6:00 A.M. This charging current is not sufficient to charge my batteries. Moreover since my house runs on AC I am using my old Genus Sure sine wave 600 VA inverter to run my appliances. I use a toggle switch to switch between inverter and charge controller. This is harming my battery as it is not getting equalizing charge. Well the solar charge controller could not charge my battery. What am i suppose to do ? I am attaching the manual of my charge controller
          Attached Files

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          • #6
            your charge profile (1a - 5.5a - 1a) tracks pretty close to the daily solar output. Why you are not seeing any MPPT effect, or why you are not getting even half of the PV panel power, I cannot explain, other than the controller may be defective.
            Try bypassing the controller at noon, and see what your charge power is at that time, you will need an ampmeter to read the charge current, as you will bypass the controllers meter.

            You will have to manage your daily loads, to be less than your daily harvest, because there are charging losses in any PV system. Also, if the angle & tilt of the panel are less than perpendicular, you will have reduced harvest.
            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


            • #7
              Mike listen to this

              Mike the problem is my panel is of 24 Volt while battery is 12 volt. Now the charge controller has the power of V1 x I1 = V2 x I2. Where 1 and 2 are input and output respectively i.e 1 is of the panel 2 is for the battery.. It lowers the V1 to about 17 or 16 volts to get 5.5 amperes. Unfortunately My panel is situated at 7th floor while i stay at 3rd floor . A long wire connects the panel to the controller. See if this helps to solve the problem.

              Comment


              • #8
                I understand how a MPPT controller is supposed to work. I also suspect your controller is not functioning properly, and/or the panel is not aimed properly.

                Until you limit your loads to the power you are able to harvest, deeply discharging your batteries will ruin them.
                Last edited by Mike90250; 05-06-2013, 06:07 PM.
                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


                • #9
                  Dear mike

                  Dear Mike I am attaching a photo of my system. The small box is the MPPT controller. Now my battery can be either connected to the controller or to the invertor depending on a toggle switch. my panel is kept absolutely flat. its max current according to the manual which i have attached is 8 amps for 24 volts. Now my battery is 12 volts. also i use a very long wire app 45 meters to connect my panel to controller ? are these causing problems ? Kindly go through the manual of the panel and the charge controller.
                  Attached Files

                  Comment


                  • #10
                    A panel mounted flat on a roof, will never produce it's full power because:
                    1) needs several inches of clearance for cooling. hot panels produce lower power
                    2) when the panel is off-axis from the sun, it will not produce full power.

                    Long wire runs need large gauge conductors to reduce power loss. Look back to my .sig, there is a link
                    to a spreadsheet based wire voltage drop calculator there, and there are many on the web.
                    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


                    • #11
                      Flat Panel

                      The panel has approximately 3.75 cms clearance from ground but is perfectly flat so that the sun is perpendicular to it at approximately 12 Noon. Shall I increase the inclination ? What other measures can I take ?

                      Comment


                      • #12
                        The panel has approximately 3.75 cms clearance from ground but is perfectly flat so that the sun is perpendicular to it at approximately 12 Noon. Shall I increase the inclination ?
                        Set the inclination so that at solar noon, the panel is Perfectly Perpendicular. If you still cannot get 80% of rated panel power, you will have to perform a Isc test at noon, to see if the panel is bad.
                        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


                        • #13
                          Originally posted by Mike90250 View Post
                          Long wire runs need large gauge conductors to reduce power loss.
                          But in your case, the power lost in the wire run will still not reduce the current through the PWM controller very much. You are in a current region (between Vmp and 0 Volts) where the current does not change rapidly with voltage at the panel.
                          SunnyBoy 3000 US, 18 BP Solar 175B panels.

                          Comment


                          • #14
                            I tried to do the Isc test

                            Mike I tried to do the Isc test by placing a multimeter in between the two pins of the plug but it only sparked but showed no reading. Pits developed on the metal piece of plug. How do you do Isc test ? What current do you expect with MPPT controller ?

                            Comment


                            • #15
                              Originally posted by banerjee_saikat View Post
                              Mike I tried to do the Isc test by placing a multimeter in between the two pins of the plug but it only sparked but showed no reading. Pits developed on the metal piece of plug. How do you do Isc test ? What current do you expect with MPPT controller ?
                              You do not test the MPPT, you test the panel. If you tested the MPPT controller and shorted it out you could have damaged it. There is a Sticky that tells you how to test ISC. Find it.
                              MSEE, PE

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