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  • Problem with 2 solar panel hookup.

    Hello there.. And thank you for helping with my problem. I am new to solar and am trying to put together a small system for my travel trailer. Mostly to keep the batteries fully charged during a weekend of boondocking.

    Here is my current setup.

    ​​​​​​2 x 100 watt ETFE flexible solar panels..
    Panel specs: 100w., open voltage 21.2, vmp 17.6V. Imp 5.68A

    Victron smartsolar mppt controller 75/15
    2 x brand new 6 volt rv batteries.
    20 amp breaker between controller and batteries.

    Here is the issue I am having. All testing done around noon in fully sunny skies, with not haze or cloud cover.

    During testing of these panels, if I connect either single panel to the controller, and to the batteries.. The result isnt far off the specs for the panel. Around 70-85 watts, 16.5V +/- 1 , 4.5-5.1 amp to the controller. ( based on the victron controller readings.).

    The problem lies when I connect the panels together In series to the controller. I end up with 68 watts 35-37V. But only 1.6-2.0 amps. To the controller.

    I understand the voltage seemingly is correct, but should the watts not be up around 150-175 or hugher, and the amps not be around the same 4.5-5.5 range?

    At this point it is better to have just a single panel connected as the amps stay up around 4.5+ range

    Please help me!


    ​​​​​​

  • #2
    Try again, but this time, before you measure the controllers output current, throw a heavy load on the batteries, if the batteries are full, the charge controller won't be doing much.
    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
      Hey thanks Mike!

      Ill try it.. But I am not sure that is the issue.


      My concern is more having to do with the power from the panels to the controller. As opposed to the power from the controller to the batteries.

      If the battery is full or drained Down.. It shouldn't affect the power to the controller from the Panels should it?

      As if I hook a either single panel up the watts, current and volts all show as they should. It is onky when Hooked together in series that the amps and watts drop from the panels to the controller.

      Thanks again for any help

      Comment


      • #4
        > As if I hook a either single panel up the watts, current and volts all show as they should.
        > It is onky when Hooked together in series that the amps and watts drop from the panels to the controller.

        Don't know what to say. First thoughts
        a) Wiring error/bad connector or cable mis-marked cable somewhere
        b) Exceeding the VOLTAGE input limit to the controller
        c) exceeding the output (battery side) limits of the controller
        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


        • #5
          These controlers have the ability to limit the output amps . Default should be 15a, have a look in the battery setting menu of the controler and see if is set to a lower value. If it is, then no matter how many panels you conect, the controler will limit its output to the setting value.
          Try connecting the panels in paralel aswel and see if any diferent.

          Comment


          • #6
            Good afternoon.. Thanks for the reply fellas..

            Raul: The issue is current form the panels to the controller, not the output current from the controller to the batteries.

            Mike: I double checked the cables, and they are all fine. I am fairly sure that I am not exceedingly the limit of the controller as it is good for 75 volts. and 15 amps. I am only giving it 36-37 volts input with 2 panels.

            Is it possible it has something to do with a bypass/blocking diode on the panel being incorrect? I think that could be an issue why this only happens when the panels are combined together. But I am not sure if that was the case why the voltage would still read as 36-37 volts like it is getting power from both panels, just little current.

            Here is a picture and a link to a video to show what is happening

            https://youtu.be/ER4kb-KIYLY



            Comment


            • #7
              I believe the current from the panels should be around 4.5-5.5 and the watts hovering around 150-180 when in series, or am I mistaken?

              Or is it something simple, like my batteries are full and it isnt requiring any current?

              I dont have my trailer here to hook it up, how do I place a load on to see if the current increases? Pretty sure a light bulb wont work unless i go buy 12v bulbs?

              Thanks
              Last edited by CanadianEhh; 07-07-2018, 09:16 PM.

              Comment


              • #8
                I see you're in absorb mode which will gradually decrease current when approaching full. If you have an inverter running in the system turn it on and connect a blow dryer or curling iron if you have one available. Otherwise just turn on all dc lights, fans and what ever you can. If your current doesn't jump up to something around 7.5 - 9 amps, midday, then you definitely have a panel/connectivityproblem. BTW have you tried connecting both panels individually. They both act normal when charging?
                Last edited by littleharbor; 07-07-2018, 10:45 PM.
                2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                Comment


                • #9
                  Originally posted by littleharbor View Post
                  I see you're in absorb mode which will gradually decrease current when approaching full. If you have an inverter running in the system turn it on and connect a blow dryer or curling iron if you have one available. Otherwise just turn on all dc lights, fans and what ever you can. If your current doesn't jump up to something around 7.5 - 9 amps, midday, then you definitely have a panel/connectivityproblem. BTW have you tried connecting both panels individually. They both act normal when charging?

                  Yup, If they are connected each on their own and not in series, they both individually produce 4-5 amps and around 17-18 volts . The problem is only when connecting together.

                  I don't have an inverter for testing, and the trailer is currently out at storage. Any other way to rest?

                  Comment


                  • #10
                    The only thing I can think of is that when you have both panels connected in series is that one is being shaded and causing the current of the string to drop. Are you sure there is NO shading when both are connected?

                    Not knowing what "out at storage" means, that doesn't help.. I suggested turning on all DC loads. Does "out at storage" include being in full sun, with no shadows?
                    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                    Comment


                    • #11
                      Originally posted by littleharbor View Post
                      The only thing I can think of is that when you have both panels connected in series is that one is being shaded and causing the current of the string to drop. Are you sure there is NO shading when both are connected?

                      Not knowing what "out at storage" means, that doesn't help.. I suggested turning on all DC loads. Does "out at storage" include being in full sun, with no shadows?
                      He little harbour. Thanks for the help..


                      What I mean is.. My solar, battery and controller setup are not in or on my trailer, I am just testing it at home. . The city I live in doesn't allow parking your traavel trailer or RV on your driveway. So we park it at an RV storage yard about 30 mins away from my house. So I do not have it available to connect the solar and batteries to to test it.

                      Forsure no shading on one panel. If you watch the video link I posted a few posts up. ( right above the picture I posted) you'll see the setup and how it was tested in full sun, no haze.

                      Comment


                      • #12
                        According to the Bluetooth app photo you provided, connected in series voltage did increase .amperage is at 4.6 like it shows. The victron display shows how much the panel is putting out, but also that 4.6 amps is how much is being sent to the batteries. I have the similar model, and still haven't figured out how the panel amperage fluctuates different from the what's going to the battery amperage . To paraphrase the display shows two different amperages it's putting out. And like they've been saying if you don't have a load hooked up you won't know much wattage is capable of being produced

                        Comment


                        • #13
                          Originally posted by Brian53713 View Post
                          According to the Bluetooth app photo you provided, connected in series voltage did increase .amperage is at 4.6 like it shows. The victron display shows how much the panel is putting out, but also that 4.6 amps is how much is being sent to the batteries. I have the similar model, and still haven't figured out how the panel amperage fluctuates different from the what's going to the battery amperage . To paraphrase the display shows two different amperages it's putting out. And like they've been saying if you don't have a load hooked up you won't know much wattage is capable of being produced
                          I belive that isnt right either based on the information I have gathered thus far. BThe input from the panels should be around 4-5 amps at 37 volts and the The current output should be up around 9-10 amps to the batteries with that mppt controller with 36-37 volts. In series.

                          When I connect a single panel I get input of 4.5-5.0 amps at around 17 volts. And an output of similar to my batteries from the controller

                          Can anyone confirm this is correct or incorrect?
                          Last edited by CanadianEhh; 07-11-2018, 06:44 PM.

                          Comment


                          • #14
                            Without connecting a load, you won't be able to tell very much.

                            Comment


                            • #15
                              I give you a clue. MPPT controlers are power in- power out. If that battery at 14.4v is capable to absorb around 70w of power , then no mater how many panels you will connect to the CC. It will still absorb 70w from one or two or three. What will change is voltage-amp ratio but the power remains the same.
                              Try with a battery at 12v or below absorb voltage and then you will see if the CC or panel is limiting the charge. At 14.4v the battery is doing the limiting.

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