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Educate me on Series or Parallel solar panned connections - Series Shading concern?

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  • Educate me on Series or Parallel solar panned connections - Series Shading concern?

    OK I read through the Solar 101 PDF - great work Jim and a bunch of other threads (here and elsewhere). As I am sending my slightly undersized MPPT controller back (100/20 model) due to exceeding the recommended PV wattage. I was double checking that the 100/30 is what I need for the series connection. Then I saw a post or two or three (elsewhere) on shading issues if in series (70% loss in output or more ??).

    A lot of the places we try to pick camp sites that has shade (SWMBO wants shade) That shade moves across the trailer, or whatever makes it through the trees. I know panel output will suffer but would Parallel suffer less?. We would be staying in these spots for several days to a week, so solar output becomes important. (I do have 2000i Honda generators (2) if things get critical) However what I am trying to figure out is as I only have 2 panels is do I series or parallel for my situation. I am seriously considering going back to parallel and dealing with up sizing the 10 awg PV wiring from the junction box to the controller (going to 8 awg for about 15' distance). My plan is 4-6V Deka DC45 255AH (20hr) battery bank. I cant get the Trojan T145's here unless I about double my budget for shipping. Please don't beat me up too bad on this. So charging voltage of 20.4V should work with the Victron MPPT 100/30 unit B+5v to start?. In parallel my panels will be close to 20 amp if I do the math correctly so the 100/30 should still work.

    So I need expert input as to the true effects of shading. I'm not sure I understood the diagrams in the solar 101 presentation as to the amount of loss.

    BTW - I know there is 8 AWG PV wire, but are there MC4 connectors sized for it? The ones I have are very very tight on the 10 awg PV wire

    Reference material

    I have 2-190Watt Go Power Panels 380 watts total.

    In series Max panel output (used open circuit numbers) is 48.18v @ 9.98 amps. Max power numbers are 40.8v @ 9.45 amps .
    In parallel Max panel output voltage 24.09.v @ 19.96 amps. Max power numbers are 20.4 V @ 18.9 amps
    Is my math correct?

    Solar cell type Mono-crystalline ( Information taken from the back of solar panel ) Does not match what Go Power has on their web page. Numbers are higher.
    Output power 190 W
    Max Power current 9.45A
    Short Circuit current 9.98A
    Max Power voltage 20.4V
    Open-circuit voltage 24.09 V

    Thanks for any help folks
    Keith
    2018 Reflection 150 Series 220RK 5th whee, Star White 2022 F350 King Ranch CC Long bed (HAL) (CCC 4062lbs), B&W 25K OEM Companion,. SteadyFast system, Trailer reverse lights, rear receiver spare tire holder, storage tube, sumo springs, Victron MultiPlus 12/120/3000, Solar, Custom 6K axles upgrade, and other modifications.

  • #2
    Yoda

    Consider first that a given wattage will result whether is comes from a parallel connection or a series connection. Parallel has higher amperage and lower voltage where series has higher voltage with lower amperage--but doing the math with both sets of numbers still results in 400W. (This ignores the issues with wire losses due to amperage, MPPT controller start up requirements, etc, etc). Again--oversimplifying for this question of shading, in a perfect scenario with no losses 4ea 100W panels will generate 400W.

    Given we're only concerned with losses due to shading, the exact same panel will have the same amount of loss regardless of its wiring if the panel has bypass diodes.

    There's an entire thread on this topic with (simple) diagrams. Please check it out: Bypass Diodes in Solar Panels https://gdrvowners.com/forum/solar/r...n-solar-panels
    Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

    2017 Ford F-350 DRW, '19 315RLTSPlus

    Comment


    • #3
      Originally posted by howson View Post
      Yoda

      Consider first that a given wattage will result whether is comes from a parallel connection or a series connection. Parallel has higher amperage and lower voltage where series has higher voltage with lower amperage--but doing the math with both sets of numbers still results in 400W. (This ignores the issues with wire losses due to amperage, MPPT controller start up requirements, etc, etc). Again--oversimplifying for this question of shading, in a perfect scenario with no losses 4ea 100W panels will generate 400W.

      Given we're only concerned with losses due to shading, the exact same panel will have the same amount of loss regardless of its wiring if the panel has bypass diodes.

      There's an entire thread on this topic with (simple) diagrams. Please check it out: Bypass Diodes in Solar Panels https://gdrvowners.com/forum/solar/r...n-solar-panels
      Thanks Howard. I believe the panels have bypass diodes at the connection point on the back of the panel (black box). I have sent an email to Go Power as I cant see a way to remove the cover with out a special tool. . I also have read through the Bypass diode PDF and the thread on possible panel damage where the diodes were cut.

      I partially understand the shading diagrams in the PDF. What I can't wrap my head around is the effect on the panel configuration output if one side gets shaded (panels will be on either side of the unit). In other words are both series and parallel installs the same when it comes to shading one side? The PDF says they will operate the same, yet I read all the posts that say in series if one panel is in the shade it kills the other panel too. Not so for parallel. I know if I believe 10% of what is written I have a 50/50 chance of being somewhat right - a lot of Betty Crocker fudge factors floating around.

      Sorry for being such a bubble head, just trying to understand. Ill do a bit more reading. Maybe there is a Utube vid on this topic.

      Please hang in there with me - still learning - sometimes the hard way.

      Thanks
      Keith
      back to my corner

      On edit I found this. Its making more sense. Depending on what GP says on the bypass diode I will stick with Series. I am also moving the panels out of the AC shade. https://www.youtube.com/watch?v=n3_lKIAcYsM

      Then again
      https://www.youtube.com/watch?v=ofo1HQyGG8s
      and one with the older 160w version of my 190W Go Power panels
      https://www.youtube.com/watch?v=1qD3mN8VotQ
      Last edited by Yoda; 01-23-2021, 05:50 PM.
      2018 Reflection 150 Series 220RK 5th whee, Star White 2022 F350 King Ranch CC Long bed (HAL) (CCC 4062lbs), B&W 25K OEM Companion,. SteadyFast system, Trailer reverse lights, rear receiver spare tire holder, storage tube, sumo springs, Victron MultiPlus 12/120/3000, Solar, Custom 6K axles upgrade, and other modifications.

      Comment


      • #4
        Yoda

        It's a balancing act trying to get the "right" configuration. Parallel sounds great until you realize the voltage is so low the MPPT may not even allow charging of the batteries and the high current requires large wires. Series sounds like the answer until the shading issue raises it's ugly head (bypass diodes help).

        To keep this short: that's why I followed TucsonJim's lead and made up series-parallel pairs of panels in specific locations on the roof of my RV (as shown in my solar install thread). While I may know a little about this stuff at this point, it's because of Jim and Will Prowse.

        If SWMBO insists on being in the shade when you're boondocking, have a generator on hand. You'll need it. The solar generated from your setup will be negligible. My honest .02. (But will work great when you're towing!)

        Howard
        Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

        2017 Ford F-350 DRW, '19 315RLTSPlus

        Comment


        • #5
          Originally posted by Yoda View Post
          OK I read through the Solar 101 PDF - great work Jim and a bunch of other threads (here and elsewhere). As I am sending my slightly undersized MPPT controller back (100/20 model) due to exceeding the recommended PV wattage. I was double checking that the 100/30 is what I need for the series connection. Then I saw a post or two or three (elsewhere) on shading issues if in series (70% loss in output or more ??).

          A lot of the places we try to pick camp sites that has shade (SWMBO wants shade) That shade moves across the trailer, or whatever makes it through the trees. I know panel output will suffer but would Parallel suffer less?. We would be staying in these spots for several days to a week, so solar output becomes important. (I do have 2000i Honda generators (2) if things get critical) However what I am trying to figure out is as I only have 2 panels is do I series or parallel for my situation. I am seriously considering going back to parallel and dealing with up sizing the 10 awg PV wiring from the junction box to the controller (going to 8 awg for about 15' distance). My plan is 4-6V Deka DC45 255AH (20hr) battery bank. I cant get the Trojan T145's here unless I about double my budget for shipping. Please don't beat me up too bad on this. So charging voltage of 20.4V should work with the Victron MPPT 100/30 unit B+5v to start?. In parallel my panels will be close to 20 amp if I do the math correctly so the 100/30 should still work.

          So I need expert input as to the true effects of shading. I'm not sure I understood the diagrams in the solar 101 presentation as to the amount of loss.

          BTW - I know there is 8 AWG PV wire, but are there MC4 connectors sized for it? The ones I have are very very tight on the 10 awg PV wire

          Reference material

          I have 2-190Watt Go Power Panels 380 watts total.

          In series Max panel output (used open circuit numbers) is 48.18v @ 9.98 amps. Max power numbers are 40.8v @ 9.45 amps .
          In parallel Max panel output voltage 24.09.v @ 19.96 amps. Max power numbers are 20.4 V @ 18.9 amps
          Is my math correct?

          Solar cell type Mono-crystalline ( Information taken from the back of solar panel ) Does not match what Go Power has on their web page. Numbers are higher.
          Output power 190 W
          Max Power current 9.45A
          Short Circuit current 9.98A
          Max Power voltage 20.4V
          Open-circuit voltage 24.09 V

          Thanks for any help folks
          Keith
          Hi Keith,
          I went through the same calculations and decisions to construct our solar system four years ago. I can tell you what decisions I made and why, and how it turned out. First, shade, even small amounts, kills solar power production on panels. This fact drove one of my fundamental decisions - I went with portable panels. My concept is that ideally I want the camper in the shade, and the panels in the sun. So I have 60 feet of 8 AWG wire. I run the panels in series to boost the voltage and reduce line loss, which is also why I went with 8 instead of 10 AWG. The MC4 connectors worked on 8AWG. The solar controller handles the voltage without any problem. With portable panels, I can point them at the sun, and have them at the appropriate angle for the season and latitude we are camping in. For example, when we camp in Michigan in the summer, the panels are at 30 degrees. When we camp in Arizona in the winter, they are at 45 degrees. So we are able to maximize the output of our panels. If we are in a shady area, I might have to move them a few times during the day to capture sunlight. If we are gone from camp I either point them south or to where there will be a significant opening for sunlight sometime during the day.

          The system has worked very well for us. I have a Honda generator for backup, but rarely use it. If you have your panels on the roof, I don't think you will gain much by going parallel. It will be unusual to have full sun on part of the roof, especially where your panels are in a fixed position.

          I hope this perspective is of use to you. I wish you the best in putting this all together. I had never done anything like this before, it was all new to me. I was very satisfied with how it turned out. Just keep reading and asking questions.

          regards, Dave
          2016 Reflection 27RL
          2015 Silverado 2500HD 6L
          B&W Patriot 18k slider

          Comment


          • #6
            Originally posted by Dave27 View Post

            Hi Keith,
            I went through the same calculations and decisions to construct our solar system four years ago. I can tell you what decisions I made and why, and how it turned out. First, shade, even small amounts, kills solar power production on panels. This fact drove one of my fundamental decisions - I went with portable panels. My concept is that ideally I want the camper in the shade, and the panels in the sun. So I have 60 feet of 8 AWG wire. I run the panels in series to boost the voltage and reduce line loss, which is also why I went with 8 instead of 10 AWG. The MC4 connectors worked on 8AWG. The solar controller handles the voltage without any problem. With portable panels, I can point them at the sun, and have them at the appropriate angle for the season and latitude we are camping in. For example, when we camp in Michigan in the summer, the panels are at 30 degrees. When we camp in Arizona in the winter, they are at 45 degrees. So we are able to maximize the output of our panels. If we are in a shady area, I might have to move them a few times during the day to capture sunlight. If we are gone from camp I either point them south or to where there will be a significant opening for sunlight sometime during the day.

            The system has worked very well for us. I have a Honda generator for backup, but rarely use it. If you have your panels on the roof, I don't think you will gain much by going parallel. It will be unusual to have full sun on part of the roof, especially where your panels are in a fixed position.

            I hope this perspective is of use to you. I wish you the best in putting this all together. I had never done anything like this before, it was all new to me. I was very satisfied with how it turned out. Just keep reading and asking questions.

            regards, Dave
            Thanks Dave
            Yep a lot of reading and thinking. I am back to series I think for the cloudy days and when traveling. The battery bank should hold up as the Inverter is a ways off and I do have the generators.

            If I may ask, where did you get the 8awg PV wire. Was it TEMCo? I have found the 8awg MC4 connectors here https://www.amazon.com/Witproton-Con...1434430&sr=8-4
            2018 Reflection 150 Series 220RK 5th whee, Star White 2022 F350 King Ranch CC Long bed (HAL) (CCC 4062lbs), B&W 25K OEM Companion,. SteadyFast system, Trailer reverse lights, rear receiver spare tire holder, storage tube, sumo springs, Victron MultiPlus 12/120/3000, Solar, Custom 6K axles upgrade, and other modifications.

            Comment


            • #7
              Originally posted by Yoda View Post

              Thanks Dave
              Yep a lot of reading and thinking. I am back to series I think for the cloudy days and when traveling. The battery bank should hold up as the Inverter is a ways off and I do have the generators.

              If I may ask, where did you get the 8awg PV wire. Was it TEMCo? I have found the 8awg MC4 connectors here https://www.amazon.com/Witproton-Con...1434430&sr=8-4
              Hi Keith, I got them from WindyNation. Attached is a list of everything I purchased, where I got it, and what it cost. Be glad to answer any questions.
              good luck,
              Dave
              Attached Files
              2016 Reflection 27RL
              2015 Silverado 2500HD 6L
              B&W Patriot 18k slider

              Comment


              • #8
                Originally posted by Dave27 View Post

                Hi Keith, I got them from WindyNation. Attached is a list of everything I purchased, where I got it, and what it cost. Be glad to answer any questions.
                good luck,
                Dave
                Sweet Thanks
                2018 Reflection 150 Series 220RK 5th whee, Star White 2022 F350 King Ranch CC Long bed (HAL) (CCC 4062lbs), B&W 25K OEM Companion,. SteadyFast system, Trailer reverse lights, rear receiver spare tire holder, storage tube, sumo springs, Victron MultiPlus 12/120/3000, Solar, Custom 6K axles upgrade, and other modifications.

                Comment


                • #9
                  howson Dave27
                  Go power got back to me this morning that they do have the diodes in their panels, Set up is similar to others. The technician recommended parallel operation with the MPPT controller.

                  I still think after reading and discussion I will go series due to the voltage increase and better operating on overcast days. I will definitely try and find a non shade area on the roof probably toward the front. When I get ready to install I will watch the shade pattern off of the vent and skylight. Due to the longer run length I am considering 8 AWG PV wire and 8 AWG MC4 fittings which are 50A rated to minimize any voltage loss. The wire is not that much more expensive, TEMCo makes it and amazon has it, but I put in an email to try and find it on the TEMCo site where I will be getting other stuff.

                  Thanks. everyone
                  2018 Reflection 150 Series 220RK 5th whee, Star White 2022 F350 King Ranch CC Long bed (HAL) (CCC 4062lbs), B&W 25K OEM Companion,. SteadyFast system, Trailer reverse lights, rear receiver spare tire holder, storage tube, sumo springs, Victron MultiPlus 12/120/3000, Solar, Custom 6K axles upgrade, and other modifications.

                  Comment

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