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  • different watt panels, a few questions for the experts please

    I have just purchased new SunPower flexible solar panels spec'd as follows.

    2x 50w panels - Ipmax 2.78A, Vpmax 18V, Isc 3.4, Voc 21.6V

    2x 100w panels - Ipmax 5.56A, Vpmax 18V, Isc 6.2, Voc 21.6V

    The selection was based on available space to mount them.

    My initial thinking was to wire them all up in series to my new Tracer 3210A EPsolar 30A MPPT Solar Charge Controller 12V 24V but I'm now reading I may have problems due to the different watts and currents.

    Can I connect the two 50w panels in series and then wire them in parallel with the other two 100w panels?

    Pros vs Cons?

    Will there be any degradation in the system?

    I would greatly appreciate input on making this work with the best efficiency and performance.

    Thanking you all from a solar newbie.

    Last edited by SprinterX; 01-07-2017, 12:54 AM.
    Drinks well with others.

  • #2
    I would think you would parallel the 2, 50 watt panels, then series wire them to the 100 watt ones.
    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

    Comment


    • #3
      Since they all have the same Voc and Vpmax and your controller can accept up to 100v input I'd just wire them all in series. Since the 50 watt panels have a lower Isc I'd wire them in the ground end of the series.

      Comment


      • #4
        Originally posted by John Galt 1 View Post
        Since they all have the same Voc and Vpmax and your controller can accept up to 100v input I'd just wire them all in series. Since the 50 watt panels have a lower Isc I'd wire them in the ground end of the series.
        The last sentence is utter nonsense. All of the elements of a series string (either individual panels or parallel pairs of panels) must conduct the same current. The current does not decrease as you move toward the ground (actually you mean minus?) end of the string.
        Since the Imp of the 100W panel is exactly twice the Imp of the 50W panels you can put the two 50s in parallel and then add the two 100s in series to complete the string.
        Just as stated in post #2
        SunnyBoy 3000 US, 18 BP Solar 175B panels.

        Comment


        • #5
          Originally posted by John Galt 1 View Post
          Since they all have the same Voc and Vpmax and your controller can accept up to 100v input I'd just wire them all in series. Since the 50 watt panels have a lower Isc I'd wire them in the ground end of the series.
          Won't work. The 50w panels will limit the string amps to THEIR 3.4amps, wasting half the capacity of each 100W panel. Littleharbor has it right, the 2 50's in parallel, and then all in series,
          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


          • #6
            MC-4 branch connecter .jpgMC-4 branch connecter .jpg Depending on their proximity to each other these will do a simple job of paralleling your 2, 50 watt panels provided they have MC-4 connecters. If they are to be separated by any distance you would need some extension cables W/ MC-4 ends too. This is assuming your panels have these type connections. They can be found online on Fleabay or Amazon
            Last edited by littleharbor; 01-05-2017, 08:19 AM.
            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

            Comment


            • #7
              Originally posted by Mike90250 View Post

              Won't work. The 50w panels will limit the string amps to THEIR 3.4amps, wasting half the capacity of each 100W panel. Littleharbor has it right, the 2 50's in parallel, and then all in series,
              Or the 50w panels will activate their bypass diodes wasting the entire 50w contributions and dropping the output by an additional ten or more watts.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

              Comment


              • #8
                Thanx very much for the input guys, much appreciated. I was afraid I had made a huge blunder adding in the 50 watt'rs. With the 300w total I should be able to sustain the 12V fridge, the odd use of the inverter and the array of LED lights. Our little boat has a pretty good house battery package with 4x 6V golf cart lead acid batteries giving 465 amp/hrs.

                My panels have the MC-4 connectors and I've ordered additional connectors to make the cables needed to connect to the CC. I will need to order a pair MC-4 connectors for paralleling the 50w panels.
                Drinks well with others.

                Comment


                • #9
                  I thought the smaller panels would simply add their voltage and the current would flow if they were on the end of the string.

                  Comment


                  • #10
                    Current (amps) in a series circuit is the SAME everywhere in that circuit. If you put a half size PV panel in, it will be the choke point and limit ALL the current in the circuit.
                    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
                      Originally posted by John Galt 1 View Post
                      Since they all have the same Voc and Vpmax and your controller can accept up to 100v input I'd just wire them all in series. Since the 50 watt panels have a lower Isc I'd wire them in the ground end of the series.
                      Who rewrote the rules of series circuits? A total lack of any understanding basics.

                      In a series circuit with panels, the lowest Isc dictates the maximum current. What you end up with if you put 100 watt panels in series with 50 watt panels with same Voc, you turned every 100 watt panel into 50 watts.

                      OP you have two options depending on your controller type being PWM or MPPT.

                      If PWM you have no choice to put all the panels in parallel. At best 200 watts from 300

                      If a real MPPT wire the two 50 watt panels in series, and parallel them with the two 100 watt panels in series. You wil get the full 300 watts.

                      If you put them all in series as John recomend if it is PWM you get 35 watts from 300 watts of panels, If it is a real MPPT you get 200 watts out of 300.
                      Last edited by Sunking; 01-06-2017, 10:58 PM.
                      MSEE, PE

                      Comment


                      • #12

                        Originally posted by Sunking View Post
                        Who rewrote the rules of series circuits? A total lack of any understanding basics.

                        In a series circuit with panels, the lowest Isc dictates the maximum current. What you end up with if you put 100 watt panels in series with 50 watt panels with same Voc, you turned every 100 watt panel into 50 watts.

                        OP you have two options depending on your controller type being PWM or MPPT.

                        If PWM you have no choice to put all the panels in parallel. At best 200 watts from 300

                        If a real MPPT wire the two 50 watt panels in series, and parallel them with the two 100 watt panels in series. You wil get the full 300 watts.

                        If you put them all in series as John recomend if it is PWM you get 35 watts from 300 watts of panels, If it is a real MPPT you get 200 watts out of 300.

                        Thanx again for the feedback guys. Just when I thought this was sorted out I'm struggling to make any conclusions as how to wire them up. Several have posted alternative methods.

                        MPPT controller.jpg

                        Here's the 30 amp MPPT charge controller I ordered around Christmas. From various reviews it's suppose to be a true MPPT CC of good quality.
                        Here's a link to it's manual. http://www.epsolarpv.com/en/uploads/...0581526220.pdf

                        As a newbie to solar it made sense to me that the two 50w panels in parallel would retain their 12V rating but would sum up and accumulatively achieve the same amperage as the 100w panel. This would effectively make them equal to one of the 100w panels. From there I could wire the paralleled 50w panels in series with the two 100w panels. Again, I'm new to this.

                        There appears to be a couple trains of thought here. I'm not looking to generate any drama or issues, just wanting to sort out the correct way to wire my panels up to achieve their maximum performance and efficiency.

                        Thanx again guys.
                        Drinks well with others.

                        Comment


                        • #13
                          Both ways described here will work. The difference is with paralleling the two 50 watt panels first and series wiring them with the other series wired 100 watt panels you will end up with 54 Vmp @6.4 amps. If you go series 50 watt parallel with series 100 watt is you end up with 36 Vmp @9.6 amps. Your controller can handle either voltage and each is the same amount of power, BUT. 36 Vmp. is basically 24 volts nominal (think PWM) charging voltage and not what your MPPT controller wants to see when charging a 24 volt bank of batteries. 36 volts will work great for a 12 volt bank though and is actually a better voltage to use if charging at 12 volts.
                          After rereading back a few entries I see you are planning on going 12 volt for your fridge so Sunking's wiring method would be best, by a small margin because of a small loss of effiency at higher voltage through your MPPT controller. I hope this makes sense.
                          BTW, the parallel branch connecters will work in either scenario.


                          Littleharbor
                          Last edited by littleharbor; 01-07-2017, 12:37 PM.
                          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                          Comment


                          • #14
                            Originally posted by SprinterX View Post
                            As a newbie to solar it made sense to me that the two 50w panels in parallel would retain their 12V rating but would sum up and accumulatively achieve the same amperage as the 100w panel. This would effectively make them equal to one of the 100w panels. From there I could wire the paralleled 50w panels in series with the two 100w panels. Again, I'm new to this..
                            As a Newb you made a lot of common mistakes. Not to worry though. Bottom line is it will cost you a more money than you needed to spend. Lucky for you not a lot of money lost. Example you chose to use very expensive battery panels, vs inexpensive grid tied panels.

                            The key is a PWM vs MPPT Controller, and using matched panels. Today any system 200 watts or larger should use higher voltage less expensive (1/2 the cost) higher voltage GRID tied panels with a MPPT controller. A 200 watt MPPT system = 300 watt PWM System in power generation. A 200 watt MPPT system cost less than a 300 watt PWM system. Not only that you could have bought a 300 watt GT panel and that would also save you a lot of money in hardware and materials.

                            OK with the panels you have assuming you have a Real MPPT Controller your best and smartest option is to wire the panels 2 x 2. Wire the two 50 watt panel in series, wire the two 100 watt panels in series, then connect both strings in parallel for 2 x 2. Any other option and you are screwed, So do not consider any other option as it is foolish like John suggested.

                            With MPPT you want to run panel voltage as high as possible. That means wiring as many panels in series as the Controller will allow you. Example if you had three of the 100 watt panels would allow you to wire all 3 in series. But to do that the panels Current Specs have to be the same because the lowest panel current rating dictates the maximum current a series string will pass. As Dave indicated if you put the 50 in series with the 100 wat panels can force them into bypass and burn them up. If it did not bypass, would result in turning you r100 watt panels into 50 watt panels.

                            With PWM Output Current = Input Current. Wire all your panels in series and current is limited to 2.9 amps (50 watt panels) in and out of the Controller. Do the math. 2.9 amps x 12 volt battery = 35 watts from your 300 watts of panels.

                            With MPPT assuming the panels are matched so power adds. Output Current = Panel Wattage / Battery Voltage. So with say three of your 100 watt panels in series input current is only 5.8 amps, however output current = 300 watts / 12 volts = 25 amps. Do the math again 25 amps x 12 volts = 300 watts, same as input power. Which is the larger number? 35 watts or 300 watts?
                            MSEE, PE

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                            • #15
                              Thank you Sunking, littleharbor. inetdog and mike90250 for your contribution to help me with my solar project. I spent many hours yesterday researching the internet and youtube to further understand the different aspects of what you presented. I still am a little confused on a couple things and hope you can see your way clear to offer up a little more clarification for me. The choice of these flexible panels was driven by their need to mount on top of a canvas bimini top on our boat.

                              I have drawn out two examples of how you thought I could wire up my panels.
                              Solar wiring example.jpg



                              In Example1 - the 2x 50w panels are wired in parallel to create one strand (18 Vpmax & 5.56A Ipmax). It is then wired in series with the other series wired 100w panels to give a total 54 Vpmax & 5.56A Ipmax array.
                              From what I learned and what was written above I want to present the mppt controller with as much voltage as possible and let the mppt circuitry do it's magic.
                              1) Doesn't paralleling the 2x 50w panels make them function the same as one of the 100w panels?
                              2) Doesn't this work the same as if I had 3x 100w panels all wired in series?

                              In Example 2 - the 2x 50w panels are wired in series to create one strand (36 Vpmax & 2.78A Ipmax ) . The 2x 100w panels are also wired in series to create a 2nd strand (36 Vpmax & 5.56A Ipmax). From there the two strands are wired in parallel to the CC.
                              1) Doesn't the differing amperage from the two strands cause problems at the Charge Controller with the result being a less efficient output to the batteries?

                              In Example 1 I'm producing a higher voltage (54 Vpmax) and equal amperage (5.56 Ipmax A) to the input of the mppt CC.
                              Where as in Example 2 I only deliver 36 Vpmax to the mppt CC and with differing amperages from the two strands.

                              Please correct me where I'm misunderstanding the theory or concept. I truly appreciate the help.

                              Go Sea Hawks!!!!!!!
                              Last edited by SprinterX; 01-08-2017, 05:29 PM.
                              Drinks well with others.

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