Announcement

Collapse
No announcement yet.

Solar Panels in series with different Voltages? What problems does this cause?

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Solar Panels in series with different Voltages? What problems does this cause?

    Dear forum

    I am new to this forum, so I hope I am posting in the correct section.

    I have been studying PV installations in my region (most of which are excellent examples of bad practice )

    I have just studied an 8yr old installation. There are 16 Kyocera solar panels of 120W, connected in 4 paralell series for a 48V system. However many of the panels are only operating at half their Open Circuit Voltage- ie some panels give 16V or so and others only 8V.

    My question is- what effects will this have on the system? Can you have panels connected in series with such different voltages?

    The total Open Circuit Voltage of the system is about 60V- but with the batteries connected no current seems to be getting to the batteries (possibly a failed charge controller)

    Thanks very much for any information

    Larry

  • #2
    Larry to sum it up quickly here is the run down.

    For series panels the Imp ratings need to be matched because the lowest Imp rating in a series string will be limited to the lowest value. So let's say you have 3 panels rated at 10 amps @ 18 volts where each panels produces 180 watts. However you have a 4th panel rated at 5 amps at 18 volts @ 90 watts. When all 4 are connected in series you would have a string that produce 72 volts @ 5 amps for a total of 360 watts, when you think you should have 180 + 180 + 180 + 90 = 630 watts. So for series voltage adds, and current is limited to the lowest value in the series string.

    In parallel circuits current adds, and voltage is limited to the lowest value. So you need the Vmp and Voc to be matched. IF you put a 18 volt panel in parallel with a 16 volt panel, you get a 16 volt block of panels.
    MSEE, PE

    Comment


    • #3
      Thanks for your reply SunKing

      That's what i thought. A strange thing though. I measured the voltage (in open circuit) over each of the bypass diodes in the panel. In the correctly functioning panels it read 8V and 8V over each bypass diode... summing to 16V (total for the panel). However in the failing panels, it read 8V for one string and almost 0V for the other string (hence 8V for the entire panel).

      Can someone enlighten me on why this would be?

      Comment


      • #4
        parallel circuits

        Sunking, I have a similar question. I have 10 panels of the same type joined in series to give a v of 450v and another 4 panels of another brand joined in series to give 272.2v.(all the 14 panels orientate west) The installers have run both the series circuits and joined them in parallel before it joins the inverter. There are now 2 outputs with different voltages? I wonder if this is the normal way of putting them together. I have a growatt 4.2kw inverter. The other mppt is running another 8 panels orientated north.thanks for helping

        Comment


        • #5
          Originally posted by newsolar View Post
          Sunking, I have a similar question. I have 10 panels of the same type joined in series to give a v of 450v and another 4 panels of another brand joined in series to give 272.2v.(all the 14 panels orientate west) The installers have run both the series circuits and joined them in parallel before it joins the inverter. There are now 2 outputs with different voltages? I wonder if this is the normal way of putting them together. I have a growatt 4.2kw inverter. The other mppt is running another 8 panels orientated north.thanks for helping
          This seems wrong, if I understand the description. This would bring the entire array down to 272.2 v (the 4 panel string)

          > The other mppt is running another 8 panels
          does this mean you have a 2nd inverter that is grid tie too ?
          spreadsheet based voltage drop calculator:
          http://www.solar-guppy.com/download/...calculator.zip
          http://www.solarpaneltalk.com/showth...oss-calculator

          http://www.mike-burgess.org/PVinfo_2.html

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister ,
          battery lugs http://tinyurl.com/LMR-BigLug
          Setting up batteries http://tinyurl.com/LMR-NiFe

          gear :
          Powerfab top of pole PV mount | 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

          Comment


          • #6
            Originally posted by newsolar View Post
            Sunking, I have a similar question. I have 10 panels of the same type joined in series to give a v of 450v and another 4 panels of another brand joined in series to give 272.2v.(all the 14 panels orientate west) The installers have run both the series circuits and joined them in parallel before it joins the inverter. There are now 2 outputs with different voltages? I wonder if this is the normal way of putting them together. I have a growatt 4.2kw inverter. The other mppt is running another 8 panels orientated north.thanks for helping
            Huh? If I understand you correctly you have one hell of a problem or problems. If they are in fact in parallel, you are dragging down the system voltage down roughly 50% which means you lost 50% of your power.
            MSEE, PE

            Comment


            • #7
              Thanks, guys you all r right. The installers are back to fix it keep you guys posted. Cheers

              Comment


              • #8
                connecting two 12v PVs wired in series and one 24 PV to get 24V

                Hi

                I am currently running a DIY solar power system with two nos of 12V 100W Im 6.1A and VoC 22.4) panels in series, 30A PWM charge controller (Max PV Voltage <48V), 4 nos of 40AH 12v batteries in series-parallel (24V) and 800VA 230V Sine wave Digital Inverter.

                I am planning to increase the PV size. But I am not able to locate similar panels.

                Recently I saw 200W 24V (Im 6.2A) and 250W 24V (Im 7.1A) panels in a store nearby. (VoC 43V)

                Is it possible to use any of these panels in parallel with my existing PV array?
                Thanks

                Comment


                • #9
                  Originally posted by portman View Post
                  Hi

                  I am currently running a DIY solar power system with two nos of 12V 100W Im 6.1A and VoC 22.4) panels in series, 30A PWM charge controller (Max PV Voltage <48V), 4 nos of 40AH 12v batteries in series-parallel (24V) and 800VA 230V Sine wave Digital Inverter.

                  I am planning to increase the PV size. But I am not able to locate similar panels.

                  Recently I saw 200W 24V (Im 6.2A) and 250W 24V (Im 7.1A) panels in a store nearby. (VoC 43V)

                  Is it possible to use any of these panels in parallel with my existing PV array?
                  Thanks
                  Yes. The 200w 6.2a panel would be very similar to your 2 100w panels and can be wired in parallel with them. While I believe having less than 3 sets of panels wired in parallel does not require any fuse protection I would build a combiner box and fuse the + wire from the 200w and the 2 series 100w panels before going to your charge controller. Having the fuses will make your system safer than not having them.

                  Comment


                  • #10
                    Originally posted by SunEagle View Post
                    Having the fuses will make your system safer than not having them.
                    Not by much really, as long as you have a single combined fuse to protect the panels against a failed CC, but I would consider putting in individual string fuses anyway to make it easier to add additional panel(s) later.
                    SunnyBoy 3000 US, 18 BP Solar 175B panels.

                    Comment


                    • #11
                      Originally posted by inetdog View Post
                      Not by much really, as long as you have a single combined fuse to protect the panels against a failed CC, but I would consider putting in individual string fuses anyway to make it easier to add additional panel(s) later.
                      Some of these small packaged portable solar pv systems don't include fusing on the panels of any type. They rely on the internal fusing of the CC.

                      So for me even if I only have two panels in parallel adding the fuses is a no brainer. As you said it also makes it easier to hook up additional panels in the future.

                      Comment


                      • #12
                        Thanks a lot. Finding DC fuses is a big problem here. I am thinking of using 10A Automotive DC fuses.
                        There are two 32A MCBs in between PV array, CC and Batteries. As it is AC MCB, it may not offer 100% protection though.


                        Originally posted by SunEagle View Post
                        Some of these small packaged portable solar pv systems don't include fusing on the panels of any type. They rely on the internal fusing of the CC.

                        So for me even if I only have two panels in parallel adding the fuses is a no brainer. As you said it also makes it easier to hook up additional panels in the future.

                        Comment


                        • #13
                          Originally posted by portman View Post
                          Thanks a lot. Finding DC fuses is a big problem here. I am thinking of using 10A Automotive DC fuses.
                          There are two 32A MCBs in between PV array, CC and Batteries. As it is AC MCB, it may not offer 100% protection though.
                          Be careful. Those automotive fuses are usually only good for 12 to 15volt dc. They may not handle your 24volt system. The voltage rating should be on the fuse somewhere along with the amp rating.

                          Comment


                          • #14
                            Originally posted by SunEagle View Post
                            Be careful. Those automotive fuses are usually only good for 12 to 15volt dc. They may not handle your 24volt system. The voltage rating should be on the fuse somewhere along with the amp rating.
                            Littelfuse and bussmann have blade fuses with 32v and 58v ratings, not sure about some of the cheapo unmarked imports.

                            Comment


                            • #15
                              Originally posted by FloridaSun View Post
                              Littelfuse and bussmann have blade fuses with 32v and 58v ratings, not sure about some of the cheapo unmarked imports.
                              hmmm... just checked the littelfuse website and they also have 80, 90 and 125 volt blade fuses.

                              Comment

                              Working...
                              X