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  • Is this small DIY panel wiring schematic correct?

    Hello everyone,

    I am a newbie to solar power and this forum. I have purchased some 6"x6" and 1.5"x4" solar cells and am in the process of planning to build two panels. One will be 18v (36 each 6"x 6" cells) and the other will be assembled as a small 16v "camper battery" charging panel. (If I would have had another four cells I would have made it an 18v panel too) I have attached a .jpg schematic of the smaller panel to this post.

    I have two questions...

    1) Is the wiring diagram in the attached schematic correct? I did this in Visio on my own so that I would have a clear plan to follow during assembly. This is my first attempt at tying tabbing wires and bus wires together. I will be terminating everything in an Evergreen Solar junction box.

    2) Four of the cells are rated at 8A, while the other 28 cells are rated at 1.5A. All have equal voltage rating obviously and will be wired in series to achieve 16v. Is there an easy calculation that would tell me how many amps to expect from a mixed cell size configuration? I'm estimating about 2.2A for the panel, but not sure.

    Any comments or pointers would be appreciated!
    Mike W.
    Attached Files

  • #2
    cells (or panels) in SERIES are limited to the lowest current element in the string, so your 4A cells will be throttled back to 1.5a No "averaging" will occur.

    16V will be just barely enough to charge daytime, and disconnect it at night, to prevent backfeed and draining your battery. If you had 17V to work with, a Blocking Diode would be in order, but at 16V, the diode Vf drop knocks you down to 15V, and charging will be reduced.

    Cells all produce .5v, and size/surface area determines amperage. If you are feeling[B] real gutsy[/B], you could try to "snap" the 4a cells in half, to create 2, 2a cells. chose a point that will evenly share the conductive "fingers" on the front side. Those conductive fingers collect the power from a transparent coating of aluminum over the front side, and pass the power along to the next cell.

    Of course, just learning to solder them, will break some cells, so I hope you have spares.
    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
      Thank you... good information

      Mike,

      Thank you for taking time to post. That is good information to have and makes complete sense. I think I will order a few more 1.5" x 4" cells so I can remove the 6" x 6" cells and do this right. It will also give me extras to cover breakage.

      Thanks again!

      ...the more I think about my schematic, I think I've got the smaller cells tied together incorrectly on the bus wire; possibly in parallel with each other as they feed into the larger cells. This would drop my Voc to 9v and increase my amps to 3A.

      Can anyone confirm that this is the case?

      Mike

      Comment


      • #4
        While at home, my computer was not displaying your sketch, and yes, I have a difference of opinion on how that will work,

        I see 2, strings of 14 cells, 1.5a + 1.5a (3A) feeding a 3rd string of 4 cells.

        total volts would be 9V under load, and 3 amps, with 5A lost from the 4 large cells


        Back to the drawing board.
        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
          Back to the drawing board...

          Mike,

          Thank you again for answering my question. I have ordered 56 more 1.5" x 4" cells so that I'll have enough for two small panels and a few extras for breakage. I will redraw this thing in Visio and will try to post again for review.

          If I may ask another question...

          With a panel that puts out 18v and 1.5A, is it necessary to use a charge controller for battery health? I will likely give one of the panels to my mother to use at her cabin and I wonder if it would over-charge her two 12v deep-cycle batteries to have this connected for weeks-on-end. The panels will have an Evergreen Solar junction block with built-in diodes to prevent any voltage from backfeeding into the cells at night. I believe her batteries are rated at ~45-50Ah each.

          If it will be a problem, I will just have her disconnect the panel each time she leaves. It would just be nice to know they were always topped off and ready to go at all times.

          Thank you!
          Mike

          Comment


          • #6
            Originally posted by woodmtw View Post
            ......

            With a panel that puts out 18v and 1.5A, is it necessary to use a charge controller for battery health? I will likely give one of the panels to my mother to use at her cabin and I wonder if it would over-charge her two 12v deep-cycle batteries to have this connected for weeks-on-end. The panels will have an Evergreen Solar junction block with built-in diodes to prevent any voltage from backfeeding into the cells at night. I believe her batteries are rated at ~45-50Ah each.

            If it will be a problem, I will just have her disconnect the panel each time she leaves. It would just be nice to know they were always topped off and ready to go at all times.

            Thank you!
            Mike
            100ah of batteries will not need a controller with a 1.5a source (8AH a day), that's barely enough to cover daily battery losses. You will need another CHARGER, besides the maintainer panel.
            (note, if these are expensive AGM or sealed batteries, a 3 stage controller IS needed. Flooded batteries, you just add water monthly.)
            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
              Schematic redrawn...questions answered

              Small-Panel-27w-18v-1.5A.jpgMike,
              You are a wealth of knowledge! Thank you for sharing it. Based on your comments, I think we have a functional schematic and I think the panel will be used only to keep the batteries "charging" while someone is at the cabin (with no expectation that this will keep them fully charged or work for long durations).

              I have attached the new schematic. The additional cells are on their way and so is the Dow Corning 6010 encapsulant. Wish me luck!

              Thanks again!
              Mike
              Last edited by woodmtw; 05-24-2011, 09:17 PM. Reason: attachment

              Comment


              • #8
                Finally, found a pretty good drawing of how the diodes should be, at this site
                http://www.windsun.com/General/tech_tips.htm and has a good writeup about them.
                Attached Files
                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
                  i am looking for a basic solar panel wiring diagram.

                  Comment


                  • #10
                    Originally posted by chaddihead View Post
                    i am looking for a basic solar panel wiring diagram.
                    Wire the + to the + of the charge controller. and then - to the - of the controller.

                    About as simple as it gets. Generally, a fuse is not needed between a single panel and 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


                    • #11
                      Originally posted by Mike90250 View Post
                      cells (or panels) in SERIES are limited to the lowest current element in the string, so your 4A cells will be throttled back to 1.5a No "averaging" will occur.
                      hi mike,
                      does this mean that on diy panels, if a cell breaks then the amp of the entire panel will reduce to the amp of a smallest piece of that broken cell?

                      Comment


                      • #12
                        generally, yes, unless it vaporizes the cell fragment, and then it all stops.
                        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

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