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Setup, Would there be an imbalance with this setup?

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  • Setup, Would there be an imbalance with this setup?

    Shed Solar setup..png
    Hey guys, just wondering , but would this wiring setup have problems? i cant think of any, but i'm just checking.

  • #2
    That isn't going to work well. The maximum current you could get through would be whatever the 4 x 20W panels in parallel could pass. The 3 x 20 + 75 W parallel group in series with it would be really restricted.

    Why not just buy a single 72 cell, 300 W panel? The money you'd save on fuses would pay for a chunk of it.
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #3
      Other than the fact it will never work, it is perfect.
      MSEE, PE

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      • #4
        @sensij Because i already have all the panels, there pieces from other projects. would there be a way to connected this, and get the full capacity?

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        • #5
          No, the best you could do would be 4 x 20 in parallel (80 W), and put that in series with the 75 W panel. Then, in parallel with that mess, put 2 of the 20 W panels in series. That leaves a 20 W panel extra that is not used.

          Really, if you can sell what you have and buy a single replacement panel, you'll probably come out ahead.

          (Your battery selection probably isn't going to work well in a solar application, but that is a different problem)

          (I'm assuming a PWM charge controller. If mppt, you have more options)
          Last edited by sensij; 08-03-2017, 11:32 AM.
          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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          • #6
            Depends on the type of charge controller you have. That will tell you the maximum allowed panel wattage and DC voltage input.

            The problem is there will be a big difference concerning the Imp rating of those 20w panels and that 75w panel. Mixing them up in the same array will result in limitations and watt losses.

            What are the specifications of those panels (Voc, Vmp, Imp & Isc). Maybe there is a way to use most of them in some arrangement that your CC will accept.

            Another thing is that the inverter connects to the 24volt battery system not to the CC. And if you wire more than 2 panels (or strings) in parallel you will need over current protection (circuit breakers or fuses) for each parallel string.

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            • #7
              sensij this setup isnt purely for making a house run, its just to power a shed for free. The 20 watt panels are from 2 - 72watt kits, which i bought on the cheap from my work. what would be the problem with the batterys?, or does the application clear that up? Also, the panels are rated for 18watts, but ive seen them produce 20 watts.

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              • #8
                Originally posted by Aspire View Post
                sensij this setup isnt purely for making a house run, its just to power a shed for free. The 20 watt panels are from 2 - 72watt kits, which i bought on the cheap from my work. what would be the problem with the batterys?, or does the application clear that up? Also, the panels are rated for 18watts, but ive seen them produce 20 watts.
                It isn't free, of course, the time and money you spend on the equipment setting it up would be what you'd compare to the cost of the energy from the grid.

                So, I see you are in Canada.. I'm not familiar with options there for solar panels, but I can understand that you might be more limited than some places.

                Batteries that are rated by their reserve capacity don't generally do well in deep cycling applications. What do you intend to power in the shed?

                CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                • #9
                  sensij The batterys are 2 Deep cycle/marine batterys, but yes. Went cheap vs anything real, just wanting to test the waters, and learn some electrical work with this. As for powering things, not much. well, tools from time to time, 2 12v lights so i could do engine teardowns and things at night, and a yard light from time to time so i could throw a ball around with my bro in the backyard, without using power from the house.

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                  • #10
                    Originally posted by Aspire View Post
                    sensij The batterys are 2 Deep cycle/marine batterys, but yes. Went cheap vs anything real, just wanting to test the waters, and learn some electrical work with this. As for powering things, not much. well, tools from time to time, 2 12v lights so i could do engine teardowns and things at night, and a yard light from time to time so i could throw a ball around with my bro in the backyard, without using power from the house.
                    Sure, for a learning system, give it a shot. You have a couple posts ago the way I'd wire the panels, but you should still look for the Ah rating of the battery and make sure the PV current and the charge controller current are compatible. If you ever actually tried to use all 1500 W available from the inverter, you'd kill the system quick, but if you keep your loads low enough, you'll only have to keep up with the drain from the relatively high idle draw of the inverter.
                    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                    • #11
                      Well, my CC can handle 40amps according to the amazon page.
                      https://www.amazon.ca/gp/product/B00...?ie=UTF8&psc=1
                      I might get close to 1500w, but not sustained load. the inverter is off most of the time, when i leave, i turn off the inverter.
                      https://www.amazon.ca/COTEK-SK1500-1.../dp/B006W9NGVI My inverter.

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                      • #12
                        Originally posted by Aspire
                        well, my CC is a 40 amp Sun Yoba unit from amazon. My inverter is a Cotek SK1500-124 .
                        That CC is a PWM type that can charge a 24v battery and accept a maximum solar panel Voc of 48v.

                        Total panel wattage for the T40 is <= 500w.

                        So based on the Voc of those 20W panels, it will determine if they need to be all wired in parallel or if you can put 2 in series.

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                        • #13
                          Voc? ok. measured around 20v Voc. (assuming Voc means Voltage Open circuit)

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                          • #14
                            Originally posted by SunEagle View Post

                            That CC is a PWM type that can charge a 24v battery and accept a maximum solar panel Voc of 48v.

                            Total panel wattage for the T40 is <= 500w.

                            So based on the Voc of those 20W panels, it will determine if they need to be all wired in parallel or if you can put 2 in series.
                            OP has already said the system voltage is 24 V... that is over 1000 W of PV on a 40 A cc. Plenty of capacity there.

                            OP has already said they are 12 V panels. 2 in series is appropriate for a 24 V system with a PWM controller. As I suggested above, 4 x18 W panels could be put in parallel first, and then put in series with the 75 W panel, to get the right voltage and match the current within the string. A 2nd string could then be used in parallel to that, with 2 more of the 18 W panels in series.

                            Op will have 183 W available if wired as I suggested. That is probably around 7 charging amps under ideal conditions.

                            The 1500 W inverter could pull 62 A when fully loaded.

                            Will the OP's battery be happy with only 7 A of charging and a discharge requirement of up to 62 A? Probably not, but as marine batteries, they might handle the higher discharge better than true deep cycles, as long as they don't get asked to provide it too often.

                            This is *not* a well designed system, but for learning, and if the parts are cheap enough, I don't think there are any gross violations of compatibility.
                            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                            • #15
                              Very much true. but i never expect to pull 1500W sustained ever, probably only 1100W max, and for 3 secs unless i acquire a table saw from someone.

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