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which MPPT controller..? which battery type..?

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  • #16
    Originally posted by inetdog View Post
    You really do not want to use 3V lights around the house unless you put them in series or use a buck converter to power them from 12V or higher. The voltage losses in long runs of copper wire will require you to use exceedingly expensive large diameter copper wire to handle the current.
    For every reduction of a factor of two in load voltage for the same power, you have to quadruple the wire size to keep the same efficiency in the wiring.

    Most people find that even wiring with 12V DC in anything larger than a single room cabin gets too expensive.
    For example, Let's say you want to power a 100 watt 12 volt light bulb or something that takes 100 watts and you have to go 20 feet with it and you allow a 2% voltage drop.
    That means that you would have to use a # 8 wire per my calculation to use that 100 watt device.

    Now if we double that voltage to 24 volts and power our 100 watt device, than the wire size can be a#10 wire now.
    And with 48 volts, it can be a # 14 wire.

    What about 120 volt DC? # 18 size wire with our example and you can power many 120 volt ' ac ' devices with that DC power like your vacuum cleaner, circular saw, Incandescent bulb, corded drill with no speed control, electric heater or toaster with no electronic control. etc etc,

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    • #17
      Originally posted by Johann View Post
      What about 120 volt DC? # 18 size wire with our example and you can power many 120 volt ' ac ' devices with that DC power like your vacuum cleaner, circular saw, Incandescent bulb, corded drill with no speed control, electric heater or toaster with no electronic control. etc etc,
      In terms of voltage drop, you could indeed go with #18, but you have to also be aware that the NEC generally does not allow use of conductors that small in building wiring at 120V. A size of #14 would be the smallest that could be protected by a 15A breaker.
      SunnyBoy 3000 US, 18 BP Solar 175B panels.

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      • #18
        I would not use a 100 watt 12 volt bulb..
        i'm talking about milliamp LED lights..

        using some LED 120 VAC bulbs and they get as hot as the fluorescent bulbs.. or close..
        i suppose a lot of that is electronics to drop the voltage from 120 VAC to 12 VDC..

        I have some LED lights up in an entry hall, 12 ft. up.. concealed from the floor in the crown molding trim.. running on a 12 volt wall blob.. provides a lot of light for little energy used when compared to most any other lighting technology I can think of at this moment..

        i believe it will be rather straight forward and 100 watts will light up the whole place..

        back to the original question..
        which would be the best MPPT controller given i will want to expand the system down the road..

        thanks,
        Bill

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        • #19
          Originally posted by billmorrow View Post
          I would not use a 100 watt 12 volt bulb..
          i'm talking about milliamp LED lights..

          using some LED 120 VAC bulbs and they get as hot as the fluorescent bulbs.. or close..
          i suppose a lot of that is electronics to drop the voltage from 120 VAC to 12 VDC..

          I have some LED lights up in an entry hall, 12 ft. up.. concealed from the floor in the crown molding trim.. running on a 12 volt wall blob.. provides a lot of light for little energy used when compared to most any other lighting technology I can think of at this moment..

          i believe it will be rather straight forward and 100 watts will light up the whole place..

          back to the original question..
          which would be the best MPPT controller given i will want to expand the system down the road..

          thanks,
          Bill
          There are a number of quality MPPT type controllers out there. Morningstar, Outback, MidNite Solar and Blue Sky to name a few. It all depends on your battery system and panel configuration to determine which CC best matches your system.

          Oh. I have retrofitted my home with a number of 120volt LED lamps. They run from 2 watt to 20 watt in size. Most were either 2ft (10w) & 4ft (20w) fluorescent style and others either go into regular table lamps or small ceiling can fixtures. Except for maybe the ones in the ceiling can's the rest run pretty cool and I can touch them even after they have been running for a while.

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          • #20
            Originally posted by SunEagle View Post
            There are a number of quality MPPT type controllers out there. Morningstar, Outback, MidNite Solar and Blue Sky to name a few.
            As someone reminded me recently - Rogue Power Technologies seems to be another very reliable controller.
            Paul

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            • #21
              thanks..
              took a look at their website..
              they make a 20 amp and 30 amp..
              i was wanting a 50 amp or 60 amp..

              not so sure now..

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              • #22
                just to bring anyone who is interested up to date I finally picked up a midnite solar 150 classic mppt controller..
                and 8 group 27 sealed AGM batteries for $150/each..

                i'm slowly coming together and refining what I want it to do when its finished..
                like run refrigerators and some LED lighting.. for now..

                next i'm looking for an inverter..
                one that will charge the batteries when the grid is up and the panels are insufficient to charge the batteries..
                I think I want it to also be a grid tie so when solar is providing sufficient charge and there is spare power it will also send power back to the grid..

                here's wishing you all a pleasant election day and following November..

                cordially,
                Bill

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                • #23
                  next i'm looking for an inverter..
                  one that will charge the batteries when the grid is up and the panels are insufficient to charge the batteries..
                  I think I want it to also be a grid tie so when solar is providing sufficient charge and there is spare power it will also send power back to the grid..
                  Then you are looking at a Conext XW-6048. [6Kw, 48VDC] With internal 60A transfer relays, grid selling (AC1), generator (AC2) and either AC source able to charge the batteries. You will also need a way to program the inverter, the Combox ($350) is a pretty decent device.

                  Outback has inverter/chargers too, but you either need 2 of them, or 1 and a 3Kw transformer to get the 240V for grid interaction. And their programming gadget too (Mate or Hub or something)
                  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

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