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Selecting and Inverter

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  • Selecting and Inverter

    So I am at the point of selecting an inverter. From reading the other posts, I know that I need to look at efficiency at idle and at load and run the smallest inverter possible that will meet my needs. I have seen many with a lot of bells and whistles and the price range is substantial. My proposed system will be small needing only a combined 200 watts if I ran everything I plan to run. How do I know if the inverter is going to be a good one. I have heard that the $100-$200 versions do not last as long. Since I do not need the 1000 -3000 watt inverters that are name brand, in the smaller range is this a area where I get what I pay for? Or should I buy a few of the cheaper ones and have them ready as back ups. System will most likely be 48 volt but I may decided to go with 24Volt. I know the 48 volt is over kill for what I need today but I want to be able to add a Chest freezer and other things later on.

    Proposed System: (Sun hours at lowest Time of year 3 hrs and 5.5 in Summer)
    48V with a needed Daily 800 watt hrs or 1000 watts to include fudge Factor
    Midnite Solar Classic 200
    1200 Watts Grid Tied Panels (4 - 300Watt in Series)
    Inverter - THE BIG QUESTION
    8- 225AMP HR 6 Volt batteries.

    Back Up Proposed System
    24V with Daily watts of 800 watts or 1000 watts to include fudge Factor
    Midnite Solar Classic 200
    660 Watts Grid Tied Panels (3 - 220Watt in Series)
    Inverter - THE BIG QUESTION
    4- 225AMP HR 6 Volt batteries.

  • #2
    At 200 watt-hours a day (8 watts average), and a peak load of 200 watts - you are probably better off with a 12V system since you can then benefit from the smaller/cheaper inverters out there. The 300 watt Morningstar Suresine is a nice inverter in that range.

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    • #3
      You need to clarify something first, is the 800 to 1000 watts maximum daily or 800 to 1000 watt hours max. daily. that is two different thing all together.

      Comment


      • #4
        Originally posted by mschulz View Post
        My proposed system will be small needing only a combined 200 watt hrs if I ran everything I plan to run.
        Proposed System: (Sun hours at lowest Time of year 3 hrs and 5.5 in Summer)
        48V with Daily watts of 800 watts or 1000 watts to include fudge Factor


        Midnite Solar Classic 200
        1200 Watts Grid Tied Panels (4 - 300Watt in Series)
        Inverter - THE BIG QUESTION
        8- 225AMP HR 6 Volt batteries.

        Back Up Proposed System
        24V with Daily watts of 800 watts or 1000 watts to include fudge Factor
        Midnite Solar Classic 200
        660 Watts Grid Tied Panels (3 - 220Watt in Series)
        Inverter - THE BIG QUESTION
        4- 225AMP HR 6 Volt batteries.
        Huh? You got all your numbers mixed up. If all you need is 200 watt hours in a day with 3 Sun hours all it takes is a 100 watt panel, 10 amp controller and a 12 volt 80 AH battery.
        MSEE, PE

        Comment


        • #5
          Originally posted by paulcheung View Post
          You need to clarify something first, is the 800 to 1000 watts maximum daily or 800 to 1000 watt hours max. daily. that is two different thing all together.
          800 Total DAILY watts. Max watts at one time 198.

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          • #6
            Originally posted by mschulz View Post
            800 Total DAILY watts. Max watts at one time 198.
            OK you are still expressing terminology incorrectly. There is a difference in Watts and Watt Hours and very important you know the difference and how to express them.

            Watts is the power being consumed at in one moment in time.

            Watt Hours = Watts x Hours and is a measure of energy used.

            For example a 100 watt light bulb uses 100 watts at any given moment in time when turned on. If that 100 watt light is on for 10 hours it uses 100 watts x 10 hours = 1000 watt hours or 1 Kwh.

            So assume you will use 800 wh in a 24 hour period with a maximum demand of 200 watts at any given moment in time. You have a minimum 3 Sun Hour Day and will use a MPPT charge controller. First thing to save some coins this is to use either 12 or 24 volt system. You can certainly use 48 volt battery but the inverters will cost you a bit more, and since your max demand is only 200 watts doubtful you can find a 300 to 400 watt 48 volt inverter. You can find hundreds of them at 12 volts for cheap, and a few 24 volt units in that small of a power rating

            Regardless of battery voltage the panel wattage required is 400 watts.

            As for charge controllers you would need:

            30 amps @ 12 volt battery
            15 amps @ 24
            7.5 @ 48

            When it comes to 48 volt controllers I do not think you can find one under 40 amps so there is another big expense of 48 volt battery which you cannot use the capacity. A 40 amp 48 volt controller is for 2000 watt panel systems. Take note here a Morningstar SunSaver MPPT is a 12/24 at 15 amps for around $200 and would be perfect for a 24 volt system.

            OK for battery capacity you need:

            330 AH @ 12 volts. Most likely use 2-6 volt 350 AH batteries in series.
            150 AH @ 24 volts. 2-12 volt 150 AH in series.
            75 AH @ 48 volts. 4-12 volt 75 AH batteries in series. More expense in wiring 4 batteries in series.
            MSEE, PE

            Comment


            • #7
              Thanks Sunking, always straight to the point. I love it. Any good recomendations for a 24 volt inverter?

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