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  • Dc only system?

    Hi,

    i apologize in advance for my lack of knowledge. I was reading if I am only powering dc devices I can bypass the dc-Ac inverter. Is this true? Do I just use a cigarette lighter attachment to the battery? Is there a better way?

    I have a 12v 100w panel and an mppt controller. I was going to use golf cart batteries.

    Thanks!

  • #2
    If you truly have only a couple small loads, (a LED light, cell phone charger) then yes. IF you have matched your panel to be sufficient to your loads.
    With a pair of golf cart batteries in series, giving 12V @ 210ah, I'd prefer to see 200W of panels feeding it, much better chance of the batteries lasting longer with a good charge.
    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
      Ya. I live in a yurt on a friends property so I use the main house as a kitchen etc... So I really only need lighting and the ability to charge a cell phone and iPad. It would maybe be nice to get my sewing machine up there one day in which case I'm guessing I'll need to get an Ac inverter?

      would you happen to know the battery life difference between 100w and 200w?

      Also im seeing mixed reviews about whether or not I should have the controller/battery set up inside or outside the yurt. What are your thoughts?

      Also I suppose I could just bypass the whole solar thing and carry the batteries to and from the house to charge but that sounds annoying and heavy.

      Thanks!

      Comment


      • #4
        I would place the controller and batteries some place you will NOT ignore them. A large plastic tote outside? Controller is never weatherproof, so it needs shelter.
        200w of panels helps insure you dont loose power. 100w would be marginal.
        Adding a sewing machine would require an inverter. You could use it 2 or 3 hours a week, anymore and you need larger battery and more solar - power has to come from somewhere, free from the sun, but the gear to harvest it costs.
        I'd suggest a pure sinewave inverter, like the morningstar sure sine 300. That surges up to 600w for 10 min, and should handle a sewing machine.
        http://www.morningstarcorp.com/products/suresine/
        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
          Hmmm. Starting to feel a bit disenchanted and maybe I should just return the panel and charger and buy some of those blow up solar lights and charge my phone in the main house and call it good.

          thanks for all the advice! I'll mull it over

          Comment


          • #6
            Originally posted by Scrange View Post
            Hi,

            i apologize in advance for my lack of knowledge. I was reading if I am only powering dc devices I can bypass the dc-Ac inverter. Is this true? Do I just use a cigarette lighter attachment to the battery? Is there a better way?

            I have a 12v 100w panel and an mppt controller. I was going to use golf cart batteries.

            Thanks!
            You do not have enough panel wattage for golf cart batteries. That does not mean what you will not work, just need a smaller battery. If you have a real MPPT controller, a 100 wat panel can support a 12 volt 65 to 100 AH battery. Two golf cart batteries wired in series is 12 volts @ 200 to 225 AH. So all you need to do is find a decent 12 volt battery of the right size. Usin glandscape light panels is a very poor decision and one you will regret.

            There is one catch no one knows if it will work or not. You have not determined your daily watt hour usage. 90% of those that guess and buy something and hope it works fail when they find out they need a significantly larger everything. You would be surprised how many folks come here like you, already bought something only to find out they have not even made a down payment. So my advice to you is first figure out how much power you need before you spend a dime. It is very rare anyone guesses and gets it right.
            MSEE, PE

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            • #7
              Ya. The company I bought it from said 100w would be enough for my needs and golf cart batteries/ doc set up would work. Next time ill get second opinions. Thanks guys.

              Comment


              • #8
                Originally posted by Scrange View Post
                Ya. The company I bought it from said 100w would be enough for my needs and golf cart batteries/ doc set up would work. Next time ill get second opinions. Thanks guys.
                A 100 watt panel will support a battery rated about 65Ah at best. Most golf cart batteries are 2 to 3 times that Ah rating so you will either have to add more panel wattage or go with a smaller battery then the golf cart type.

                Or another idea would be to get a 200 watt panel because it should be less cost per watt then 2 x 100 watt panels. Just an idea for you to save some money.

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