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Solar powered LED project questions

Discussion in 'Electronic Basics' started by [email protected], Jun 2, 2005.

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  1. Guest

    Hi all

    I'm pretty "green" when it comes to electronics so i'll appologise in
    advance for my ignorance. =)

    I'm interested in building a Solar Panel -> Battery -> LED light system
    to put on/In a Geodesic dome i've built. The idea being that the panels
    charge the Battery during the day and then i flip a switch (or
    something) at night and the LEDs come on (lighting the inside of the
    dome), being powered by the battery.

    so my questions are as such:

    1) i was thinking of using 3-LED bundles - perhaps 3 of them (so 9 LEDs
    total) since i don't need TONS of light, just enough to not be tripping
    over stuff. Is a rechargable 12V battery (like this one >
    large enough.. or TOO large to power the LEDs for the entire night?

    2) if a get a 12V solar panel (like this one >, do i need any circuitry
    between the panel and the battery for it to charge correctly/safely
    (assuming the battery and solar panel are the same/similar voltage)?

    3) do i need any circuitry between the Battery and the LEDs?

    i searched High and Low on google, but couldn't find much DIY project
    info on this kind of thing.. which surprised me as i figured lots of
    people would be into it?!?

    any help, suggestions etc are apprecited.

    Chris Lev
    chrislev at gmail dot com
  2. Ban

    Ban Guest

    The panel is a good choice.
    you will need a charge controller like the one on the bottom of the page to
    not overcharge the battery. If your panel puts out 1.2A max., you might
    receive around 6-8Ah every day. Your battery is a bit small for this, that
    means it will not be able to absorb all of the charge, but after half day
    the panel is switched off by the controller and the capacity is wasted.
    A good rule of thump is to use a battery with 3-4 times the dayly output, so
    a 24Ah would be better. If you use the lighting every day, your consumation
    should be a little less, lets say 5Ah. This avoids a run-down battery, which
    shortens its life a lot. also the battery should never be discharged to less
    than 50% to keep it alive for a couple of years.
    white LEDs are very expensive and do not give much light either, I would go
    for the depicted flourescent light with 11W/12V, at least as a main light,
    which outputs the equivalent of a 40-60W incandescent bulb. It will consume
    about 1A, meaning that you can run it for 5 to 6 hours every night without
    stressing the battery. If you want to run the lights a lot longer, there are
    2.5W LED-arrays(18 or so) in a 50mm halogen fixture that will last 3times as
    long, so you can run them the whole night.
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