Wiring several battery powered LED light strings together

Discussion in 'The Projects Forum' started by BenjaminAB, Dec 7, 2015.

  1. BenjaminAB

    Thread Starter Member

    Aug 25, 2010
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  2. ian field

    Distinguished Member

    Oct 27, 2012
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    The Xmas lights I got very cheap use 2x AA cells - I would expect a fairly narrow margin of operation before the terminal voltage lowers and most of the LEDs drop out. I just wanted a bunch of blue LEDs as cheap as I could get them.

    To actually use one (or more) of those light sets, I'd try an off the shelf power LED driver - it might even work.

    A blocking oscillator style Joule thief inverter would probably run a few of those off a single D cell.
     
  3. Dodgydave

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    Jun 22, 2012
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    Choose whichever batteries you want you need 6V, bigger capacity will last longer, (more maH) i would use a rechargeable pack.
     
  4. ian field

    Distinguished Member

    Oct 27, 2012
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    The cheap one I bought was just 25 blue LEDs all wired in parallel - 6V wouldn't do it much good.

    Mine had a holder for 2x AA cells, I imagine it would have a pretty narrow margin before some of the LEDs faded out.

    The TS pictured a battery holder with 2x lithium coin cells - this is a common arrangement in cheap keyfob lights - intensely bright, but doesn't last long.

    For more strings in parallel, I'm thinking a blocking oscillator Joule thief inverter running off a single D cell.
     
  5. BenjaminAB

    Thread Starter Member

    Aug 25, 2010
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    I am assuming this battery pack would be wired in series to give it 6V and that C batteries should keep the lights at full brightness for days.

    http://www.amazon.com/Rectangle-Pla...8115&sr=8-2&keywords=wired+2+C+battery+holder

    I am thinking wiring 6 sets of the lights in parallel to each 4 C Battery pack. How does that sound?

    "For more strings in parallel, I'm thinking a blocking oscillator Joule thief inverter running off a single D cell."​

    This is beyond my understanding of electronics.
     
    Dodgydave likes this.
  6. JohnInTX

    Moderator

    Jun 26, 2012
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    I would use 4 D cells in a battery holder. That makes 6V like the 2 2032's in series that come with the set.

    LEDs are polarity sensitive so make a note of which wire connects to + and - on the existing batteries and match them up on the new holder.

    Have fun!
     
  7. Dodgydave

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    Jun 22, 2012
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    Yes D type will last longer, just wire all the strings in parallel, like said bigger capacity battery will last longer,

    if you want go for rechargeable batteries you would need 5 in series for 6V, or a lipo pack,

    Joule thief is a flyback type oscillator circuit it will drive an led from a single 1.5V battery like this...
    http://m.instructables.com/id/Make-a-Joule-Thief/
     
  8. ian field

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    Oct 27, 2012
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    Most cheap LED key lights have 2x CR2016 coin cells in series, it relies on the cells internal resistance - it doesn't do the LED much good, and the battery has a short life.

    I'm surprised at a string of LEDs running off a pair of coin cells - have you actually run it long enough to see how quick the batteries die?
     
  9. iONic

    AAC Fanatic!

    Nov 16, 2007
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    I suppose it all depends on what you will do with the lights once wired up. Will you be carrying them? How long do you want them to be on for? If it's not a portable situation, you can use a 6V wall adapter, perhaps even a 5V wall adapter with some sacrifice to LED brightness. For all we know, as cheaply as these LED wires are designed, there may not even be proper current regulation.

    The Joule Thief concept allows you to run a 3V(or more) rated LED with a single 1.5V battery. I have a very bright single LED flashlight that uses a single 1.5V AAA size battery. Not sure if the curcuitry is classified as a "Joule Thief," but the end result is similar.
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    Either wall adaptor will give you the minimum brightness possible.

    The cheapo coin cell LED lights rely on the cells internal resistance to limit LED current - a wall adaptor with no current limiting device will blow the weakest LED, that will fail short circuit, and either crack apart or shunt all the others out. Shunting out wont do the adaptor much good either.
     
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