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  1. #1
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    What Voltage to Choose For 1000 Lumens DIY L.E.D. Headlamp?

    Dear Friends,
    I want to build a 1K lumens D.I.Y.headlamp but don't know how to decide what voltage the battery should be.

    What question do I have to answer to decide?
    I know that I want the light to be able to last for at least two hours, if not more, between charges.

    I understand technical stuff better than average folks and I completed a Basic electronics course thirty years ago, yes I am a bit rusty but I am up to the task.
    Sincerely Jon

  2. #2
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    Add up the forward voltage of the LED's you're using, and add 2v for the driver you're planning on using and thats about where you should be. You can use a higher voltage battery, but you lose efficiency if you're going nuts. No need for a 20v battery to drive a single XML.

    ... in short, just buy a 8.4v battery made up of four 18650 cells. Thats pretty much the standard. It'll do 1000 lumen easy, for a couple hours easy. I would use two LED's instead of blasting one with enough current to made 1000 lumen, to keep heat down.

  3. #3
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    Pretty solid advice ^.

    I'd change one thing though. If you are using a switching type driver, then the ~2V overhead is good advice. If you are using a linear regulator type driver then less difference is better.

    In doing your calculations, work with 7.4V for a 2S battery. Though it will be ~8.4 fresh off the charger, they quickly drop to ~7.4 under a load.

    Post pics of what you build!!!
    GoPro adapters for bike lights http://www.pacifier.com/~kevinb/index.html

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