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Thread: Cheap led flashlight current draw?

  1. #1

    Default Cheap led flashlight current draw?

    Hey guys. I have tried searching this site and google for a while and can not find an answer to this question.

    I have some performance tool 55 lumen flashlights that use 3-AAA batteries.

    I want to use the LEDs out of them because I like their brightness. I need to know what kind of current they need. I'm assuming they are around 3.5 volts. I'm hooking them upto a 6 volt 10 amp power supply and need to know the resistor value needed.

    Thank you

  2. #2
    Join Date
    Sep 2009
    Fresno, CA

    Default Re: Cheap led flashlight current draw?

    That's the same question I had when I was looking at my Coleman light. It has an XR-C 7090 emitter. The highest I'm pushing mines is 1.4a with a copper computer heat sink. It'll have to wait until I finish my current project.

    I honestly don't play with Nichia emitters. Others may want to chime in on it....BUMP

  3. #3

    Default Re: Cheap led flashlight current draw?

    Start with a resistor that you know is too big and work your way down until heat sink etc. becomes an issue.

  4. #4

    Default Re: Cheap led flashlight current draw?

    Since I made the post I went to RadioShack and bought resistors to give me 20ma, 40ma and 80ma. I also went on nichia's website and looked at the specs for all the LEDs with this form factor. The currents ranged from 20-70ma.

    With 20ma the brightness was about halved compared to using 3 AAA. I then went upto 40ma and the brightness was about equal. I left it running for 2-3 hours and everything seems fine.

    Now I can wire up 8 of these for my 1/6 scale RC truck : )

  5. #5
    Flashaholic* AnAppleSnail's Avatar
    Join Date
    Aug 2009
    South Hill, VA

    Default Re: Cheap led flashlight current draw?

    They run at about h half a watt (150mA@3.5v) in those 3aaa lights. Do a current measurement at the tailcap to be sure.
    My biggest light-hog is my camera.

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