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  1. #1
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    Cree XRE Q5 Led Direct to Battery??

    I have a left over XRE from a previous DIY light,and I am going to be using it for a trail running head light,
    I have 3x AAA rechargeable NiMh battery to power it.
    Would it be ok to connect the LED direct to the batterys (I will be using a simple on off switch in series) or will I need a resister/driver?

  2. #2
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    Since 3 x AA's give 4.5 v a 3.9ohm resistor to give an output of 350mA or just use 2 x AA and no resistor. To get an output of 500mA use a 2.7ohm resistor with the 2 xAA's.

  3. #3
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    I have a flashlight that uses 3 alkaline AAAs and drives a Luxeon 3 directly. It works even though the voltage is higher than the Vf of the LED because the AAAs can't deliver more current than the LED can tolerate. I have never tried it with NIMHs so your result may differ.

  4. #4
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    Quote Originally Posted by brad72 View Post
    Since 3 x AA's give 4.5 v
    I was thinking of using the 3 x AAA to keep the weight and size down since NiMH cells have a run voltage of 1.2V(as far as I know),and I'm sure the XRE was rated at 3.7V

  5. #5
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    Quote Originally Posted by Vancbiker View Post
    I have a flashlight that uses 3 alkaline AAAs and drives a Luxeon 3 directly. It works even though the voltage is higher than the Vf of the LED because the AAAs can't deliver more current than the LED can tolerate. I have never tried it with NIMHs so your result may differ.
    The batterys I'm using are 850mAh,and again not sure,but I think the XRE was rated at 1 Amp

  6. #6
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    I've done it from a single 18650...yes it smoked the XR-E

  7. #7
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    AAA`s are not very powerful, you will be ok direct driving,
    of course the XR-E will need to be on a heatsink of some sort!
    ...Scun.thorpe, UK

  8. #8
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    Well,here's the finished product...









    ....Ugly as hell but gets the job done
    I had a look around,and found a DX driver I had ordered a while back and never used.
    Took it out for a 40min run last night,it gives off plent of light for running.

    And while I'm at it,these are my bike lights I built a few years ago(soon to be converted for bar mounting)






  9. #9
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    Quote Originally Posted by Goldigger View Post
    I've done it from a single 18650...yes it smoked the XR-E
    No wonder! I'm squeezing 3.5A out of 3000mAh freshly charged ultrafires

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