DIY 100W LED flashlight

in hacks, LEDs by DP | 2 comments

In this video Julian Ilett demonstrates his DIY 100W LED flashlight:

I discovered that due to a lucky co-incidence of voltage and internal resistance, a 100W LED can be connected directly across the terminals of two 18V Nickel Cadmium power tool batteries. And that means you can build a 100 Watt (7,500 Lumens) flashlight for less than $10 (not including batteries).
Note: Don’t try this with other battery types – you’ll almost certainly fry the LED!

Via Hacked Gadgets.

This entry was posted in hacks, LEDs and tagged , .


  1. KH says:

    Over-hyped and a non-practical toy. Is it going to work for 1 minute with that heat sink? Didn’t even check (or mention) the current draw. This is never going to work as a practical flashlight.

    The LED module is nice, but cooling the thing at 100W is non-trivial. It will die quickly with bad cooling — it’s a few strings of LED chips and one weak chip will kill a string. There will also be a high current pulse before the battery packs settle at a lower voltage. I worry about its reliability. A more practical way is to run the thing at a lower rating. Use 1 battery pack and add a boost converter plus an MCU to control brightness. Add a better heat sink and a small fan.

    For an actual practical flashlight, running the thing at 100W will be rare. Since light is logarithmic to the eye, 10W is much more useful than 100W, and it’s easier to run it at 10W for 5 minutes than 100W for 5 minutes. But I concede that many flashlights these days are marketed for bragging rights rather than as a practical tool.

    I guess the primary reason for the video is for the author to boast that he can make a big ass flashlight for $10. I hope readers here are see these vids with a critical eye rather than accept such nonsense.

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