Surefire KL4 efficiency??

One of my favorite lights is the KL4 head on an E1 body. However, you can't help but notice just how hot it gets. I know the harder you drive an LED the more heat it produces and 65 lumens is nothing to sneeze at. I can't help but wonder if it is less efficient than other 5 watt LEDs or if the heat is simply more noticeable due to the compact size and less heat sinking capability. Any
input from you tech heads would be appreciated.

Paul

It has nothing to do with the 1 cell body because I have 2 KL4 heads and the one I have on my 2 cell body runs hotter.


ETA It never get to hot to hold. It seems it would barely suffice at being a handwarmer. Hold a USL and get back with us.

Thanks Fred, I guess I need to elaborate a little bit more. I know the KL4 gets hot regardless if it is used with one or two cells. My comment about the small size was in reference to the bezel not the body.

:naughty:

Paul

How hot is it getting? to hot to touch?

You should be comforted to see your KL4 to get hot. It means the heatsinking is good. You should be worried if it stays cool....

Are you running your KL4 on the single cell body with a li-ion cell? If so, a good bit of that heat is coming from the converter, because the converter works a lot harder running a li-ion cell than it does when running on 2X123. If it's just getting hot on the single cell, but not as hot as it get when running on 2X123, it's just the luxeon. Lux Vs generate tons of heat anyway.

When the KL4s first came out, I taped one to the handle bars of my bike for some night mud riding. When it came time to change the batts, the light was too hot to touch.

I ran a test a couple weeks back. A kl4 with a pila 168s will reach about 165F lying on a table in still air.

That's too hot to pick up. That's too hot to even touch for over 1/2 second.

That sounds about right. When I run the KL4 on a 150s and a homemade spacer in my E2e body, it gets hoooott. But the body stays quite a bit cooler than the head which makes me a little weary of running it for an extended period of time.

Many think that the KL4 runs too hot for comfort. Considering the test that Turbodog did, it tells me that a KL4 will cook itself, given the chance. I heat lights in an oven to 170 to "break" the factory seals on them and what Turbodog came up with comes mighty close to that.

If heat is a concern for you, I'd recommend getting a McE2S tail switch with 22 ohms of resistance for a nice low mode. You'll probably find that you'll use the low mode most of the time.