KL4 runs hotter than PR-T-DB917

I had a discussion with a flashlight lover who like me, has both the PR-T-DB917 (PR-T) bezel on an E2e body, and a KL4 bezel on an L4 body. He stated that his KL4 runs hotter than his PR-T. Both of our PR-T bezels have Luxeon IIIs with a TYOJ bin code. We don't know the bin codes of our KL4s.

I noticed that my PR-T bezel gets pretty hot after 10 minutes of continuous "non-contact" use, but is not too hot to pick up after the 10 minutes. The body is just warm. The KL4 gets much hotter after 10 minutes. It can still be handled, but there is a big difference in the initial sensation of heat when I pick it up.

Would anybody tell me if they have had a similar experience with these bezels?

The KL4 is one of the hottest running lights I've ever used. It get's even hotter than the E2E/MN03 and A2 lights.

Yes same experience, I think part of it, if not all of it deals with the amount of metal in the PR head helps it run cooler as compared to the KL4. The KL4 also is dissipating more wattage...

My guess would be more surface area from the PR-T and increasing heatmanagement with that along. /ubbthreads/images/graemlins/thinking.gif

Also, the boost convertor in the KL4 likely makes more heat than the buck convertor in the PRT.

Good point. /ubbthreads/images/graemlins/wink.gif

Also the 5W LS could create more heat compared to the LuxIII used in the PR-T, the bin could have influence on that, too.

The L2 is the hottest running flashlight I've ever used.
I measured a temperature of 173°F (78.3°C) on the head, and 157°F (69.4°C) on the barrel, after approximately 50 minutes of continuous operation in "high" mode.
Now that's definitely hot enough to hurt. /ubbthreads/images/graemlins/eek.gif /ubbthreads/images/graemlins/icon15.gif /ubbthreads/images/graemlins/eek.gif

I have 2 x PR-T-DB917, 2 x PR-DB917, 1 x PR-T-BB500, 1 x PR-BB500, 1 x KL3-1200mA and 1 x KL1-700mA, all with 3W LS. When continue to run for 15 minutes, the hottest is KL1, then follow by PR-T-DB917, PR-DB917, PR-T-BB500, PR-BB500, and the least hot is KL3.

You also have to consider the the wire bulb produces a lot of infared energy that is projected beyond the flashligh. Hold that puppy against your hand for a couple of minutes to capture that infared and you will come to know heat. The LED produces almost no infared but instead produces heat during the conversion from electrical to light energy. This heat is entirely contained within the light and must dissipated through the light body.

Wired lights will generally produce more heat but in a different form than LED.

Uh, shouldn't the KL4 be expected to run MUCH hotter than a PR-T/DB917/Lux III? We're talking about a five-watter vs. a three-watter here.

Also, note that the temperature of the outer body of the flashlight in and of itself is not always indicative of the heat generated by the LED. Given two lights with similar power consumption, efficiency, and outer surface area, one that has better thermal management may actually be warmer to the touch, as more heat is making it away from the emitter to the surface of the light. Then again, if they have similar thermal paths from the emitter to the surface, the one with more suface area will be cooler since there is more exposed area from which heat can escape to the outside air.