who else feels KL4 runs too hot?

I have done short run tests with my KL4 head on both a single rechargable CR123 (about 1400mA) and on two primary CR123 cells (about 950mA).

I am not saying that it is going to be "normal" to always run the KL4 unattended (say to light a room after a power failure), but after 5-10 minutes of running on top of my desk (just pointing up) with me not touching the light, my KL4 gets VERY hot. I can still hold it in my hand, but barely so. This can't possibly be good for the longevity of the KL4.

True, in my hand I do help with the heat disipation, but it seems to me that maybe the KL4 is just too small to properly dissipate all that heat.

Who else has found their KL4 run this hot?

Will

Both of mine stabilized at just over 160°F as measured by an IR thermometer after about 10 minutes of constant-on. Pretty hot indeed - that is what we have our water heater set at.

160ºF= 711ºC

one hundred sixty degrees Farenheit equals seven hundred eleven degrees celcius? /ubbthreads/images/graemlins/thinking.gif

I find the same, very hot if left standing on its own.

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greenLED said:
160ºF= 711ºC

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/ubbthreads/images/graemlins/thinking.gif


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LitFuse said:
In doing runtime tests, the bezel cap of my L4 has gotten as hot as 161 F. The body stays about 20 degrees cooler. This is not comfortable to hold onto in my experience. The temperature was measured with a Raytek "MiniTemp" infrared thermometer. The light was sitting on a tiled countertop in 80 F ambient air.

I seem to average about 60 minutes of regulated light with the 17670 Li-ion cells. I've seen it range from 55 to 72 minutes with a sample of 3 different KL4s.


Peter

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L4 Temp. measure thread

Yep, it gets pretty toasty, more so with the rechargeable batteries. I don't think there is anything that can be done though, it's just the price that has to be paid for getting that impressive "wall of light" out of such a small package.

Peter

Just think of what the runtime would be if the temp only went to 90F.....wouldn't be wasting all that battery power converting it into heat! /ubbthreads/images/graemlins/grin.gif

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greenLED said:
160ºF= 711ºC

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160ºF= 71.1ºC

Decimal added.

Thank you guys. I feel better now in that it is a known "problem".

I wonder if this KL4 5W solution would work better (cooler) in the slightly larger 6P body - I guess that would be like the L5, right?

Will

Yes it does. Not sure about the L5's design but I think the U2 and the L5 are close cousins, my U2 on full blast does not get anywhere near as warm as the L4.

Yes, I also do find my KL4 quite hot for continuous use, as the LuxV is known to be driven at around 650ma by the boost circuit.

You could underdriving it with 1xCR123 (in an appropriate 1-cell body), but light produced is no longer regulated and quite less bright.

Another 'solution' is to use McGizmo's McE2s 2-stage tailcap -- tailoring your resistor (low light) to your liking.

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KevinL said:
Yes it does. Not sure about the L5's design but I think the U2 and the L5 are close cousins, my U2 on full blast does not get anywhere near as warm as the L4.

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Well, if the same amount of power goes into the two lights, and the KL4 gets alot hotter, that means the U2 would have poor thermal transfer to the body. The body getting hot is a good thing, shows good thermal transfer.

Thanks for catching the decimal point, guys! I need a new keyboard, the "x" is also not working properly.

I thought it was too hot until I put a 2 stage switch on it, now it's perfect. Of course on cold days my GF would say it's just about right for a hand warmer. /ubbthreads/images/graemlins/crazy.gif

-LT

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KevinL said:
Yes it does. Not sure about the L5's design but I think the U2 and the L5 are close cousins, my U2 on full blast does not get anywhere near as warm as the L4.

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Also there is a lot more thermal mass and surface area with the U2 so it can radiate the heat much better.

When actually using the thing outside and moving around, it does ok. Still quite warm, but not burning hot ...
But honestly, without a 2-stage (or using the L2 instead) it's half as useful to me.
bernhard

Sounds like the most obvious "cure" is a two stage switch. I must admit that for most things up close, the KL4 is just too bright. What value resistor do most of you with the KL4 recommend?

First thing I did, was put the Z52 LOTC on my L4's. Then I resolved to never twist them on. Used the button for intermittent use only. Now I have the McE2s on them. My L4's have never gotten too hot. /ubbthreads/images/graemlins/grin.gif


EDIT: For long runtimes, on high, I use my Turbo L4. (KL5, E2C, L4 body, McE2s)

I like the heat, I suppose it could be a psychological thing with the amount of power it consumes. I rarly use the "momentary" function, I am an "all on", or "all off" guy, Thanks to Pilas.

IS this also the case with the L2? I can imagine it is..

-tom