P60 format Cree drop-in thermal issues

So has anyone ran into heating issues with their Surefire P60-style Cree drop-ins.

I'm rather hesistant in buying

I bought the BOG premium cree for the G2. I was worried about heat as well, but the standard P60 lamp feels much warmer to the touch than the cree drop-in, ever after staying on for a few minutes (from my own person experience).

See this thread for more info:
https://www.candlepowerforums.com/threads/166300&highlight=bog+cree

WTH said:

I bought the BOG premium cree for the G2. I was worried about heat as well, but the standard P60 lamp feels much warmer to the touch than the cree drop-in, ever after staying on for a few minutes (from my own person experience).

See this thread for more info:
https://www.candlepowerforums.com/threads/166300&highlight=bog+cree

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Uh, you're comparing an incandescent with a LED.

Incandescent put out more IR, hence the heat.

I guess my lack of knowledge is apparent so all I can say is with the light on after a few minutes, there is no noticeable heat or problems that I can detect.

If IR = heat, and you're worried about heat, why does it matter the source of the heat?

Im interested in a dropin for my G2, but since my P3D CE , i got no real use for my G2 other than comparing

WTH, someone told me recently that LEDs like this type of drop-in can run dangerously cool, in a sense. Since they don't radiate heat out the front of the light like incandescent bulbs do, the heat accumulates inside instead, especially in a G2 with no metal body to "sink" the heat away. This apparently can shorten the life of the LED, though who knows if you'd ever notice since their lives are so insanely long.

That said, I've been running a Wolf Eyes 130 lumen Cree drop-in in my G2 a few minutes at a time for a month now and haven't noticed any problems. I love it.

Jbviau, thats for the insights. I hadn't heard about this type of issue. So basically the problem is the heat causes pressure buildup in the case since its airtight, and there is a chance of explosion or something?

Sounds like it could be dangerous...if my G2 explodes I'll just send it back to Surefire I guess .

Apparently the drop-in I have uses a brass heatsink, so hopefully this helps...

Ha, well I think the risk is more that the LED may eventually suffer in terms of performance if you run it constantly in a plastic flashlight. I doubt you'd risk an explosion! I'll let people more knowledgeable than me weigh in...

G2 is plastic on the outside, but the inside of the case is all metal. I don't know if that matters since the plastic coating may insulate the heat inside anyway.

jbviau said:

WTH, someone told me recently that LEDs like this type of drop-in can run dangerously cool, in a sense. Since they don't radiate heat out the front of the light like incandescent bulbs do, the heat accumulates inside instead, especially in a G2 with no metal body to "sink" the heat away.

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Probably a flawed way of looking at things since the visible and IR radiation put out by a hot filament isn't really cooling things that much. Around 5% (?) of the energy put into an incan bulb is turned into light. The rest goes into making the filament, and thus the entire bulb hot.

Incans are simply more tolerant of heat than LEDs. The real question is if the equilibrium temperature of a LED inside of a plastic bodied flashlight is high enough to negatively impact the LED. The answer to this question? I haven't a clue. I guess if someone was that worried they could always seal the mating surfaces of the bezel and the dropin, add oil into the compartment, and seal the mating surfaces between the battery tube and the dropin. It's a pretty cool idea if someone would volunteer their G2...

ynggrsshppr said:

Probably a flawed way of looking at things since the visible and IR radiation put out by a hot filament isn't really cooling things that much. Around 5% (?) of the energy put into an incan bulb is turned into light. The rest goes into making the filament, and thus the entire bulb hot.

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The 5% is the fraction that goes into visible light. A huge fraction of the remainder goes into infrared radiation. You can observe this yourself by taking an incandescent and LED flashlight having similar power consumption, and testing the beams against your skin (face works best ). The beam of my Surefire E1E feels much hotter than the beam from by KL1, even though the latter is putting out about 2X as much visible light.

so if I wrap a drop-in module with copper wick to bridge the gap, would that help dissipate heat?

Point noted asdalton, but I think it can still be agreed that most of the energy is put into heating the filament. The EM radiation is just a useful secondary effect.

I don't know if wrapping it in copper wick would help, the problem is getting good contact with the surfaces. So I suppose you'll need a whole bunch jammed in there.

I ran my G2 with DX dropin for a little over an hour with some generic DX CR123 3.6V rechargeables. After that period I stopped since the batteries went down to 3.6V from 4.2V. The battery that made contact with the dropin was hot, and it did concern me. It was uncomfortable to hold onto but not scalding hot. Does anyone know how safe this is? The rest of the flashlight body was quite hot as well, I can only guess at the dropin's temperature. There was no discernible short term performance degradation, long term effects are unknown.

ynggrsshppr said:

Point noted asdalton, but I think it can still be agreed that most of the energy is put into heating the filament. The EM radiation is just a useful secondary effect.

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Maybe I should be clearer: All of the electrical energy that goes into an incandescent lamp is expended heating the filament. Most of this energy is then radiated away as electromagnetic waves, with the exception of the small amount that is conducted through the gas in the bulb or down the filament legs. The colloquial difference between "light" and "heat" produced by the lamp is a consequence the human eye being sensitive only to wavelengths in the range of 400 to 700 nm.

I'm not sure if the crop of new drop in LED replacement bulbs are designed for continuous use. As I understand it the incandescent Surefire bulbs such as the P60 & P61 were designed to be used for short periods of time in keeping with tactical needs of LEO's and the military.

If these lights are used for general illumination tasks lasting for sustained on- periods they are not cost effective or particularly suitable due to the build up of heat which their small mass cannot easily dissipate.

Although no manufacturer has stated that their new high output LEDs are not designed for continuous use I suspect that none of them are really up to the task due to the drawback of the limited amount of heat sinking that can be achieved in the smaller form factor of the 6P size. This problem will simply be magnified in Nitrolon bodied lights which can only disssipate heat to the reflector and metal parts of of the light. Unfortunately in the case of the G2, G2z etc., the heat has no satisfactory escape and cant easily and rapidly be got away from the LED itself. This will cause a deterioration of the LED and premature failure. Of course how quickly will depend on a variety of factors and will probably be so gradual that the operator wouldn't easily notice.

Used in the same way that the incandescent bulbs are the high output LEDs like Cree's should provide greater output which will be longer lasting and have a more efficient use of batteries than it's incandescent predecessors.

If you ever wondered why Maglite and Nightops to name but two manufacturers have used electronics to throttle back the output of the LED when used continuously it is because they are aware that the LEDs they use will suffer permanent damage if heat isn't controlled adequately.

BTW I'm not saying that LED lights can't be used continuously because plainly they can. However, in the case of the high output LED drop ins that are being sold for Surefire and similar lights I personally think that you shouldn't think of it as an utility bulb. If used for short periods of time they will probably cause no problem and provide a useful and more efficient replacement for the incandescent bulb that they are designed to replace.

Doug

Anyone ever ran their high-powered cree-dropin for a full hour?

BBL said:

Anyone ever ran their high-powered cree-dropin for a full hour?

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i've run my 6-mode q2 cree module (on high-1.4a draw) for a long period of time. not an hour, but it hasnt created any problems for me.

ynggrsshppr said:

...The battery that made contact with the dropin was hot, and it did concern me. It was uncomfortable to hold onto but not scalding hot...

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Interesting observation. I have the BOG premium drop in for my 6P. After a few minutes the entire unit gets warm. I will check the batteries next time.