Another noob question. Bear with me !
How hot is considered really hot for safe flashlight operation ?
This is quite unclear since every person has different perception.
When the flashlight body is getting “very warm” (another personal perception) in the hand, is it still safe for the flashlight ?
Some flashlights will get very warm easily in High mode after 5 min, causing slight uncomfortable feeling holding it, but still definitely holdable. Is it still ok to continue?
This heat issue always cause some paranoia in me. I have to turn it off every 5 min when my hand starts getting warm, but I also find it annoying that I have to cool it down every 5 min. J)
Too hot is when it hurts to hold it. Solid state electronics could be boiled in water, you can’t. Unless the construction is so poor that no or little thermal path exist from the led to the host its going to get too hot for you before it gets too hot for the electronics.
I’ve found that they can be run pretty hot without any damage. My XM-L headlamp is frequently hot enough that I can’t comfortably hold my hand on it anymore, it might even burn me. I’m not sure how how that is, but it runs like that for hours on end. I’ll bet that much more than that may be detrimental, but I’m not sure.
an xm-l chip can take 150ºC before there are any problems, which is 50% above the boiling point of water
Your hand will burn at less then half that, so if you can hold it its not a problem.
Keep in mind that that if you threw your flashlight in a bbq or fireplace (without a battery that could explode) then a replacement LED is well under $10. People on this forum have abused the living hell out of the LEDs and had almost no failures (you almost have to design it to fail), they are more rugged then your body is
I left a SRK on high for 10 min on accident (bezel standing) and when i realized it and went to shut it off i burnt my hand pretty bad (if you dont know, this light gets too hot to hold after about 3 min). Light was still 100% fine and it was way to dang hot to touch, never mind hold so heat isnt really an issue for the components as it is your hands
The cells in a light are more sensitive to heat damage than the electronics. You don’t want to let them get warmer than 60C. If a light warms up the cells when it gets hot I like to measure how warm the cells are getting.
If a light is used outdoors there should be some airflow, so it shouldn’t be a problem. Indoors, things can get warmer. I’ve let a J18 tailstand on medium for a runtime test without a fan to cool it. At 35 minutes the head was at 58C and the tailcap was at 41C. The cell closest to the head reached 46C. This was using only two cells and the light was running at the medium level. Repeating this test on High, with three cells (I haven’t done this yet) will likely get the light and the cells much warmer.
i noticed this as well, but i find it to be a self limiting problem, if the light is too hot for me to hold, then its going to heat its battery by a lot, simple conduction but that takes a long while
my nitecore tm11 steps down from turbo if it gets to 60°C (that is what the instruction manual says)…BUT…i have never measured nothing close to 60°C with testo 805 infrared meter anywhere on the body and i have indeed noticed the step down when it gets hot (if i turn it off and on again it does go again to turbo for a while) so i guess it measures the temperature inside the head, i did check the batteries and they were even cooler than the outside head…
When a light gets too hot to hold, the led (especially when on a copper board) has no problems at all with that (as mentioned above as well), and I found it still takes quite some time before the batteries are that hot also, they are actually quite well thermally insulated from the body of the light by the plastic wrapper and the only metal contact being a narrow spring. Eventually of course they get as hot as the body, but usually by that time in such a hot light the batteries are drained enough for the heat problem to be reduced.
Don’t forget that the numbers published for maximum operating temps for the LED is the LED chip itself. And that is inside the chip, not the body of the flash light, or the pill, or even the star. The better the thermal path, the smaller the difference in temperatures along the path, but that difference has to be taken into account.
Too bad there isn’t a way to measure the temp of the LED as there is with computer CPU’s.
What about the other components like the driver board itself, etc ? I mean, the cree led itself might have high temperature resistance, but can the other components do the same ?
After reading a while here & there over the internet, I guess I’m indeed a little too paranoid.
But still, the high temperature on the flashlight body always gives the creepy feeling that it might do harm to the electronic components inside. That’s why I try to cool it down every 5 minutes when I feel my hand starts getting quite warm because I’m worried I’m going to kill the flashlight very soon.
Now I know it’s not as fragile as I thought . :bigsmile:
I wonder at what temperature does the flashlight body start burning our hand in 10 secs.
Between 60-65 C ?
That is a very interesting feature. I wish every flashlight has that. It’s like Turbo Boost in Intel processor. 
If you have a medium mode that runs at 50% of full output you will barely notice any drop in output and will gain a ton of runtime
60 C
It might seem alarming that the light is getting hot, but it’s better because the heat is being transferred away from the LED to the body. I’d be worried about the temperature of the cells before anything else.
Do you have a temperature probe? It might help set your mind at rest if you knew the exact temperature.
the electronics are cheap as well, which light do you have?
I have C8 XML running 2.5A. It feels hot in 5 minutes.
The component might be cheap, but my knowledge about how electrical stuffs work is not any better than a 10 year old.
Even a simple soldering takes me 5-10 minutes with messy result (burnt cable, etc) :bigsmile:
If something is broken, there’s no way I can ever fix it myself. I’d rather buy a new one to save myself from headache. 
2.5A is no big deal at all, the LED is rated for 3A officially and many forum members have gone way above that. It may get hot, but it won’t damage anything inside the light
you can buy a convoy c8 for cheap with no modification necessary so if you did use a hammer to destroy your current flashlight (or a propane torch) you will not be out a lot of money so enjoy your light without any concern, or buy a shelf queen backup if you are still worried
Yeah, I think I’m a little paranoid. I’ll try not to get too concerned about it.
A hot body is actually a good thing because it means the heat is transfered effectively like a cpu heatsink. It makes sense to me now.
If it gets damaged aferall, then I’ll have a good excuse to buy Convoy L4 which keeps lingering in my mind for some time now 
Such a beautiful look….so hard to resist.
If you cream milk for your coffee, you soon learn that 65C is the temperature at which you can no longer hold onto the bottom of the milk jug.
So if you can hold it, it's under 65C
some people have far more temperature tolerance then others, my aunt can hold very hot water for short periods