How hot is TOO HOT?

I measured 160F in the button area of a WOWTAC A4 V2 light I reviewed here.

I didn’t have a battery for my IR Thermometer when I did the run time tests.
When I was powered up again I took some readings and at 90s the thing hit 160.
I quite at that point. I have no idea how hot it got during the rundown tests, but it must have been really cooking.
The whole light gets really warm. Not just the head.

So how hot is too hot?
What are the max temps you have seen during testing?
All the Best,

I got 225 degrees Fahrenheit on a custom Adventure Sports Flashlights Maglite. The Dr. Jones Guppy interface has since been programmed to drop down to 50% brightness after two minutes. This is not for children.

160F would be too hot for comfort for me. I’ve observed about 150F on my Convoy S2+, and that too was way too hot to handle.

I would say that’s pretty much the limit (70°C). I mean it can probably take more. Someone let their MT09R get to over 100° and it was still fine. I set the temp limit to 65° on my anduril lights. I’m not worried about the light itself but rather the batteries. I think some samsung cells have a limit of 70° or something like that. I’ve noticed in my EC01 and MF01S the battery is about 5° less than the hottest point on the light. In the E07 it was a bit less as far as I remember. So yh the light most likely can handle more but I would check the battery temp.

As far as how much my hand can take…a bit under 45°. Body is always cooler than the head so maybe 50°.

225? Egads!
Terry you need to make a water jacket for that sucker!
Or rent it out as a branding Iron!

There are several considerations regarding temperature:
How hot is too hot to hold? ~60C
What operational temperature are lithium ion cells generally rated for ~60C
What is the max LED junction temperature? Usually 150C

To calculate led junction temperature you need the thermal resistance of the LED, for example 3 C/W. If you’re running 10W to the led (Amps x Volts) then the junction temperature is theoretically 30C higher than the heatsink temperature. If the heatsink is at 60C the LED junction should be ~90C, assuming good thermal paths. If you’re pumping 30W into that led, the junction would be 150C. If you’re pushing an LED hard this is worth considering.

The lithium ion cell temp and comfortable handling are usually the limiting factors.

There are other temperature considerations. It is possible to melt TIR optics, melt orange peel coating, melt led domes, unsolder LEDS from their pads, etc. These things happen at the extremes.

If the flashlight body is at 70C then the led is far above 100C, which is not very good.

depends how hard driven the LEDs are, if you run a quad with each XPL-HI at like 3 or 4A 70°C flashlight body is no problem at all

How does the heatsink of the light body cool off LED(S) mounted on a fiber wafer?

I concur with Hoop, I max out my EDC flashlight heads at around 140°F (60°C). At that temp, it gets uncomfortable to hold and for small flashlights the temp will continue to rise very quickly in turbo mode.

I feel if it gets much hotter than that, the LED (s) may have a shorten lifespan. But I have nothing to back that up.

When it melts the sheath on your belt and burns a hole in your work pants and vehicle seat. :open_mouth:

Obviously - This is the correct answer.

and your tushie.

Chocolate Bhutlah, tasty but WOW! Too Hot!

Oh, right before the emitter fries, in the blue zone, too hot.