TK40 and question about heat generation

I've had my TK40 a while now and its a joy to use. But there is a question that I've always wanted to ask but never did.
On its high setting its suposed to give 277 lumens, and on Turbo 630.
But why then is the light 6 times hotter, even more, when used only 3 minutes on turbo than when its used non stop on high for 45 minutes? 630 is only 2.27 times more than 277. Why 6 times the heat?
It does not bother me as it never gets too hot to hold or anything. It get about as hot as my Unicross 2700mah AA's gets fresh of the charger(Maha 808)

lightseeker2009 said:

I've had my TK40 a while now and its a joy to use. But there is a question that I've always wanted to ask but never did.
On its high setting its suposed to give 277 lumens, and on Turbo 630.
But why then is the light 6 times hotter, even more, when used only 3 minutes on turbo than when its used non stop on high for 45 minutes? 630 is only 2.27 times more than 277. Why 6 times the heat?
It does not bother me as it never gets too hot to hold or anything. It get about as hot as my Unicross 2700mah AA's gets fresh of the charger(Maha 808)

Click to expand...

heat and lummens produced by the led do not have linear coorelation. also how did you get 6 times figure? did you actually mesure?? if not try mesuring, i doubt it is really 6x the difference.

if you can bench 200lb 10 times it doesn't mean you will bench 400lb 5 times.

No I do not yet have a meter to measure heat. But on high the light barely warms up. Its just a bit more than when not used. On turbo there is a big difference. I would say 6 times more yes. But without measuring equipment I can't confirm it, it just feels like that

Lightseeker...you are exaggerating quite a bit...

40 degrees Fahrenheit multiplied by 6 would be 240 degrees Fahrenheit. The light is a lot warmer than 40 degrees when it is on "High"...and you could not hold a 240 degree light without burning your hands.

And as already noted, heat ramp-up is not linear, but a curve.

LEDs are not as efficient when they are driven at higher levels I believe, that is they produce more heat then photons.

Guys maybe we lost one another in translation
I know it can't be 6 times 30 degrees. It can than replace my kettle lol. This is what I meant.

Lets say when its off its at 26 degrees celcius. Now when I put it on high it goes to 30. Thats an increase of 4. But when I put it on turbo it goes to 50 degrees. Thats an increase of 24 degrees, 6 times more than only the 4 of when its on high. I hope I do make a bit more sense now? It really barely heats up on high. I'm sure I could use it on high till the batteries are used up with no concerns. On Turbo Fenix recommends to only use it for a max of 15 min at a time. But at only 3 min I'm feeling ''quilty'' to leave the light on longer. It just feels too hot.
Like I said its measured by feeling, not by proper equipment. The figures given are only approximates. I always wanted to buy an infrared thermometer. I think now is the time.

Well, it all comes down to thermal equilibrium, which I know we all love reading about at 130 in the AM. Heat transfer is roughly proportional to the difference in temperature between two bodies - here, the flashlight and the air.

When the flashlight is OFF, it will reach the same temperature as the air, with 0 heat transfer.
At low power, the flashlight has a bit of heat being produced inside it - so it will warm up. This raised temperature means heat will transfer out of the light (Into air, or hands). That rate is complex to determine, so we'll pretend that it's not going to change except based on flashlight temperature. Low power, small temperature difference.

At really high power, the flashlight must reach a higher temperature to get rid of enough heat to reach steady state. That is, if the flashlight is producing 10x more heat, it'll have to warm up some to release 10x the heat as before. That does mean a 10x greater temperature differential. (As a side note, there is an absolute scale for English temperature called Rankine, where the freezing point is 491.67 degrees Rankine).

LED flashlights are far less efficient at high currents. For one thing, LEDs require more than double power for double output. Secondly, the batteries tend to waste more power as heat at high current draws, and the drive electronics tend to be less efficient at high power.

The best equipment to measure the change in heat output is a calorimeter. Put the flashlight in a freezer. Then put the flashlight in a cooler with a precise amount of ice at 32F. You can calculate the heat release by measuring how much water melts, assuming all of the heat comes from the flashlight.

Just an update for those interrested.
I received a digital thermometer today.
On the off setting the light was 22.4 grades celcius, on high it went up to 28.3 and on turbo it went to 45.6.