How hot should a light get before theres cause for concern?

Few weeks ago I gave my dad my TK10 as he was doing some mechanic work on the car.
He knows I really like this light and already knows not to scratch it, damage it etc so I trusted him with it.

He was trying to tune the car with the engine idling and it was a hot day, the light was on turbo mode and it can already can get really hot on turbo mode.

So as he was using it, it stopped working and he called me over, when I grabbed it it was EXTREMELY HOT, not only did the engine heat contribute to the light heating up it was also on turbo mode.

I put in my fresh backup AW's and it worked again, this time I gave it back to him in "normal" mode so it doesn't get as hot.
(P.S, I was sure when it stopped working it was the batteries finished because I was expecting that after using it a fair bit and were running dry)

Would anything have happened if I didn't notice sooner how hot the light was or would it have inflicted any damage on the light/LED itself?

The light works great as always, no worries at all thank god!

EDIT: Even after using it for 5 minutes on turbo mode it can get hot and I start worrying and I drop it back to normal mode.

I consider it normal when a light gets hot when it is outputting a lot of lumens. It is a sign of good heatsinking to the body which drains the heat away from the chip.

Take my Sunlite Eagle for example. On turbo it gets too hot to touch after about 7-8 minutes. But it will reach a maximum temperature after 20 minutes and not get any hotter.

What you don't want is for the heat to be contained at the emitter for that will reduce efficiency and take life away from the LED.

unique said:

when I grabbed it it was EXTREMELY HOT,

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when still grippable --> about 55-60 deg. C
... not perfect (= no cooling from blood when gripped all the time) but no problem


as Ryan typed, a light that gets hot quickly, shows good heatsinking (and much power to the led), no problem with that
(imagine one of comparable size and power, that not gets hot at the outside, where does its heat go to?)

If you can hold it without burning yourself, you should be fine.

My TK11 doesn't get hot enough to damage itself on turbo mode (yes, I've checked!)

Jarl said:

My TK11 doesn't get hot enough to damage itself on turbo mode (yes, I've checked!)

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Thanks for the info.
Is that while you are holding it, which provides some heatsinking, or while it is left untouched and without any outside cooling?

Good question. I've wondered myself how risky some high current lights are running on li-ions. Isn't it correct that the max. operating temperature for li-ion is around 60 C (or 140 F)? If a light is properly designed/heatsinked it should pull the heat away from the LED. But what about the inside of the battery tube? Don't the batteries get hot on their own from the high draw rate, not to mention the heat from the LED? What temperature will the battery be subjected to if the outside of the light is say 120 F?

Cagmag said:

Good question. I've wondered myself how risky some high current lights are running on li-ions. Isn't it correct that the max. operating temperature for li-ion is around 60 C (or 140 F)? If a light is properly designed/heatsinked it should pull the heat away from the LED. But what about the inside of the battery tube? Don't the batteries get hot on their own from the high draw rate, not to mention the heat from the LED? What temperature will the battery be subjected to if the outside of the light is say 120 F?

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In a word, no. Li-ion can take up to 130'C core temperature before getting angry. As for heatsinking, if anything, the body of the light helps this- I have a light that I run a 18650 in with a couple of wraps of paper to stop the cell rattling. If I run it and any other 18650 light together, then turn them off, the paper wrapped cell is hotter than the cell that touches the aluminium.

edit: The test on the TK11 was done with no outside cooling- I completely forgot I'd turned it on and went to pick it up half an hour later... the entire body was hot, but not too hot to hold.

I had an L4 that got so hot you had to put it down or get blistered. Even holding onto it for the whole run within 15 minutes you were past the point of being able to use it.
Surefire felt it was fine and I didn't so it got modded!

I appreciate good heatsinking but it can get to the point where it is still too much heat and emitter damage is being done. Not insta-death heat usually but still enough heat to kill the emitter in less than half of the lights supposed lifetime.

Thanks for the help, its good to know that the lights natural heat will not have affect but possibly added heat like I explained might reduce its actual life time.

I must check the manual, but as I'm not at home, I can't do it right now. But, I think the "turbo" on the TK10 isn't a turbo like on the L or P series and IIRC they don't mention that you shouldn't use it more than 10 minutes etc.

For a 2 stage light, it would be annoying if you can't use the high continuously.

So, I believe it IS built to be capable of running on turbo without taking damage, in normal conditions. Each heatsinking has a limit, and if you put it on turbo next to a hot engine for a long time, you may or you may not reach that limit...