So, what happens when.....

The other day I was "playing" with my lights (no, you never did that?) and after doing so, I was putting them in a basket on my desk. Some of them are end switched and others are side switched only. After 1/2 hour or so, I reached into the basket to find one of them was HOT! Hot enough that I couldn't handle it without flipping it around in my hands. The hot light was covered by the others (all had sheaths on) so the heat had no place to go and the hot light was in a sheath too.

Question: What would have happened if I had not found the hot light in the basket? AFAIK, there is no thermal protection in lights, nor in batteries for that matter. At least I have never seen a spec on either lights or batteries. I ask this b/c some of these lights are going to find their way to the glove compartment and the same thing could happen there. And, I'm sure lights find their way to confined spaces all the time. Would the heat increase the current draw to shut down the battery? Just how hot can these lights get? Mine was a Nitecore P12 on high power (1000) lumens.

never mind

smooth2o said:

The other day I was "playing" with my lights (no, you never did that?) and after doing so, I was putting them in a basket on my desk. Some of them are end switched and others are side switched only. After 1/2 hour or so, I reached into the basket to find one of them was HOT! Hot enough that I couldn't handle it without flipping it around in my hands. The hot light was covered by the others (all had sheaths on) so the heat had no place to go and the hot light was in a sheath too.

Question: What would have happened if I had not found the hot light in the basket? AFAIK, there is no thermal protection in lights, nor in batteries for that matter. At least I have never seen a spec on either lights or batteries. I ask this b/c some of these lights are going to find their way to the glove compartment and the same thing could happen there. And, I'm sure lights find their way to confined spaces all the time. Would the heat increase the current draw to shut down the battery? Just how hot can these lights get? Mine was a Nitecore P12 on high power (1000) lumens.

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Cells do have a basic form of thermal protection. Some protection circuits add another layer of thermal protection (Orbtronic, for example, touts this as part of their circuit). Still, you shouldn't depend on that. You should lock out your lights (unscrew the tailcap on the P12 even a sixteenth of an inch, and you won't have a problem with accidental activation). Some lights do have thermal protection (Zebralight SC600 Mk II L2 is one example, there are many others) as well, if you are unwilling to do that.

As for leaving an 18650-based light in the car, I would recommend against it. Storing lithium-ion at full charge, and in a hot environment, is the very worst thing you can do, besides puncturing or crushing it. You might lose twenty percent or more capacity in a single year. If you insist on leaving a light in the car, it is much better to use primary (non-rechargeable) lithium cells, since they have a better shelf life and are FAR less susceptible to damage from heat.

5S8Zh5 said:

What battery was in it? What model light?

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Nitecore P12, 18650.

And now, back to the main question. Besides the possibility of having a small fire/explosion in your sheath, my understanding is that seriously overheating an LED will shorten its life drastically, if not outright destroy it. I had an incan G2 get turned on accidentally in its holster, but all it did was bubble the lens before I felt it on my hip. Since then, I always lock out a light before putting it in a holster.

Timothybil said:

And now, back to the main question. Besides the possibility of having a small fire/explosion in your sheath, my understanding is that seriously overheating an LED will shorten its life drastically, if not outright destroy it. I had an incan G2 get turned on accidentally in its holster, but all it did was bubble the lens before I felt it on my hip. Since then, I always lock out a light before putting it in a holster.

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So, the answer is.......<drum roll> ...... it will keep on cooking, thereby causing a fire and eventually (likely) explode! Damn, with all that circuitry in the light, you'd think there would be a thermistor.

smooth2o said:

So, the answer is.......<drum roll> ...... it will keep on cooking, thereby causing a fire and eventually (likely) explode! Damn, with all that circuitry in the light, you'd think there would be a thermistor.

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Some lights do have thermal protection that dims the light if it starts getting too hot. Unfortunately, most do not.

smooth2o said:

Damn, with all that circuitry in the light, you'd think there would be a thermistor.

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Thermal overrun is a well-known failure mode of electronics. It says a lot about the priorities of flashlight manufacturers who design high-power, fairly expensive lights, with no sense of their own temperatures. A modern CPU isn't likely to commit suicide by thermal breakdown - Most shut off at a set temperature. But then, a modern CPU costs at least $80 and is expected to protect itself. Some light makers go the simple route - There are no reasonable circumstances in which a 2xAA 3W light will overheat, and a 3W LED will easily product 200 lumens these days. I worry about my Minimag AA when using it in an oven; otherwise overheat is no concern there. Others install thermocouples or other methods to detect temperature increases, and change modes accordingly. Others don't, and foist the problem off on the users. These lights don't protect themselves from mistakes, and could destroy themselves in an emergency. Some manufacturers wants their lights to be considered "extreme output" machines - Next year they might include "Danger: Explosion Hazard" in their advertising literature.

Timothybil said:

And now, back to the main question. Besides the possibility of having a small fire/explosion in your sheath, my understanding is that seriously overheating an LED will shorten its life drastically, if not outright destroy it. I had an incan G2 get turned on accidentally in its holster, but all it did was bubble the lens before I felt it on my hip. Since then, I always lock out a light before putting it in a holster.

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The LED is not likely to be the point of failure. Cree bins them at 85C, and they are rated up to a max temp of 150C. The driver is MUCH more likely to burn out, meaning the light will simply shut off, and stop drawing current. Even in a worst case scenario, with serious overheating, you are VERY unlikely to have a genuine safety issue. Almost all safety problems happen with mismatched or poor quality cells (or both). That is why we constantly insist everyone buy quality cells, and check voltage especially when using multiple cells in series.

WalkIntoTheLight said:

Some lights do have thermal protection that dims the light if it starts getting too hot. Unfortunately, most do not.

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Yes, but from what I have seen, these are only timeouts. So after 3 minutes or so, the light switches to the next lowest mode ostensibly to "prevent overheating and save the battery". There doesn't seem to be any temperature sensing going on.

smooth2o said:

Yes, but from what I have seen, these are only timeouts. So after 3 minutes or so, the light switches to the next lowest mode ostensibly to "prevent overheating and save the battery". There doesn't seem to be any temperature sensing going on.

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There are lights with true thermal protection. The Nitecore TM series have temperature sensors, not timed stepdowns. As mentioned earlier, the Zebralight SC600 Mk II L2, has a temperature sensor, and dynamically adjusts output to keep the light within a safe temperature range. (I.e., the light will stay brighter longer in a cool environment.) Many lights do just have timed step-downs, but if you want more advanced regulation, you can get it.

thedoc007 said:

There are lights with true thermal protection. The Nitecore TM series have temperature sensors, not timed stepdowns.

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Uhh, yeah well, one place you'd think you'd have to have it. But not in most everyday lights.

Hmm my p12 starts to step down after a time given. I have left mine on for 3+ hours and it slowly stepped down from Turbo to medium than low. It never got hot enough to not handle.

I guess it shows each flashlight is different...?

As long as you get a light which has at least timed step down (which seems like all lights these days) you should be fine. It's really unlikely it would get jostled and ramp up then again continuously so that the timed step down couldn't cool it down.

If you are worried then don't keep 18650's in hot environments in the lights and lock out lights if possible.

Mr. Nobody said:

Hmm my p12 starts to step down after a time given. I have left mine on for 3+ hours and it slowly stepped down from Turbo to medium than low. It never got hot enough to not handle.

I guess it shows each flashlight is different...?

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If you remember from the above discussion, my light was buried under several other things and in it's sheath so there was little or no way to dissipate the heat. I think that made quite a difference, it might have even stepped down and have been on a lower setting....

smooth2o said:

If you remember from the above discussion, my light was buried under several other things and in it's sheath so there was little or no way to dissipate the heat. I think that made quite a difference, it might have even stepped down and have been on a lower setting....

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After reading a few reviews on the P12 light, it steps down from High (turbo) to lower settings to avoid damage due to heat.
Selfbuilt reported http://www.candlepowerforums.com/vb...-2xCR123A-RCR)-Review-BEAMSHOTS-RUNTIME-VIDEO two step downs on the P12 light.

What may have felt hot to you may have been well within the temperature range for the light. Not saying it was a good thing for the light to be left on, but should not have caused an issue.

I had a TM15 in the holster activate in my coat pocket. I don't know how long the light was on, but it slightly melted the top of the holster. The battery tube was warm, but no problems with the light. After that I started locking out the battery by loosening the tube instead of just using the light lock out feature.

smooth2o said:

If you remember from the above discussion, my light was buried under several other things and in it's sheath so there was little or no way to dissipate the heat. I think that made quite a difference, it might have even stepped down and have been on a lower setting....

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Yes I have also tested my light with it on Turbo 1000lm in my pocket for 2 hours and it got very hot. So I understand ur situation where it being confined in a sheath under other objects could cause it to br super hot. But the cool down is quick once the light drops to high.