Fenix L2D Q5 Premium Turbo mode warning?

[mighty82]

My l2d rebel 100 and q5 runs much cooler than my old p4. Never gets very hot at all. I remember i fell asleep with the old l2d on turbo beneath my pillow. Don't ask me how I just woke up because it was burning my hand.

 

[Handlobraesing]

Would you like a car that, when it sense it over heating in the slightest, just shut down in the middle of the freeway? Or, as the design should be, rely on the user to make an informed decision on what they are doing?

Who said something that shuts off at the slightest?

Microwave ovens, hair driers, laser printers, lighting ballasts all have thermal cut offs that powers itself off when the sensing point heats up beyond pre-set limit, but not at the "slightest signs" of overheating.

Even VCRs and such have a fuse inside that permanently cuts power to it when the current exceeds a set limit, which is far above "slighestly" overcurrent.

Many cars today do kill injection to some cylinders in the event of a cooling system failure or a gross overheating to allow the engine to cool by operating as an air pump, giving you the chance to limp along to the shoulder without destroying itself.

MagLED is thermally throttled for example.

A flashlight that's no worse than the generic ones out there would allow itself to heat up to destruction or hazardous conditions.

Someone asked how reviews are getting away with it. Chevofreak, a guy here who did the runtime test have said in posts that he fan cools lights under test, even though its not explicitly stated on the runtime chart.

 

[tobjectpascal]

just by experience if i leave my little flashlight going it gets almost too hot to touch but if i hold it in my hand the thing only gets a few degrees warmer than my hand, i do believe your hand will act as a heatsink, however i read that these new powerful LED's first have to be baked at 80c to remove moisture and the cree talks of 200 degrees (c) of heat to be sustained for 20 seconds or so to solder them .... point was if i'm holding it, it gets a little uncomfortable but it gets a hell of a lot hotter if i'm not holding it...

 

[TONY M]

My l2d rebel 100 and q5 runs much cooler than my old p4. Never gets very hot at all. I remember i fell asleep with the old l2d on turbo beneath my pillow. Don't ask me how I just woke up because it was burning my hand.

Hehe. Don't get me wrong I love the Q5 but the thing sure gets hot when left on turbo inside a well insulated coat pocket - really hot. So yes DO be careful where it is when its on turbo mode!

BTW. "mighty82", Do you personally prefer the tint of the r100 to the q5 outside? I'm just wondering if a warmer tint is better for outdoor work and mountainbiking.

Thanks

 

[Handlobraesing]

Hehe. Don't get me wrong I love the Q5 but the thing sure gets hot when left on turbo inside a well insulated coat pocket - really hot. So yes DO be careful where it is when its on turbo mode!

BTW. "mighty82", Do you personally prefer the tint of the r100 to the q5 outside? I'm just wondering if a warmer tint is better for outdoor work and mountainbiking.

Thanks

You can reasonably expect such will happen. If the light is capable of becoming damaging or dangerously hot, it should have a means of preventing it. This is more practical if the light already has a means of solid state dimming, as it would just need to implement thermal sensor input to override user setting.

Most LED lights don't have the power density of the lights in question here. I would think there are generic ones that can get really hot and to say "well that one gets hot too" is basically saying "ours are no worse than rest of them".

 

[tebore]

Would you like a car that, when it sense it over heating in the slightest, just shut down in the middle of the freeway? Or, as the design should be, rely on the user to make an informed decision on what they are doing?

I'm sure a car would operate for 2.5 hours after it has started to overheat and as soon as you change the coolant it'll be perfectly fine. The analogy doesn't work. Plus some cars can actually reduce power to limp home the Caddy Northstar engine comes to mind

Most high end lights, even Maglite has some sort of Thermal management. All the lights that have this don't just shut off but they go to a lower power level.

Fenix really needs to get some sort of thermal protection and reverse polarity protection in their lights. Not everyone is looking for max output, people who pay >$60 for a light are looking for some sort of piece of mind.

As far as I know all Crees still use glass domes but yes they feel squishy because they are allowed to move. Under the glass is silicon layer that allows for thermal expansion and absorb shock.

 

[Jarl]

I'm sure a car would operate for 2.5 hours after it has started to overheat and as soon as you change the coolant it'll be perfectly fine. The analogy doesn't work. Plus some cars can actually reduce power to limp home the Caddy Northstar engine comes to mind

And i'm sure it wouldn't. Friend of mine hit a badger, taking out the cooling to his engine completely. As soon as he could stop, he did; the engine was permanently damaged (the cylinder columns had warped or something) and the whole engine had to be replaced after less than 5 minutes of driving with no cooling.

I'd give it 15 minutes before an engine with no cooling tore itself apart (literally).

 

[Handlobraesing]

And i'm sure it wouldn't. Friend of mine hit a badger, taking out the cooling to his engine completely. As soon as he could stop, he did; the engine was permanently damaged (the cylinder columns had warped or something) and the whole engine had to be replaced after less than 5 minutes of driving with no cooling.

I'd give it 15 minutes before an engine with no cooling tore itself apart (literally).

Not every cars are equally tolerant. An anecdotal evidence is not necessarily a representation of typical.

 

[kongfuchicken]

If Fenix provides a warning, it should strike everyone that they had a good reason to. Why would we want to dispute it on the basis that someone has done it and doesn't see damage (as if anyone could detect early signs of damage with naked eyes).

Turbo mode is meant to be some kind of last resort notch 11. It overdrives the emitter far beyond its rated specs as well as beyond the heatsinking capabilities of the small flashlight body. It was NOT designed as high mode (or it'd been called high mode) and to use in the same manner as a regular level such as high.

Will it damage your light to run it for more than 10 minutes? Who knows? I don't and even Fenix is probably not sure. There isn't some magic timeline where the emitter goes poof at a round number of minutes; every second the emitter is running hotter than it should damages its efficiency and lifespan somewhat. 10 minutes is conservative and probably based on how fast it takes the body to heat up to an uncomfortable level. Would you damage your light if you left it on turbo in your coat for 2.5 hours? Would you damage your car engine if you ran it beyond 8000rpm for the entire gas tank? Like I said, who knows?

Would I take a chance? Meh... these lights are cheap enough that I probably wouldn't care as much. But in my opinion, turbo mode doesn't provide much utility other than impressing people into liking them and greatly reduces the reliability of the light.
Like a lot of us, after seeing turbo mode on, I am quite tempted to leave it on turbo; high mode, runtime and reliability lose all meaning.

Oh and as much as I agree with Handlobraesing that implementing thermal regulation (it's embedded in most regulator chips already, for crying out loud) would be better engineering, the few products that did weren't quite as well received as the ones that didn't.

 

[Jarl]

Erm, "drives emitter far beyond it's rated specs". No it doesn't- it drives it at 700ma for 180 emitter lumens. That's well within specs. However, overheating is a fair point. IMHO, providing it doesn't get hot to hold, it's fine. Not like it'll get used for 50,000 hours anyway!


@ hand: Although my anecdotal evidence is by no means a good, randomised, normalised sample, IMO it's good enough to make me sure that driving a car without cooling for 2.5 hours will cause permanent damage.

Since it won't cause permanent damage, perhaps you want to empty your coolant and drive around for 2.5 hours to prove me wrong?

 

[tebore]

You do realize the post about driving around overheating for 2.5 hours is sarcastic right?

 

[kongfuchicken]

Within specs for an emitter properly sinked; I wouldn't say tiny flashlight bodies are anywhere close to an adequate sink to dissipate the heat generated by an emitter driven at 3W.

If it were, why would the manufacturer need to put on such a warning?
I'm not the one who's telling you not to run it for more than 10 minutes, Fenix is; you can bet the they know quite more about the reliability of the lights they designed than you or me.

 

[Handlobraesing]

Erm, "drives emitter far beyond it's rated specs". No it doesn't- it drives it at 700ma for 180 emitter lumens. That's well within specs. However, overheating is a fair point. IMHO, providing it doesn't get hot to hold, it's fine. Not like it'll get used for 50,000 hours anyway!


@ hand: Although my anecdotal evidence is by no means a good, randomised, normalised sample, IMO it's good enough to make me sure that driving a car without cooling for 2.5 hours will cause permanent damage.

Since it won't cause permanent damage, perhaps you want to empty your coolant and drive around for 2.5 hours to prove me wrong?

I didn't say you're wrong. I was saying your/your friend's experience isn't necessarily typical of the duration w/o coolant before having serious problems. One might have an anecdotal evidence that he fell off a roof and got away with scratches and I might argue that might not necessarily be typical, or plain "untypical" if I have the data from similar accidents.

That's not encouraging people to go off the roof.

 

[4sevens]

I didn't say you're wrong. I was saying your/your friend's experience isn't necessarily typical of the duration w/o coolant before having serious problems. One might have an anecdotal evidence that he fell off a roof and got away with scratches and I might argue that might not necessarily be typical, or plain "untypical" if I have the data from similar accidents.

That's not encouraging people to go off the roof.

Handlo, do own a L2D that you can speak from experience?

 

[JasonH]

You may be true on several counts. (I do have a lot to learn about flashlights and thermodynamics) I am curious where you get hand having 24x thermal transfer than air. Any data on that? Air is obviously a good insulator, as everyone knows that trapped air in the form of styrofoam, house insulation and double paned windows, is quite a good insulator. While not as good as water (back to your radiator example), air-cooled engines perform quite well when there is air flow.

Doesn't really matter, but I thought I'd say it. It's not "air" in between double paned windows, it's argon gas, completely different.

 

[Jarl]

Doesn't really matter, but I thought I'd say it. It's not "air" in between double paned windows, it's argon gas, completely different.

If you want to nitpick, it used to be air, and probably still is in cheaper windows. Air is a very poor conductor of heat (though it convects very well).

 

[Irishsentry]

It could also be like the "Danger Hot Coffee" labels at McDonald's. SOME fool SOMEPLACE either has burned or WILL burn himself and sue.....just a thought. So they CTA by saying Danger Hot......

 

[Julian Holtz]

Well, I left my L2D on turbo mode under the pillow for 30min. It was a little hot, but not so hot that one might think that something would be destroyed.
I let it cool down, put fresh eneloops in it, and left it lie for half an hour in a drawer (no airflow). It was just lukewarm. I cant see how this light should be damaged if it is not purposely heat insulated.
During normal operation, there is no danger at all.

 

[RoyJ]

I think the best argument to date is "do you REALLY want to keep a light for 50,000 hours"?

Assuming an average 1 hr per day, which is fairly high even for flasholics, that's 50,000 days, or 137 years! Keep your Cree on the low setting and no doubt it'll last that long. But WHY?

I know that when a 200 lm/w, AA/18650 sized quad emitter light comes out in a couple of years, I'd much rather have that than my made in 2007 L2D Q5 running on "medium" to conserve LED life.

 

[Handlobraesing]

Oh and as much as I agree with Handlobraesing that implementing thermal regulation (it's embedded in most regulator chips already, for crying out loud) would be better engineering, the few products that did weren't quite as well received as the ones that didn't.

The one in Maglite didn't perform so well, as it was designed to operate in existing Maglite host. I think they did a good job of using thermal throttling instead of setting the module to operate at the low level from the start though, so the user can enjoy the full output for the first few minutes and often time, people use flashlights for few minutes at a time.

Mag design lets users take advantage of full power while still allowing continuous use without damage.

This is just one example of thermal management, but there are many different ways to implement it, such as full output being available until certain temperature, say 50°C on body is reached then throttle down to prevent temperature from going above 50°C. Once the body cools below an unlock temperature(say 45°C), full output can be activated again. This deliberate hysteresis ensures the light wouldn't hunt between full output enabled and disabled.