Overheat Protection

[UFO]

As a new member, I don't know if this has been covered yet. If it has, I do apologize.

I have a question about what some companies call: "Intelligent Overheat Protection", or a "Step-Down". I understand the need for this but I don't clearly understand how it works.

Case in point: Let's say I have a flashlight with 3 brightness settings: 1000 Lumens, 350 Lumens, and 40 Lumens.

The instruction manual says after 5 minutes or so on the brightest setting, the level will drop down to a lower, safer intensity when it detects dangerous heat levels. Okay, but how far will it drop? Will it drop down to the next highest level (350), or will it drop down to something less than 1000 but above 350?

No company I've seen has ever stated how far the brightness level will drop. They just tell you it will.

How do you know how far these flashlights (Fenix, Nitecore, Olight) etc, will drop down in brightness? Is there any way to determine that?

_________
Mike

 

[crn3371]

I'm new here, so take what I say with a grain of salt. Most (all?) lights, especially on Turbo mode, will step down due to heat issues. I think a lot of the listed mfgr ratings are on the optimistic side and the only way to get a true sense of performance is to look for user reviews.

 

[jon_slider]

How do you know how far these flashlights (Fenix, Nitecore, Olight) etc, will drop down in brightness? Is there any way to determine that?

there are reviews with runtime graphs like this:
(pic is a link)

 

[Fireclaw18]

I have a question about what some companies call: "Intelligent Overheat Protection", or a "Step-Down". I understand the need for this but I don't clearly understand how it works.

There's no single standardized answer to this question.

How a light ramps down to handle heat depends on its internal programming. Different lights will be programmed differently. One might step down to 35% at 3 minutes, another might stepdown to 50% at minute, and another might gradually rampdown when too much heat is detected. The only way to know for sure is to look at a graph posted by a reviewer, like in the post above.

However,

Many older generation LED lights tended to use a timed step down method of controlling heat. They would run for a fixed period of time at full power... perhaps 1 minute or 3 minutes, then step down to a lower setting.

Many newer LED lights no longer use a timed stepdown. Instead they have a thermal sensor and are programmed to gradually ramp down when the sensor detects too much heat, and then ramp up when heat goes down. Output can vary wildly on these lights depending on whether you hold the light in your hand or not, air temperature, and if there is any wind. This is generally considered to be a superior method of heat control compared to the older timed stepdown method.

 

[UFO]

Thanks guys for taking the time to explain this. I'm starting to understand how this works now. Most appreciated.

_________
Mike

 

[Juggernaut]

How aggressive is modern day heat step down programing? Do lights ramp down at the point of possible damage to the LED? Or is it much safer than that and they ramp down at a point before longevity of the LED could be compromised. I remember back when the step down function of a high powered LED light was to turn it off when you could no longer hold on to it. 120-140 degree external temp Talking direct drive P7, MCE, multi bank Cree P4s etc. It was considered perfectly fine for the LED if you could still hold onto the light near the head.

 

[aznsx]

UFO - I agree that most lights are ridiculously under-documented where this is concerned, and it also annoys the heck out of me. In the case of my Streamlights, at least they almost always include a rough-but-effective output graph in their 'Fact Sheet' that tells me most of what I need to know. There's nothing quite as good as a graph. Some other manufacturers also provide such output graphs (I think Fenix often does as I recall, but I'd have to check), and probably some others, but far too few. Even then it may not conclusively tell me if it's a time or temperature function.

I often tend to gravitate towards manufacturers who know how to document products. I figure if they don't know how to document their products, they may not know how to design / build them very well either. It's an indicator, but the two things don't always track of course. As JS points out, reviews are often the best / only source of such info, but I shouldn't have to get that from the aftermarket. The better manufacturers should provide that themselves. If they don't, I consider that a bit of a 'red flag'.

 

[UFO]

How aggressive is modern day heat step down programing? Do lights ramp down at the point of possible damage to the LED? Or is it much safer than that and they ramp down at a point before longevity of the LED could be compromised. I remember back when the step down function of a high powered LED light was to turn it off when you could no longer hold on to it. 120-140 degree external temp Talking direct drive P7, MCE, multi bank Cree P4s etc. It was considered perfectly fine for the LED if you could still hold onto the light near the head.

When I read about the "Overheat Protection", my understanding is that the light will step down in brightness when it detects "Dangerous Heat Levels". They don't ever specify exactly what that means.

And that brings up (for me), a completely new set of issues. The majority of some lights like Fenix, Nitecore, and Olight, have lights with 1000+ Lumens. I've heard stories from my friends that some of these lights, even with the stepdown, get so hot that you can no longer hold on to it. So I ask myself, what good is a flashlight that I can't hold in my hand?

My Streamlight Stinger LED puts out about 425 Lumens. That's not too bright considering the 1000+ lights out there, but it will continue with that level of brightness (no stepdown), until the battery goes dead, and I can hold on to it for that entire time.

Some people say that Streamlights designs are archaic and old fashioned, but I don't mind that at all when I consider the above scenarios.

 

[UFO]

UFO - I agree that most lights are ridiculously under-documented where this is concerned, and it also annoys the heck out of me. In the case of my Streamlights, at least they almost always include a rough-but-effective output graph in their 'Fact Sheet' that tells me most of what I need to know. There's nothing quite as good as a graph. Some other manufacturers also provide such output graphs (I think Fenix often does as I recall, but I'd have to check), and probably some others, but far too few. Even then it may not conclusively tell me if it's a time or temperature function.

I often tend to gravitate towards manufacturers who know how to document products. I figure if they don't know how to document their products, they may not know how to design / build them very well either. It's an indicator, but the two things don't always track of course. As JS points out, reviews are often the best / only source of such info, but I shouldn't have to get that from the aftermarket. The better manufacturers should provide that themselves. If they don't, I consider that a bit of a 'red flag'.

I agree with everything you just said.

 

[jon_slider]

there is a difference between Maximum output and
Sustainable output

as a rule of thumb, from a single 18650 LiIon
1000 lumens is not Sustainable
400 lumens IS Sustainable

so old lights, that use RCR123, and have "low" outputs (less than 500 lumens), do not have the heat challenges of the newer lights, that claim 1000 lumens (for 30? seconds).

assuming a target of 1 hour runtime on maximum, an RCR123 can only Sustain about 200 lumens.

So, the choice of battery is an important factor in what the possible Maximum output will be, and also what the possible Sustainable output will be.

you really have to look at runtime graphs for the specific model, and battery type, you are considering. (sometimes not easy to find)

 

[bykfixer]

Blame it on 'the lumen wars' ufo. See, we can't let that other brand know our light has to step down 55% in order to not commit suicide by heat when pushing an LED way beyonds its safe limits. I have a SureFire light that boasts 1200 lumens from a pair of CR123 batteries for about a minute and a half, then steps down to "somewhere areound"……lol. But by the time that 90 seconds is up the batteries are so warm I get the sense I'm walking around with a hand grenade and the pin fell out somewhere in the tall grass.

Now at least Gene Malkoff came right out and said what's what with his BodyGuard model flashlight.

I'd rather have a good heat sync and a reasonable output than some over the top mega-boost that feels like you need an oven mitt in 24 seconds.

 

[jon_slider]

Now at least Gene Malkoff came right out and said what's what with his BodyGuard model flashlight.

yeah, 800 lumens, drops to 175 lumens after 8 seconds, and the battery lasts 15 minutes... on Maximum... if the operator keeps switching off and back on every 10 seconds to get the Turbo back

I was unable to find a runtime graph but that output and stepdown sound pretty ridiculous, to me..

my interpretation is that it is a 175 lumens sustainable, with a battery killer mode that gives 800 lumens for less than 10 seconds before a timed stepdown..

it is not even thermal regulation..

the lumen wars have created some ridiculous high lumen claims..

800 lumens from One CR123 is just bragging rights.. not sustainable at all.

compare and contrast to the HDS output strategy
250 lumens maximum from one CR123
timed step down to 166 lumens after 40 seconds.

(pic is a link)

neither of those outputs produces significant heat, plus the driver also has thermal regulation, that would lower the output even more, IF the light could get hot at that output (it cant).

as you can see again, 166 lumens is the sustainable output.. not the 250 lumens.. and the battery lasts over an hour, instead of 15 minutes on the Malkoff at 800 lumens..