High output LEDs in plastic bodies.

[Melkor]

Will the heat buildup damage the LEDs when used in a G2 or something? By high output, I mean like Luxeon III, Cree and the like.

 

[Gunner12]

Depends how hard the LED is driven and how long it is ment to run. The Streamlight Propoly Luxeons use a Plastic body but the LEDs are not overheating even during extended usage.
For a modded plastic light to high power LED, I would recomend driving the LED at a resonable amperage and get the biggest heatsink that will fit in the light.

 

[Melkor]

I was thinking along the lines of a Luxeon or Cree drop in. Probably Wolf Eyes, maybe Bug Out Gear, or something like that.

Actually, I'm an idiot. I just remembered the flashlightreviews.com test in which a Wolf Eyes Luxeon was used in a G2 and the heat buildup caused the output to fluctuate wildly.

Okay, so how about Cree LED drop ins in a G2? Do they get as hot as Luxeons?

 

[jbviau]

I've got a Wolf Eyes D26 Cree drop-in running in my SF G2. It's the new-ish 130 lumen one with a voltage range from 3.7V-13V. The longest I've had it running continuously is 3 minutes or so, and the body didn't change temperature noticeably at all. With a regular P60 incan bulb, you can feel the heat coming out of the front of the G2 within a few seconds of turning it on. With this one, there's no heat at all. The Crees are just very efficient, I guess, at least for normal (i.e. not extended) usage. Anyway, that's one man's unscientific opinion. A runtime plot would be nice. Anyone?

 

[2xTrinity]

IMHO an LED drop-in designed for plastic bodies should definitely have some sort of thermal feedback, similar to the Maglite drop-in design. Actually, that would be a good idea for just about any LED light, even a metal light -- as there's always the possibility of a light being left on inside of an insulated jacket pocket or something. Having the light lower the output as the temp gets dangerously high would be a good idea. If the heatsinking is good enough, of the on-time is short enough, then the light will stay at full output safely.

 

[ringzero]

IMHO an LED drop-in designed for plastic bodies should definitely have some sort of thermal feedback, similar to the Maglite drop-in design. Actually, that would be a good idea for just about any LED light, even a metal light -- as there's always the possibility of a light being left on inside of an insulated jacket pocket or something.

Excellent point 2xTrinity! Agree 100%.

There was a thread on this very topic not long ago. Several people on that thread were ridiculing the whole concept of thermal limiting circuitry for LED lights - mocking it as an unnecessary complication. That attitude demonstrates ignorance of the basic properties of semiconductors.


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[Gryloc]

Hmmm, that would be nice in more flashlights! I have a Seoul running at about 500mA in the plastic ProPoly 4AA. I was using it one day, and I set it down when I was distracted. About 3-4 hours later, I grabbed for it to snoop around the house when I noticed that it was still on! Argh! It was sitting face down on the table and when I picked it up, it was very dim and I was worried that the heatsink got too while it was running. I had just charged the batteries, too. Everything is fine as it must not have gotten that hot to do any damage. Heck, even the batteries were in good shape after charged. I got lucky. I have left the the same light on before while in my backpack. Luckily, another student asked why might backpack was glowing. :laughing: Yeah, I bet a current reducing circuit would have helped for such plastics flashlights as the PP.

I do not think that plastic lights are not that bad for higher powered LEDs, though. At one time, I had the Seoul cooking at 800mA in the PP 4AA when using the Downboy circuit, and it would only get too hot to touch (the bare aluminum heatsink/reflector assembly) after about 10 minutes. Yeah, that is not really that good, but you get a brilliant light for your "few minute" uses. A switcher chip went bad on the circuit due to my error, so I switched back to the stock circuit. I am lucky that the light was only powered at ~500mA when I left them on unattended.

I can see how the thermal circuitry would be annoying to some due to the output fluctuation, but I am sure that the circuit could be perfected and the odd fluctuations can be diminished. Maybe some local private LED driver circuit makers can incorporate this into their future driver circuits (hint hint).... That would be nice and I would buy it. Make it user adjustable (temperature) and have it so you can solder on your own thermistor I am sold!


-Tony

 

[bfg9000]

the body didn't change temperature noticeably at all. With a regular P60 incan bulb, you can feel the heat coming out of the front of the G2 within a few seconds of turning it on. With this one, there's no heat at all.

That's the problem--with a plastic light the body won't get hot at all while the LED bakes. Incan lights project infrared heat out the front while LEDs transfer heat backwards to their heatsinks.

The difference in heat produced by a Luxeon, SSC or CREE at the same drive level and Vf is negligible. It's just the SSC and CREE are twice as bright there...

350-400mA is perfectly fine in a plastic light with just a star. Lots of cheapie LED lights like Dorcys come straight from the factory this way and they do OK since they are driven at <1.5w or so. Sure they get pretty hot, but not enough for them to noticeably degrade before they go obsolete anyway. The problem with those drop-ins is they often run at ~600-700mA and 2.5w in an insulated light is probably too much without some sort of thermal regulation.

 

[Melkor]

Thanks for all of the information, guys. Although I love the looks of the olive drab G2, I guess I'll go with an aluminum bodied light just to be on the safe side.