Could the sun "cook" an led...?

As the title implies...could the sun cook an led in a light that is kept in a vehicle?

Long story short, my dad was looking for a light that would illuminate a feeder he has in his back yard about 150 feet from his deck. I figured I would start with the light I kept in my truck which was a Dorcy 220 lumen thrower, ac/dc rechargeable with a Nicad battery pack. It has a deep smooth reflector the same diameter as a Mag. I left it with him along with the car charger and told him to charge it because I hadn't charged it lately. So he did. When I asked him how it worked, he said not very good. He said it barely shone on the feeder and was a weak yellow color. I thought this was odd as 1) it throws really well, even if not fully charged and 2) its a cool white emitter. ..no yellow what so ever. So I brought the light home and the led is visibly "brown" in color and barely puts out any light.

So that brings me to my original question...could the sun, if shining through the windshield and directly into the reflector, cook the led of a light left in a car?

I know that the light didn't accidentally get switched on as it has a small, hard to activate side switch and it would be shinig directly onto my climate controls and radio due to its position in the truck, which was always pointing upward from under the seat by the hump in my Ford Ranger pickup. Its this very position, with the head poking out from under the seat where the sun could hit it, that makes me wonder if this is possible. I have no other explanation if not.

I put my Solarforce MPP1 in my truck this morning, back in the same spot the Dorcy rode. On my way home this evening, I was thinking about this again and decided to move this light to the glove box.

I would like to hear what you guys think about this.

Collimation goes both ways... light travels out of and into an LED in almost the same manner. In a flashlight, light is emitted from a single point outwards, most of this is directed forward by the reflector and out the window. Apply the same concept backwards.

LEDs create heat, but they can also sink heat when off. Put a LED flashlight with a nonblack body bezel up in sun light then hit it with an IR thermometer you'll find the LED is hotter than the rest of the bezel. Constant bombardment of high intensity sunshine long enough will cook the phosphorous light brown.

On a different side, LEDs can be used as photodiodes. Applying light to an LED from the outside creates a voltage potential through the junction. An easy way to illustrate this is to solder two LEDs together, positive to positive negative to negative. put a sheet of cardboard in between. drop light on one and look at the other. You'll notice its glowing nicely. While not usually a concern, some drivers may have longevity problems if you feed power backwards long enough. One more reason to store lights bezel down in the car.

And its not just sunshine shining into the bezel that one should worry about. I used to have a Honda CRX. For those who aren't familiar with the design, it was a small two-seater with a sloping glass hatch back. Even with the windows cracked it got hot inside. I used to get manufacturing related samples in the mail, and one of them was a small strip of cardboard with what looked like a series of small Hershey's kisses on one side. What they were were slump cones. Each one was designed to slump at a different temp. They were used to calibrate manufacturing processes that used heat. Well, the Honda had a dash board storage tray with a lid in the middle of the dash. I left the strip in there one day in mid summer. When I came back and checked, they had all slumped up to the 145 F cone. So the only place I leave my flashlight these days is under the seat or in the center console, which gets less direct sunlight is better insulated than the glove box.

I somewhat doubt the heat inside a car could fry a decent LED light no matter how hot it got.

Modern LEDs are designed to be reflowed onto stars at relatively high temps with a soldering iron or other heating source without suffering damage. I think this would probably be much hotter than any conceivable heat from just leaving the light in a car even if you lived in Death Valley.

Regarding the sun: a previous poster stating the collimator goes both ways. So if you leave the light with its bezel facing directly at the sun for an extended period, that's a lot of concentrated light right on the led surface. Not sure if this would be enough to fry it though.

I think a more likely explanation is that the light isn't well built and simply lacked adequate heatsinking. In poorly built lights or incorrectly assembled lights it is relatively common to have LEDs overheat during operation and suffer damage that matches exactly the damage you described.

Illum said:

Collimation goes both ways... light travels out of and into an LED in almost the same manner. In a flashlight, light is emitted from a single point outwards, most of this is directed forward by the reflector and out the window. Apply the same concept backwards.

LEDs create heat, but they can also sink heat when off. Put a LED flashlight with a nonblack body bezel up in sun light then hit it with an IR thermometer you'll find the LED is hotter than the rest of the bezel. Constant bombardment of high intensity sunshine long enough will cook the phosphorous light brown.

On a different side, LEDs can be used as photodiodes. Applying light to an LED from the outside creates a voltage potential through the junction. An easy way to illustrate this is to solder two LEDs together, positive to positive negative to negative. put a sheet of cardboard in between. drop light on one and look at the other. You'll notice its glowing nicely. While not usually a concern, some drivers may have longevity problems if you feed power backwards long enough. One more reason to store lights bezel down in the car.

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this is really interesting stuff !! thanks. however in the ops case and thinking about it, although possible i think the light would have to have been directly facing the sun yes ?
most likely just a light faliure.

Also consider VOC contamination: Chemical Compatibility If it's a brown smudge on the phosphor, this is possible. If it's the cause, open the bezel up and run it for a day or so. If things improve, great! If not, the phosphor got cooked.

Dashboards have been recorded up to 215F. ( Im willing to bed some dashboard somewhere has been hotter ).
That is dang hot. Add the reflector and your talking oven temperatures, so yeah I think it would have significant impact. On its own ( no dash ) pointed towards the sun on a 110F day - once, Im not personally sure, probably?
Repeatedly definitely.

yes, i had the same thing happen to flashlight that was sitting head up on the windowsill, it still worked, but the led was brown.

agreed. i best be more careful !

Yeah & in a vehicle I'd keep it out of the sun anyway so it's not in plain view.

ForrestChump said:

There you go, 2,740 posts with a join date of 2005.

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Hey you're on pace for ~35,000 posts in as much time, if you can maintain your current posts per day rate (keep it up)!

You my friend are observant.

Im a tad bit mental so when I focus on a subject I tend be as involved as possible. All I do is read. Im addicted to information.

I hope lots of posts aren't frowned upon here? Mods?

Unless there's a ton of fluff I wouldn't worry much about it. This brownie effect on the phosphorous though...I've only seen it on LEDs inadvertently isolated from its thermal relief during operation at spec. I have yet to notice it on LEDs in storage.

This all makes me wonder if I could do a bit of "tanning" on my streamlight with its bluish beam to turn it into a warmer color temp. I'd gladly lose 50- 100 lumens for a nice nw beam.

Heat was likely the problem. That and a not-so heavy duty LED.
Facing up in between the seats of a Ford Ranger wasn't like setting it on the dash.
You might consider a window shield though. Keeps temps a LOT cooler when the front window has direct sunlight. I keep my back window cracked on one that sits idle for months at a time. That and the side windows open about 1/8" or so with a shield over the front window really keeps the inside from getting so hot.

But you now have a nice warm beam with low output for 2am nature calls. :twothumbs

And get your pop a new model mini mag to hang by his back door. About $15 at box stores, runs fine off eneloops if he prefers rechargeables and will not only light up an area 150' away, but can fit in his pocket if need. You can get 5 packs of lanyards for like $5 online at the big A.
The trick to the mini mag is to twist the head like you like it and turn it on/off by the tail cap.

Edit:
This thread reminded me to check on the light in my truck...
An old incan that stays in the door...since I bought tthe truck in 98...


^^ had to clean up some alka-leak residue and sand the bulb housing...but she went right back to working.
A 2A all plastic with a brass runner with brass switch parts and spring at the tail.
Still had the original batteries.
Has some lithiums now.