Cheap LED Aux Lights - Interesting Failure

[kdtrull]

I ordered a set of these a couple weeks before the 2018 Colorado trip:

https://www.amazon.com/gp/product/B01MDJK1AJ/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1



They're pretty bright and hard to beat for 18 bucks.

At about the one day old mark, one of them partially failed.....about 1/4 brightness of normal/good unit.

I don't think I've ever seen this particular failure mode in a LED.  At first, I just assumed it was the driver circuit.  Considering the affordability, I just ordered another set and replaced the failed light.

Then I disassembled the bad one.

This dark charred spot in the middle used to be a crystal clear and really bright LED.  But, somehow it's roasted on the outside yet continues to operate...very interesting failure mode to me:



As shown below, it still functions to the extent that it emits a fair amount of light considering the amount of crud on the surface.  The driver circuit is fully operational.



I still think is a fine deal for the money.

[sctparker]

discolored primary optic failure is common in chinese leds using pmma plastic lens (not silicone) at that price it's a good chance it's not silicone

And if it is a silicone lens the  brown discoloration is from exposure to VOCs . This discoloration of the lens is on the top of the LED chip, localized to the area just above the chip surface, closest to the source of heat  The VOCs in the  free space within the lens  do not cause permanent damage to the silicone material or the LED chip.
Some of the time  removing a secondary optic or venting the LED's environment will allow it to clear and recover in just a few hours of operation. But  the discolored VOC in the silicone polymer will not clear if the LED's operating environment remains saturated with the VOC.

Oh forgot to add Why  a dumb old redneck has this info in his head
I know this from a meeting with a led guru about some lights we have installed lately and are being denied warranty, ( $ 300 in lights plus labor out of my pocket so far to replace ) that did the same thing .not buying those anymore

[kdtrull]

Great info.  I might like to do some more reading on this....not for any particular reason....just to understand better.

[norton73]

What's VOC?

[kdtrull]

Volatile Organic Compounds...I think.  I still don't understand the effect....need to read more.

[kdtrull]

Fairly short and to the point:

https://www.lrc.rpi.edu/resources/newsroom/pdf/2012-2013/LED-VOCs8511.pdf

[sctparker]

Volatile Organic Compounds...I think.  I still don't understand the effect....need to read more.

Thats it

My understanding ,if I remember right,  from Mr. Steinke lll (spelling) ,he works/worked for cree in North Carolina, it happens in blue,violet  and white leds because they have a short wavelength and higher photonic energy than red, amber and green leds .

The chinese acrylic lens gets hot and actually gets brittle and turns brown from heat from the diod and can be removed but the diod will be exposed

[LawnmowerRG]

Interesting I may do a little research on this myself. Thanks for the info Scott.

[kylepeterson]

I have a stack of old led bars, and 4-5 new ones. the old ones go on for "I gotta have light"rides, and I consider the new ones experiments.

you just can't trust a new part.