The lifetime of white LEDs is touted by manufacturers and sellers as 100 thousand hours. From my own tests, I’ve found that to be far, far from the truth. I’ve purchased white LEDs on eBay from manufacturers in China and Hong Kong, and set them up on a power supply to test their lifetimes. I usually put four on so that I don’t get misled by a single bad one.
I have put the following types of white LEDs on 24/7 test:
3mm white LEDs
5mm everyday common white LEDs
8mm “superflux” four-legged white LEDs
“strawhat” white LEDs
10mm 5-chip, 1/2 watt white LEDs
10mm 1 watt white LEDs
Most of these were bought on eBay from foreign sellers, typically in China. I put them on a power supply set for constant current, typically at half their rated max current.
About 2 months after I have put the LEDs on 24/7, I found them to be getting dim. They have lost more than half of their brightness. A month is about 730 hours, so 2 months or actually 62.5 days is equal to 1500 hours.
To give you an idea, the lifetime written on the side of a 75 watt incandescent light bulb package is 1200 hours. The LEDs are not doing much better as far as lifetime is concerned. A CFL has a much greater lifetime, something over 10 thousand hours. This comparison shows the LEDs have very short lifetimes. The main difference is that incandescents and CFLs usually don´t fade away, they abruptly end their life with failure. Instead, LEDs just get dimmer until they no longer emit enough light to do the job.
Here is one of my blogs about the lifetime of 10mm1 watt single chip white LEDs.
Have you ever tested other color lifetime leds, like red or green?
If yes, what did you get?
I have indirectly. I bought a few Xmas tree LED lights year before last and strung them up in the bedroom after xmas for the last year or so. They have gone out three times, each time because a blue LED failed. The remaining blue LEDs are getting dim, unlike the other colors which are still bright. This lease me to believe that the blue LEDs have a somewhat shorter lifetime than other colors. One explanation I’ve heard is that the shorter wavelengths have UV rays which cause the epoxy to deteriorate. But I have never seen any visible thing that looked like deterioration. I think it’s because the blue LEDs are made cheaply and don’t have the right design and chemicals to prevent failure. That sounds kind of broad, but then I’m not a LED engineer.