When the lights on my bench came on one of them started flickering in intensity. Initially I thought it was the driver failing, but it turned out that one of the series arrays of LEDs was flickering on and off. It soon stopped, but is now dead. That means the full 20W of power is now being dissipated by the remaining string of 10 LEDs, so I don't think they're going to last too long.
Then I noticed that in the other light where I had used a 50W LED (5 series strings of ten chips in parallel) the middle one had gone out. So now the 20W is being shared amongst four strings which still equates to half their rated current.
But it shows that this appears to be the failure mode of these high power LEDs. Progressive loss of strings in the array with increased burden on the remaining ones. The intensity also drops noticeably as the overdriven LEDs are much less efficient.
So I guess it pays to use the larger wattage LEDs to have some built in redundancy. But it also suggests that you do need to check and possibly change the LEDs in these floodlights now and then.
Then I noticed that in the other light where I had used a 50W LED (5 series strings of ten chips in parallel) the middle one had gone out. So now the 20W is being shared amongst four strings which still equates to half their rated current.
But it shows that this appears to be the failure mode of these high power LEDs. Progressive loss of strings in the array with increased burden on the remaining ones. The intensity also drops noticeably as the overdriven LEDs are much less efficient.
So I guess it pays to use the larger wattage LEDs to have some built in redundancy. But it also suggests that you do need to check and possibly change the LEDs in these floodlights now and then.
I like your videos but it's "milli amps" dude. You're the only person I've ever heard say "mill amps".
My 100W LED torch has failed in the same way, one of the strips of 10 died. So for now I just tweaked the driver to run at 90w instead.
I think if you put one resistor probably 4ohms 5watts in series of this LED chips will save them! here in my area one electronics store is selling these type of LED Chips with resistor attached to it and they are pretty reliable. I'm using one of these on my desk.
oh great….
so i can expect to be doing some repairs soon then lol, i used them in my 806 camper
I bought one from ebay, it failed within a few hours of owning it. Reason= no thermal paste on the Aluminium heatsink.. £3 and 30mins later, fixed! Still works to this day 🙂 Althought the fins on the back get up to about 60C.
The problem with these is that individual leds are not balanced. it could be that most of the current flowing through one row of leds. Have you played with better quality leds yet?
How about swapping the led out and replacing it with a series of cree XML-2 ?
Aha! Another Won Hung Lo factory reject I guess.
LED chips there all still work, just the cheap and nasty bond wire has fractured off of the top of the die. the flickering is it cooling and heating up till it finally moves far enough away to lose contact, possibly with some of the soft encapsulant moving into the space to fill it. If you apply pressure over each led you probably will be able to see which one has fractured, though do this at low current so you can see the chips.
I guess the more chips that are in series the lower the overall reliability. That probably means a 10 chip led will be 10 times more likely to fail than a single chip. The weakest chip failing, shutting down the whole strip. So much for the 30,000 hours life!
Maybe the heatsinking is not good enough, specially as you have increased the power