Author Topic: Why/how do these LED lamps fail so fast?  (Read 5285 times)

0 Members and 1 Guest are viewing this topic.

Offline soldarTopic starter

  • Super Contributor
  • ***
  • Posts: 3595
  • Country: es
Re: Why/how do these LED lamps fail so fast?
« Reply #25 on: September 24, 2023, 12:02:20 pm »
Have you measured the voltage across the LEDs which do work?
I did some testing with the first few LEDs of the strip and, apparently they are grouped in groups of 4 LEDs in parallel. I put about 40 or 50mA through the first group , which would mean 10 or 12 mA through each LED and they light OK and measure about 2.8V.

I then connected the two first groups and, sure enough, at the same current level I get about 5.6V. So those two groups are in series.

If all the groups of 4 LEDs were all connected in series we would have about 25 groups adding up to about 70V.

The PSU says 240mA and 40 to 76V which would mean a max of 18 W which is less than the 20W listed on the fixture.

240mA which would mean 60mA through each LED. Hmmmm....  But 60mA x 2.8V x 100 LEDs= 16.8W which is less than the 20 W nominal for the fixture.

In any case it does seem like the LEDs are being driven with too much power.

If the group of failed LEDs were shorted the others would just light normally. If they were open circuit the others could not light at all.

I measured the failed LEDs and they are opened, not shorted. I then soldered a 68 ohm resistor across in the hope that it may repair the problem but it does the same thing, it blinks on for just a moment.

Quite baffling to me.

ETA: I shorted the bad LEDs and the others now work correctly. I might shunt some current away. I will keep experimenting.
« Last Edit: September 24, 2023, 12:14:51 pm by soldar »
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 

Offline soldarTopic starter

  • Super Contributor
  • ***
  • Posts: 3595
  • Country: es
Re: Why/how do these LED lamps fail so fast?
« Reply #26 on: September 24, 2023, 01:07:03 pm »
I measured the current the PSU puts out and it is about 275mA which is in excess of the nominal 240mA.

That is about 69mA per LED.

If I put a 1K resistor in parallel it shunts about 70 mA away from the LEDs ... wasting about 5W but making life easier for the LEDs.

I might do that on all the other similar LED fixtures I have. That should prolong their life.

It would be better to adjust the PSU to output less current but I have no idea how to do it. I am attaching a photo.
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 

Offline T3sl4co1l

  • Super Contributor
  • ***
  • Posts: 22436
  • Country: us
  • Expert, Analog Electronics, PCB Layout, EMC
    • Seven Transistor Labs
Re: Why/how do these LED lamps fail so fast?
« Reply #27 on: September 24, 2023, 01:32:29 pm »
Probably there is a shunt resistor towards the output that could be increased, but if you can't identify the circuit and ICs, probably better not to screw with it.

You might also just have poor quality LEDs.

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline hobbylad

  • Newbie
  • Posts: 1
  • Country: gb
    • Hobbylad's blog
Re: Why/how do these LED lamps fail so fast?
« Reply #28 on: November 23, 2024, 03:38:21 pm »
I was equally puzzled seeing so many of my LED lamps fail. I could not resist doing an autopsy. Posted the results in my blog below:

https://hobbylad.wordpress.com/2024/11/17/the-curse-of-the-failing-led-lamps/
 
The following users thanked this post: BILLPOD

Offline tunk

  • Super Contributor
  • ***
  • Posts: 1099
  • Country: no
Re: Why/how do these LED lamps fail so fast?
« Reply #29 on: November 23, 2024, 04:09:19 pm »
If you double the resistor value, the current will
be halved, reducing the temperature. This should
increase the bulb life.
 

Offline cosmicray

  • Frequent Contributor
  • **
  • Posts: 343
  • Country: us
Re: Why/how do these LED lamps fail so fast?
« Reply #30 on: November 23, 2024, 06:27:53 pm »
From the wordpress document ...

Quote
The PCB is glued to an aluminium heatsink

That is a sign that the LEDs are being run out towards the datasheet limits. Normal practice is that 50% of the power is being dissapated as heat, but a Cree Thermal Management document says to plan for as much as 70% heat. The heat is what destroys the LEDs. Get rid of that heat, and they will last a very long time.
it's only funny until someone gets hurt, then it's hilarious - R. Rabbit
 

Offline jmelson

  • Super Contributor
  • ***
  • Posts: 2851
  • Country: us
Re: Why/how do these LED lamps fail so fast?
« Reply #31 on: November 24, 2024, 12:19:19 am »
From the wordpress document ...

Quote
The PCB is glued to an aluminium heatsink

That is a sign that the LEDs are being run out towards the datasheet limits. Normal practice is that 50% of the power is being dissapated as heat, but a Cree Thermal Management document says to plan for as much as 70% heat. The heat is what destroys the LEDs. Get rid of that heat, and they will last a very long time.
Yup, I built my own fluorescent tube retrofits with a commercial constant current supply, see :
http://pico-systems.com/Lighting.html
I did this about 11 years ago.  I made a very conservative thermal design, with PC board as the thermal sink, and they have lasted quite well.  Possibly there is a tiny bit of brightness loss over this time, but I am REALLY happy with the results and longevity.  I am running 20 1W LEDs in series, at just about the 1 W level each, total power draw from the mains is a measured 21 W.
Jon
 

Offline Pid

  • Newbie
  • Posts: 1
  • Country: au
Re: Why/how do these LED lamps fail so fast?
« Reply #32 on: November 24, 2024, 08:48:03 am »
Anyway, regarding LEDs: they are extremely long lived, in and of themselves, when ratings are respected.

The phosphor is actually the higher wear element, as it tends to fade over time.  The power density on it is quite impressive, for just a powdered mixture of ceramics that have this one magical property (fluorescence).  The blue LED chip itself also declines, but slower.

But that's just the LEDs themselves.

What's powering them, is another matter.

Lifetime can always be lower, and when it is economical to do so, it absolutely will be done.  Electrolytic capacitors are the most obvious and worst offender, with 2khr 85°C parts being common picks.  Put that in a stuffy lamp fixture and it might last mere months!

Exactly, the "50,000 hour operating life" specification is a fantasy based on the operating life of the LEDs to reach 50% brightness and has nothing to do with operating life and reliability of the LEDs and ballast.

When California passed their LED bulb mandate, they based the economics on that 50,000 hour operating life saying that LED bulbs would actually cost less over the long term.  (1)  After a few years, they admitted in a report that that operating life was grossly exaggerated (I knew that) and that the economics were so bad that incandescent bulbs were better; the extra cost of the LED bulbs was greater than the extra cost of the power for an incandescent bulb.  (2) Unfortunately, but not surprisingly, California has since censored that report and removed access to it, because fuck you citizens.

A reliable electronic ballast needs to not use operating life limited parts like aluminum electrolytic capacitors, be significantly derated, and include protection circuits which themselves will not fail.  Because of operating temperature, it probably also needs to use hybrid construction.

(1) I do not believe that politicians are stupid enough to fall for this.  They did it deliberately for purposes of rent seeking, so fuck them.

(2) I have had the same experience with government mandated electronically commuted motors which replace less efficient shaded pole motors.  Their operating life is short and replacement cost is high so their total cost of ownership is higher despite the power saved.

My understanding is that LEDs are rated by average rated life the same metric used for incandescent lamps.
 

Offline cosmicray

  • Frequent Contributor
  • **
  • Posts: 343
  • Country: us
Re: Why/how do these LED lamps fail so fast?
« Reply #33 on: November 24, 2024, 11:27:04 am »
Anyway, regarding LEDs: they are extremely long lived, in and of themselves, when ratings are respected.

The phosphor is actually the higher wear element, as it tends to fade over time.  The power density on it is quite impressive, for just a powdered mixture of ceramics that have this one magical property (fluorescence).  The blue LED chip itself also declines, but slower.

But that's just the LEDs themselves.

What's powering them, is another matter.

Lifetime can always be lower, and when it is economical to do so, it absolutely will be done.  Electrolytic capacitors are the most obvious and worst offender, with 2khr 85°C parts being common picks.  Put that in a stuffy lamp fixture and it might last mere months!

Exactly, the "50,000 hour operating life" specification is a fantasy based on the operating life of the LEDs to reach 50% brightness and has nothing to do with operating life and reliability of the LEDs and ballast.

When California passed their LED bulb mandate, they based the economics on that 50,000 hour operating life saying that LED bulbs would actually cost less over the long term.  (1)  After a few years, they admitted in a report that that operating life was grossly exaggerated (I knew that) and that the economics were so bad that incandescent bulbs were better; the extra cost of the LED bulbs was greater than the extra cost of the power for an incandescent bulb.  (2) Unfortunately, but not surprisingly, California has since censored that report and removed access to it, because fuck you citizens.

A reliable electronic ballast needs to not use operating life limited parts like aluminum electrolytic capacitors, be significantly derated, and include protection circuits which themselves will not fail.  Because of operating temperature, it probably also needs to use hybrid construction.

(1) I do not believe that politicians are stupid enough to fall for this.  They did it deliberately for purposes of rent seeking, so fuck them.

(2) I have had the same experience with government mandated electronically commuted motors which replace less efficient shaded pole motors.  Their operating life is short and replacement cost is high so their total cost of ownership is higher despite the power saved.

My understanding is that LEDs are rated by average rated life the same metric used for incandescent lamps.
The finished consumer device (a light bulb) may well be rated like that, some of this discussion is about the component parts (i.e. the LED chip). Those tend to have a much longer life span, when not pushed to the electrical maximum ratings.
it's only funny until someone gets hurt, then it's hilarious - R. Rabbit
 

Offline David Hess

  • Super Contributor
  • ***
  • Posts: 17427
  • Country: us
  • DavidH
Re: Why/how do these LED lamps fail so fast?
« Reply #34 on: November 24, 2024, 05:57:58 pm »
My understanding is that LEDs are rated by average rated life the same metric used for incandescent lamps.

No, the operating life of the LED bulbs was rated to be the operating life of the LEDs which is based on how long it takes for the LEDs to reach 50% brightness, so 50,000 hours or whatever.  This is irrelevant because LED bulbs fail in other ways, long before that number is reached.  Incandescent bulbs are rated by mean time to failure and designed so they say for a 1000 hour life.
 
The following users thanked this post: Pid

Offline coppice

  • Super Contributor
  • ***
  • Posts: 10031
  • Country: gb
Re: Why/how do these LED lamps fail so fast?
« Reply #35 on: November 24, 2024, 06:07:12 pm »
Has anyone seen screw in or bayonet LED bulbs that are rated for use in an enclosed or semi-enclosed luminaire? For both CFL and LED bulbs the life has a lot to do with their running temperature, which can be changed a lot by the air flow. CFLs go downhill several times as quickly with the restricted air flow in an enclosed luminaire, but look so ugly out in the open. LEDs seem to be similar. I wonder how the average life of luminaires with integrated LEDs, that have some space to breath, compare with bulbs that can get pretty hot, even without restricting their air flow.
 

Offline floobydust

  • Super Contributor
  • ***
  • Posts: 7678
  • Country: ca
Re: Why/how do these LED lamps fail so fast?
« Reply #36 on: November 24, 2024, 06:48:26 pm »
I haven't and doubt they exist for the reason below. There's screw-in but no bayonet bulbs aside from old automotive this side of the Atlantic.

I say the main reason LED bulbs are crap is because of the sea of patents particularly on heatsink design.
So getting convective cooling in an enclosed fixture, it can't be done, legally. Cree has the patents for heatsink fins, along with related litigation with Feit etc. 
Meanwhile, households get smooth body bulbs that can't expel the required heat.

I just replaced a bunch of Ecosmart bulbs (enclosed fixtures), Home Depot/Walmart pretty low quality and they run very hot. Maybe 12-18 months life.
Autopsy showed the plastic body had cracked in two, 130°C rated 15uF Aishi cap seems worn at 10uF plastic wrap cooked and linear IC seems to have issues. They just sit there very dim. LED's look OK.
10 years ago Ecosmart were smoking and burning, a few fires so those were recalled 554,000 bulbs. Interestingly, they had fins and design house "Lighting Science Group" did EcoSmart, Sylvania, Westinghouse and Definity.
So you see the problem with one design being flawed and many brands get affected. Or the skirting the patent issue, there is massive litigation still going on.
 

Offline IanB

  • Super Contributor
  • ***
  • Posts: 12537
  • Country: us
Re: Why/how do these LED lamps fail so fast?
« Reply #37 on: November 24, 2024, 07:44:56 pm »
Has anyone seen screw in or bayonet LED bulbs that are rated for use in an enclosed or semi-enclosed luminaire? For both CFL and LED bulbs the life has a lot to do with their running temperature, which can be changed a lot by the air flow. CFLs go downhill several times as quickly with the restricted air flow in an enclosed luminaire, but look so ugly out in the open. LEDs seem to be similar. I wonder how the average life of luminaires with integrated LEDs, that have some space to breath, compare with bulbs that can get pretty hot, even without restricting their air flow.

Try looking at filament design LED bulbs like, for example, the Philips Ultra Definition kind. In these bulbs most of the heat is dissipated by the filaments, and less by the electronics in the base. The bulb itself does get warm over time, but it never gets hot to the touch. If you run them on a dimmer they get even less warm.
 

Offline floobydust

  • Super Contributor
  • ***
  • Posts: 7678
  • Country: ca
Re: Why/how do these LED lamps fail so fast?
« Reply #38 on: November 24, 2024, 08:47:14 pm »
Isn't that the worst possible configuration for getting rid of heat?
The filament in free space, enclosed in the bulb. Dissipate 5-12W? With tungsten, yeah but I'm not an optimist.
It might be as you say that these filament bulbs have no LED driver, just the series string so a bit less heat.
"...average life of 15,000 hours/13.7 years... 3 year warranty" (Feit)
Mainly radiation and a little conduction heat transfer on the one end.

"Feit Electric announced that it owns a set of patents directed to covering the yellow material used on LED filaments." against GE and against Ledvance LLC etc.

It must be some high temp material  :-//

Feit Electric Announces First Patent Enforcement Action Against Infringing White LED Filaments

Then Seoul Semiconductor (sold under Philips name) and Seoul Viosys are suing Feit again.



All this litigation just costs us, it gets added onto the bulb price and circumventing a patent usually means compromise ala hot running short life for other manufacturer's offerings.
 

Offline cosmicray

  • Frequent Contributor
  • **
  • Posts: 343
  • Country: us
Re: Why/how do these LED lamps fail so fast?
« Reply #39 on: November 24, 2024, 09:11:26 pm »
Isn't that the worst possible configuration for getting rid of heat?
The filament in free space, enclosed in the bulb. Dissipate 5-12W? With tungsten, yeah but I'm not an optimist.
It might be as you say that these filament bulbs have no LED driver, just the series string so a bit less heat.
"...average life of 15,000 hours/13.7 years... 3 year warranty" (Feit)
Mainly radiation and a little conduction heat transfer on the one end.

For incandescent bulbs, base down is best for heat convection (because the filament is where the heat is). For LED bulbs (with the one side PCB backed with aluminum), base up is better (because otherwise you are using the heat to slowly cook the LEDs/electronics). Sealing everything in a constricted air space is probably bad for both types.
it's only funny until someone gets hurt, then it's hilarious - R. Rabbit
 

Offline coppice

  • Super Contributor
  • ***
  • Posts: 10031
  • Country: gb
Re: Why/how do these LED lamps fail so fast?
« Reply #40 on: November 24, 2024, 09:13:16 pm »
The filament style LEDs keep the heat away from the base. So, the driver, and especially the capacitors in the driver, are not being roasted. The driver itself is only a small part of the dissipation of the lamp in any sanely designed LED lamp. The interesting thing is at first sight those filaments look like their cooling will be really poor, but they actually seem to get the heat into the surround gas quite effectively. An IR camera doesn't show them as major hot spots. This is great for a reasonably cool running exposed lamp. However, if you put one in an enclosed luminaire, do they slowly cook if the lamp runs for hours?

A general problem with luminaire design is their designers still seem to be living in the era of incandescent lamps, and haven't even caught up with CFLs. Their idea of adequate cooling is based on an incandescent lamp which is more efficient with poor cooling, and heat issues are all about not catching fire, or setting fire to the surroundings. I mean, its pretty common for luminaires to keep falling off the ceiling if you use incandescent bulbs and fix them with plastic screw hole plugs. The designs assume they won't be able to set the ceiling material on fire, but don't allow for softening a plastic hole plug enough for the screw to gradually pull out.
« Last Edit: November 24, 2024, 09:20:12 pm by coppice »
 

Offline IanB

  • Super Contributor
  • ***
  • Posts: 12537
  • Country: us
Re: Why/how do these LED lamps fail so fast?
« Reply #41 on: November 24, 2024, 10:13:05 pm »
Pictured below is the packaging for a Feit Electric bulb. It shows an enclosed outside lantern fixture as a possible use.

Also pictured is the packaging for a Philips bulb. It says "Suitable for use in enclosed fixtures."

The packaging for some GE candle bulbs (not pictured) says "Use in totally enclosed fixtures may result in lower lamp life."
 

Offline coppice

  • Super Contributor
  • ***
  • Posts: 10031
  • Country: gb
Re: Why/how do these LED lamps fail so fast?
« Reply #42 on: November 24, 2024, 10:27:24 pm »
Pictured below is the packaging for a Feit Electric bulb. It shows an enclosed outside lantern fixture as a possible use.

Also pictured is the packaging for a Philips bulb. It says "Suitable for use in enclosed fixtures."

The packaging for some GE candle bulbs (not pictured) says "Use in totally enclosed fixtures may result in lower lamp life."
Those Philips Ultra Definition bulbs seem to hit all the right points. Dimmable, suitable for enclosed luminaires, low flicker, high CRI, and cheap. They don't appear to offer anything similar in Europe, and the less capable products they do offer are more expensive.
 

Offline David Hess

  • Super Contributor
  • ***
  • Posts: 17427
  • Country: us
  • DavidH
Re: Why/how do these LED lamps fail so fast?
« Reply #43 on: November 24, 2024, 10:42:19 pm »
After testing various LED bulb brands from Home Depot and Lowes to quick destruction, I starting buy just Cree bulbs online and I started experimenting with their smart bulbs not long after Cree was sold and everything broke when their bulb designs were silently changed.  I have been using Wiz bulbs since, but 100 watts equivalents (14.5 watts) are not bright enough for me.

I thought tunable bulbs would help me with seasonal affective disorder but I cannot tell any difference.
« Last Edit: November 25, 2024, 08:38:34 pm by David Hess »
 

Offline coppice

  • Super Contributor
  • ***
  • Posts: 10031
  • Country: gb
Re: Why/how do these LED lamps fail so fast?
« Reply #44 on: November 25, 2024, 02:56:10 pm »
I was just looking at the Philips LED offerings in the UK. They have this page https://www.lighting.philips.co.uk/consumer/led-lights/quality-of-light-led-lighting on the importance of high CRI. That page links to their actual high CRI lights, where it says "We can't find any products that match your selection". :)
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf