LED Household Bulb Longevity

[Martin]

1224 hours (=51 days) ago, I bought an LED household bulb that I am running 24/7 since that day.
When I first switched it on, I felt it was really bright but over the weeks, it dimmed. At least I had a notion it did. Recently I felt that it was pretty much on one level with some of my keychain flashlights, so that I ordered a second one of these houshold bulbs, same spec.
I put them both side-by-side. Here are two shots with different exposure:

Observation: The new bulb (left) is so much brighter than the used one (right), it appears that the used one is not even on. Yes, it is on and I swear its initial brightness was impressing like the left side bulb. I consider this the end of the "useful life".
The used-up bulb has spent all its life mounted upright in free air in a cool hallway.

These bulbs are branded "Lunartec" and I bought them at Pearl.
One has an E27 base, the other one an E14 base, but the specs are the same: 24 LEDs, cold white, as bright as a traditional 25W bulb, power draw 2W, 100000 operating hours.

I'm pretty much disappointed. I got 1.2% of the advertised lifetime and most of the bulb life it was below the advertised brightness.
The shop advertised these bulbs as being very economical, which is just not true. They cost EUR 9.90 each, lifetime was no longer than an incandescent bulb where I get a 5-pack for EUR 2.

What is your experience with LED household light bulbs ?
Is there a brand that is confirmed to achieve the advertised runtime ?

 

[2xTrinity]

The problem with the bulbs using discrete 5mm LEDs, is that those epoxy-encapsulated emitters are horrible for long-term use for anything brighter than an indicator light -- They trap the heat inside of them (rather than allowing it to dissipate). Enclosing THOSE in a plastic dome along with an inefficient driver circuit, that probably isn't very well regulated, makes the heat buildup even worse, and makes the LEDs prone to getting destroyed due to a voltage spike in the outet.

A LED emitter that woudl be likely to last longer would be ones that use high-powered LEDs, with integrated heatsinks, and with a very well regulated power supply -- provided they are NOT used in a recessed fixture that traps in heat. Downlight type fixtures should be designed as dedicated fixtures in order to work properly. There, the temp can at least be within acceptable range, and lifespan should be significantly longer.

The 100,000 hour lifespans are all bogus. Those are based on the lifespan of the emitter itself (assuming ideal heat conditions), not taking into account degradation of the phosphor (the portion that converts blue light into other colors). Phosphor life is the biggest limitation of fluorescent lamps and white LEDs -- lamps that have been on a long time tend to get discolored and lose efficiency compared to new ones. The only way to really have an LED last many tens of thousands of hours of real use, would be high quality*, well-heatsinked separate red, green, and blue emitters (no phosphors). One major problem with that though is that the green emitters are very inefficient, around 5% efficient compared to 40%-50% efficient for the best red and blue.

If there existed a green LED as efficient as red and blue (>40%) it would be emitting over 240 lumens per watt! If that breakthrough ever happens, I expect to see a lot more RGB type lights. Another advantage of RGB is that the color temperature could be varied on demand to achieve a cool white (stronger blue) or a warm white (stronger red).



*As far as I know, no such product exists yet.

 

[EngrPaul]

I've had a horrible time with 5mm LED's turning dark (nite lights). I've upgraded them and they went dark even more quickly than the originals. I'm now trying some power LED's instead, we'll see...

 

[mchlwise]

I bought two multi-led "bulbs" a few months back. They're on for about 6-8 hours each night.

One burnt out (or whatever, it doesn't light up anymore) a month or two ago. The other one is still working fine (for now).

From my experience, these are pretty hit-or-miss.

 

[Canuke]

<i>The problem with the bulbs using discrete 5mm LEDs, is that those epoxy-encapsulated emitters are horrible for long-term use for anything brighter than an indicator light</i>

Would that be true even if driven at spec (20mA)? My first thought is that these lights are probably equipped with cheaper diodes, then overdriven to compensate.

 

[2xTrinity]

<i>The problem with the bulbs using discrete 5mm LEDs, is that those epoxy-encapsulated emitters are horrible for long-term use for anything brighter than an indicator light</i>

Would that be true even if driven at spec (20mA)? My first thought is that these lights are probably equipped with cheaper diodes, then overdriven to compensate.

It would be true at spec as well. Most indicator lights are a couple mA at most, and those are the only LEDs I know of getting 100,000 hours of lifespan.

I know I've had some household bulbs -- using 5mm LEDs, driven right at 20mA. Even bulbs that are underdriven may have problems, as most cheap bulbs simply limit the current using a capactior in series (impedes AC), then rectify that current with a simple bridge and filter cap, and often direct drive from there. Others may use essentially a linear regulator with a resistor to bleed off excess voltage. Either way though, I think those kinds of cheap circuits are very susceptible to power surges/spikes, which could cause a small increase in voltage and burn out LEDs in a sudden "event".

 

[LEDninja]

I have a 48 LED bulb in which half the LEDs went black after about 1000 hours. 3 hours/night for about 1 year.
My 36 LED PAR 20 replacement has gone about 1 year now. Brightness holding up pretty well. I do not have a new bulb to compare but I compared it (rated 51 lumes) to my 2C MagLED (measured 52 lumens at FLR) and the MagLED is clearly brighter. I have PRESS & SEAL over the window of the MagLED so I am comparing flood with flood.
Try and stay with Luxeon based bulbs. The emitters are more rugged and should hold up better.
I like the tint of WARM WHITE luxeons but they are quite dim to start. Also the reflectors tend to produce a kind of hotspot so illumination is not very even.

There have been a couple of posts in which DX 61LED bulbs died in less than 2 weeks.

I would stay away from Cree XRE bulbs at this time. The ones sold now (DX/ebay) have unknown manufacturers with unknown design skills and unknown quality control. Don't have regulatory approvals either (CSA, UL, CE). I would wait for the manufacturers listed here to start shipping before I buy.
Cree to Showcase LED Lighting Solutions at Lightfair
http://candlepowerforums.com/vb/showthread.php?t=163733

 

[mmmflashlights]

I bought one of the 5mm LED cluster lights from FifthUnit about a year ago, I think it was around 36 LEDs. The piece of shet started having significantly dimming and/or failing LEDs within a few hours in 'room temp' in the open air. I had intended to use it to replace a CFL for 24/7 use, and it was basically completely shot within maybe 4-5 days. Heat was definitely the flaw in the light from what I can tell, and the conditions it were used in were not harsh at all.

 

[jrmcferren]

2xTrintity, yes such a device exists. They are made by Enlux and use red, amber, green, and blue in an array with proprietary technology. Second they have good thermal management (The body of the bulb is the heatsink). Also the floodlights meet the incandescent equivalent rating in lumens for the 45 watt spec (15 watt LED). The product described is the R30 floodlight and can be checked out at http://www.enluxled.com/.

 

[AndyTiedye]

Added to LED Fixed Lighting Threads

 

[racer7]

IMO, LEDs at present are not an economical or sane choice as a routine replacement for tungsten bulbs despite Euro regs and greenies in CA trying to push alternatives along. Maybe we'll get there eventually but it will take some serious technical jimps. Right now, compact flourescents are still only usable in some applications and they'be around a long time. They're still pretty worthless any place where you need a lot of light AND "fast on" because they require warmup time in larger sizes. (The first time I lit a major brand "50/100/150" compact fluorescent substitute, I thought it was defective - takes nearly 5 minutes to come to full power! I can read the main section of a newspaper in less time.)

IMO, at present LEDs can subsitute for undercounter lights and some strip lights in a few limited applications but even then are too costly so its more of a hobby or custom build exercise than anything else. I've got too many other things I want to to spend time designing and configuring led replacements for that sort of thing in my house.

Next household bulb changes for me are to try a few compact flourescents in some of my indoor floods but I figure that as about a 50/50 chance due to the usual lack of color balance control in compact flouresecent manufacturing (try getting a couple dozen matching ones), the problems with slow start, and the inability to use most of them on dimmers or other way to provide variable output. And there's no way they can replace the hi wattage halogen spots I use in some locations.

Racer7

 

[Martin]

The consumed bulb pictured above eventually met its definite end due to not being kid-proof. With the glass globe shattered, I had access to the PCB and measured the LED current. It is 16mA. Looks like a reasonable value, not overdriven. LEDs are getting warm but not hot. So probably the LED quality is the issue, here.
I replaced one of the LEDs with a JELED 50K, its focusing dome cut off to be comparable to the other LEDs on the PCB. Here are two photographs: Tissue diffuser and direct view of the LEDs:

Bottom line: Some LEDs, though driven at spec, last a lot less than 100,000 hours.

 

[jtr1962]

I suspect more than half the problem here is the driver circuit. Even if the LEDs are driven to spec, if the driver circuit doesn't filter spikes then the LEDs will degrade within a short time. A second problem is the assumption that driving the LEDs at 15 or 20 mA is OK. For really long term use figure on driving at 5 mA, 10 mA tops, if the LEDs are mounted on a PC board with fat traces for heatsinking. The problem with driving at spec is the LED's thermal resistance. For a 5mm LED this is around 300°C/W. Driving at 20 mA will cause a temperature rise of 0.02A*3.3V*300 = 20°C. Put enough LEDs in an enclosure with poor thermal transfer, and the body temperature of those LEDs can already be 30°C above ambient, meaning the junction is 50°C over ambient. This could mean junction temperatures of 90° to 100°C if used outdoors in warm weather. Even in a cool room it could mean 65° or 70°C. These kinds of junction temperatures result in very rapid dimming. For longevity it's best to keep the junction under 40°C. If you drive at 5 mA then your junction temperature rise over LED case temperature is only about 5°C. A well designed fixture will limit case temperatures to 5°C over ambient. The lamp should last tens of thousands of hours before dimming appreciably, even if used in warm weather. The reason this isn't done is that you obviously need about 3.5 times the number of LEDs for the same light. To replace a 40 watt bulb (~550 lumens) with LEDs driven at 5mA, you would need around 350 of the most efficient whites, or maybe 500 average whites.

5mm LEDs really only make sense in things like nightlights. 5 or 10 driven at 5 mA can provide ten or so lumens, more than enough for getting around. For higher outputs power LEDs make more sense in terms of initial cost, assembly cost, and longevity. You can replace the same 40 watt bulb mentioned above with 4 Cree XR-Es driven at 600 to 700 mA, depending upon bin. Total power consumption would be about 12 watts plus ballast losses. You would still need a decent-sized heat sink. Direct replacement of anything much larger than about 40 watts isn't really feasible at this point in time due to the size of the required heat sink, although it is easily possible with a dedicated (i.e. much larger) fixture. Once the 150 lm/W LEDs are out in a few years direct replacements of incandescents up to 100 watts, perhaps even 150 watts, should be possible.

 

[Martin]

Today, I visited a newly-opened DIY store. They were nicely stocked with Philips LED household bulbs.

I checked the lifetime (it is written on the packing): All colored ones are rated 20,000 h while both the warm white and the cold white ones are rated 6,000 h only. So we're moving away from the 100,000 h claim ? Good !

I believe the Philips figures are pretty close to reality, since it's a reputable company. And I assume they know how to build converters that don't dramatically reduce the LED lifetime. The difference b/w colored and white lifetime should be caused by the phosphors used in white LEDs.

With these lower figures, one of the big selling points of LED bulbs has dissolved. The 6,000 h for white LED bulbs are really not that spectacular, given that white fluorescent bulbs are rated 8,000 h.

 

[mchlwise]

I just had another multi-led "bulb" quit working on me over the weekend after less than a month of intermittent use.

It was a cheap $5 internet thing, but I could have gotten a CFL that would still be going strong for a LOT less.

 

[Illum]

clustered 5mm LED lights claim to be long life in fixed lighting running on AC really isn't. only place I would use one is to replace the ball in the refrigerator

for one thing the clustering of LEDs driven at spec or sometimes overdriven creates hotspots that increase the phosphor decay rate of the LEDs that eventually cook themselves to death.

I would much prefer a SSC/CREE based household bulb with [can't stress this enough] a suitable sized heatsink.

 

[3rd_shift]

It's not just the phosphors.
I have watched some of the blue leds in my led Christmas light sets dim and in some cases fail, while the rest of the other colors on the same string kept working.

The "all white" Christmas led sets have also dimmed a little after over 200 hours of use.

I have also had the oem "solid state" led in my 2002 4AA Dorcy, dim quite a bit after a few hundred hours of use with rechargeable nimh batteries for nightlight purposes. :candle:
This was my 1st led flashlight in 2002.

 

[lctorana]

Honestly, for night-light use, you can't beat neon. I know it's 120-year old technology, but horses for courses.

As for LED lighting for the home, I am eagerly awaiting this concept to go mainstream:
http://www.dealextreme.com/details.dx/sku.5766
It's a bit dear just yet, but give it time.

In the short term, now that high-wattage CFLs are on the market, we just don't need LED lighting.

But you can bet your house that when decent LED home lighting is made, CPF forum members will be the first to use it.

 

[Illum]

a little off topic

The "all white" Christmas led sets have also dimmed a little after over 200 hours of use

do you see very vet rapidly flashings in the white LEDs during normal use? assuming 60Hz....I'm assuming each LED is attached with a resistor of very high value since there was no wall worts on mine of any kind

 

[lctorana]

Persistence of vision maxes out at about 20Hz, otherwise you would see ANY light bulb flicker to some extent.