How long do LED shop/ceiling lights really last at full output anyway?

I don't run statistics, but I appreciate what you wrote because my fluorescent lamps don't last more than a year or two, it seems.

I used to mark the bulbs with a Sharpie, but I stopped doing that long ago. I don't think I *ever* got anywhere near the claimed life.

But we turn them on and off a few times each day.

Reply to
Algeria Horan
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This is good to know because the whole point of this thread is to nail down the actual life of the lamps.

Of course, you can't expect me to NOT buy at Lowes or Ace or Home Depot, for quantities such as we buy for a home as replacements, so the word 'quality lamps' is to be taken with a grain of salt.

But at least it's good to know that you *understand* that an LED is never as bright as it was on its first day, and that cycles, and heat, and vibration exacerbate the existing cracks between crystals, such that LEDs drop off exponentially in light output over time.

As stated in the standards that Jeff kindly referenced early on in this thread, the diminished light output is very difficult to detect, since it happens over time, and since there may be other bulbs compensating for the lack of output, such that an LED bulb that has actually reached it's L70 lifetime may not be easily observed by you.

Nonetheless, if the driver failed, which I think can be the weakest point (that premise needs to be explored), you'd know that. But you might not know when any particular bulb has reached its L70 point without isolating the bulb and actually measuring the output (since the gradual decline in output isn't going to be suddenly noticeable, according to that report Jeff referenced).

My point is that things failed, perhaps, and you don't realize it. But that needs to be explored since you'd know of some failures (but not all, unless the bulbs are isolated, and if you have a keen eye for such things).

Reply to
Algeria Horan

I should have guessed it was you. I like to explain how things work, without offering a judgment or opinion. This type of question really belongs in Candlepower Forums.

It happens. I have some marketeering experience somewhere on my resume. Speaking of bullshit: "How LED Lighting May Compromise Your Health"

Nice summary. Sounds about right. I believe there are a few other standards that I missed. Standards are a good thing. Every company should have one.

Nope, because it's all we have to work with. Like I ranted, nobody does 30,000 hr life tests. Therefore, nobody knows the "real world" lifetime of an LED light. The best we can do is parametric testing, accelerated life tests, and the usual guesswork. The first two are quite valid and result in numbers that usually come fairly close to reality. The guesswork, you can guess what I think.

It's much like MTBF (mean time between failure) which attempts to estimate the life of a device based on historical tests and operating conditions. These component estimates are conglomerated into a figure for the device. However, the intent is not to estimate the lifetime, but rather the number of expected failures in a population of LED's. "What Every LED Engineer Needs to Know About MTBF" (Note: I haven't read through this yet)

600lumens / 9watts = 67 lumens/watt. Barf. Philips claims 200 lumens/watt and Cree claims 300 lumens/watt: You may not see that at Costco for a while, but maybe if Philips and others get back into the LED biz. It's not too obvious, but both claims assume that the LED is cooled to approximately room temperature.

For good reason. From the point of view of the manufacturer and vendor, the ideal product blows up 1 day after the warranty expires. I've ranted on the topic before, where simulation and modeling tools are used to insure that multiple parts all fail just after some preset time limit. My favorite example are GE(?) water heaters with 6, 9, and 12 year warrantees, and roughly proportional pricing, but where the only difference is the type and size of the anode rod. Details if anyone wants them.

Talk to me in 30,000 hrs and we'll compare notes.

You have a talking clock?

Reply to
Jeff Liebermann

Which is impossible to do based on unreliable anecdotal evidence in an usenet newsgroup read by perhaps a hundred people.

Reply to
Scott Lurndal

One more. ARL: "Average Rated Life (ARL) is how long it takes for half the light bulbs in a test batch to fail" I seem to recall others, but I'm too lazy to Google.

Reply to
Jeff Liebermann

How does the cost of a Kwh contribute to the rated lifetime of an LED-based illumination device? I smell a red-herring. Costs of electricity vary widely nationwide. Yes, California has more expensive electricity (specifically to encourage conservation) than other parts of the country, but that is not a factor in rated lifetime.

Tj and cycles (on/off) would seem to be the two major controlling factors, just as they are for incandescents.

Tj = Junction Temperature.

Reply to
Scott Lurndal

Well, you're entitled to invent a new testing standard, along with yet another collection of artificial test conditions, that will satisfy your vision of a "real world" test. I've only had three LED light failures. All were in the bathroom, all were failures of the driver electronics, two were mounted inverted (base up), and all were retrofitted into incandescent fixtures with miserable ventilation. Therefore, I propose a bathroom LED test, which includes heat, condensing and non-condensing humidity, on-off cycle time, over voltage, erratic power glitches by PG&E, limited ventilation, and dust accumulation. Such a test will clearly define what might be expected from "typical" bathroom LED service. The EU micro managers have specs and tests for almost everything and will surely appreciate your efforts on their behalf.

I think you need a major dose of testing reality. Instead of LED's, let's try drug testing. In order to release a new drug, one of the tests that a pharmaceutical company must survive is a cancer test. This is usually done with mice or rats. However, they're not ordinary mice or rats. If such a cancer test were performed on the common and ordinary breeds of mice and rats, the number of tumors found would be very small and therefore statistically useless. In order to get statistically significant numbers, mice and rats that are genetically predisposed to developing cancerous tumors are used.

For LED testing, much the same trick is used. If you don't have a sufficient number of failures during the test period, and you can't extend the test period, you do whatever it takes to produce those failures. The easiest is to elevate the temperature. For incandescent lamps, raising the filament voltage also works. By plotting a trend line of different temperatures or voltages, one can extrapolate the graph to obtain a fairly good approximation of the expected lifetime at more sane temperatures and voltages. That's how one avoids multi-year tests.

There are quite a few products that suffer from inflated specifications. Battery capacity (in particular 18650 cells), flashlight output in lumens, wi-fi range/speed, laptop battery life, laser printer toner cartridge pages, inkjet cartridge pages, etc. All of these are characterized by inflated claims contrived to make the numbers bigger. I can explain any of these in detail if you want to know how it works. The reasons are competitive pressure and product differentiation. Every manufacturer and vendor are trying to sell on the basis of everything except price. So, they push service, warranties, packaging, bonus junk, etc. Eventually, they run out of these fringes, and start inflating the specifications on the assumption that the typical customer doesn't understand the specs. I think this thread demonstrates that this is true. Instead of inflated, perhaps "grossly exaggerated" might be more accurate.

Sniff...

Reply to
Jeff Liebermann

I remember reading in your prior reference that the time for half to fail isn't useful for LEDs though, since they fail differently.

Reply to
Algeria Horan

Yeah, it's me. My friends joke I'm half the Internet alone.

I'm always solving problems, asking questions, delving deeper, etc., as are you (but you don't like to admit it).

You have always been balanced, ever since I learned from you how to set up my WiFi rooftop antenna on a.i.w years ago, when you still frequented that forum (before you absconded to s.e.r that is).

Me too, truth be told (but I try to hide my curricum vitae far more so than you do).

When I was in Marketing, we made hay with any advantage we could, and we swept under the rug all the disadvantages. Plus we said things like "better" and "new" and "more" since they couldn't be easily disputed.

Basically, we took whatever it was that the engineers gave us, and we marketed the shit out of it, so that it *looked* like gold in the literature.

But it was no different than anything else was. Every good thing had a bad downside to it.

Like everything on this planet does.

OMG. I'm losing out on all that healthy infrared radiation! And that EMF is the "leading cause of blindness" in the USA! Quick. Gimme one of those famous infrared saunas in Santa Cruz hippytown!

:)

Thanks for noticing. I generally read all your references. If you are gonna go to the trouble to reference them in a thread I authored, I'm gonna go to the trouble to at least skim them (I read fast, very very very fast, faster than most people can talk, and I type fast too, so it's easy for me. When I was a kid, I was in a special reading program for the gifted, where they had a machine that forced me to read faster and faster and faster - dunno why my parents subjected me to that - but they did.)

I think the important point is that we each can pick the standard that makes the most sense to us, but also, that information has to be readily available to us.

I'm not sure yet, which is the readily available standard, but I'd prefer the L70 myself, to be the standard that I get the information on.

At the moment, I'm guessing the one LED lamp I have will last no more than 4 or 5 years. (Call me up in 5 years and I'll let you know how it turned out.)

Except that every once in a while, there will be failures in the drivers that I don't think are being tested here. Are they?

Understood.

Makes sense.

The abstract mentions MTTF, which is essentially what I'm asking in this thread, I believe, whereas MTBF is for repaired items (according to the abstract).

It implies that we should use MTTF since we're gonna throw out the LED fixture once it fails us.

That Fairchild paper goes into details (e.g., how to accelerate and what happens if the failure rate is 0), but that's the net I take out of it by a quick skim.

The funny thing is that there are so many stupids out there who talk about "warranties" as if they're NOT purely marketing bullshit!

On the car forums, I hear all the time people comparing batteries by their warrantee, as if the warrantee conferred some magical quality on the electrical and lifetime properties of the battery!

They even compare *tires* by warrantee! Geesuz. It's sad how stupid people are, in general. Very very sad. Sigh.

Interesting. Very interesting. I just had a water heater go, in fact, and, um, I shouldn't say this, but I had never replaced the anode. All that was left was some whitish stuff and the inner steel wire. The heater corroded in

7 years, but that was my fault for not replacing the anode (although it was almost impossible to twist off, so, if you're gonna replace anodes, at least crack the top hexnut every six months or so).
Reply to
Algeria Horan

Fair enough point.

Reply to
Algeria Horan

Good point. I don't even remember how we got into the costs, other than I made a joke that I'd love to live in Louisiana where the costs actually were listed as around that amount.

Agreed. We're talking actual lifetime of the LED "unit" (which includes whatever can be replaced, which, for a household unit, is usually the driver and chips and the housing, all in one package like my Costco setup).

Interestingly, the paper Jeff originally cited mentioned three main factors, all of which exacerbated existing physical cracks between crystals:

  1. Cycles
  2. Heat
  3. Vibration

To that, Jeff noted his bathroom fixture had a few more, mainly: a. Humidity/moisture b. Dust & orientation (aka heat retention or dissipation) c. Voltage variations (e.g., we have *many* power outages per year here)

I'm only about 30 miles from Jeff (give or take) but we lose our power so often that I don't know of many people who don't have a built-in generator out here (plus we need the power to pump the water to fill our sinks).

So, overvoltage is key here. Very key. (I have holes blown in some of my appliances, for example - even though I can't prove what caused it - certainly I can see the burn marks and the high failure rate of fixed appliances.)

Reply to
Algeria Horan

Fair enough response.

I believe that. I suspect, but without personal experience, that the LED drivers are the weak link in the LED setup. I haven't looked at one yet, but a single electrolytic cap would tell me as much. I know you know electronics well, so you'd know more of what to look for, but, I know wet caps dry out (among other things that go poof over time).

Yup. You had 'em all, especially:

- Heat

- Cycles

- Humidity (which wasn't mentioned in the previous articles)

- Overvoltage (which also wasn't mentioned, but happens all the time) etc.

Fair enough assessment.

I have one degree in the life sciences, so, I'm familiar with details.

I have another degree in engineering, so, again, I'm familiar with details (remember, I invited you to the inventors club, long ago?).

Ummm... er.... almost *all* products suffer from inflated specs. You know this from looking at anything built by Apple, for example.

Yup. I was in marketing myself. The stupids outnumber the intelligent parsers 10,000 to one.

There are still people who believe Techron (aka polyetheramines) are something special to Chevron, for example, or that high-octane fuel is somehow (magically?) better than regular octane fuel.

Or, that a battery with a longer warrantee is somehow, electrically, better than a battery with a shorter warrantee.

Back to LED lifetime claims, I'm shooting for 4 or 5 years. If my one LED fixture meets that expectation, I'll be happy as the Philips wacko sized fluorescents lasted 1/4 that each time, until I got sick of replacing them.

Reply to
Algeria Horan

You've still failed to challenge any of the methodology listed in Appendix C.

I'm not challenging any facts. I know damn well I don't have any. All I have is my own experience. Those would be anecdotes, not data.

But unlike yourself, I don't go around saying the experts are wrong. I look at the source, the methodology, think about any motivation the source may have to falsify and judge who to believe.

If that chart shows an average price for California that doesn't square up with your experience, then maybe other consumers in California pay less. What you see on your bill is irrelevant to the average price of electricity in California.

So, you started out with the completely specious claim that LED lifetime was for the LED component and not the driving electronics. That is still ridiculous.

LEDs work and work well. Most people can buy them and never have to change the bulb again. You running around making blind assertions isn't going to change any of that.

So, how long to shop/ceiling lights _really_ last? Why not read the package and believe what it says? If you want to challenge the published numbers, it stands to reason, you have to use better methodology than that shown in Appendix C. Good luck with that.

Reply to
Dan Espen

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