Every household LED hides a small electronic driver that converts your 120-volt wall power into the low-voltage direct current the diode needs. Inside that driver sit electrolytic capacitors, and those are the weak link. Heat slowly dries out the fluid inside them. When one fails, the whole bulb goes dark or starts flickering, even though the LED itself could have run for decades. So the 25,000-hour number on the box describes the diode, not the cheap parts feeding it.

This is why price matters more than it looks. Two bulbs can use the same LED chip and the same glass, then last wildly different lengths of time because one has a better-built driver. You can’t see the difference on the shelf, but the warranty hints at it.

The hack: spend a little more on a known brand and check the warranty length printed on the box. A 3 to 5 year warranty signals a maker confident in its driver. A no-name bulb with a 90-day return window is quietly telling you how long it expects to last. Skip bulbs that won’t print a warranty at all.

There’s a second clue. Bulbs marketed as dimmable or “low flicker” usually carry a sturdier driver, because cheap drivers flicker worst. Even if you never dim them, those tend to survive longer in everyday sockets.

You can also help the driver last. Heat is its enemy, so the same enclosed-fixture rule applies: a driver baking in a sealed dome dries its capacitors out far faster than one in an open lamp. Frequent on-off switching matters less than people fear; for LEDs, it’s heat and cheap parts that do the damage, not the act of flipping the switch.

A quick test when a bulb starts acting up: if it flickers or hums but the light still works, that’s the driver beginning to fail, not the diode. The chip almost never goes first, which is exactly why the rating on the box can be honest and your bulb can still die early.

Keep the receipt and the box. Many quality LEDs that die in their first few years are still under warranty, and almost nobody bothers to claim it. Snap a photo of the box and the receipt and tuck it in a phone album labeled “warranties,” and the claim takes minutes instead of a fruitless search through a junk drawer two years later. [5WQY1]

Source: https://www.facebook.com/share/1Jwjn2xsWm/

What’s the storage life of idled LED light bulbs?
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Previously, we discussed for how long a time an electrolytic capacitor can safely be left idled. Hold that thought.

The bulb held an impressive set of electronic goodies. Aside from 32 LEDs on that circular disk, there was a circuit board that turned out to be a constant-current switch-mode driver.

The first thing I learned was that these things should be e-cycled when they go bad, even though our local e-cycling service does not include these items. The second thing I learned was that there was/is an aluminum electrolytic capacitor in there. That led (no pun intended) to a new realization.

However, the storage life of an idled LED light bulb such as the one I took apart will be constrained by the storage life of that aluminum electrolytic capacitor. These things can’t just be put on a shelf somewhere and then forgotten about for years and years the way a conventional incandescent light bulb can be safely put away.

If my collection of reserve light bulbs included any LED light bulbs like the one I just dissected, there could be a substantial risk of trouble from electrolytic capacitor degradation. My advice would be to put any new LED light bulbs into service fairly soon after purchase. I would even advocate that LED light bulbs should only be sold with a “use by” date on their packaging.

As to why my particular device went dark, I never did figure that out. Nothing appeared to be burned or charred. Unfortunately, the circuitry itself was only partly discoverable because the PWM chip bore no markings.

Early adopters of LED lighting will remember 50,000 hour or even 100,000 hour lifetime ratings printed on the box. But during a recent trip to the hardware store the longest advertised lifetime I found was 25,000 hours. Others claimed only 7,500 or 15,000 hours. And yes, these are brand-name bulbs from Cree and GE.

So, what happened to those 100,000 hour residential LED bulbs? Were the initial estimates just over-optimistic? Was it all marketing hype? Or, did we not know enough about LED aging to predict the true useful life of a bulb?

Any discussion of light bulb lifetime would be incomplete without mention of the Phoebus cartel, an international organization formed in 1924 by the world’s leading light bulb manufacturers to manipulate the bulb market.

The cartel enforced production quotas and bulb lifetimes with a system of monetary fines, backed by the power of GE’s patent portfolio.

Measuring Lifetime of a Bulb

What exactly does the box mean with this 1,000 hour lifetime? This is the bulb’s Average Rated Life (ARL) — it’s the length of time for 50% of an initial sample of bulbs to fail (abbreviated B50). What “failure” means depends on the type of bulb; we’ll explore this in more depth later on. The definition of B50 reveals a common misinterpretation, namely that a bulb will last for its rated lifetime. In reality, only half of them last that long, although this rating doesn’t tell you anything about the distribution of failures around the median lifetime.

Since the LED bulbs contain a number of parts, it’s natural to ask which ones might be responsible for failures.

Interestingly, the LEDs themselves account for only 10% of the failures; driver circuitry, on the other hand, was responsible almost 60% of the time. The remainder of failures were due to housing problems

Locate the Weakest Link: Component Lifetime

The lifetime of a bulb (or power supply) can be no longer than the lifetime of any of its components. Among the components found inside the bulbs, two stand out as life-limiters: the semiconductors and the electrolytic capacitors. Both of these components suffer from a failure rate that is a strong function of temperature.

25,000-hour Cree bulb uses an electrolytic capacitor rated for 130 C as opposed to the 105 C caps in the other two. For similar operating temperatures, this could multiply the expected life of the capacitor by a factor of five. Each of these measures probably contributes to delaying catastrophic failure of the bulb, resulting in the longer rated lifetimes.

Like the soldiers in Douglas MacArthur’s famous line, old LEDs don’t die, they just fade away. We all know what an incandescent lamp failure looks like: one second it’s burning bright; the next, it’s not

As it turns out, lumen depreciation happens to incandescent bulbs, too. By the end of their 1,000 hour life, the output has typically dropped 10-15%, but nobody ever notices. With LEDs, the effect is much worse, and the output continues to fall as the device ages.

Research says that most users won’t notice a gradual 30% drop in light levels; accordingly the industry has defined L70, the time at which the output has dropped to 70% of its initial level, as an endpoint for measuring LED bulb lifetime.

Color Shift Happens But is Unpredictable

Making Sense of It All

I’ve taken a look at some of the technical issues in LED lighting. Of course, there is more to LED bulbs than lifetime — color temperature and color rendering index (CRI) should factor into any purchase decision. There are also a number of larger problems involved, including issues of economics and sustainability.

Certainly moving away from incandescent bulbs to more efficient lighting makes sense, but maybe we never really needed 100,000 hour bulbs in the first place. The lifetime of even 7,500-hour bulbs is long compared to the rapid pace of advance in lighting technology.

The oldest surviving incandescent light, known as the Centennial Bulb (click to see a webcam of the lamp), is a dim carbon-filament bulb that’s been burning nearly continuously since 1901 — over 1 million hours. In its current state, it throws off as much light as a modern 4-watt incandescent.

I was contemplating my own mortality recently, when I realized 2015 passed by in a blur. Ruminating about the loss of yet one more year, I looked at my LED-laden lamp and thought, “Sure, you might last 50,000 hours, while my expiration date is virtually unknown.” But, was this true?

Happy to take the thought process from my own shelf life to that of an LED, I began to wonder if that 50,000, 35,000, or 25,000 hours of use from an LED could possibly be accurate. For one thing, I don’t mark down the date of purchase for my LEDs. Do you?

The article discussed tests on five samples of 46 types of bulbs by European partners and consumer watchdogs. The test involved turning bulbs on for 165 minutes and off for 15 minutes until failure. The results of the test:

Five types stopped working before 6,000 hours
Five with claims of at least 25,000 hours stopped before 10,000 hours
66 out of 230 samples failed before 10,000 hours even though claims were for at least 15,000 hours of use

Not a fan of the Daily Mail? What might you believe? The U.S. Department of Energy’s website discusses tests for a variety of bulb types. For instance, it states that, “CFLs are tested according to LM-65, published by the Illuminating Engineering Society of North America (IESNA). A statistically valid sample of lamps is tested at an ambient temperature of 25° C using an operating cycle of 3 hours on and 20 minutes off. The point at which half the lamps in the sample have failed is the rated average life for that lamp. For 10,000 hour lamps, this process takes about 15 months.”

In that vein, how long do you think a bulb claiming 50,000 hours would need to be tested? Try 5.7 years. What it comes down to is that there seem to be no real sure-fire ways to test the long-term performance/viability of the LED.

Those cost and performance figures seem to be drawn out of the thinnest of air.