LED bulb failures?

I've read on this forum about people that have had LED lights "die" on them after a couple weeks or months. I was curious as to how common this is. They're supposed to last 100,000 hours by what I've heard. I would hate to put out $20 or $30 and have it konk out after such a short time, especially if it was the light I really depended on.

What light has failed on you? How long did you have it? Was it just the bulb, or some other part?

Some manufacturers overdrive their LED's in order to be able to print impressive output figures. Another culprit could be folks using lithium batteries in a LED light designed for alkalines. Lithium batteries (even rated at 1.5v) can output much higher voltage (closer to 1.8 to 1.9v) for an extended period of time during their life which would drastically overdrive a LED designed for 1.5v alkalines.

So far, none of my LED's have exhibited this problem, but then I never use lithium batteries.

Generally LED failures occur because the end user (either the manufacturer of the flashlight or the modder) fails to drive the LED properly. LEDs are current-driven devices, not voltage-driven ones. Any drive circuit therefore must regulate current. Also, while mild overdrive is OK if there is enough heat sinking, inadequate heatsinking cause cause early failure of even LEDs driven within spec.

Two other causes of failure are using resistors and direct drive. Using resistors to regulate current is at best imprecise. You can have optimum current over some of the battery's discharge curve, but the current will be too high with a fresh battery and too low with a nearly depleted one. Direct drive is just a bad idea, period. You're basically hoping that the battery's voltage matches the LED's forward voltage at the proper drive current. LED forward voltage not only varies quite a bit, but also changes as the LED ages (usually in the downward direction) and with temperature (it goes down as temperature rises). In short, direct drive is a hit or miss proposition, usually miss. With inadequate heat sinking it can result in ideal conditions for thermal runaway (i.e. the LED gets hot, Vf drops which causes more current to flow which makes it hotter which in turn drops Vf some more until the LED fails).

One of my Costco 2AA 1w lights dropped about 24" onto my concrete sidewalk and was dead. Further investigation showed that the LED and tail cap were fine, but the problem was somewhere in the electronics module or "pill", which is very difficult to open up. It still doesn't work.

I use them to ready by since 97 and never had a failure. I use regular batteries and replace them when the light is too dim for use as reading. I have a range of lights from walmart, ccrane, cabelas and target.

I did however buy a dorcy 2 aa light that had some problems out the package. 1 of the 4 leds wouldnt light and the others were dim. I returned it.

I have however seen led traffic lights with failed led segments, caution signs with failed leds, tail lights on commercial trucks where a pie shaped part fails and from time to time those 3rd brake lights with a failed led.

Low powered LEDs in clock radios last over 10 years, which I suspect is where the 100,000 hour rating comes from. High power LEDs due to thermal and other issues do not last as long. IIRC posts by CPFers working on LED lifespan show 5000 to 10,000 hours at normal drive currents. That is still over ONE HUNDRED battery changes.

The life is much reduced when the LED is overdriven voltage and/or current wise or when the LED gets too hot.

Coin cell keychain lights (2x2016) overdrive the LEDs but are no problem as the batteries give out before the LED.

Cheap 3xAAA LED flashlights on ebay or from far east vendors are a problem. They are usually direct drive. Alkalines will give 4.5V and NiMH or NiCd will give unlimited current at over 3.6 volts hot off the charger. This is more than the 3 to 3.6 volt 20 mA reting of most 5mm LEDs.
The exception to the rule are the 3xAAA 3 watt Luxeon or clone. These LEDs can take 700 mA which an AAA alkaline battery will be hard pressed to produce for any length of time. No garuantees though.
Cheap also means shoddy construction. Bad clicky switches, cold solder joints, springs that are not long enough, painted over or corroded contact surfaces and a total lack of quality control may mean a non functioning light even if the LEDs are good.

Brighter is not necessary better if you are worried about LED life. A while back flashlightreviews reviewed two 4 AA 7 LED lights - The Streamlight propolymer 4AA 7LED measured 21 total output (x1.43=~30 lumens) and the Nightbuster Aqualed measured 14 (x1.43=~20 lumens). The rating of the Streamlight was later dropped due to reports of burned out LEDs.

Be careful of heat dissapation requirements when modding or upgrading an incan. flashlight. Terralux warned the maxstar should only be used with the maglight (metal body). There was no warning with the Quadstar but I managed to burn out both of mine the 1st evening in PLASTIC flashlights. The 4 LEDs in the Quadstar produced as much light as the 7 LED Aqualed (way overdriven). And they were HOT when I transferred them between lights. I did not have problems with other admittedly dimmer bulbs from Sino Union, LedCorp, Tectite and SuperbrightLEDs.

In general LED lights will last at least 20x as long as an incan light with the original bulb. Buy only brand names from a retailer with a good replacement policy just in case you get a dud.
And stay away from lights that are trying to be the brightest in it's class. Currently there is a fierce competition over whether the Peak Marathon Ultra or the Arc AAA-P is brighter. Both companies are driving the LEDs to the design limits. If I want the 'best AAA light' I would probably get a NON ULTRA 3 LED marathon instead. The LEDs will probably last longer and 3 LEDs will give me the same amout of light. As I am not too fussy or rich I ended up with a Dorcy AAA in my pocket (US$6 at Walmart USA or C$13 at Sears Canada) and a UK 2AAA eLED on my keychain (US$12. at pocketlights.com and diving shops)

I would suggest the Dorcy 1AAA 1LED as a good starter LED light. It is relatively inexpensive. Small and pocketable so you have it with you always to try out in different situations. Can be mouthed comfortably leaving both hands free.
In a month or 2 you can make up a list of wishes for your definitive LED flashlight - brightness tint runtime size weight and go to town at flashlight reviews, LED museum, runtime plots by Roy and the CPF reviews forum.

How about the 2AAA River Rock at Target? I heard it's twice as bright as the nite ize conversion for the Mini mag. Is this one of those lights that are being pushed too hard for its size?

Genxsis said:

How about the 2AAA River Rock at Target? I heard it's twice as bright as the nite ize conversion for the Mini mag. Is this one of those lights that are being pushed too hard for its size?

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I am curious about this too, just having bought one of the 2 x AAA River Rock LED flashlights. It does state it has regulated circuitry.

I tried to buy a Nite Ize conversion unit at Walmart, but they don't have them at the one in my area, so I'll have to find another source.

Currently there is a fierce competition over whether the Peak Marathon Ultra or the Arc AAA-P is brighter.>>>>>>>>>>

That's Matterhorn.

I have however seen led traffic lights with failed led segments, caution signs with failed leds, tail lights on commercial trucks where a pie shaped part fails and from time to time those 3rd brake lights with a failed led.

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When you see LED's go outlike that; it is the circuitry, and it is often bad weather that does this, including the cold. I'll bet that it is the fact that they give off little heat which allows the circutry to be damaged by cold and wetness where incandescents keep it warm and dry.

Yeah, I've noticed a trend in manufacturers minds that says "hey, it's a durable LED, we don't have to do all the seals and so forth and we can save money". But an electical circuit is still and electrical circuit so cutting corners is coming back to haunt these manufacturers.

@Genxsis

Yes boardies reported that some leds failed.
So there is more than degration..

They can failed if the regulation don´t prevent the LED from Voltage spikes.

But also the electronic can fail.

maybe read that.

http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1094,P9892

in my eyes: Very important things:
-Open/Shorted LED Protection
-Automatic Soft-Start Limits Inrush Current
-LED Disconnect in Shutdown(!)

i didn´t realised this since my little 15 EUR papst fan died.
the reason was a 20V spike when i turned my cheapo Powersupply OFF.
With a analog Voltmeter you can see that very good.

Unfortunatley this happens sometimes not always so this happens when i put my most expensive
fan at it. err...



;-)