SFU2 Led Questions

Hi, I'm new to the forum, been lurking for awhile, decided to join. Just bought a Surefire U2 after much debate and research here about the potential tailcap issues, etc. I have heard that the luxeon V led only has a rated lifespan of 500-1,000 hours, would this be true of the U2 if I used the lower levels alot? Also I've seen the K2 led on lumileds website. Has that been released yet and if so can it be put into a U2. I liked the increased lifespan vs. a Lux V led. Hope thats not too many questions. I have done several searches, thanks.

dcowboyscr said:

...the luxeon V led only has a rated lifespan of 500-1,000 hours, would this be true of the U2 if I used the lower levels alot?

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No.

The Lux V in the U2 will last a LOT longer if you mostly stick to the low levels. I have no scientific basis for this, but I'd wager that every output level you drop probably doubles the lifespan of the Lux. If you get 500 hours out of the highest level, I'd bet you get 1000 out of the second highest, and 2000 out of the level after that...

It's mostly the heat that kills the emitter. If I run mine on the second highest level all the time, it barely gets warm to the touch.

Don't worry about the lifespan, it'll be a long, long time until that LED wears out..

Ohh, and welcome to CPF!!

I'll go further and say that each step down in intensity with the U2, which halves the power to the LED with each step, will more than double lifespan. I wouldn't be surprised if the life of the LuxV were 10 times greater at half the power output (level 5), but I don't know how to substantiate this.

Don't worry about the LED lifespan. As ACMarina says, it should last a very long time. If it should ever fail, Surefire will replace it.

The problem isn't about LuxV failure. It is the drop in output over time. Supposedly, in the first 100 hours or so, Vf will drop and light output will increase. Then, as the hours rack up light output will fall. I forget what percentage drop in output the 500 hour lifespan is benchmarked against, is it 30%?

In any event, though none of us would be happy with 30% less light at 500 hours, I doubt SF would replace it because of that.

The good news is that the U2 has exellent thermal management, and I'll bet the LuxV die temp is kept quite a bit lower than the temp that gave the 500 hour rating. Plus, few of us use the U2 at full output for long periods of time. Even if you did, whether using a Li-ion rechargeable or 2xCR123, the output of the light does not remain at maximum power for long before voltage drops reduce power to the LED a little bit.

Don't worry about it. I'm a long term user of the U2 (18 months), carry it every day, run it hard, and have not noticed a drop in lumens.

Psychologically, it might happen - it did to me. I THOUGHT my U2's output dropped, until I compared it to another L4 I have that is seldom used, the U2 blew the L4 away and my confidence has been restored.

500 hours lifespan would involve running the U2 at full blast through 1000 batteries, or 500 lithium ion charge cycles, enough to exhaust even a rechargeable cell. I doubt I am anywhere near that amount of power-on hours. By then you've gotten more than fair use out of the U2

If all else fails, the U2's bezel can be opened and the LED field replaced - by us, that is. By the time that happens, hopefully I can get my hands on a much better binned LED, and do the field upgrade myself.

Thanks for the replies. The U2 is a great light, I've had no problems with it so far. I did however order a spare tailcap to be safe as a backup. Clicked it 4 times and it locked up

dcowboyscr said:

Thanks for the replies. The U2 is a great light, I've had no problems with it so far. I did however order a spare tailcap to be safe as a backup. Clicked it 4 times and it locked up

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If you call surefire and let them know that you have a bad tailcap,
they will send you a new one free of charge.