Lumapower Overdriving XR-E ?

Hi:

This one is tempting me:

Battery Junction: "SPECIAL EDITION LumaPower LumaHunter MRV DIGITAL Tactical LED flashlight w/ Cree Q5 WC 265 + lumens!"

But it says it drives the LED at 1.1A. The Cree datasheet says the max is 1.0A. I don't like the idea of a design overdriving a part. That's a big no-no in my field of EE. Any thoughts on this? It's also risky since the LED would need effectively ideal thermal management at that level of drive, which is unlikely in a flashlight.

How do people feel is the reliability of Lumapower lights? I have one at work, but hardly ever use it. It works when I turn it on though.

I want a thrower for my car.

Dereelight is driving all their new digital Q5 lights and drop-in modules at 1.2a, and people are gobbling them up like they're going out of style.

http://www.cpfmarketplace.com/mp/showthread.php?t=171053

There's been some discussion on Deree's manufacturer's corner thread about the emitter/driver being able to handle this and Dereelight confirmed that could without any problems. Some mentioned that with the emitter being driven at 1.2a you may not get the full 50,000 hours out of the LED. But who really cares about that when by the time you've put 10,000 hours on the LED there will be 5 new generations of LEDs out by then and we will have all moved on anyway... I've even seen requests for them to produce a 1.5a and 2.0a driver, but Deree said that would be pushing it and he curcuit and emitter couldn't handle it reliably. Dereelights have some of the best heat-sinking designs around, so heat is not a problem with these lights being driven at 1.2a.

BTW - the link above takes you to the king of throwers....

So who cares if an LED is overdriven a little?
They are rated at, like, a zillion hours runtime, and if putting some stress on one means that it only lasts half a zillion hours, it's a not big deal.

You'll be upgrading it to the next generation emitter LONG before that Q5 starts to hiccup.

As was mentioned, Deree is already pushing their Q5's to 1.2amps with no reported problems of any kind (including my own which is trucking along quite merrily.. and brightly).

I have the MRV-SE/Epsilon on order and am curious to see how it compares to both my "safely driven" Tiablo A9s and my "way over boosted" DBS.

Zenster said:

So who cares if an LED is overdriven a little?
They are rated at, like, a zillion hours runtime, and if putting some stress on one means that it only lasts half a zillion hours, it's a not big deal.

You'll be upgrading it to the next generation emitter LONG before that Q5 starts to hiccup.

As was mentioned, Deree is already pushing their Q5's to 1.2amps with no reported problems of any kind (including my own which is trucking along quite merrily.. and brightly).

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That is not a statistically rigorous analysis. The trouble is, the degradation effects of overdriving an LED are likely to be highly non-linear. Both a function of current density, and heat. Thus, sudden catastrophic failure is not out of the question.

If I could be certain for instance, of an MTBF of 10000 hrs., then yes I would agree that's a fair price to pay for increased output. But I don't think it's that simple. And like I said, it's a big no-no for professionally engineered electronics to ever exceed maximum ratings. The only exception I would consider is something backed up with extensive long-term statistical testing.

Zenster said:

I have the MRV-SE/Epsilon on order and am curious to see how it compares to both my "safely driven" Tiablo A9s and my "way over boosted" DBS.

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Wow, I would like to hear the comparison of all three as well.

Thanks for the input, and... Good day!

Actually, most high power LEDs are rated at XX hours to 70% output, not to 0% output.

There is also quire a bit of heatsinking in the metal. Even if all the energy was heat, it won't get too hot.The Cree LEDs have been taken to 2 amps without much measurable difference(though this wasn't extended running)

And buy the time the LED actually gets to a low point, which might take quite a few years, most would have probably moved on to a different LED or flashlight(at least here).

I don't know much about electrical components so this is all that I have read.

Noting is going to raise my eyebrow unless it's being overdriven in a tinly little light, without obvious quality heatsinking, or well over 1.5A. Just because Cree rates it at 1A doesn't mean it can't handle more. I have my lights for super high dependability, and then I have the sweet stuff.

I think the main concern is you're buying the light for the high output and the heavy drive current prematurely kills your high output. Check out the graph and comments at the bottom of this webpage.

http://www.molalla.net/~leeper/seoulmy.htm

Xe54 said:

That is not a statistically rigorous analysis. The trouble is, the degradation effects of overdriving an LED are likely to be highly non-linear. Both a function of current density, and heat. Thus, sudden catastrophic failure is not out of the question.

If I could be certain for instance, of an MTBF of 10000 hrs., then yes I would agree that's a fair price to pay for increased output. But I don't think it's that simple. And like I said, it's a big no-no for professionally engineered electronics to ever exceed maximum ratings. The only exception I would consider is something backed up with extensive long-term statistical testing.



Wow, I would like to hear the comparison of all three as well.

Thanks for the input, and... Good day!

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Well if there was some sort of statistical catastrophic failure it would just be another excuse to buy yourself a new flashlight.
Anyways according to Ohm's law the switch or some other part is more likely to fail before the LED. Oh wait is that Moore's law? Never mind I meant Murphy's law.

I would not be in too big of a hurry to accept the Lumapower offcial specs. Check the reviews before jumping (hopefully there are reviews).

NA8 said:

I think the main concern is you're buying the light for the high output and the heavy drive current prematurely kills your high output. Check out the graph and comments at the bottom of this webpage.

http://www.molalla.net/~leeper/seoulmy.htm

Click to expand...

Wow, that's some solid data which doesn't lend much credence to the idea that LEDs can tolerate overdrive without accelerated degradation of output.