2000 lumens claims from a XM-L T6?

I have seen some flashlights for sale on amazon and ebay that they claim they can deliver 2000lumens from a single CREE XM-L T6 LED? For example the UltraFire W-878 claims 2000 lumens and uses a single CREE XM-L T6 LED. The specs for the CREE XM-L T6 LED are 11000 lumens. I know it is possible to overdrive the LED and with adequate cooling you can increase the lumens output but still how can one get twice the rated lumens? I don't believe it is true but I thought I'd ask you.

You are right - some things are too good to be true. Yes, you can overdrive an LED and get more light at the expense of heat and lifetime, but not double the lumen output. There is a reason the CREE spec sheets only show output up to 2 amps, and most reputable manufacturers don't drive them any harder than 3 amps (~1000 lumens).

It's good that you know enough to go looking for secondary sources like the LED datasheets to verify a claim like this. Unfortunately, too many don't and fall for these claims. That is one of the reasons why we all belong to CPF, to help others understand and protect themselves.

And in case anyone hasn't said it yet, "Welcome to CPF!"

Timothybil said:

You are right - some things are too good to be true. Yes, you can overdrive an LED and get more light at the expense of heat and lifetime, but not double the lumen output. There is a reason the CREE spec sheets only show output up to 2 amps, and most reputable manufacturers don't drive them any harder than 3 amps (~1000 lumens).

It's good that you know enough to go looking for secondary sources like the LED datasheets to verify a claim like this. Unfortunately, too many don't and fall for these claims. That is one of the reasons why we all belong to CPF, to help others understand and protect themselves.

And in case anyone hasn't said it yet, "Welcome to CPF!"

Click to expand...

According to these tests you can get close to 1800lumens when you overdrive a XM-L2 it at 6A with a large copper heat sink but I doubt these budget lights are made to be overdriven and handle the extra heat. I also saw this Jax Z1 mod, using a XP-G2 overdriven at 5A. How many lumens can you get from a XP-G2 at 5A? The emitter tests only go up to 4A.

[h=2]2000 lumens from a XM-L T6=BULLSHIT[/h]

Timothybil said:

You are right - some things are too good to be true. Yes, you can overdrive an LED and get more light at the expense of heat and lifetime, but not double the lumen output. There is a reason the CREE spec sheets only show output up to 2 amps, and most reputable manufacturers don't drive them any harder than 3 amps (~1000 lumens).

Click to expand...

Actually if you look at the Cree LED Components IES LM-80-2008 Testing Results report, they do test the XM-L and XM-L2 at 3 amps, to estimate the lifetime of the LEDs at various drive currents and case temperatures.

One of the interesting things I've noticed in that report, is that the expected lifetime of the LEDs has very little to do with the drive current, it's almost completely dependent on temperature. For example, the expected lifetime of the LED is exactly the same whether you drive it at 1000mA or 3000mA, as long as the temperature is kept the same. In this example, a temp of 85C results in the LED having 98.5% brightness after 3000 hours. (Estimated to last 72,000 hours before going under 70% brightness.)

It's heat the kills the LED, not current. (This may not apply to currents beyond 3000mA, but I suspect if you can control the temperature using excellent heat sinks, it probably doesn't hurt the LED very much.) Above 85C seems to start decreasing the expected lifetime of the LED, and above 105C is really starts getting bad. Below 55C, LEDs seem to last almost forever.

Now, I know that trying to hold a metal flashlight where the tube has reached more than 45C-50C will be painful (and possibly lead to burning). But does anyone know how hot the LED junction point has to get on a typical flashlight design for the body to reach such temperatures? If it means the LED junction point is less than 85C, I wouldn't worry about it.

XXXfire = Bad.

SureFire = Good.

I doubt it, it's probably no where near, as a manufacture can't risk of burning and damaging the led as it will produce lot's of heat and in long period of time it will burn out, flashlight will looks much different as it will need massive cooling fins.
just buy it, mesure the current and give the seller bad feedback that he lies in his descriptions.

Fivemega Dude oo: I just bought a TrustFire model x 100

7 X CREE XM-L T6 of 8000 lumens 5 modes flash light , has yet to received it, don't make me feel I bought a misleading flash light. lovecpf