XM-L2 led for dive light

J

Jsub

Newly Enlightened
Joined
May 22, 2013
Messages
4
Hi.

Has anyone used the XM-L2 for a dive light project yet?

I can see the U2 version circulating around so i was thinking of maybe ordering one. The tint of the U2 might not be great though being a bit more blueish or am i wrong?

Cheers,
John
 
J

jspeybro

Enlightened
Joined
Aug 13, 2009
Messages
586
Location
Belgium
I have the impression that most people miss the point of the XM-L2 LED.
People seem to think that they will get a better result using them over an earlier XM-L led.
If you check the numbers, they actually put out less light.
So why this LED?
For thermal reasons as far as I understand it. This LED produces less heat so you can use smaller heatsinks for the same output.
Since we typically have enough cooling in a well designed dive light, I don't see the point of paying more for this new led when you can get the same result with a cheaper led.

this is just what I think about it, others may disagree :)
regards,
Johan
 
DIWdiver

DIWdiver

Flashlight Enthusiast
Joined
Jan 27, 2010
Messages
2,715
Location
Connecticut, USA
I disagree:). The XM-L data sheet specifies luminous flux values at 25C, while the XM-L2 is specified at 85C. That's a big difference.

The cool white U2 bin XM-L has minimum 300 lm at 700mA, calculated 742 lm at 2000mA, 25C.

The cool white U2 bin XM-L2 has minimum 300 lm at 700 mA, calculated 728 lm at 2000mA, 85C.

To compare apples to apples though, you have to use the XM-L2's calculated output at 700mA, 25C. That's 340 lm.

So the XM-L2 is actually substantially brighter UNDER THE SAME CONDITIONS, compared to the XM-L.

As for thermal reasons, they are minimal. The thermal resistance of the package is identical (2.5C/W). The forward voltage spec is a tiny bit lower, but that's probably entirely due to it being specified at 85C instead of 25C.

You do get more light at the same power input, so that means a little less heat. We don't have numbers to calculate accurately, but we can do a little better than a WAG. If the XM-L is 25% efficient at 10W, which seems like a reasonable estimate given numbers I've seen here and there, then the XM-L2 might be 340/300 times 25%, or 28% efficient. So the heat generated would be 7.2W instead of 7.5W. Keep in mind I put together numbers that don't belong together in order to get this estimate, so it's not to be counted on. However, it should be in the ballpark.
 
Last edited:
J

Jsub

Newly Enlightened
Joined
May 22, 2013
Messages
4
DIWdiver thanks for the info and the explanation. I had the same impression, that for the same power consumption you would get a little bit more lumens. In a dive light the same heatsink used for XM-L would provide the same heatsinking result for the XM-L2.

What is the equivalent of a T6 tint for the XM-L2?
 
DIWdiver

DIWdiver

Flashlight Enthusiast
Joined
Jan 27, 2010
Messages
2,715
Location
Connecticut, USA
T6 isn't telling you tint, but rather brightness, AKA luminous flux, related to Luminous Efficacy. Higher letters and higher numbers mean brighter.

Tint, AKA chromaticity, would be the next suffix, a number from 0 to 8 and a letter from A to D. Low numbers are cool, high are warm.

All XM family parts use the same binning codes, so an XM-L-T6-1C would be the same brightness and color as an XM-L2-T6-1C. However, I suspect gen2 parts will start at U2 flux bin, so you probably won't find a T6.
 
J

Jsub

Newly Enlightened
Joined
May 22, 2013
Messages
4
Thanks for the clarification DIWdiver.
 
D

darkavenger

Newly Enlightened
Joined
Apr 6, 2013
Messages
27
All XM family parts use the same binning codes, so an XM-L-T6-1C would be the same brightness and color as an XM-L2-T6-1C. However, I suspect gen2 parts will start at U2 flux bin, so you probably won't find a T6.

No. The XM-L is binned based on it's physical temperature being 25C or 77F. The XM-L2 is binned at 85C or 185F. An XM-L2 Led running at 25C would be about 11-12% brighter than it's rated(T6 for example) An XM-L running at 85C is about 11-12% dimmer than it's rated(based on 700mA current) These numbers may vary with current differences.
 
DIWdiver

DIWdiver

Flashlight Enthusiast
Joined
Jan 27, 2010
Messages
2,715
Location
Connecticut, USA
Yes, you are right. They would be the same if each was running at spec condition. If they were running under the same conditions, the gen2 would be brighter.
 

Similar threads

350xfire
Replies
24
Views
6K
350xfire
350xfire
B
Replies
14
Views
5K
350xfire
350xfire
P
Replies
5
Views
4K
Klem
D
Replies
21
Views
8K
jspeybro
J
Pizeer
Replies
35
Views
25K
Nwdiver
N
Top