# XM-L2 "review" (mostly lumen and CCT testing)



## foxtrot824 (Jan 4, 2013)

At work I have to test various LEDs and fixtures, today I had an XM-L2 5000K in a T6 bin to test so I decided to take a few measurements. This was in a 12" sphere using instant on measurements. I allowed for the jig to cool as the test currents increased so the LED temp ranges from 25c on up as it got warmer, probably not 85c at any point but certainly warm.

I tested from 100mA to 3A in 100mA increments. I measured lumen values as wells as lumens per watt, CRI, and CCT.


Test CurrentVfLPWLumensCCT (in K)CRI0.1
0.2
0.3001
0.35
0.4
0.5001
0.6002
0.7001
0.8002
0.9001
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3
2.695
2.756
2.8
2.819
2.836
2.868
2.896
2.923
2.946
2.984
2.996
3.016
3.034
3.049
3.067
3.084
3.1
3.115
3.128
3.177
3.177
3.186
3.195
3.206
3.218
3.23
3.27
3.275
3.282
3.291
3.3
170.87
169.36
165.35
163.22
161.1
156.96
153.06
149
145.46
142.98
139.12
135.73
132.34
129.36
126.31
123.21
120.21
117.28
114.55
115.45
111.46
108.2
105.08
102.15
99.28
96.44
97.73
94.45
91.27
88.36
85.43
46.05
93.34
138.9
161
182.7
225.1
266.1
305
342.9
384
416.8
450.3
481.9
512.8
542.4
569.9
596.2
621.3
645
696.9
708.3
723.9
738.7
753.3
766.7
778.9
830.9
835.3
838.8
843.4
845.8
4721
4755
4786
4802
4816
4840
4867
4888
4915
4927
4959
4976
4996
5028
5046
5064
5082
5101
5137
5125
5155
5176
5200
5220
5245
5270
5279
5308
5342
5372
5406
73.3
73.2
73.2
73.2
73.3
73.3
73.3
73.3
73.3
73.3
73.4
73.4
73.5
73.4
73.4
73.6
73.7
73.8
73.9
73.5
73.8
74
74.2
74.4
74.6
74.8
74.4
74.7
75
75.2
75.5


Sorry for the poor chart, if anyone wants Cx and Cy coordinates feel free to ask. Below is the CCT drift as current increases. While it does increase in CCT going towards blue it does stay pretty close to the black body unlike the Nichia 219 which drifts off the line fast.


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## THE_dAY (Jan 4, 2013)

Thanks! 

That's a pretty broad CCT range (4700-5400K).


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## moozooh (Jan 5, 2013)

Hmm, that looks more like T5 bin. Cree's XM-L2 datasheet says T5 bin's "default" brightness is 260 lm @ 700 mA and 325% that at 3 A, so that should make it 845 lm at 3 A, which is spot-on with your measurements. Besides, there is no NW in T6 bin per that datasheet. I'm guessing that the lower current numbers can't be sustained over time; could you try measuring them after several minutes or at least at some constant temperature?


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## IMSabbel (Jan 5, 2013)

Nice data.

But it looks like there is heating involved, as it scales worse than it should.

A good idea is to always meassure once in both directions for this kind of stuff...


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## ergotelis (Jan 5, 2013)

thanks for doing this, may i ask what was the pcb of the led at the test?cooling?


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## Changchung (Jan 5, 2013)

Thanks for do this test for us... Nice info and data...


Sent from my phone with camera with flash and internet on it...


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## easilyled (Jan 5, 2013)

Very interesting, thanks for sharing your results.

From your figures it looks like 2.6A is the ideal current for it to be driven at, since it gains only 15 more lumens at 3.0A

The tiny jump from 2.5A to 2.6A, however, provides an astonishing 50+ increase in lumens.


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## foxtrot824 (Jan 6, 2013)

I think I need to make a few clarifications. One thing we need to remember is that this was a sample of 1 LED and only 1, not a great sample size by any means. There is always the possibility I fried the LED in the reflow process as well since I did it on a hot plate instead of setting up the oven. When I was doing the testing (which takes a little bit because you have to wait for it to measure the output and to change the current you need to open a new window change it, wait and then close it again.) I ran the first 10 samples before pulling the port tester out to see how warm it was. I really wish the jig had a thermocouple built in but it doesn't so I don't know exact temperatures.

Looking at the numbers again I see some places where I think it's obvious I let it cool for a while. I may just do a retest where I test it at 3 or 4 currents and do an instant on and then after 1 minute to allow it to warm up. I would also allow the jig to cool completely in between test. Any thoughts on specific test currents people want to see? I was thinking 700mA, 1500mA and 3000mA.


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## easilyled (Jan 6, 2013)

foxtrot824 said:


> I think I need to make a few clarifications. One thing we need to remember is that this was a sample of 1 LED and only 1, not a great sample size by any means. There is always the possibility I fried the LED in the reflow process as well since I did it on a hot plate instead of setting up the oven. When I was doing the testing (which takes a little bit because you have to wait for it to measure the output and to change the current you need to open a new window change it, wait and then close it again.) I ran the first 10 samples before pulling the port tester out to see how warm it was. I really wish the jig had a thermocouple built in but it doesn't so I don't know exact temperatures.
> 
> Looking at the numbers again I see some places where I think it's obvious I let it cool for a while. I may just do a retest where I test it at 3 or 4 currents and do an instant on and then after 1 minute to allow it to warm up. I would also allow the jig to cool completely in between test. Any thoughts on specific test currents people want to see? I was thinking 700mA, 1500mA and 3000mA.



I think it would also be good to try to establish at what point diminishing returns are in operation before 3000mA, if this is possible thanks.


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## psychbeat (Jan 6, 2013)

I'd be curious to see how the VF ramps at currents above 3a. More like 4-6amps area 

I know that Vinh was having trouble pulling more than 4.5-5 amps direct drive off of a 26650. 

A first gen was pulling 7+

Might be the 3bond wires vs 2?


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## RoGuE_StreaK (Jan 6, 2013)

psychbeat said:


> I'd be curious to see how the VF ramps at currents above 3a. More like 4-6amps area


Ditto. Keep going til you see the magic smoke! :naughty:


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## jh333233 (Jan 7, 2013)

Unfortunately their "high" LPW could only be achieved in low current situation
Under heavy driving, its efficiency is even worse than old school LED


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## LEDAdd1ct (Jan 12, 2013)

Thanks for the stats!


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## neutralwhite (Jan 12, 2013)

talking of this 4000K,..im not so sure what im talking about here really if im correct, but would a CRI on say a 4000CCT LED be better than a 5000CCT CRI?.
i have the PD32UE, and looking at also getting something 4000CCT-same colour as that bulb...

something that is more good for the eyes rather than more brightness, or is the PD32UE 5000CCT better? 

what CRI would that be at ?. 75 if im correct...
would it beat 4000k?.

hope that made sense...
thanks.


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## jmpaul320 (Jan 12, 2013)

more than 400 lumens at 1 amp... thats impressive


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## LEDAdd1ct (Jan 12, 2013)

—and I'm looking from the other direction:

46 lumens for just 100mA?

Nuts!


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## vestureofblood (Jan 26, 2013)

foxtrot, 

Thank you so much for providing us a piece of real world data for these fine emitters. If you do plan to do more testing I would be very interested to see what kind of returns we get on currents above 3A Even going as high as 4 would be great. 

Thanks again


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## p7united (Feb 1, 2013)

vestureofblood said:


> foxtrot,
> 
> Thank you so much for providing us a piece of real world data for these fine emitters. If you do plan to do more testing I would be very interested to see what kind of returns we get on currents above 3A Even going as high as 4 would be great.
> 
> Thanks again



This, also I would be interested in performance sub 100mA.


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## AnAppleSnail (Feb 1, 2013)

p7united said:


> This, also I would be interested in performance sub 100mA.



That will depend more on the individual LED than any general trend.


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## p7united (Feb 3, 2013)

AnAppleSnail said:


> That will depend more on the individual LED than any general trend.



Interesting I wasn't aware, that said I still would still like to see some data. If nothing else it's maximum efficiency at how many mA would be useful.


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