It was suggested to me it could be voltage ripple ImA4Wheelr. I could not confirm this.
So where is the best place to buy old XML2 emitters 
MRsDNF wrote:
It was suggested to me it could be voltage ripple ImA4Wheelr. I could not confirm this.
Yes, my understanding too. Just wondering if this apparent emitter failure issue was part of the problem too.
RaceR86 was using the same driver but a different power supply in testing. Using his results some leds will run higher than 6 amps with his power supply where as some wont. My gut feeling for what its worth is that the leds have changed not allowing the higher current and this has come about with the new generation of XML-2s and 3s that have the higher forward voltage requirements. This is unsubstantiated though.
I went through a heap of leds before I found 3 that would run at 6.6 amps before RaceR86 contacted me.
Just measured a XM-L2 U3 1A and 2A.
3A: 1A, 3.34v. 2A, 3.64v
4A: 1A, 3.50v. 2A, 3.85v
5A: 1A, 3.68v. 2A, 4.10v
Both on 20mm Noctogons, 18 gauge wires, sinked to a 4x4x5 chunk of Aluminum. Power supply: Kenwood PD18-20D.
This is where I get my XM-L2 T6 emitters from I have good luck with driving their emitters very hard. I don’t have the testing equipment to say exactly how high, but high enough that it will kill many XM-L2’s.
Thanks Racer that is some fantastic information.
I have a 7amp driver showing up soon for a TK61. I’ll try the original emitter that is in it first and if it kills that one I’ll put in one of the XM-L2 T6’s I get from aliexpress. I have had good luck with them.
I have killed many emitters mostly from shorting them but also my fair share by overdriving them. I was wondering why I could get some that would die a quick death while others seemed to handle whatever I threw at them (within reason).
I might just have to stock up. In fact now I wish I had bought more when they had them on sale for 11/11
Thanks again Racer, great stuff!
We need to show that these leds in question are putting out more light at the same forward voltage as the older style XML-2 if that makes sense. All may not be lost if this is the case if running in a light with two or more batteries in series. They just cant run at the higher current but will have more light output. Ok, I'll be quiet now. I know what I'm trying to say. 
How about dedoming and then putting something on the bond wires to cool them or to reduce their resistance? Oil if one can find one with a high enough boiling point, or something like Arctic Silver. Best would be something metallic that would reduce resistance as well as conducting heat well. There does exist paint with very high silver content so that it is a good electrical conductor.
As cars became more thoroughly engineered they were harder to hot rod.
Thank you very much for such useful information RaceR86. 
IMO measuring the actual lumens output is necessary to find out if CREE has changed these emitters for good or bad. Although the acceptable peak current of these emitters have reduced but on the other hand the Vf has increased, this could mean that the total power the emitter see can still be about the same? For example the emitter in your video died at 5.70A but the Vf at that moment was 4.04V, that is still a whopping 23W already.
Indeed. I wish I had a weekend to just sit and test.
And I also wish I had the equipment.
Thank you guys for the information. For those of you with the icharger 106b (and maybe other models and clones or originals), who are willing to test LEDs, the motor drive function can be used as an approximate power supply.
Thanks to the OP for all the information.
To me, if Cree did cut the production costs somewhere along the lines, be it cheaper gold bond wires, or in some other area, I can't fault that, since producing in the US is getting higher priced every day. Maybe they have gone the same way of many manufacturers, where they count on process control being their quality control, in an effort to cut overall personnel costs. No matter what, it does go to show that modding anything beyond the stock specifications is a risk and can have bad side effects.
What we do should never be seen as poor quality of Cree emitters, as what we do is abuse pure and simple. When they start blowing at 3 amps consistently, then Cree will have a problem.
I haven't touched an XM-L2 in a long time. Don't seem to care for them any more. I am still stuck on MT-G2 for most everything right now. I hope they don't go South too, but I have gotten to where I don't bother with the super high amps any more though. Just isn't that much more impressive or useful to be worth it. Like they say, once you've seen two LEDs, you've seen 'em all.
ImA4wheelr, If there there is a need I could start a spreadsheet. I dont think it will be necessary though. Might also be higher chance that people report more data if its kept simple. That way people can post what they know. At the end of the day, I don't think there are too many people who have that much data when it comes to these things. Especially not beyond the capabilities of direct drive. Im not going to encourage people to push their emitters as far as Im often willing to test. I like to know that I got some headroom. When that is said. 5A seems to be a nice place to measure Vf.
[quote=rjorge] Just measured a XM-L2 U3 1A and 2A. 3A: 1A, 3.34v. 2A, 3.64v 4A: 1A, 3.50v. 2A, 3.85v 5A: 1A, 3.68v. 2A, 4.10v Both on 20mm Noctogons, 18 gauge wires, sinked to a 4x4x5 chunk of Aluminum. Power supply: Kenwood PD18-20D. [/quote]
WOW. Looks like you won the U3 1A lottery.
That looks like a U3 binned emitter that could potentially handle 7A+ (not saying you should try it). Are you able to do a light output comparison between the two emitters at similar amps (3,4,5A) ? That would be very interesting. Any more info? Vendor? Date ordered? :D
@18sixfify. Keep is updated on your adventures. :)
[quote=bibihang] Thank you very much for such useful information RaceR86. :beer: IMO measuring the actual lumens output is necessary to find out if CREE has changed these emitters for good or bad. Although the acceptable peak current of these emitters have reduced but on the other hand the Vf has increased, this could mean that the total power the emitter see can still be about the same? For example the emitter in your video died at 5.70A but the Vf at that moment was 4.04V, that is still a whopping 23W already. [/quote]
:beer:
I agree. More output data would help. There are limits to how much time I can put into testing. I was mainly trying to achieve 6,6A with the best possible emitters. Hopefully others will share what data they have as well. I find it strange that the U2s Ive tested either die around 5,6A, or they are good for much more. So far I have not seen anything in between.
Yes, the U2 died at 23W (5,7A). Its a lot of energy for a 10W emitter, but at the same time, its not that high for an emitter on copper. In comparison the U3 1A I tested died at 27,33W (6,4A). And the "China T6" emitter was still going strong at 30,2W (7,6A). I would not be surprised if that emitter could be pushed beyond 33W. 10W more compared to a bad U2 emitter.
Needless to say, Id like to get my hands on well performing top binned emitters that are capable of 25W+.
Id pay extra to get emitters that was verified to do high amps for the most hardcore builds. Right now it seems to me that emitter performance can be a lottery.
No doubt that everything beyond 3A is at our responsibility. But its its CREE`s responsibility to produce emitters that are within spec. (Although I dont know what tolerances they have. Anyone knows? Look at the differences in the emitters rjorge posted.
One U3 emitter had a Vf of 3,34V. Which is where they ideally should be. Problem is when another similar binned emitter have Vf of 3,64V then something is off. That is a massive difference. They should be at 3,33V. Yes, our copper mcpcb`s can make that a bit higher, but 3,64V...
If its not something Cree have done then I wonder if there could be something wrong with the re-flow process. Maybe I should stick to only buying bare emitters. I dont know...
I wonder if OL would comment the same way if we were discussing MTG-2 leds and not XML-2? 
Just thinking... if the U3's have such a high Vf but do have U3 output, they are still very suitable for <2amp single li-ion flashlights. Driving the XM-L2 lower than 2A sounds a bit odd in general BLF-thinking, but it makes a very efficient flashlight. The higher Vf is not very relevant because overhead voltage is burned off anyway by the driver and at these low amps the voltage is still low enough for the flashlight to stay into regulation for most of the battery drain.
Yes, yes it does.
Sounds very unnatural. Who would do such a hideous thing? Think about that poor helpless little emitter. It would be freezing. I take good care of them, put them on copper and make sure they run close to rated temperature. I help my emitters live up to their true max potential. Once they enter my house they have a bright future ahead of them. 0:)
My most efficient flashlight is a Uniquefire S10 with 2x7135 driver and a XM-L2 T6 0D, at 90 OTF-lm/W.
:evil: emitter torture! :evil:
EDIT: pointless question (deleted)
Not at the moment, but hopefully soon. I got them from RMM a couple of weeks ago. Not sure what to do with the 2A, I had planned to put it in a SupFire L5 and LD-1. Not anymore!