Emitter data and talk. A look at Vf, amps and some crash testing (Updated with more data 10th of December)

My thoughts exactly and maybe cost cutting as well if the above is founded.

'Elementary, my dear Watson'

That was a huge undertaking RaceR, I would never have had the time to do so many emitter tests! Thanks for the hard work on this. So it looks like Cree has introduced a manufacturing change for the worst recently.

A question: the XM-L2 in my BLFX6 died with intact bond wires, that was the first dead XM-L2 I have seen that does that, I always saw fried bond wires before. How about the many dead XM-L2's from your test?

So we have to start hoarding old-production XM-L2's for our overdrive builds now I guess

Thanks for comments guys.

Djozz, what happened to the emitter in your BLFX6? You also mentioned that you had fried some XP-Ls over in the XM-L2 U3 thread? Any more info from your adventures?

I have seen various types of damage on fried emitters, everything from super obvious like the one in this picture that you posted:

To obvious burnt wires (old picture I had of one):

To the very subtle that you can not see by eye. (Old pictures of an XM-L2 U2 I believe)

In my two last pictures I believe its the slightly dark area on the bond wire that is damaged.

I did not bother to study the ones I fried this time. They quickly went in the trash without any pictures. I noticed that some looked like in your picture and some I could not tell by eye they had been damaged. I probably covered all the common types of damage when I was on my killing spree. :D

Thank you for the testing Racer. This must have taken quite some time to do!

A shame we are as of yet unsure about the output. A while ago I read somewhere that Cree was implementing production changes that should increase output approximately 20% but that they were not going to change the binning system or generation numbers since it would be across the board of current production led's. Maybe the side effect of that is giving us headaches like the above. I will just add that I never pursued the information to verify its source. Eg. I don't know if it was from Cree's homepage or some lesser source.

Thanks, I will have another look at the BLFX6 emitter, perhaps the bond wires were damaged after all, in a less obvious way like you show above.

I fried the BLFX6 one by foolishly trying out 2x18350 cells in series (surprisingly the driver survived). The bond wire damage may be different than I am used to because in a emitter test they fry while already warmed up, and at just over the maxiumum current they can handle, and not way too much all of a sudden.

The XP-L's were two 7A1 80CRI ones from intl-outdoor, I tested them out before use in a flashlight (they never came that far :-( ) because I wanted to repeat the test I did earlier with a cool white XP-L that showed no output loss after dedoming. But they both died under 7A, so no dedomed test was possible.

Oh no. Some XP-Ls cant even breach 7A now.. :_( I had hoped the XP-Ls could be a safer option after having so much issues with some of the XM-L2s. Did you get any voltage data when you tested it?

I hope my incoming XP-L V6 2C will not get the same fate as I plan to test it.

BTW, last year I specifically bought a descent old-tech heavy lineair power supply because of rumours that switch-mode power supplies could suffer from voltage spikes (which I do not believe is true, but I'm an electronics noob, who am I to claim anything ), so the chance is minimal that spikes are a reason for fried leds in my tests.

Good thread. So for our high current builds, we should record Vf around 5 amps (for xm-l2), then report here on the measurement and ultimate result (fried, didn't fry & x amps, etc)? Would it be hard for you to set up a collaborative spreadsheet like the LED database?

RMM reported frying like around 20something xml-l2 working with the HX-1175b driver. Not sure if he has any data of the emitter Vf's. I think he did see issues with the driver's output on a oscilloscope. So it may not be relevant.

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 :frowning:

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. :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.

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.