Cree XP-G3, testing a S5 3A emitter

Instead of boiling gas to dedome faster, one could simply put it in the fridge to slow it down and let the dome swell slowly…?

Maybe diluting the gas would be a better idea than putting it in the fridge, if only there was a BLF MEMber who could tell us the ratios :wink:


You just become MEM’s lawyer. Cheers guys :beer:

I did not ask him to reveal de doming secret but to reveal results in XP-G3 vs OLD (not new) XP-G2 S4 2B de domed battle. Is this also a secret? Don’t make me laugh :slight_smile:

Djozz already did such test(only with sliced XP-G3) with B158 host and he got about 50% lower performance than with de domed old type xp-g2 s4 2b.

Well known variables are that de domed vs sliced emitter should have maximum 20% better performance over sliced so properly de domed G3 will still not be able to reach OLD xp-g2 s4 2b. He could reach and have better performance than new production s4 2b but it will never reach old S4 2B. Learn difference between new and old production process xp-g2-s4 2b emitters(Gaston01, other guys and myself learned that on a hard way).

Real variables would be :

- de domed g3 v de domed OLD production type XP-G2 S4 2B(cause that emitter was king of throw until Cree messed it with new production process XP-G2 S4 2B)

- same host

- same driver

- same battery

  • same lux meter(and it does not have to be super accurate to tell % difference between them)

Djozz did all that with B158 host only with sliced G3 and not de domed one. Add max 20% gain on de domed one and it will still not reach it.

I would really like that G3 or any other new emitter could have same or better throwing potential than old production XP-G2 S4 2B emitter and I am among the first one that would buy larger quantities of it.

Thanks for the effor Djozz, Appreciated.

I still need to see (or experience) this to believe it… I believe the ‘old’ XP-G2 S4s are still the Throw King, by far.

PS: I’m also worried about the beam profile of the XP-G3s. To me, it does not look promising. And, the other caveat, as we all know, to have this LED properly dedomed, we’ll have to send them to MEM for some ‘special’ attention. Yep MEM, you’re probably smiling while reading this… :wink:

+1 BLF is becoming a Secretive Endeavor… Secrects, Secrets, Sectrets… :beer:

A thought…

I’m just combining some information I gathered from being here for a while, I do not know the exact physics behind it (I’m a biologist, in led physics just a BLF-amateur, i.e. DrJones knows better than me what happens to photons).

*The Cree leds used to have a very smooth phosfor layer and showed a lot of tint shift and gained a lot of illuminance upon dedoming
*I have had Luxeon Q leds, Oslon Square leds, Nichia leds that all have rougher phosfor layers. I dedomed or sliced them all and the illuminance never became anything impressive. The tint shift was also less (qualitative observation).
*The latest XP-G2 and XP-G3 have a rough phosfor layer and thusfar the throw after dedoming them seems less than impressive.

The source of improved illuminance upon dedoming (following DrJones’ explanation from back in 2012) is that after passing the phosfor layer, remaining blue photons that are leaving the phosfor layer at high angles are reflected back into the die and have another chance of being absorbed by the phosfor and then emitted at increased wavelength (and thus luxvalue) and at a perhaps lower angle that will escape the die, thus adding to the illuminance and causing a tint shift away from blue.

What if the outer edge of rougher phosfor without silicon dome, that has less surface area parallel to the die surface than a smooth layer of phosfor (this is entirely my own assumption), shows much less internal reflection in the first place, so even without dome the light at high angle can escape anyway? Then less photons are ‘recycled’ (is this word also patented by Wavien? :wink: ), and illuminance and tint shift are less increased. So less throw.

That’s certainly a possibility I suppose. The thickness of the phosphor on the edges could also play a role as well, but that’s only a guess on my part.

Either way, unfortunately, I guess there’s not much we as end users can do about it one way or another.

Thanks again for taking the time to do the testing.


My dome would swell quite rapidly (due to repeated hits from a 2x4) once my wife discovered the jar containing gasoline I simply put in the fridge.


Ice packs and chilled water in a lunch cooler outside?

well, 2 days after, this is the result: (Dome was swollen and separated at the edges of the emitter and, as you can see, some of the phosphor left on the dome, also some of the silicone from the dome left stuck on the entire die, usually, after this time die is left nice and clean with XP-G2 or XM-L2, I just have to clean silicone around the die and it’s nice and slick but with XP-G3 … well you can see, I would call it a fail and I have siriuos doubts that “diluted” this or that actuall works as stated by MEM.)

I did few quick tests, just connected some batteries directly to this leds and observed current draw

Bettery dedomed XP-G3 dedomed XP-L
Panasonic NCR18650PF - 4.04V 5.60A 2.97A

Samsung ICR18650-26FU

laptop pull in good shape - 4.13V

4.44A 2.78A

generic battery pack 3P

configuration - 4.0V

unbranded cells

6.30A 3.26A

Whats the next move? :weary:

You, my friend, have a knack for problem solving. Marital bless, and my somewhat dimmish dome, shall be maintained if I ever try a slow dedome. :slight_smile:

Well, I wouldn’t call it a complete failure, the phosphor is still intact, and it does light, so partial failure at worst.

I’d call it Success with complications.

Whats the beam pattern like? Did the tint shift significantly?

Sirius, you do know that the square in the middle is the die, right? That phosphor around the edge doesn’t even matter. You can probably just scrape it back to get straight edges again and it will be fine.

Of course I know that and I thought to scrape it off but I wanted to show to BLF members first how it looks after slow chemical dedome without beauty treatment :slight_smile:
Also, you can probably notice that top and left edge of the emitter die is missing some phosphor, that phosphor was stuck on the silicone dome and this was not caused by my forcing the dome but was already like that when I pullet the emitter from the gasoline, swelling of the dome caused that.

So what if we combine gas dedoming and hot dedoming? instead of just sitting the emitter in gasoline, hook it up to a power source and run it at 1amp or so while it sits in the gasoline. It would also keep the gas a bit warm I would think.

Warm? Maybe…

3v isn’t going to cause any sparks (especially submerged), and liquid gasoline isn’t that flammable anyways.

Yeah, I know. :stuck_out_tongue:


So, who’s going to try it on a G3?