Can someone help me with the math on a triple? EDC+ claims they tested their triples in an integrating sphere for true out-the-front lumens. If 3 XP-G2s are driven at 2A then each one is getting something in the neighborhood of .667A, right? So if Cree claims at 700mA a 254 lumen output at the emitter, how is it possible for the EDC+ to make 720 lumens out the front when Cree’s numbers at the emitter add up to 762lumens (@ 700mA) That would be some very high efficiency would it not? Would this drop-in run comparatively cooler because of those numbers? Especially in a solid copper pill? This will prove interesting. Can’t wait to see mine, going into 8 weeks after backorder.
720 out the front in an L2P will be nice, gonna have to get some copper to wrap it with for sure.
This would probably be better discussed in another thread, but since you posted it here I will respond here for now.
They were indeed tested in a 10-20K integrating sphere setup. We had 3 samples from each LED type tested, then picked an average number and rounded it. If I recall correctly we had some test out at about 710, 720 and 730 or so lumens, so we chose 720 as the official OTF rating. The output varied because some LED’s are slightly brighter than others, and some drivers may put out a few mA more than others.
Now let me clarify a few things about the XP-G2 spec sheet. XP-G2’s are binned at 85C. ANSI standards test OTF lumens after 30 seconds to 2 minutes. In this time period no way does the LED get anywhere near 85C. XP-G2 is about 15% brighter than XP-G.
Now unfortunitly, Cree hasn’t bothered to update their Cree PCT tool with the latest XP-G2/XM-L2’s. If we go off the XP-G spreadsheet for 25C at an average of .667A per LED we get 249.97, or 250 Lumens for the sake of rounding. Then if we go off the Cree datasheets and compare an 85C XP-G to an 85C XP-G2, the XP-G2 is 13.2% more efficient. So lets take our 250 Lumen figure, multiply that by 3 then by 1.132. We get 849 LED lumens. Then if we multiply that by the 89% optical efficiency of the optic, we get 755.61. Then take off another 2% for a quality AR lens, we get 740.49. Then obviously there will be a few lumens lost because of some heat during the 30 second - 2 minute ANSI lumen test. Also all these figures were quoted for bottom of the bin XP-G and XP-G2 R5’s. So efficiency could be up to 6% brighter (or maybe 3% on average if you got LED’s that were of average flux bin in the R5 group).
Being pretty new at all this, I’ve of course seen the 25C and 85C stuff, just didn’t know how all that added up to the real world out the front lumens. I wasn’t doubting that the sphere said so, just wondering how all the math made sense. All the percentages and efficacies that are posted here and there are difficult to make sense of until put the way you did right there, so thank you very much for the beautiful little ribbon complete with bow…now it all makes sense and I am now that much more eager to get that drop-in installed!
Sorry if I posted the question in the wrong place, seemed to fit what was being discussed. Perhaps I’m learning bad habits from bad people…<< cough>>
