…offering efficacy of 160 lumens per watt at 350mA. Output is as high as 340 lumens at 700mA (bin U3, which is still rare) therefore it is more efficient and puts out more light at any current than earlier single-die Cree LED’s…
Source:Cree - Flashlight Wiki
In the XM-L, U2 and U3 typically have higher forward voltage than the T6. That is the point, just as the XM-L2 may have as well. The example speaks for itself, the brightness bin chart makes no mention of forward voltage, so I don’t know what Cree says is typical for each bin and you can’t calculate efficiency from just that alone.
Based on what data? I have seen nothing to prove this yet. All XM-L emitters are built the same way, and binned based on their performance. I’ve seen no test results that conclude higher bins have a higher Vf.
XM-L2 is built on a completely different process, which has been shown to produce higher Vf at the same temperature when compared to XM-L.
Using one example to prove something is not a good idea. You would need a much larger sample size to prove a correlation between efficacy and Vf.
My original question was about the xml2 and if it had a higher forward voltage and if that means doing a direct swap will give full benefit for the new emitter? My example was just to show the importance of forward voltage. But it was also the actual findings of the light builder Lambda in his testings of T6 and U2 xmls.
Thanks for clarifying. I wasn’t refuting the individual findings. However, I would caution anyone from using such a small sample size for a claim that XM-L emitter efficacy is directly proportional to Vf. To prove this with any certainty, one would need several samples from different production lots in each bin and do very controlled tests.
Very interesting discussion. My peabrain struggles to keep up but I’m trying to learn.
I don’t mean to change the subject but a T6 to U3 swap into an Ultrafire 980L made an incredible difference. Maybe an XML-2 swap will yield similar results since it’s direct drive on high. With a Panasonic CGR18650CH battery for the brief amount of time it delivers 5 amps it burns paint.
Just a thought.
If U2 or U3 bin really do have a higher forward voltage, its not really a decreased efficiency using a 7135 driver………instead of more waste heat from excess voltage we get more light.
At least……that’s how I assume it would work
I told myself that the next time I saw someone mention that EA4 with IS’s L2 upgrade I would/might pull the trigger on one, just been trying to ignore that particular itch.
What is it that you guys seem to like best about this light? And which batteries are recommended - Eneloops?
Me glads I not only one brain hurts reding this , but I likes to try.nig wurds lots of numbers I dos get intimidated reading such technological posts but I grasp. A little bit more eveytime.