I know a lot of people are looking for a good updated version of their favorite lights but with the updated emitter. But, I wonder what is necessary to get a light actually optimized for the XM-L2? Since the package was basically the same as the previous version, I don’t think anything would have to be done with the reflector or optic, but what about the driver? Isn’t the forward voltage a little different and wouldn’t it benefit from a driver designed with it in mind rather than just the old one?
Maybe every thing is a straightforward replacement and that would be great, but things are usually no so simple. Thanks.
i think it is a valid point… its difficult to drive an xml2 in single cell applications … not sure what driver could improve this? the only solution i think is a constant current buck/boost type driver with multiple cells behind it
No it’s not, it drives just fine with standard drivers. I put one in my USB charger flashlight and the output went up 200 lumens… and that was going from a cool white XML T6 to a neutral white T6 XML2 which is 15% less efficient than cool white.
That’s interesting, but I bet quite a bit of that gain can be attributed to the SinkPad mounting alone. 200 lumens is a lot but good thermal path is more important than anything.
I have put a couple in, one in place of a SST-50 so that is hard to compare as it’s apples to oranges but it rocks. The other is just a super cheapy 501B I bought three bodies and one has a XM-L2 U2 and one a regular XML-T6 both 2.8 drivers, pills are both copper. The XM-L2 is brighter by a lot. Not so much the throw as the flood it just really goes bam now, I’m actually kind of shocked at how bright this thing is. Much more comparable now to a decent C8. The old T6 is an ok walk around light. But this is a much more usable light now. On medium or low it’s nice for in the woods and when you hit a clearing the high really lights it up pretty well. Nice improvement at least for me.
the forward voltage thing, match retracted his data as he later found he did not trust the test equipment.
I’ve found xm-l2 emitters are less inclined to pull high current but since they give more lumens at any given current over xm-l, why worry? it just means your switch gets an easier time, cell gets an easier time and lasts longer between charging, less heat.
Dont forget, the idea behind the emitter is to get more output from an existing system, ie better efficiency, not force you to build a new system to suit the new technology.
As texaspyro points out, the big thing for me too, is more output with a nice tint.
So, I guess since I don’t have my xml2s- do they have higher forward voltage or not? What I’m saying is that if they require higher voltage than a first gen. Even though at say 3A they produce more light than an xmlA- they still use more power to do so at equal current levels because of the higher forward voltage.
I'm still waiting for a final verdict on this. Which is better for single li-ion use and what kind of runtime / lumen trade-offs do you get with a single li-ion. We need a good thorough test.
I could put a c8 xm-l2 pill together with a nanjg and try it if you’ll sleep better? I already have a nw xm-l2 c8 upgrade built but its got my favourite driver in, not really a fair comparison to my work c8. I really don’t believe there will be a noticable difference in run time, I’ve certainly not picked up on it yet, just build and be happy.
Here was the example I was given. Now this only involves XM-Ls but different flux bins and shows what different vfd does. So, this is why I bring up this discussion.
—
—
— U2 @ 3.9v 3A = 11.7w 320L
T6 @ 3.6v 3A = 10.8w 300L
So for another 1.8 watts you get 20 more lumens with the U2.
But if you bump up the T6 current just a bit (200mA):
T6 @ 3.6v 3.2A = 11.52w 360L
You get 40 more lumens than the U2 with less power consumed using the T6.
I did a big bunch of XM-L2/SinkPAD single cell builds - Pana PD's or Samsung 20R's is the way to go. Yes there's drop off, but agree with Gords, still hugh benefits. Really like the 26650 single cell builds because the KK ICR or MNKE IMR do really well with them.
What we are talking about are flux bins in the example. That has to do with brightness. LEDs are spec’d at specific Amp ratings. So you can see in that example the U2 is brighter, higher binned, at 3A. Amperage is just one part of the equation along with the Voltage.
That example was from Kevin at lambdalights when he was explaining this to me. So, I’m not sure if you are saying that that example is wrong or you don’t understand. But basically it comes down to flux bins don’t necessarily correlate with efficiency.
i don’t have personal data to refute this, but the rather detailed cree datasheets make no mention of this, and someone on this forum would have noticed it by now, so perhaps this fellow got a few samples that deviate from the average in voltage/current or you have mentioned a discovery no one else has made or quantified yet.