I think I have posted this elsewhere but cant find it. The measurements were taken at the led for both current and voltage. Keep in mind that my DMM are not calibrated. Power was supplied by a bench power supply.
XML-2 U2 XML-2 U3
Volts Amps Volts
3.11 1 3.1
3.4 2 3.38
3.64 3 3.69
3.86 4 3.87
4.11 5 4.08
Taking into account tolerances these are pretty much identical for both leds. It was suggested to me that the way that I was driving the leds that perhaps I had an issue with voltage ripple killing the leds.
I'm not trying to derail the thread but maybe there is a change in these leds apart from the higher voltage requirements that others may have picked up on as well?
Die over 5A? or 5.5A? So do you mean it kills the LED at 5.5A? Are the fine wires melting? Dunno - most of my stock is older. Only have a couple U3's and the ones I've built up in a light are not being pushed (under 4.5A).
All testing was carried out with heavy wiring to try and eliminate losses. The leds are dying around the 5.5 amp mark. The driver in question about the voltage ripple is a taskled and my power supply was also suggested as being suspect. Hooked directly to the led regulating either the voltage or current from the power supply made no difference to the outcome. I hate to think how many good leds have died in testing and in my lights trying to get above 5 amps. In my C83 l went through a heap of leds until I found three to reliably run at 6 amps each. In the XMTG light I settled on 5 amps per led after lots of testing.
On the top end it’s hard to say the amount of light output—If you were to have a medium at 5.4 amps and a high at 6.5 amps not sure if there would be much difference
What I have noticed is I buy drivers pre programmed (I’m older and can’t see s….t) the lower modes are always lower than programmed to be—with the patience of RMM I have drivers more to my satisfaction—this is more of an issue to me—lets face it who uses their lights wide open for any period of time
Some of them seem like they are coming pretty close to that. DBCStm has measured some lights with a U3 at around 5A that are doing about what the old ones did at around 6A. Dale, care to chime in? I know that the M6s I build with the U3s all measured 400-500 lumens higher on average than the U2s did. I have built 100+ of these and measured dozens, so I know the usual range, and the average U3 was as good as the best U2s I've ever measured. This surprised me a bit, but I can't argue with those numbers. In some lights, however, the lumens have gone down a little bit but the efficiency has still improved.
Hmm, needs to be someone with access to cells of all types, hosts with DD drivers, well acquainted with high current testing, and the means and time to do so. It would also help if they were handy with a camera. Hmm…
Ive got some emitter data that might be interesting. Various testing with driver circuit and batteries or powersupply only. Sometimes with a capacitor on the output. I have been thinking about starting a thread on it for some time, but I have not gotten around to it yet.... I have used a camera and recorded video when testing many of the emitters. Some that I have blown... Might be some interesting data despite that its not a super scientific testing.
Time will tell when I get around to post about it. I have not looked that much at the clips I made yet. But im not super surprised to hear what chops728 reported.
Btw MRsDNF.. Im running 6,6A now. Short story, I found the right emitters.
I'm willing to do testing if someone can tell me what they want done below 5 amps. Anything above 5.5 amps and I can only blow them up. I also do not have any older generation spare XML-2 U2 or U3 leds. I could pull them from lights though if needed.
Really dunno - dunno what's going on. Seems like conflicting info: Richard says his M6 builds get more output (lumens) with the U3's, but djozz's tests indicate high Vf, mediocre output with the U3's he tested. Your tests in post #11 show virtually no difference in Vf from 1A thru 5A. Others have found high Vf with the new LED's as well, but your tests are the only ones I've seen or heard of where the Vf is basically unchanged between a U2 and U3. Obviously we don't have all the info, and no idea whether sourcing and tint variations is partially to blame.
