Testing a Cree XHP50.2 J4 3A led

Direct drive on 2 freshly charged litokalla 26650s = 14.5/15a of juice showing on my clamp meter. Suprised it didnt pop it. Host got very hot but no immediate problems

If the host got “very hot” that probably means the LED got to 100 or 150C…

Aww Man!

You can do that with MCE’s too! :wink:

It’s not a desired effect. Blew it with two 14250 cells :laughing: . Bad reflow.

I’m going to keep running it at max power see how it goes i didnt even put a driver in and all springs are bypassed 22 gauge wire so no resistance

Reflow very important to have an excellent thermal path. Also soldered the sinkpad the brass pill (i have a copper pill too but the xhp70.2 is going on there when i can get one!)

Just because it has a good thermal path doesn’t mean it has good cooling.
Also, unless you use a superconductor there is going to be resistance.

I’ve got 3 of the 5000K 50.2’s in my latest scratch build, pulling 21.12A from a pair of Sony VTC6’s for 11,696 lumens. The cells were at rest at 4.13V at the time of the test. The KaiDomain triple reflector makes for a decent hot spot, just a hint of a dark spot but I probably don’t have em perfectly located height wise. I’m using 20Ga Teflon wires, cut out the area’s around the side of the reflector where the pads are for clearance, have filed down centering rings.

They rock, for sure!

You have taken my post to literally by no resistance i meant there is no FET/springs to reduce the current thus its a low resistance as it possibly could be.

You could use 8 gauge wire like I do, that has less resistance than 22 :wink:

It also means that with a regulated driver(either boost, buck, or linear) the more efficient lower Vf led will stay in regulation longer and half a volt means something there.

Another great test thread Djozz!

Boost or buck? yes and and no. Without enough voltage difference between source and load you just shouldn't be using a buck. With too much, you shouldn't be using linear. Once you get to where a buck (or boost) works well, further marginal differences in voltage won't matter, and it becomes a big advantage of a buck. In the transition though I'd turn this around as a disadvantage. Lower Vf led's are bad because they require a buck, and because without one the setup on the whole becomes more and more inefficient.

If you sliced the dome off your xhp70 you would also get a little less lumen’s, but more throw.

Then I wonder if the new xhp50.2 is an upgrade or pretty much the same?

One advantage the xhp50.2 may have over a sliced dome xhp70 is less of a donut hole. Then again, I think the K60 has an OP reflector so it’s not likely to ever get a donut hole. On a SMO like my L6, the xhp50.2 may have a slight advantage.

Do you guys know off hand if a sliced dome xhp70 has a smaller or larger hot spot compared to a dome-on xhp50?

There is a donut hole on the Thorfire S70 and also on the new Eagle Eye X9, both use the XHP-70 and both have heavy orange peel reflectors.

The XHP-50 and 50.2 fit on the XM-L footprint and can use the XM-L reflector. The XHP-70 is a much larger emitter physically, albeit not as large as the MT-G2. So comparing the 50 to the 70 is not an equal comparison. The 50.2 version has less gap between emitters but not as tight as the XHP-35 so there are still some issues. The 50.2 utilizes a phosphor covering much like the XP-G2 and as such it would be difficult to do a clean de-dome. Slicing the dome may well yield better throw but the center of the hot spot would still suffer from the gap between dies.

The XHP-70 can do substantially more lumens than the 50 or 50.2 variant, as well.

So your saying swapping in the new xhp50.2 is not gonna be any kind of an upgrade over a sliced dome xhp70.

Well, that’s a bummer.

Maybe the new xhp70.2 will be a real upgrade.

Well, it’s maybe not as straightforward as that. Depends on several factors. And for the record, whether or not the XHP-50.2 shows a donut hole is reflector dependant, it can still show that just maybe not as bad.

I got the new Eagle Eye X9 today and there was visible donut hole from the XHP-70 beam. I was about to put in an 50.2 and thought about slicing the dome off the 70. That made all the difference in the world in this particular light and it’s still making just over 3000 lumens at 4.84A so I’m thinking I might leave it just like this. Since djozz showed that the 50.2 maxes out around 5000 lumens and some 10A, it’s doubtful that it will best the 70 in this light without more extensive modification.

So there are always mitigating factors that make it more complicated than simply the emitter.

Edit: Maybe some expansion on my reasoning would help. The XHP-50.2 is similar in structure to the XP-G3. I don’t like the G3 for it’s beam profile and am finding a large similarity to this G3 in the 50.2. Sometimes it’s not all about power, given an ugly beam profile with odd color shifts the power levels aren’t winning it over for me. That’s just me though, and just my singular experience with my triple in a single triple reflector. I might find I love it in a different light or different reflector. Won’t know that until I try and I have a single 50.2 to play with…

I have a dumb question about the LED. I want to reflow one and can’t figure out where is + and - :person_facepalming:

Dang dunno offhand, but check the CREE datasheet and usually there's a mark on the underside to indicate anode or cathode side - I always forget which is + and - and always looked it up. Finally wrote it down, but my notes are @home . I sanity check all the new LED's now - used to be easier.