Testing a Cree XHP50.2 J4 3A led

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.


This should solve that, but it is not how it looks, I soldered the led the wrong way around on this board :person_facepalming:

So I say the round dot is + and the square dot is -

If you look at picture in the OP, the side with the square is the cathode (-) side and the side with the circle is the anode (+) side.

EDIT : beaten by djozz :person_facepalming:

Put the two dots on the bottom, plus is on the right. :wink:

This is on the XHP-50.2 ONLY! Most modern Cree emitters have the plus on the side of the bond wires. The XHP series makes it more difficult to tell but of course you can always check the data sheet, way at the bottom end.

I have a xhp50.2 on the way. I will do a direct comparison of beam size and shape with my sliced xhp70 in my L6 with SMO reflector.

I’m curious which will be the better thrower.

I have a question. I have a TN31 modded with a K40M driver (resistor mod) and a dedomed MT-G2 Copper added to the LED side and driver cavity + spring baypass. Would a XHP50.2 be an upgrade (throw or total output)?

XHP50.2 is on the way, can’t wait to mod it to my nitecore EC4

The more amps those 2 see the more the 50.2 pulls away. At 5 amps for instance, the MG-T2 does about 2800 lumen and the 50.2 does 3500. So I’m sure you would gain brightness.

Since the 50.2 is a smaller die, you would probably gain throw as well.

In the areas of tint, my 5700k 50.2 has a pretty noticable yellow corona (looks square shaped as well). I just installed it though, so I’ll need to try it out at night and see how it looks. In my Convoy L6 with lowered smooth reflector I do see a slightly dark center. No where near as bad as my sliced dome xhp70, though. Reflector height plays a large factor here.

So yeah, I would think it is a good upgrade to the MG-T2.

The jury is still out whether it’s better or not than my sliced dome xhp70. I’ll post up hot spot size comparisons tonight.

Here is my light. A Convoy L6 with an SMO reflector that has the bottom removed. This drops the reflector down just under a millimeter (roughly). I use very thin copper shims to raise the emitter to fine tune the focus. Right now I’m using 2 shims. I reduced the camera ISO to better see the beam shape.

Here are the shots all from the same distance.

Now here is the same with me raising the reflector slightly. This would be closer to a stock SMO.

You can see that the first pic has a less defined edge on the hot spot, a smaller corona and a slight donut hole shape.

The second pic has a more defined edge, larger corona and less donut shape. This looks better in real life, but does not deliver the highest lux. If your chasing lux then the first picture will give you the highest readings.

Here are the same basic pictures as above taken with a more realistic ISO setting.

In real life the donut hole in the first pic is quite subdued, but you kind of notice it a little as you move the light around. The second pic it’s less noticable and a nicer looking beam in general.

I will compare this xhp50.2 to my sliced dome xhp70 in just a little while. One interesting thing is that the corona on the xhp50.2 is noticably square shaped at close range. It’s kinda odd. Lol

Here is a pic of the same light with the CW xhp70 in it.

You can see the left pic has a smaller hotspot. I’m not sure if that’s due to the reflector going closer or the dome being sliced off. Maybe the dome. It looks pretty much the same size as the 50.2 with its dome on. The dome off xhp70 might be a tad smaller.

The left pic usually has a very noticable donut hole, but I’m using a trick to reduce it. I moved the emitter slightly off center to the reflector. It doesn’t eliminate it, but it helps reduce it.

One other difference between the xhp70 and the xhp50.2 is that the 50.2 gets noticable hotter. I haven’t had a chance to take tail cap amp readings, but I’m thinking it’s higher than the 70. I’m using an FX-30 driver with a wire over the sense resistors and liitokala batteries.

Overall brightness between the sliced dome CW 70 and stock 5700k 50.2 is pretty close. I don’t have my meter right now, but i can tell the 50.2 is a bit weaker.

I was quite let down with the reduced lumens after cutting the dome off my xhp70. I’m probably going to go back to a domed xhp70. I might wait for a 70.2, but which ever I choose, I want a 6500k version.

About color, I’ve had the xhp70 N4 1A and N4 1C, both were about the same to my eyes. A bit on the nuetral side to me. I don’t care for it. I’d rather have a cooler white. This new xhp50.2 in 5700k is noticably more yellow. The corona is definitely more yellow, but the hotspot is only slightly more yellow. Combined together they create a more yellow overall looking beam compared to the CW xhp70.

I hope this helps someone.