1. At the same output - yes, though you won’t notice.
2. At peak output - yes, this should be a bigger difference….because the peak output is lower.
Yes, XPG2 runs noticeably cooler in this light and is slightly brighter than the Nichia.
XPL HI should run about as cool as XPG2 and be brighter and throwier than either XPG2 or Nichia.
Not brighter according to the maker:
I guess that makes sense. My understanding is XPG2 S4 2B is more efficient than Nichia 219C and produces more output… at the same current. But in this light Nichia is running at a higher current.
Any estimations of xp-l hi candela?
There is an obvious relation between efficiency and heat generated (or how cool it operates). However in this case with FET I think something counter intuitive might be/is happening. It’s like a Ferrari going 50 miles per hour has got better fuel consumption than a Prius going 120 miles per hour. I haven’t checked the data, but you know what I mean.
I received my XPL HI D4 with V2 firmware yesterday and it is awesome. The build quality is top notch and the UI is so effortless it makes it so you don’t want to put the light down. The intuitive UI alone will have you reaching for this light for most of your daily tasks because the D4 is flat out fun to use. I went with the XPL HI because of the extra brightness and I could really care less about a neutral tint. It’s a flashlight…I use it when its too dark to see something with the ambient light. Bright is good. It completely crushed my S41 when compared side by side outdoors last night, but did get warm and stepped down nicely without me being concerned at all about it becoming too hot to handle. To me it seems like they have the step down set up perfectly. I plan on ordering a couple more in a few weeks when they are restocked but consider myself pretty lucky to have grabbed this one before they went out of stock again. I was thinking about getting a Zebralight SC63 before I ordered the D4, but this thing blows it out of the water.
This got me curious so I measured output on the default 350mA mode:
- Nichia 219c: 138 lm
- XP-L HI: 145 lm
- XP-G2: 161 lm
These used the same battery, and were measured in that order. I took the stable output level each one settled to.
So it does appear that XP-G2 is the most efficient, at least with my small sample size of one.
How do you know? The values you have shown are for all three emitters with the same 350mA. But Vf may vary, therefore P (=I*Vf) may vary as well. Hence, it seems it is not possible to say which emitter is most efficient (lumen/P) here. Maybe I’m not understanding something?
These are caused by the same thing. XP-G2 has a much higher Vf than Nichia 219c. This makes it draw fewer amps on direct drive, because the emitter Vf meets the battery’s voltage sag at a lower current. However, the higher Vf also means it’s wasting less of the current it receives at lower levels, so it can be more efficient.
With a different type of driver, one which converts extra voltage into current, the 219c might be more efficient. Instead of burning off the voltage difference, it could be put toward making more light. But this isn’t that type of driver. So the 219c’s wider voltage gap goes toward making more heat.
Frankly, I don’t understand the analogy, but when it comes to FET+1 lights like D4 it goes like this:
- The lower voltage forward curve of the LED, the higher amperage.
- The higher amperage, the higher voltage forward (you’re moving up the curve)
- The higher amperage and voltage forward, the higher power consumption.
- The higher amperage, the lower efficiency.
- The higher amperage, the higher output, despite efficiency loss. That’s up to a limit that a properly designed light won’t cross.
- In FET+1, all modes above the 1*7135 have similar efficiency. If you move a notch above 7135, runtime falls of the cliff.
- At high currents, 219c has lower voltage forward curve than XP-G2, but higher than XP-L.
- At low currents, Nichia has the lowest voltage forward curve, XP-G2 second, XP-L - highest.
- (7) and (1) mean that XP-G2 will run at the lowest current, 219c in the middle and XP-L - the highest.
- XP-G2 is the most efficient at low current, probably slightly less than XP-L at high. Nichia is worst either way.
- (10) means that at the 1*7135 mode XP-G2 will be the brightest, XP-L distant second, Nichia the worst. Runtime will be very similar with all diodes, with minimal differences because of (8)
- XP-L is probably the most efficient at high current, XP-G2 close second, 219c worst.
- From (9) and (12) it’s natural that XP-L is the strongest. It turns out that higher amperage trumps efficiency gains, making Nichia stronger than XP-G2.
- From (3), (7) XP-L will be the hottest, Nichia close second, XP-G2 coolest.
- With lower currents, batteries deliver more energy.
- From (9), (12), (15) With FET, XP-G2 has the lowest current and the highest efficiency curve, making it easily the most efficient. Nichia has lower efficiency curve than XP-L, but runs at lower current. I can’t predict which will be more efficient here.
Note: I assume flux bins being XP-G2 S4 (confirmed), XP-L V2 (that’s what intl-outdoor sells separately) and 219c D260 (like XP-L). Though I wouldn’t be surprised if Nichia was be actually better.
Hank, could you confirm flux bins?
I don’t think that’s correct. I’ve built triples with high quality FET drivers and bypassed springs. Tried both triple XPL-HI and triple-Nichia 219C in the same light.
In ALL cases, the lights got much hotter much faster when using Nichia 219C. When run on 100% FET power, Nichia pulls significantly more amps on a fully-charged Samsung 30Q and you feel it as extra heat when you touch the light.
How about this: XP-L is more efficient than XM-L. But if you run a lot more current through an XP-L, then it gets hotter than an XM-L, although XP-L is more efficient. Back to D4: an emitter can be more efficient than another, but due to different Vf it gets hotter than the less efficient emitter.
After your discussion, I’m more confused than before. 
Will I go wrong if I choose Nichia or is it better to choose Xp-g2?
Which holster do you recommend for this FL?
Impressive.
I stand corrected. I actually looked at fonarevka PCT. There, 219c has quite high Vf curve. In Texas Ace’s tests that’s entirely different matter. I guess I should make major amendments to the predictions above.
Got it now.
BTW, another prediction:
Once temperature control kicks in, XP-G2 will be brightest, XP-L close second (maybe first actually), 219c last.
How do I know? The measurements quoted above. In this torch, XP-G2 makes the most light at 350mA, the highest regulated level of current. Results may vary at other currents.
My quick measurement also agrees with djozz’s tests. The test shows more lumens from XP-G2 for the entire graph, compared to 219c, until the point where the current exceeds what XP-G2 can handle. This is defining efficiency only in terms of lumens per amp though, not lumens per Watt. Because lumens per amp is what matters on this type of driver.
XP-L HI isn’t on that graph. Normally I’d expect XP-L (domed) to have the highest lumens per amp, but perhaps the XP-L’s advantage doesn’t start until it gets to higher currents? Or maybe the HI’s lower bin eliminates the advantage? Let’s check the measurements… Going from djozz’s test data, I see…
- XP-G2 S4 @ 1A: 440 lm
- XP-L HD V6 @ 1A: 490 lm
- XP-L HI V3 @ 1A: 400 lm (estimated)
- Nichia 219c @ 1A: 390 lm
But at higher current, XP-L HI may be more efficient…
- XP-G2 S4 @ 5A: 1330 lm
- XP-L HD V6 @ 5A: 1820 lm
- XP-L HI V3 @ 5A: 1486 lm (estimated)
- Nichia 219c @ 5A: 1200 lm
The estimated HI values are the HD values / (1.07 3), since Cree specs each bin as 7% brighter, and HI is three bins lower.
It looks like the intersection point is at about 2.8 amps or ~980 lumens. … which I think works out to about 11 amps and 2850 OTF lumens in this light. So, in the D4, XP-G2 is likely the most efficient up to about 2850 lumens, and then the XP-L HI is the most efficient for higher levels.
XP-G2 has the highest Vf though, so it’ll have the most sag on a low battery. Nichia 219c should have the least sag.
For practical purposes, they’re all good choices… so pick whichever one has the tint you like. Tint is much more noticeable than the other emitter differences.
In my D4 with the stock XPG2 emitters, with the light cold and then turned on to max turbo I could go maybe 20-25 seconds before the head gets too hot to touch. Now that I’ve swapped in 219C emitters I can go 13-15 seconds.
I’m still undecided if I want to leave it like this. I like the tint, output and high CRI, but it gets super-hot way too fast.
I compared it side-by-side with a Sunwayman I’d modded into triple XPL HI 5A2 running on an 18500. With both lights cold, the D4 Nichia produced more light, but the XPL HI triple had more throw.
After a full minute of operation the D4’s temp regulation had dimmed it to maybe 10% power while my Sunwayman without temp sensor but with timed stepdown to 50% was still touchable and produced noticeably more light.
It may just be XPL HI is a better choice of emitter for this kind of hot-rodded light.
I’m not sure if I want to try swapping in some XPL HI into my D4 tonight or wait until my next D4 arrives and do it on that one.
One possible solution to this problem would be a firmware update: Allow the user to manually cap the maximum output of the light. It wouldn’t be as bright, but might be more practical.
In the measurements I’ve seen, 219c has significantly lower Vf at all current levels, compared to XP-G2 or XP-L.
For example, at 5A, djozz measured:
- XP-G2: 4.05 V
- XP-L: 3.90 V
- 219c: 3.43 V
It can also apparently handle a ridiculous amount of current before it pops, which is fortunate since the low Vf allows it to draw so much more current. But with the highest current and the lowest efficiency, it’s going to make the most heat.
This is probably correct, and an interesting way to look at it. XP-G2 should have the least heat, and the most lumens after regulation stabilizes.