XHP35 HI vs XML2 in heat generation

Hello all,

Trying to get a feel for the XHP35 HI in terms of heat generated in comparison to XML2. Basically I want to figure out how much faster the XHP35 HI generates heat when compared to XML2. So say it takes an XML2 light to reach 50*C in 5 minutes how long would it take XHP35 HI in the same host? Seems silly to ask but it would give me a good feel for the LED and what to expect when purchasing future lights that have XHP35 HI in them. Most of the lights I own are XML2 so I know their capabilities.

Thanks

According to Cree the XHP series all run more efficiently and run cooler. How much cooler? Have no clue there are no numbers on Crees own data sheets about this. I just know the XHP35 HI in my SC600 MkIII HI takes twice as long to get hot than my XML2 SC600 MkII.

below the 1000 lumens range their efficiency isn't that different, for any amont of energy pumped into those leds they should produce around the same amount of heat and visible light, any differences in heat generated that you think your perceive is due to other factors.

Awesome, nice thank you both for the info [emoji3]

CelticCross74 said:

According to Cree the XHP series all run more efficiently and run cooler. How much cooler? Have no clue there are no numbers on Crees own data sheets about this. I just know the XHP35 HI in my SC600 MkIII HI takes twice as long to get hot than my XML2 SC600 MkII.

Click to expand...

That's pretty amazing, and good to know! Wish I still had my MK II to try this myself.

The XHP35 draws only 1 amp at the LED from what I have read.

The XHP35 is a 12 volts LED, one has to think in term of watts to compare different leds, W= V x I

One can compare different cree LEDS with their product characterization tool, under 1000 lumens the efficiency of the highest bin XHP-35 HI and XM-L2 are virtualy identical, that means same amount of heat and light emitted.

romteb said:

The XHP35 is a 12 volts LED, one has to think in term of watts to compare different leds, W= V x I

One can compare different cree LEDS with their product characterization tool, under 1000 lumens the efficiency of the highest bin XHP-35 HI and XM-L2 are virtualy identical, that means same amount of heat and light emitted.

Click to expand...

I am not the person to answer the question, but it is my understanding that the advantage of the XHP was lower amps at the LED.

If the same amount of heat is generated with XHP-xx and XM-L2 at the LED what was the advantage to change? I thought that the advantage of XHP-xx was lower cost of production and lower current needed at the LED.

Amps dont exist in a vacuum, you have to multiply them by the voltage to estimate the power (in watts), the efficiency is expressed in lumens/watts, your "3 volts 3 amps" led and your "300 volts 0,03 amps" led use the same amount of power, if their lumen output is identical they have the same efficiency and produce the same amount of heat.

There's also driver efficiency to consider. Inefficiency in the much higher needed voltage boost may end up cancelling out any efficiency gains at the emitter. I'm curious to see, for example, whether XHP 35 ZLs are more, less, or as efficient as the XML2 ZLs at equal output, in the absence of PID (sufficient cooling provided to eliminate step down).

Indeed, it could actually be worse, i think what confused people in the first place (apart from marketing BS) is the fact that the XHP has a lower thermal resistance (it sheds the heat it generates more easily in whatever support it is mounted on) wich would make no difference in a flashlight (if anything it would actually make the flashlight body hotter)

Its interesting that the XHP35 HI is the single emitter of choice in the Axebeam K70 which the manufacturer specs say achieves 2600 lumens on high.

No doubt the XHP35 HI is overdriven in this light to achieve this.

BUT as far as I know, there is no single emitter XM-L2 light that achieves even half of this output.

So something is going on that enables the XHP35 HI to have the potential to perform in such a stellar fashion in the K70. Something that nobody seems able to explain in terms of theory so far.

easilyled said:

So something is going on that enables the XHP35 HI to have the potential to perform in such a stellar fashion in the K70. Something that nobody seems able to explain in terms of theory so far.

Click to expand...

Yes, it has a much bigger die, are you guys trolling ?

romteb said:

Yes, it has a much bigger die, are you guys trolling ?

Click to expand...

Since when was asking a question that hasn't been answered trolling? Are you sure you're not trolling?

Trolls are not usually members for 12 years and go to the effort of posting numerous courteous posts and pictures of their collections as far as I know.

That was rude sorry Easilyled

romteb said:

That was rude sorry Easilyled

Click to expand...

Ok, apology accepted.

I wasn't aware that the die of the XHP35 was so much bigger than the XM-L2 but I've admittedly been too lazy to look them up.

Would you happen to know what the respective die sizes are?

Cree doesn't give die area numbers, th XHP35 is actually 4 little adjacent dies (that's why it's 12 volts).

The XM-L and XP-L have the same die size, you can compare XM-L XP-L die size with XHP35 in the following picture by looking at the high intensity variant of both leds.

@romteb, from your diagram, it seems to me that Optical Source Size is the relevant row for comparing relative die areas.

So the XHP35-Hi is 1.4 times the size of an XP-L Hi yet in the Acebeam K70 it achieves 2.5 times the lumens that any XM-L2 or XP-L flashlight does.

I think its worthwhile to point that out and to question why/how Acebeam considered it possible without endangering the life of the emitter.

who cares about getting just a quarter (or even less) of the oft quoted 50,000 hours LED lifetime? that would still be 520 days CONTINUOUS

Acebeam mounts them on really big and thick copper MCPCBs w/ direct thermal path. shouldn't be too long before they start watercooling those things

easilyled said:

@romteb, from your diagram, it seems to me that Optical Source Size is the relevant row for comparing relative die areas.

So the XHP35-Hi is 1.4 times the size of an XP-L Hi yet in the Acebeam K70 it achieves 2.5 times the lumens that any XM-L2 or XP-L flashlight does.

I think its worthwhile to point that out and to question why/how Acebeam considered it possible without endangering the life of the emitter.

Click to expand...

If you look at the maximum lumens in the cree slide it corelates with the 1.4 area increase, Acebeam simply overdrives the XHP35, one could as well overdrive an XP-L / XM-L, here is a graph from Djozz of BLF that shows that if one is willing to pump 7 amps in those leds you can have 2000+ lumens.