# XP-G driven at 1A vs 1.4A



## Black Rose (Aug 20, 2010)

Trying to figure out which drivers to use for my next builds.

Would there be a big difference in visible output with an XP-G driven at 1A vs being driven at 1.4A?


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## ShineOnYouCrazyDiamond (Aug 20, 2010)

IMHO - big difference no, but completely visible difference - yes.


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## old4570 (Aug 20, 2010)

In a word = Yes 

I use the SB 1.4A driver with one Xp-G R5 P60 and its almost as good as the ones driven much harder ..

Its a good combo ... and the LED is not driven so hard as to suffer a lot of heat related sag .


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## Bullzeyebill (Aug 20, 2010)

Might make a difference if the host is something like a Surefire C series, or clone. Need really good heat sinking to use the C series head if you are going to 1.4A's compared to 1A to the LED. If not that good heat sinking, your 1.4A will be running at the same output as the 1A'er or lower, very quickly.

Bill


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## Black Rose (Aug 20, 2010)

I'm curently using the SB 1.4A driver in a few builds (P60 drop-ins and some Aurora V6 hosts) and was thinking of trying the L-Mini II driver with XP-Gs due to the amount of heat that is being produced.

A lead wire came off one of my SB 1.4A drivers long after it was installed in a drop-in - not sure if it produced enough heat to unsolder the wire from the board end.


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## nailbender (Aug 21, 2010)

Black Rose said:


> I'm curently using the SB 1.4A driver in a few builds (P60 drop-ins and some Aurora V6 hosts) and was thinking of trying the L-Mini II driver with XP-Gs due to the amount of heat that is being produced.
> 
> A lead wire came off one of my SB 1.4A drivers long after it was installed in a drop-in - not sure if it produced enough heat to unsolder the wire from the board end.



HI 

I use bryan's 1.4 amp drivers all the time with no problems, you probably had one that already had a loose wire or one not soldered quite tight. 
You will get about 320 lumens with the 1.4 amp driver and about 300 lumens with the L mini 1 amp driver so there is not a lot of difference. The l mini runs much cooler and adds about 30 minutes runtime compared to the 1.4 amp driver

Dave


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## ShineOnYouCrazyDiamond (Aug 25, 2010)

I was looking through some XP-G spec PDFs and there is a section on relative luminescence. The basis for the rating is the standard 350mA flux rating is the 100% brightness point.

For 1.0 A the relative rating is 250% and for 1.4A it is approx 320%.

So for a Q5 rated @ 107lm @ 350mA.
1A = 107 x 250% = 107 x 2.5 = 267.5lm
1.4A = 107 x 320% = 107 x 3.2 = 342.4lm

Keep in mind this is all relative to other ratings. Can the driver maintain 1.4A? Relative brightness drops with junction temperature. More drive = more heat. OTF losses, etc.

YMMV


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## vaska (Aug 25, 2010)

ShineOnYouCrazyDiamond said:


> I was looking through some XP-G spec PDFs and there is a section on relative luminescence.



Why not to have a look at this instead of speculating?


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## ShineOnYouCrazyDiamond (Aug 25, 2010)

vaska said:


> Why not to have a look at this instead of speculating?



Excuse me - I never said I was speculating. 

I took exact figures straight out of the PDF document.

The information you have linked to is ONLY good for R5 flux bin XP-G LEDs. The information on "Relative Luminescence" is valid for any flux bin XP-G LED as long as you know the lm/w information for that bin.


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## vaska (Aug 26, 2010)

ShineOnYouCrazyDiamond said:


> I took exact figures straight out of the PDF document.



According to my experience datasheet diagrams are rather rough. You can chech their accuracy by the data from the linked table. For example, according to it 1A/350mA factor is not 2,5 but 2,42. And 1,4A/350mA factor is 3,04 - not 3,2.


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## ShineOnYouCrazyDiamond (Aug 26, 2010)

vaska said:


> According to my experience datasheet diagrams are rather rough. You can chech their accuracy by the data from the linked table. For example, according to it 1A/350mA factor is not 2,5 but 2,42. And 1,4A/350mA factor is 3,04 - not 3,2.



Like I had mentioned above - _Keep in mind this is all relative to other ratings. Can the driver maintain 1.4A? Relative brightness drops with junction temperature. More drive = more heat. OTF losses, etc._

So if you factor these things in you will get the drop to the numbers you are describing.

Since OTF losses can not be mitigated that much, the other factors which can be controlled are heat dissipation and current supply. Larger batteries or better drivers (ie: buck/boost to maintain a constant forward current) will help as will good flashlight design with proper heat sinking.


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## ti-force (Aug 27, 2010)

I have a Quark 123-2 XP-G R5 that I modded with a Shiningbeam 1.4A driver, but I added an additional 7135 chip to bump the current up to roughly 1.7A. Here are my OTF results for this light, and for an un-modded Quark 123-2 XP-G R5:


_____Quark 123-2 XP-G R5 SB 1.7A mod____
___1 sec______357.6___________
__30 sec______305.5_________
___1 min______297___________
___2 min______292.1_________
___3 min______289.7_________


_____Quark 123-2 XP-G R5______
___1 sec______257___________
__30 sec______241.2_________
___1 min______238.8_________
___2 min______236.4_________
___3 min______235.2_________


As you can see, the 1.7A mod loses 67.9 OTF lumens from 1 sec to 3 min, while the non-modded 123-2 Quark only loses 21.8 OTF lumens.

At 1 sec the 1.7A mod is 100.6 OTF lumens higher than the non-modded Quark 123-2 at 1 sec. At 3 minutes the 1.7A mod is 54.5 OTF higher than the non-modded Quark 123-2, while it's 64.3 OTF higher at 30 sec, so most of the losses are within 30 sec, and it seems to fall fairly steady from there. I would expect the losses to be less with a drive current of 1.4A, but I couldn't say how much unless I tested one. I would also expect the losses to be less with an XP-G R5 with 1.7A drive current in a light that has more mass for heatsinking than the Quark has.

I wish I had one modded with the 1.4A driver without the additional 7135 so we could see how much of an increase there is from the factory Quark driver (roughly 900mA) to the 1.4A SB driver, but I don't.


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## MikeAusC (Aug 28, 2010)

You'll have no trouble measuring the difference in Light level from 1 to 1.4 amp, but the eyes response is not linear.

The brightness steps in multi-level drivers are usually between two and three times because just perceives a 2 times change as a small change.


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## wachtel (Sep 1, 2010)

Hi ti-force

I modded an Aurora V6 with Cree XP-G and SB 1.4A driver. 

The LED is fixed with Arctic Silver 2-comp. at the pill and the pill is
screwed into the battery body with
Arctic Silver 5 thermal paste to realize
the best thermal transfer which is possible with that small sized lamp.

Here is the temperature curve I measured in High mode

(German flashlight forum)

http://www.taschenlampen-forum.de/modding/642-bau-fahrrad-alltagslampe.html


Wachtel


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## ShineOnYouCrazyDiamond (Sep 1, 2010)

I just received my 1A NB drop-in yesterday and have been doing some comparisons.
- NB XP-G Q5 3000K 3-level 1Amp regulated
- NB XP-G Q5 3000K 3-level 1.4Amp regulated

Completely non-scientific white wall hunting and tree illumination tells my eyes and brain that for all practical purposed these two lights are pretty much equal in brightness.


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## ti-force (Sep 1, 2010)

wachtel said:


> Hi ti-force
> 
> I modded an Aurora V6 with Cree XP-G and SB 1.4A driver.
> 
> ...



Thanks for posting, but I'll have to wait until I'm on my home computer before I can view the thread you linked to; my German isn't that great 




ShineOnYouCrazyDiamond said:


> I just received my 1A NB drop-in yesterday and have been doing some comparisons.
> - NB XP-G Q5 3000K 3-level 1Amp regulated
> - NB XP-G Q5 3000K 3-level 1.4Amp regulated
> 
> Completely non-scientific white wall hunting and tree illumination tells my eyes and brain that for all practical purposed these two lights are pretty much equal in brightness.



Yes, I agree that for up close use you probably won't notice much difference. At a longer distance the output may be more noticeable. I usually can't see differences in brightness against a wall because the human eye adjusts to the brightness, so I usually compare at a distance to see small differences in brightness. Of course everyone's eyes are different, and age plays a role too (like everything else ).


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## ShineOnYouCrazyDiamond (Sep 1, 2010)

ti-force said:


> Yes, I agree that for up close use you probably won't notice much difference. At a longer distance the output may be more noticeable. I usually can't see differences in brightness against a wall because the human eye adjusts to the brightness, so I usually compare at a distance to see small differences in brightness. Of course everyone's eyes are different, and age plays a role too (like everything else ).



The trees I was illuminating were not "up close" but also not more that 50-75 feet out. I'll be doing some walking in the woods over the next day or two and will bring both of these lights with me. I'll report back as I do agree with the statement that distance can bring out the subtle, yet still present, difference in the brightness.



ti-force said:


> and age plays a role too (like everything else ).


......So...... what're you trying to say?   LOL :nana:


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## ti-force (Sep 1, 2010)

ShineOnYouCrazyDiamond said:


> The trees I was illuminating were not "up close" but also not more that 50-75 feet out. I'll be doing some walking in the woods over the next day or two and will bring both of these lights with me. I'll report back as I do agree with the statement that distance can bring out the subtle, yet still present, difference in the brightness.
> 
> 
> ......So...... what're you trying to say?   LOL :nana:



I usually shine out 50+ yards; I find that distance makes it easier for myself. See if you notice the difference better at that distance. The age comment was aimed towards the pupil not able to dilate as much as we age. It seems like we hit a certain age and everything starts to fall apart


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## luxrc (Sep 1, 2010)

good result (+28% @1.55A) achieved when a thermally enhanced copper core board is used:






I update my experiments with XP-G running at high currents in this thread:
https://www.candlepowerforums.com/posts/3495590&postcount=45


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## ShineOnYouCrazyDiamond (Sep 2, 2010)

ti-force said:


> I usually shine out 50+ yards; I find that distance makes it easier for myself. See if you notice the difference better at that distance. The age comment was aimed towards the pupil not able to dilate as much as we age. It seems like we hit a certain age and everything starts to fall apart



ti - I went out tonight for a nice long walk. To be honest after 30 minutes in the dark woods with some real long distance throw sections I really couldn't tell any discernable difference between the 1A and 1.4A XPG lights.

For comparison I also had a SST-90 P60 drop-in light with me running at about 3.4A on high. It had about the exact same throw as the XPG but with a much larger spot.


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## luxrc (Sep 3, 2010)

ShineOnYouCrazyDiamond said:


> To be honest after 30 minutes in the dark woods with some real long distance throw sections I really couldn't tell any discernable difference between the 1A and 1.4A XPG lights.


 
as I said one posting above, driving the LED at 1.4-1.5A is not enough to produce a tangible increase in output. The overheating rapidly nullifies the effect of 1.4A. In my experiments XP-G worked fine @1.5A only when soldered directly to a massive *copper* sink. No thermall conductive paste or glue should be used here. Otherwise you just drain your batteries and shorten the LED lifespan in vain.


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## ShineOnYouCrazyDiamond (Sep 3, 2010)

luxrc said:


> as I said one posting above, driving the LED at 1.4-1.5A is not enough to produce a tangible increase in output. The overheating rapidly nullifies the effect of 1.4A. In my experiments XP-G worked fine @1.5A only when soldered directly to a massive *copper* sink. No thermall conductive paste or glue should be used here. Otherwise you just drain your batteries and shorten the LED lifespan in vain.


 
^ A more scientific approach to my non-scientific measurement methods. I've ripped apart a Nailbender drop-in before (sorry Dave!) and they are pretty well heat sinked. Soldered directly to a 17mm board and mounted to a decent metal pill. The heat does tend to flow into the reflector which is metal, and I use some metal duct sealng tape to wrap the reflectors so they fit snug in SF C size head. I find this give great heat flow away from the LED to the body of the light.

Another thing to consider is that the 1.4A driver Nailbender has are regulated, but buck only. So once the voltage of the cell drops below Vf of the LED you will see the current flow start to drop down to the 1.1-1.2A range. So no real gain there IMO.

The 1A L-mini II driver is a buck/boost. I've run that off a 18350 LiIon and it started the run pulling 960 mA and the increased the draw from the battery upwards to ~1150mA before moon mode kicked in. That means on a 1200mAh rated battery which is closer to 850-900mAh in reality I got a full 45 minutes with the LED being driven at 1A. That is a HUGE win in my book over a marginally brighter LED which will dim over the run and also experience up to 25-30% shortened runtime.


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## ti-force (Sep 3, 2010)

ShineOnYouCrazyDiamond said:


> ti - I went out tonight for a nice long walk. To be honest after 30 minutes in the dark woods with some real long distance throw sections I really couldn't tell any discernable difference between the 1A and 1.4A XPG lights.
> 
> For comparison I also had a SST-90 P60 drop-in light with me running at about 3.4A on high. It had about the exact same throw as the XPG but with a much larger spot.



I guess everyone's eyes are different. I can see the difference between a 230 lumen light and a 290 lumen light at the right distance, but I pay close attention to everything that's being lit up. Also, the beam profile between the lights being compared need to be the same or similar. If one of the lights is mostly flood, and the other is mostly spot, the one with mostly flood would look less bright, even if it had the 60 lumen advantage. Like I said though, everyone is different, and one man might want the additional 60 lumens, while the other man doesn't care either way. Personal preference.





luxrc said:


> as I said one posting above, driving the LED at 1.4-1.5A is not enough to produce a tangible increase in output. The overheating rapidly nullifies the effect of 1.4A. In my experiments XP-G worked fine @1.5A only when soldered directly to a massive *copper* sink. No thermall conductive paste or glue should be used here. Otherwise you just drain your batteries and shorten the LED lifespan in vain.




While I may not have as much experience as you, I certainly find the increase in my Quark XP-G light, driven at 1.7A to be tangible. Even if it were driven at 1.5A I'd find the increase welcome, but that's my personal preference. It also depends on how the user plans to use his light. *I rarely use this light on high for longer than 30 seconds at a time*. I don't have a need for that amount of light for any longer period of time, and if I do, I'll grab a bigger (and *MUCH* brighter) light. IMO, that's why the light has different modes. If I want less light and/or a longer runtime, I'll simply switch to a lower mode. In my case, I'm gaining roughly 100 OTF lumens at turn on, down to a gain of roughly 60 OTF lumens at 30 seconds over the factory Quark XP-G being driven at a lower current.

Like I said, it depends on how long the user plans to run the light at the higher drive current. In my case, I don't need a massive copper heatsink with the emitter soldered directly to it. I get away with a small aluminum mounting surface and thermal paste, but it only has to be reliable for myself; I don't build lights for others, and I don't sell my modified lights. I see where you're coming from though, and I understand what you mean.


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## ShineOnYouCrazyDiamond (Sep 3, 2010)

ti-force said:


> I guess everyone's eyes are different. I can see the difference between a 230 lumen light and a 290 lumen light at the right distance, but I pay close attention to everything that's being lit up. Like I said though, everyone is different, and one man might want the additional 60 lumens, while the other man doesn't care either way. Personal preference.


 
Believe me, I do have VERY sensitive eysight and can tell even the most minute differences in brightness. If a light is just the slightest bit brighter - I can tell - especially in a side by side comparison. I was looking at details in a tree brach, cracks in the bark, etc 50-75 yards out. The illumination and the detail were there.

Also - to rule out other nay-sayers who will say I wasn't using good batteries - the 1A drop-in was running off a 18350 cell and the 1.4A drop-in was running in a 6P off a fully topped of AW black 18650 cell. It was definitely getting 1.4A.

Anyway - if you can tell the difference that is fine. If you want to overdirve a 1.5A max LED at 1.7A with diminished lifetime, that is fine as well. But that is not a fair comparison, and not what the OP was asking. Personally I will be very happy with my 1A XP-G with less heat and better runtime. But YMMV.

Anyway - I don't hear anyone else saying they are going out and directly comparing a 1A and 1.4A driver from Nailbender with the same exact flux and tint bin LED - in the EXACT SAME reflector with the exact same lense glass (that is very important as well - a different lens could produce more of less throw and totally skew the results).


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## ShineOnYouCrazyDiamond (Sep 3, 2010)

And, if I might add, comparing the brightness of a light during the first 5 seconds of running is silly. Let the light run for 5 minutes and simulate real life and then compare.

Also - be realistic in what you expect to achive with a XP-G drop-in. If I want to set the night on fire I will be pulling out a MAG85 or better for sure.


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## ti-force (Sep 3, 2010)

ShineOnYouCrazyDiamond said:


> Believe me, I do have VERY sensitive eysight and can tell even the most minute differences in brightness. If a light is just the slightest bit brighter - I can tell - especially in a side by side comparison. I was looking at details in a tree brach, cracks in the bark, etc 50-75 yards out. The illumination and the detail were there.
> 
> Also - to rule out other nay-sayers who will say I wasn't using good batteries - the 1A drop-in was running off a 18350 cell and the 1.4A drop-in was running in a 6P off a fully topped of AW black 18650 cell. It was definitely getting 1.4A.
> 
> ...



Yes, like I said, everyone is different. Yes, I will overdrive an emitter if I want to, and I'm not worried about the life since it's rated at over 50,000 hours of bulb life anyway. All I was trying to do was share my OTF results so the OP could get an idea of OTF lumens of this emitter at a higher drive current and make his decision, but apparently my data isn't appreciated here, so who gives a rip!? Also, get your pant*ies out of a wad.

*Un-subscribing!* Have a nice day :shakehead


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## luxrc (Sep 3, 2010)

Only testing in a sphere will reveal the truth. You guys talk not about the same light, so the comparison is meaningless. Probably one has a more efficient thermal path than the other.

What I'm going to do soon is to pass some independent tests in a good-calibrated sphere. 

I'm still pretty confident that only materials like copper or pure silver may provide adequate thermal path for XP-G running at 1.5 amp and up.

Aluminum can't cope with this job good as provides 2-3 times higher thermal gradient, especially closely to the die very small sink where thermal flux density is very high. That's a mere physics, just refer to this thermal conductivity table:
http://en.wikipedia.org/wiki/Thermal_conductivity

I admit that a copper-core board (with LEDs soldered directly to the copper assy) CAN be installed on a AL sink or into an aluminum lightweight flashlight body. Ideally with no help of paste or glue, polishing and tight pressure works better. But I hardly recommend aluminum MCPCBs as the output is seriously reduced in this case, laboratory tested.


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## Kestrel (Sep 3, 2010)

What you're saying makes a lot of sense luxrc, thanks for posting. I'm very much looking forward to using what you're working on.


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## ShineOnYouCrazyDiamond (Sep 3, 2010)

ti-force said:


> Yes, like I said, everyone is different. Yes, I will overdrive an emitter if I want to, and I'm not worried about the life since it's rated at over 50,000 hours of bulb life anyway. All I was trying to do was share my OTF results so the OP could get an idea of OTF lumens of this emitter at a higher drive current and make his decision, but apparently my data isn't appreciated here, so who gives a rip!? Also, get your pant*ies out of a wad.
> 
> *Un-subscribing!* Have a nice day :shakehead


 


There's always one in a crowd who has to ruin a thread be dragging it off course and then be a **** about it. Too bad - or maybe not, he wasn't really contributing anything usefull to the OPs question anyway.


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## ShineOnYouCrazyDiamond (Sep 3, 2010)

luxrc said:


> You guys talk not about the same light, so the comparison is meaningless.


 


ShineOnYouCrazyDiamond said:


> Anyway - I don't hear anyone else saying they are going out and directly comparing a 1A and 1.4A driver from Nailbender with the same exact flux and tint bin LED - in the EXACT SAME reflector with the exact same lense glass (that is very important as well - a different lens could produce more of less throw and totally skew the results).


 

Funny - I thought I was, no?


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## Tally-ho (Sep 4, 2010)

luxrc said:


> In my experiments XP-G worked fine @1.5A only when soldered directly to a massive *copper* sink. No thermall conductive paste or glue should be used here. Otherwise you just drain your batteries and shorten the LED lifespan in vain.


I haven't done any experiments so i will not deny yours, but from Cree's data sheet an XP-G.R5 @ 1.5A is nothing but the max drive current, like 1A for an XR-E.R2. Nobody has insist until now to solder directly an XR-E.R2 @ 1A on a massive copper heatsink.

I suppose that Cree applies margin tolerance that are more or less scaled to their different LEDs types, so i do not understand why an XP-G.R5 @ 1.5A has to be treated with far more care than a XR-E.R2 @ 1A.


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## vaska (Sep 6, 2010)

Tally-ho said:


> i do not understand why an XP-G.R5 @ 1.5A has to be treated with far more care than a XR-E.R2 @ 1A



Just because its thermal pad is much smaller.


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## luxrc (Sep 6, 2010)

I just carried out an experiment of using a 14W heat pump (small 15x15mm ceramic Peltier module) with a 16W triple XP-G board with LED current set @1.55 amps.







(http://products.cui.com/adtemplate....&catky=341122&subcatky1=&subcatky2=&subcatky3=)

Guys, the result was terrific! The steady output increased on about 40%. The peltier kept the copper core temperature at 16-17C. But the heat-pump consumes about 18W so the overall consumed power exceeded 30 watts. 
 
From this pov using more LED’s driven at lower current may be a more power (and cost) efficient solution.


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## Tally-ho (Sep 6, 2010)

vaska said:


> Just because its thermal pad is much smaller.


Cree already knew that the thermal pad of the XP is smaller than XR. So if this smaller thermal pad is really a problem for an XP-G.R5 @ 1.5A, why Cree gives max drive current 1A for XR-E.R2 (no particular care) and 1,5A for XP-G.R5 (massive copper heatsink) ?

Think to the XM-L with the same thermal pad as XP series running @ 2A or 2.5A
What do we need, ultra massive silver heatsink ?


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## uk_caver (Sep 6, 2010)

For the XP-G, does the 1.5A apply just to the R5 or to all luminous flux bins (I assumed it was the latter)?

Generally, if the major concern was thermal issues, I'd have thought it made sense for a manufacturer to base maximum current recommendations on the _least_ efficient LED in a given range that they were likely to be producing.


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## luxrc (Sep 7, 2010)

Tally-ho said:


> Think to the XM-L with the same thermal pad as XP series running @ 2A or 2.5A
> What do we need, ultra massive silver heatsink ?


 
XM is larger than XP. But again, you missed the idea. The critical point is thermal conductivity of the material which immediately contacts to the LED sink. The heat flux density right under the LED is very high (about 3-4 w/mm^2). So the objective here is to dissipate the heat flux to the larger section area where other less efficient materials can be used.

"ultra massive heatsink" was used in a laboratory to minimize self-heating effect, but no one said that you need it for your flashlight.


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## Tally-ho (Sep 7, 2010)

luxrc said:


> but no one said that you need it for your flashlight.



When you said... 


luxrc said:


> In my experiments XP-G worked fine @1.5A only when soldered directly to a massive *copper* sink. No thermall conductive paste or glue should be used here. Otherwise you just drain your batteries and shorten the LED lifespan in vain.


...i understand, not only in a laboratory for experiments, but also and mostly in flashlights.



luxrc said:


> Guys, the result was terrific! The steady output increased on about 40%. The peltier kept the copper core temperature at 16-17C. But the heat-pump consumes about 18W so the overall consumed power exceeded 30 watts.


More power for more output but for less time :thinking:
With something (module peltier) that is probabbly not so easy to integrate into a flashlight. Yes it produces cold on one side but also produces excessive heat on its other side. Well, at least it helps remove heat away from the LED but its additional excessive heat will probably not be very cumfortable.
What is the temp of the other side of the peltier ? In a flashlight, you will have to treat with this additional heat and probably condensation.

What do you think of a graphite base (to mount the LED on) included in a larger cooper base ?
Well, it would be simpler if manufacturers would improve LED sink.


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## Justin Case (Sep 7, 2010)

vaska said:


> Just because its thermal pad is much smaller.


 
That doesn't appear relevant. The Cree datasheets for the XR-E and XP-G give thermal resistances of 8 C/W vs 6 C/W, respectively. Thermal resistance already accounts for contact area.


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## uk_caver (Sep 7, 2010)

One might wonder why no-one really seems to be offering XP-Gs LEDs mounted on copper boards, rather than aluminium ones.
If there was a perceived demand, presumably it wouldn't be hard for cutter, etc to order in some copper boards to solder their emitters to?

Though copper might be 2-3x 'better' as an MCPCB base material, what does that actually translate to in real usage?

luxrc, do you have the thermal measurements for the copper and aluminium versions of your 3x1.5A XPG boards?


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## Connor (Sep 7, 2010)

uk_caver said:


> One might wonder why no-one really seems to be offering XP-Gs LEDs mounted on copper boards, rather than aluminium ones.



Price, I guess. Copper is a quite expensive metal.

Copper: http://www.kitcometals.com/charts/copper_historical_large.html
versus
Aluminum: http://www.kitcometals.com/charts/aluminum_historical_large.html


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## uk_caver (Sep 7, 2010)

The amount actually used to mount an emitter on isn't exactly huge.
A regular aluminium 20mm star board I have here is 1.35g, so a copper one would only be ~4.5g, 

Working with a copper price of $4-50/lb (or roughly $10/kg, 1 cent/gram), that's something like a raw metal cost of 4.5cents.

Clearly, there'd probably be various additional costs for using a less-mainstream material for MCPCBs, (copper alloys may well cost rather more than the price of bulk copper, machining costs might be higher, etc) but if there really was a demand to be satisfied for which copper was vastly better, it wouldn't be an impossible thing to do at a vaguely economic price.


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## Connor (Sep 7, 2010)

With the same reasoning in mind, why mess with copper, if you could get even better thermal conductivity with silver?
The amount needed for a pure silver heat sink should be less than a half-ounce, so < $10. Still very affordable.

The problem is the price again ... to produce in higher numbers, you need to buy silver rods by the meter, which becomes expensive.


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## Tally-ho (Sep 7, 2010)

Connor said:


> if you could get even better thermal conductivity with silver?


Not that much compared to copper.
Copper is used in huge quantity, for example in buildings construction, for its electrical conductivity, why couldn't it be use in far less quantity in flashlights for its thermal conductivity ?
Luxrc will probably explain it better.


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## Tally-ho (Sep 7, 2010)

double post


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## vaska (Sep 7, 2010)

Tally-ho said:


> why couldn't it be use in far less quantity in flashlights for its thermal conductivity ?



Copper is an inappropriate material for mechanical treatment in contrast to aluminium.


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## Tally-ho (Sep 7, 2010)

vaska said:


> Copper is an inappropriate material for mechanical treatment in contrast to aluminium.


Yes but you "just" need a press to cut the base we are talking about.

The issues you like to rise are more digressions than real issues. Yes, they are true for copper (as a material) in general but not for a small base with a very basic shape.
It is not a real problem for a manufacturer. For example manufacturing flashlights or LEDs in a "developed country" is way more expensive than replacing a small piece of aluminum by the same one in copper.


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## uk_caver (Sep 7, 2010)

How do the copper triple-XPG boards compare with the equivalent aluminium ones?


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## -Gast- (Sep 7, 2010)

Just buy a bare xp-g and solder it on a copper-block.

Where is the problem? Its easy.


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## HumanLumen (Sep 7, 2010)

How do you connect to the terminal on the xp-g if you 'just' attach it to a copper heatsink?
HL


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## luxrc (Sep 7, 2010)

uk_caver said:


> How do the copper triple-XPG boards compare with the equivalent aluminium ones?


 
wow wow wow... so many messages in a day, I'm impressed!

well, I'm working on the datasheet now in which I'll reveal the difference. But guys, believe me, it's impressive. And it's worth money spent on 100%! 

Having a vast experience in metal treatment, Vaska is absolutely right, it took lots of efforts to prepare these samples. First of all since the material is very special and hardly offered in "prototyping" quantities. Another problem, copper cannot be milled by a CNC router. We cut it using a quite expensive precision mold (admitted tolerance is 0.1mm, board assy clearing is 0.2mm from the edge). 

We start mass production on copper in mid-Oct. Larger qtys should help to optimize the price. 

Silver is another good option. It's just a bit better in terms of thermal admittance (no a big deal) but it's an electrochemically neutral. Copper may cause problems when used in humid conditions in contact with aluminum and some common alloys. Silver does it but the price....


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## Justin Case (Sep 7, 2010)

HumanLumen said:


> How do you connect to the terminal on the xp-g if you 'just' attach it to a copper heatsink?
> HL



The XP-G has very tiny, square solder pads for LED+ and LED-.


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## MikeAusC (Sep 8, 2010)

ti-force said:


> . . . I'm not worried about the life since it's rated at over 50,000 hours of bulb life anyway. . . .


 
If you're assuming that an LED rated at 50,000 hours at 1 amp will run for 25,000 hours at 2 amps, you're in for a suprise !


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## vaska (Sep 8, 2010)

Justin Case said:


> The XP-G has very tiny, square solder pads for LED+ and LED-.



Did you ever try to solder those "pads", covered with thin insulation film?


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## -Gast- (Sep 8, 2010)

vaska said:


> Did you ever try to solder those "pads", covered with thin insulation film?


Scratch it away before soldering...

Or make a heatsink which only contacts the thermal pad so you can use the bigger pads for wires...
of course this is nothing for mass production.


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## Kestrel (Sep 8, 2010)

luxrc said:


> Silver is another good option. It's just a bit better in terms of thermal admittance (no a big deal) [...]


In the distant past I had done some research with regards to thermal management as an undergrad in college, and I'm not a fan of silver for heatsinks at all:
*Thermal* Specific _Den _*“Thermal*
*conduct* HeatCap _sity _*volume”*
(W / mK) (J / gK) (g/cc)_ (J/ccK)​Aluminum *250* __0.85 ___2.7___ *2.3*
Brass..... *110* __0.38 ___8.6 ___*3.2*
Copper... *400* __0.39___ 9.0___ *3.5*
Silver..... *430 *__0.23 __10.5 ___*2.4*

“Thermal volume” is for a fixed-size part – i.e. an internally-mounted heatsink. For example, a 1 cubic centimeter brass part requires 3.2 joules of heat to raise it by 1 degree Kelvin (or Celsius).

-----

So as far as conducting heat, yes sliver is slightly superior to copper, but with regards to heatsinking, silver is rather poor, absorbing much less heat than copper for a fixed-size part such as a heatsink for the same rise in temperature.


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## uk_caver (Sep 8, 2010)

Surely for most lighting applications, the heat capacity of parts is of limited relevance, since the light will generally be on long enough to end up at least approaching a thermal equilibrium with the environment, and all that really matters there is the chain of thermal resistances from source to ultimate sink?


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## Kestrel (Sep 8, 2010)

Yes, but why go to more hassle & expense pursuing a substrate material that is only a little better in heat conduction while being much worse when it comes to heating up quickly?

However, the major relevant factor is the difficulty of fabricating & manufacturing as *luxrc* has suggested. Obviously there are *machining* & *soldering* considerations with regards to aluminum / copper / silver that are of paramount importance compared to some of the more minor differences in thermal performance.


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## uk_caver (Sep 8, 2010)

Kestrel said:


> Yes, but why go to more hassle & expense pursuing a substrate material that is only a little better in heat conduction while being much worse when it comes to heating up quickly?


I'm not sure that anyone would, for thermal reasons, and certainly not for economic ones.

luxrc was only really mentioning its superior chemical properties.

In any case, the extent to which a substrate heats up is for most applications principally a matter of how well heat is removed from it, and not really a matter of the substrate's heat capacity.


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## MikeAusC (Sep 8, 2010)

Kestrel said:


> Aluminum *250* __0.85 ___2.7___ *2.3*
> Brass..... *110* __0.38 ___8.6 ___*3.2*
> Copper... *400* __0.39___ 9.0___ *3.5*
> Silver..... *430 *__0.23 __10.5 ___*2.4 *


 
It's great to have the real facts when making decisions - thanks for compiling this very handy table.

Interestingly the Thermal and Electrical conductivity relativities for Alumium, Copper and Silver are very close !


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## uk_caver (Sep 8, 2010)

The tricky thing is that when it comes to thermal conductivity, probably the most important thing in the majority of non-transient applications, 'aluminium' in practice can cover a fairly wide range, with pure metal being around ~230, typical alloys anywhere between the middle 100s and 200-ish, and things like diecasting alloys maybe not much over 100.

For example, some simple angle strip I've been using to mount LEDs on to the wall of a diecast box for a little photo light unit is 6082-T6 or 6063-T6, and so (according to http://www.matweb.com/ ), has thermal conductivity of 170 or 200.

The box I'm mounting the strip to, on the other hand, looks like it's probably more like ~110 (couldn't get a perfect match for the material on matweb), and so is possibly not far off being half as good as the angle strip.


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## Kestrel (Sep 8, 2010)

MikeAusC said:


> Interestingly the Thermal and Electrical conductivity relativities for Alumium, Copper and Silver are very close !


I know, pretty cool stuff. That's because ~98% or so of their thermal conductivity is due to thermal transport via free electrons - i.e. metals. When you get to thermal conductivities of electrical insulators, it gets more interesting, then the primary factors are atomic bonding strengths and grain size - thermal transport via _phonons_.

*Unfortunately*, I'm afraid this is getting a bit OT for the OP's thread though, sorry ...


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## Connor (Sep 8, 2010)

A few more numbers of thermal conductivities:

Diamond: 900 - 2320 :devil: :shakehead
Graphene: (4840±440) - (5300±480)

From Wikipedia.


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