Testing a Cree XHP50.2 J4 3A led

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JasonWW
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I’m glad you did the research. Thumbs Up

Some folks just add stuff and then wonder why their stator coil burned out or why their battery is always low. Facepalm

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Jensen567
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stormrider88 wrote:
Jensen567 wrote:
Yes the LED will draw current proportional to the output voltage you set that module at. Regarding those DC-DC modules though, I would recommend one with Constant Current capability. There are many varieties available.

The DC-DC modules themselves do make great drivers if you get a CD version. I use many different kinds in various projects of mine, so far they hold up pretty well as long as you don’t drive them too hard.

I checked those modules, in fact, they may be useful only if I need to get a lower current output (compare to the none CD version) is that correct? In any case, I want to feed the emitters with 1.5 to 2 amp maximum in order to preserve their lifespan and avoid too much consumption. 1000 lumens of warm light would be perfect in my application (2 unit with each light its own module, around 2000 lumens…)

Let’s say I want to feed an XHP50 12V with 2 amps, the non CD module should work just fine, isn’t it? 14.5V in, set at 12V should do the job without damaging the circuit or the led… I just want to be sure which LED’Voltage I should order for such a configuration.

Sorry, that “CD” should have been “CC”. Phone autocorrected, I went back and edited the post.

The CC is useful no matter what because these modules use very cheap and imprecise pots for their adjustment, so every time you feed them power they might start up at 0.2V higher or lower than the original set point. This could cause a fairly large current shift at the LED. As the temperature changes the LED will also draw more or less current at the same voltage.

With CC mode, you are setting the current directly, so it will be constant regardless of temperature or any other factors. It really is the right way to do it. It can be done without a CC module, but you will find the brightness changes depending on conditions, how significant the change is will depend on a number of factors.

Here is just one cheap example of a suitable CC module. At the price there is really no reason not to get one with CC.

http://www.ebay.com/itm/191673918658

JasonWW
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I was just reading on another thread that a fella burned up his xhp50.2 using 2 little 14250 cells in series.

Does this surprise anyone here?

Comments on thread starts here and go down:
http://budgetlightforum.com/comment/1130154#comment-1130154

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CRX
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Sounds familiar Smile
I posted that in this thread somewhere I think.

Yeah that was direct drive, I thought I had done a bad reflow at first but now I’m not too sure, probably the voltage killed it as I don’t make msitakes Big Smile

It started off fine, dimmed then the dies went one by one.

JasonWW
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CRX wrote:
Sounds familiar Smile
I posted that in this thread somewhere I think.

Yeah that was direct drive, I thought I had done a bad reflow at first but now I’m not too sure, probably the voltage killed it as I don’t make msitakes Big Smile

It started off fine, dimmed then the dies went one by one.


Yeah, I see it. 2 months ago. No one commented on it and you thought it was a bad reflow.

Maybe someone who is more knowledgeable than myself will comment about those little cells killing the 50.2.

I would have assumed the low current delivered by those cells would power your light just fine, but if its too high a voltage, then that just sucks. Hopefully Cree will not drop production of the older xhp50 and xhp70.

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Texas_Ace
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With the super low Vf of the .2 version of the XHP it doesn’t surprise me. They need a driver and/or some resistance to keep things in check. The 14250 surprises me that it had enough power to pop it but possible I suppose.

Also keep in mind that these LED’s can produce upwards of 80W+ of heat and need a very good heat path to keep them alive.

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Voltage itself does not damage a led, it only kills a led when that causes a too high current. The XHP50.2, when reflowed on a DTP board and the heat can get away, can handle close to 15A, and I doubt that 15A will ever come out of a 14250 cell.
I must be something else that killed the led (overheating after all perhaps by a bad reflow?)

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djozz wrote:
Voltage itself does not damage a led, it only kills a led when that causes a too high current. The XHP50.2, when reflowed on a DTP board and the heat can get away, can handle close to 15A, and I doubt that 15A will ever come out of a 14250 cell.
I must be something else that killed the led (overheating after all perhaps by a bad reflow?)

You would be surprised how much peak current can come out of a lithium cell.
Many times what is advertised as “max current” if there is no circuitry limiting it.
staticx57
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I can tell you what did my 50.2 in. I used a MTN FET driver with two HG2s. It was reflowed by Richard onto a copper dtp mcpcb. It was only on for a total of 30 seconds and not all at once.

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I used the Russian driver mentionned above on my Bandit to feed a pair of XML2 in series at 3A.
It’s been a full year with daily use, no problem even on long ride in the night with high beam always on (I use them with high beam only)
I plan to add 2 more, or swap the XML2 for XHP50, didn’t decide yet

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Texas_Ace
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staticx57 wrote:
I can tell you what did my 50.2 in. I used a MTN FET driver with two HG2s. It was reflowed by Richard onto a copper dtp mcpcb. It was only on for a total of 30 seconds and not all at once.

What was the star mounted to or installed in? Did you use thermal paste? Was it clamped down tight?

I recently built a C8 with an XP-L2 and noticed I gained about 100-200 lumens by sanding the threads down to get more clamping force on the star. This can be seen in my thermal tests as well.

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It was mounted to a UF-1405 with all the hardware provided to keep it tight. Moderate amount of thermal paste, aware of too little and too much.

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the 1405 is not the best design around but it should be enough to keep it alive for more then 30 seconds. You screwed down the retaining ring for the LED nice and tight correct and it was actually pressing the star into the pill?

When building mine I remember that I thought it was tight but the LED started turning blue, turned out the threads had jammed or something and I had to re=install it with a different centering ring to get it to properly press it into the pill.

Although it is possible that the LED just died, these are pretty new and it is unknown exactly how well they handle direct drive. I would personally use PWM to drop the current down some or at the very least some long thin wires. I usually cram as much 24awg wire as I can into the pill to drop the current.

At some point we will get some drivers that can regulate the current for these LED’s but that is still a ways off.

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This was my second go with the same build. The first failed within seconds and neither time I remember any blue. The first I chalked up to a faulty LED. I even tried reflowing it and it worked for a second or two to which it died again in quick order. Again I chalked it up to a faulty emitter.

It is my belief intighted it as a much as I can. I can go and verify it was down all the way later today when I’m home. Assuming it was on tight, even with that modest pill the time on turbo would not lead me to believe it overheated.

Based on what I would expect from an overheating emitter I don’t think this is it. I used two high drain 18650s.

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Yeah, high drain cells and a low resistance build would not mix well with the xhp.2 at all. You want as much resistance as you can get in there, within reason. Thin long wires, low drain cells ect.

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I’m thinking the .2 is much more sensitive over the previous generation.

I think I’ll got with a mountain buck driver for the next go around of this build. On the bright side the 50.2 looks pretty decent in an aspheric, all things considered.

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staticx57 wrote:
I’m thinking the .2 is much more sensitive over the previous generation.

I think I’ll got with a mountain buck driver for the next go around of this build. On the bright side the 50.2 looks pretty decent in an aspheric, all things considered.

I think they are a lot tougher actually based on how tough the L2 and G3 are. The issue is that they have a much much lower Vf then the last gen XHP and that means they are under much much more stress.

For example I would hit 12A with the old XHP, you could easily be pushing 15-20A+ with high drain cells into these .2 versions based on the Vf difference.

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I can accept two 18650 blowing a single 50.2 but still puzzling two 18250 did so as well.

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3A total will be around 10W of heat, a fair amount but not a ton. The video link doesn’t work so I can’t say much about it. Although it should be ok at that level. Even an S2+ is ok with 10W of heat.

The triple setup won’t give you much extra light over a single LED if driven so mildly and it will be much floodier. So depending on what you want, you might be better off with a single LED if you want more throw.

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Using the CREE PCT here, an R2 bin XP-G3 puts out 317 lumens at 1A, so 950 lumens total, but that's max, not taking optics loss's into account.

Dunno bout the heat - not enough info.

I would think in theory, using the LED's in series will help. The driver efficiency increases they say, so the driver should be cooler running. You would have to feed them 1A then - all 3 LED's would get 1A, roughly 9 watts one way or the other, 3A from the driver for the LED's in parallel, or 1A from the driver for the LED's in series.

 

I had a Convoy S2 at 2.8A get burning hot when run continuously on max for a few minutes. 10 watts can be a lot of heat - all depends on the heat sink and design.

 

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Tom E wrote:

I had a Convoy S2 at 2.8A get burning hot when run continuously on max for a few minutes. 10 watts can be a lot of heat – all depends on the heat sink and design.


 

Remember though that burning hot to your hand is different then burning hot for the components.

Djozz tested the S2+ on high till the cell died and it never got above a safe lever for the components inside. I think it peaked around 100C, which is way too hot for your hand but still safe for the components. Most of which are rated to at least 125C and can handle more with reduced lifespan.

Since this light would not be hand held, it is not limited by what we can hold. The final output could be adjusted to find the ideal output to heat ratio.

Running the LED’s in series is the best idea if driving them from a 12V power source, less work for the driver and you ensure that all the LED’s share the load evenly.

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True - even though it took a while for it to cool down enough to touch, no damage whatsoever. From surface temps I've tested, 55C gets feeling very hot, but that's not much compared to the 125C rating on the MCU's or the 150C ratings on the LED's.

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If the LED’s are wired in series then each LED will get 2.4A. If they are wired in parallel then they will each get 0.8A.

In this case wiring them in series would be best and reduce the drive current. That driver doesn’t appear to be adjustable but many other are if you look around. You can even get 17mm drivers for flashlights that could handle that small amount of current and would be easier to fit. Although finding a single mode driver could prove interesting.

Or on those drivers they appear to use 2x R100 sense resistors. If you removed one of them, you should cut the current in half. That would give you 1.2A to each emitter or around 11W worth of power.

I just looked at the youtube video, those are pretty small and a better heat path would be a very good idea indeed but I don’t see an easy way to do that without a lathe.

Although it does look like you could fit a flashlight driver in the back side and keep it all contained if you could find a buck driver with the specs you need. Pretty sure I have seem some floating around that would work, although no idea where.

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stormrider88 wrote:
… bigger host… larger heat sink… something budget light style…

Maybe some Baja Designs stickers on it…

>>>> Steve BLF to the core!

I like the styling, mind if I copy this later? Wink
I have some square cans. Will retain the label and everything to it.

- Clemence

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I am seeing it said that converting voltage and current to wattage is expressed in terms of heat. Like a 3V emitter at around 3A making 10 watts is 10 watts of heat. Somehow that isn’t ringing true, what am I missing? I know that emitters are more efficient at lower currents, less efficient when pushed hard. So the simple voltage x current equation isn’t all there is to it… heat comes in where the inefficiency takes over, as the idea behind an LED is to convert energy to light, not heat. So it would depend on the efficiency how much of the power being applied is being converted to heat. Not all 10 watts, for sure.

This can be seen in a triple or quad XP-G2 as compared to the same set-up with XP-L2 emitters. Pushing the G2’s hard results in a higher percentage of heat as compared to light output while the L2’s will fare better at lower temps while making considerably more lumens. Thus, the Manker quad in 18650 that gets ridiculously hot in seconds… the small emitters are being overdriven and producing much more heat.

Just ruminating on proper thermal design having to take into consideration the end goal of the output target as part of the equation, as well as which emitter at what power level. On the maximum end of things, it gets a lot more complicated huh? Wink

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LEDs might be around 40% efficient at low currents. At maximum power maybe half that. The rest of the consumed power is heat.

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So in a 10W set-up, only about 50% is heat. Undoubtedly much more than that in a 120+W set-up…

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DB Custom wrote:
So in a 10W set-up, only about 50% is heat. Undoubtedly much more than that in a 120+W set-up…

It depends on the LED but generally 30% is a good number. So yes, in a 10W setup, about 7W will be converted to heat. Although if the LED is overdriven then that number could easily drop down to 15-20% or even less.

Since most flashlights are overdriven, talking in terms of wattage in +/- wattage out is good enough. We are not doing exact calculations, all that matters is that a 20W LED setup will create about twice the heat of a 10W setup. Exactly how much more can be skewed by 10-20% depending on the LED efficiency but that is not worth worrying about for what we do.

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stormrider88 wrote:
just like in a flashlight, the heat-sink is enclosed inside an hermetic case,

What? That’s not correct. Why are you thinking this? You want the heat source to be exposed to as much air as possible. So get the heat to the outer surface.

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JasonWW
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Your using the word heatsink incorrectly. The pill and mcpcb are not heatsinks. Only the outer parts exposed to air is considered a heatsink. The inner metals are more like thermal masses.

When you say potting, are you asking about thermal grease or thermal epoxy? Are you trying to make a permanent connection or temporary?

Common products are from Arctic Silver. They have stuff to glue things together and Arctic Alumina Thermal Paste which does not glue. I’m not sure where you live, but you can check out the thermal products from MTN Electronics. http://www.mtnelectronics.com/index.php?route=product/category&path=25_74

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