Safe current for XML2 on Aluminum MCPCB

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Funtastic
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Safe current for XML2 on Aluminum MCPCB

I have a lot of XML2’s I’m wanting to use in Convoy hosts with Convoy’s ramping driver without the spring bypasses.

I have one in an S2+ which measures 4A on High with a 30Q and 3.7A using a Sanyo NCR18650GA. I’ve used good Arctic MX-4 thermal compound as well

Is that okay since I’m not using DTP? These will be for sale so I need a reliable answer.

Thanks

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Geuzzz
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No I wouldn’t do this. I would stay below 2 amps on a non dtp mcpcb.

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Whatever you offer for sale, I say you go for the most reliable of answers – a stress test. Take that thing in a hot room and try to kill it.

Funtastic
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Geuzzz wrote:
No I wouldn’t do this. I would stay below 2 amps on a non dtp mcpcb.

Convoy has been selling their S2+ and C8 at 2.8 – 3A for years without issues

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everydaysurvivalgear
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Yea 4 amps should be okay but it may kill the LED after time because of excess heat. Generally any thing over the stock current amount Cree states is high which is 3amps with a XML2. Up to 3amps should be okay for a XML2 but a little over won’t matter.

Funtastic
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I found this thread for testing on both Aluminum and copper.

Seems like 3.7A would be okay?

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Geuzzz
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Funtastic wrote:
Geuzzz wrote:
No I wouldn’t do this. I would stay below 2 amps on a non dtp mcpcb.

Convoy has been selling their S2+ and C8 at 2.8 – 3A for years without issues

You are right, probably I am to cautious. But I would not go over 3 amps.

Funtastic
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everydaysurvivalgear wrote:
Yea 4 amps should be okay but it may kill the LED after time because of excess heat. Generally any thing over the stock current amount Cree states is high which is 3amps with a XML2. Up to 3amps should be okay for a XML2 but a little over won’t matter.

I’ll use one for awhile to make sure all is okay. I’ll just state to only use with up to a 10A battery for 3.7A. This current would be less with the tail switch in place.

I’m currently charging a Panasonic NCR18650B with pcb to see what current it runs at.

I could also state to only use High for 1-2 min

I purchased 40 XML2’s 3 years ago so am wanting to sell off to get some $ back

This Convoy ramping driver is very cool though with excellent regulation

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everydaysurvivalgear
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Its hard to say the article is old and the XML2 has changed production process which could change the way the LED acts. Older XML2s use to able to do up to like 8+amps now they burn out at much less current.

If you try, The LED won’t die straight away it will heat up and go blue and you will be able to turn it of before you damage the LED.

Funtastic
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I appreciate the replies.

I think I’ll just use the 2.8A biscotti driver to play it safe for selling.

Quote:
If you try, The LED won’t die straight away it will heat up and go blue and you will be able to turn it of before you damage the LED.

If the heat is too much would the output decrease as a sign? I have a lumen tube so I could monitor it. Since each LED varies I think maybe I’ll just use the biscotti driver. This new driver was a few $ cheaper so was hoping I could of used it.

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everydaysurvivalgear
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Might be cheaper to buy drivers from Fasttech if you don’t min the standard 3 mode setup? These are the 3/5 mode drivers. Last ones i got where Convoy branded.
https://www.aliexpress.com/item/4000004827705.html?spm=a2g0o.productlist...

When i tested my LEDs i direct drive them and they went blue after only a few seconds like maybe 10 seconds max. The XML2 might be able to handle a little more current compared to the XPL because it uses the larger footprint 5050 vs 3535 so that will more heat through. If it over heats to much you will lose output.

Geuzzz
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everydaysurvivalgear wrote:
Might be cheaper to buy drivers from Fasttech if you don’t min the standard 3 mode setup? These are the 3/5 mode drivers. Last ones i got where Convoy branded.
https://www.aliexpress.com/item/4000004827705.html?spm=a2g0o.productlist...

When i tested my LEDs i direct drive them and they went blue after only a few seconds like maybe 10 seconds max. The XML2 might be able to handle a little more current compared to the XPL because it uses the larger footprint 5050 vs 3535 so that will more heat through. If it over heats to much you will lose output.

The old xlm2s were pretty robust, but the more recent ones seem to burn out much faster.

Barkuti
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Grab some ∅16mm 5050 DTP boards and reflow your leds:

 

 

Warning: the ∅20mm 3535  board sold in the above ad is not DTP, or at least it wasn't many months ago. Thermoelectric separated ∅20mm copper boards here.

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Frankly, the light output between 3A and 4A would be so little as to be almost unnoticeable. Heat, though, not so much.

Already, given the downward-pointing parabola of output vs current, it’s already on the flattening-out part of the curve and could be very well be headed on the downward slope. So, 30% more current for maybe 5%-10% more light?

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Yokiamy
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Lightbringer wrote:
Frankly, the light output between 3A and 4A would be so little as to be almost unnoticeable. Heat, though, not so much.

Already, given the downward-pointing parabola of output vs current, it’s already on the flattening-out part of the curve and could be very well be headed on the downward slope. So, 30% more current for maybe 5%-10% more light?

This is so true, i actually downgraded several S2+ lights because of this exact reason.
Now running safe at 2,8A max happily Cool

Lightbringer
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And even at that, if you let it tailstand even 5-10min or so (ask me how I know), it’ll get too hot to even turn it off, let alone grab it.

It was like grabbing a curling-iron by the wrong end, that it fell to the ground, still on. Had to use a shirt as an “oven mitt” to just grab it long enough to click it off, and even then, had to let it air-cool a loooooooong time before I could pick it up.

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BlueSwordM
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@Funtastic, Simon has been using DTP MCPCBs for a long while.

Just use them normally, and don’t exceed 3A on them.

My very own high current Beryllium Copper springs Gen 3:
http://budgetlightforum.com/node/67401
Liitokala Aliexpress Stores Battery Fraud: http://budgetlightforum.com/node/60547

Funtastic
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Okay, 3A limit it is or I’ll have a go reflowing.

Cheers

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Yokiamy
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Lightbringer wrote:
And even at that, if you let it tailstand even 5-10min or so (ask me how I know), it’ll get too hot to even turn it off, let alone grab it.

It was like grabbing a curling-iron by the wrong end, that it fell to the ground, still on. Had to use a shirt as an “oven mitt” to just grab it long enough to click it off, and even then, had to let it air-cool a loooooooong time before I could pick it up.

No questions asked. I know how it feels, they can become burning hot, i have lended some of my lights when someone asked for a light, and exact the same thing happened.
Now i try only to hand over lights which are safe for persons not knowing the power of Li-ion operated lights. (a.k.a. noob lights)

See Djozz his temperature measurements with a S2+ over here

WalkIntoTheLight
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Dumb question…

Why is running at 4 amps a problem? Is it just because it’s an aluminum board? There’s plenty of FET-driven C8 lights that work perfectly fine at probably 4A-5A (mostly using XPL, though). I presume they’re likely using copper head sinks. Do all of them? And, are they all safe at the higher amps? I haven’t noticed any issue, myself, for stock lights.

The difference in output between Convoy’s 2.8 amp driver, and a FET driver, is very noticeable (about 50% brighter by my measurements). Yes, the FET light gets hot quicker and eats up the battery faster, but it would be a shame to limit the current to 2 or 3 amps if it’s safe to go higher.

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WalkIntoTheLight wrote:
Dumb question…

Why is running at 4 amps a problem? Is it just because it’s an aluminum board? There’s plenty of FET-driven C8 lights that work perfectly fine at probably 4A-5A (mostly using XPL, though). I presume they’re likely using copper head sinks. Do all of them? And, are they all safe at the higher amps? I haven’t noticed any issue, myself, for stock lights.

The difference in output between Convoy’s 2.8 amp driver, and a FET driver, is very noticeable (about 50% brighter by my measurements). Yes, the FET light gets hot quicker and eats up the battery faster, but it would be a shame to limit the current to 2 or 3 amps if it’s safe to go higher.

The thing is, since you are planning to sell these lights, we are just giving the advice not to run them on very high current, just because of safety reasons.
Djozz his test shows the light with a standard 2,8A driver already hits 90 °C, which is already sky high.

if you are planning on running 4~5A, these lights will even exceed 90°C, which is just not smart because of safety reasons (burning wounds)

everydaysurvivalgear
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I added the wrong link damn it. Check out these drivers.
https://www.fasttech.com/p/8727400

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My next answer would be a very unpopular opinion in BLF
Running any LED beyond manufacturer’s max rating is bad for LED lifetime. Even if you can make the LED base temperature cool.
The reason manufacturer use conservative max current limit is the thermal path bottleneck at the LED substrate level. There’s thermal build up in the die. This heat will degrade the light produced by the die overtime. I tested many LEDs and the result always the same: after overdriving beyond max rated current the voltage and the output permanently reduced. And this doesn’t take many hours to happen, only few seconds. Permanent output loss is very prominent past 1,5x max rated current. High CRI and warmer CCT suffer more than low CRI cooler CCT due to thicker phosphor layer (hotter die).

[Clemence]

WalkIntoTheLight
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clemence wrote:
My next answer would be a very unpopular opinion in BLF
Running any LED beyond manufacturer’s max rating is bad for LED lifetime. Even if you can make the LED base temperature cool.
The reason manufacturer use conservative max current limit is the thermal path bottleneck at the LED substrate level. There’s thermal build up in the die. This heat will degrade the light produced by the die overtime. I tested many LEDs and the result always the same: after overdriving beyond max rated current the voltage and the output permanently reduced. And this doesn’t take many hours to happen, only few seconds. Permanent output loss is very prominent past 1,5x max rated current. High CRI and warmer CCT suffer more than low CRI cooler CCT due to thicker phosphor layer (hotter die).

[Clemence]

I’m surprised you say it’s only a few seconds (or even hours) at high current before LED damage is noticed.

I have plenty of FET-driven lights, that generally max out at somewhere around 5A per XPL with a high-drain cell. With throwers (like a C8), I exclusively use them on max. Even smaller lights I do that with, at least until they get too hot to hold (which I admit isn’t that long). They’ve had many hours at full output, and I don’t see any noticeable drop in output.

I totally understand that over-driving will decrease the expected usable lifespan of the LED. But, my assumption was that it would drop from 50,000 hours to something like 10,000. Or even if it was only 1,000 hours, that would likely be more than I’d ever use.

But just a few hours? Or seconds?!? I’m not seeing that.

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Get yourself a decent lux meter and 5 digit volt meter. And see for yourself. Initial drop from “virgin” output is the fastest.
I discussed this with Djozz few months ago. And he got the same conclusion too. After few hours resting, the output back to normal but requires more current. All damaged LEDs needs higher input current to get the same output/voltage/temp reading.
In your case with FET driver, as the LED voltage gets lower, the current input gets higher. This is why you don’t see much reduction in output, the driver compensates by increasing the current.

[Clemence]

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Yokiamy wrote:

No questions asked. I know how it feels, they can become burning hot, i have lended some of my lights when someone asked for a light, and exact the same thing happened.

 

The above may not look enticing to you, but let me say the above game was a real crack up in multiplayer due to its insane and bizarre broadcaster quotes. And of course, if you were to be set on fire by someone you would hear your own character shouting “It burns! It burns! Aaah! Aaaaah!” aloud. Big Smile

 

I do not think the high temperature thing is much of a problem because any resonably common sensed human being will notice the flashlight getting hot in his hands. He/she should know that is going to happen much faster if not hand held…

Anyway, I refuse to lend my flashlights unless the recipient is sufficiently knowledgeable or he/she's within vigilance range.

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Funtastic
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My readings with a Neutral White at 4A

1050 lumens – turn on
900 – 30 sec
860 – 1 min
765 – 3 min

Max temp was 62 degress

Neutral White with 2.8A 7135 biscotti

820 – turn on
780 – 30 sec
767 – 1 min
737 – 3 min

Max Temp 53 degrees

Measured with my calibrated lumen tube

Texas Ace Lumen Tube calibrated with maukka lights

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Lightbringer
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WalkIntoTheLight wrote:
I’m surprised you say it’s only a few seconds (or even hours) at high current before LED damage is noticed.
Lasers (vcsel chips, particularly fussy) can go “pouf!” in microseconds with hit with slight overcurrent.

In some cases, lasing current and overcurrent isn’t all that much (eg, 1.5:1 or 2:1). Even transients like a flashlight’s “pre-flash” can kill a laser.

I’ll let laser mavens go into more detail, as I generally don’t get into laser design.

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clemence wrote:
Get yourself a decent lux meter and 5 digit volt meter. And see for yourself. Initial drop from “virgin” output is the fastest.
I discussed this with Djozz few months ago. And he got the same conclusion too. After few hours resting, the output back to normal but requires more current. All damaged LEDs needs higher input current to get the same output/voltage/temp reading.
In your case with FET driver, as the LED voltage gets lower, the current input gets higher. This is why you don’t see much reduction in output, the driver compensates by increasing the current.

[Clemence]

Do you still have any of the test data for this? I’d be interested in looking through it. I’m not surprised that there is a loss in brightness, but the fact it’s rapid does surprise me slightly. The sinkpad marketing videos show the die being much cooler with a DTP board when viewed through an IR camera, and one might expect that to carry on when the LED is overdriven. That’s just an assumption though, I’ve never seen it tested. Next time I get a new LED for a FET light I might test the output before / after the first turbo run

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I never really write it down because crash test any LED in my opinion, is a one way destructive test. The first time I noticed this was when I skipped a current setting (yes I do all the test manually). For example, let’s say I plan to test an LED from 100mA all the way to 5A with 100mA resolution. Then at 3,3A I forgot if it was 3,3A or 3,4A. So I wait several minutes and rerun the test from 3A, in all cases, whenever I passed too far outside max rated current, the second reading always reads lower.

I don’t think you will get accurate reading with FET based driver. As I mentioned above, damaged LED (by over current) has almost always suffer reduced forward voltage. Lower forward voltage means higher current in FET driver. It’s self balancing.
My measurement done with constant current DC power supply in a controlled total loss cooling system.

[Clemence]

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That is very surprising. With all the FET-driven lights that BLF users love, there should be more complaints about damaged LEDs. Whether it’s higher current consumption, or lower output, this board should be full of complaints about all the high-output lights people buy.

Even if the output is compensated with reduced forward voltage, that can only give a little more time before the problem is noticeable. It’s not like you can shove 10 amps through one of these LEDs.

You’re talking about damage in seconds. Everyone should notice that.

Okay, you’ve got me interested enough that I’m going to dig out my test results on some of the FET lights I reviewed when new, and re-test them now that I’ve used them for a year to two.

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