The self-healing xm-l

LED Flashlights – General Info
1

Quick story I thought I'd share, since I'm pretty impressed w/ Cree quality...

I've been playing w/ a tractor supply 3xD zoomie. I added mass to the pill, put in an xm-l u2, tried direct drive w/ the stock alkalines and they'd only feed an amp.

put in some energizer Ds - poof - nothing happened, visually (output or physically...on the emitter itself) but no more light will come from that emitter.

next xm-l u2 - tried KD 3xAA holders w/ 1600mah Panasonic NiMh (3s3p). Got about 2 amps. Did some resistance fixes to the holders, the switch and the tail and got about 2.8A.

Should have stopped.

Took 3 Tenergy 10A Ds, charged to ~1.36V, and just tapped the ammeter at the tail - it would flash over 3A. Held it for a second or so and removed the leads when I saw a bit over 5A.

Went to 2 of the KD holders and 1D. got about 3.5A so I did some white wall hunting and saw a big, bluish, line across the emitter image when focused

So, I inspected it and there seemed to be a crack in the emitter, but it was hard to tell.

There was certainly a crack inside the dome that didn't reach the outside. this started at the emitter but didn't reach the top of the dome and was almost all the way across - and it looked like the crack a stone would make in your windshield.

Well, I figured, the heck w/ it, I'll use it and when new emitters (and proper drivers) arrive, I'll put that xm-l in a flood light.

Well - 20 minutes of direct drive use later (3.5 waning to ~2.5A) it has healed itself - the crack in the dome has almost completely disappeared and the emitter surface looks fine.

weird

2

Maybe the optical silicone they fill the dome with hardens in contact with air and has the same refractive index as the dome material.

At least that's my guess.

Lucky you didn't damage or melt the bond wires inside the dome.

3

Self healing huh...hopefully it won't start chasing down your enemies and demanding a blood sacrifice ala Christine...

Kidding aside, my guess is that the heat on DD helped to cure the small internal crack. I've abused the tar out of cree emitters and they've always impressed me, but this is the first time I've heard of this phenomena.

4

that could be - or it is running so hot it melted back together lol

the pill is actually a great (copper and aluminum) heatsink but I filed a penny very flat and arctic epoxied it between the emitter and pill to get better focus - I suspect it is grossly inefficient...

5

Nice one. I still won't get near a 50's Plymouth Fury to this day. I think she was a '58.

6

LMAO

7

Exactly, a '58 model according to the book and the film. They did use a few '57s though, both Belvederes and Furys; slight differences in exterior trim being the giveaway.

That film still makes me want to put a reverb unit on my car's AM radio!

8

I have an XM-L in a C8-style light that I inadvertantly touched the emitter with the tip of my soldering iron. Still works, but the hotspot is more muted and sort of blends in with the spill.

You think if I run the heck out of it on high it will regenerate itself into a nice hotspot again?

9

probably not, this crack was internal - and is completely gone after running the light tonight. I should have taken a picture...it looked wrecked.

anyway, I've touched up some (xm-l) domes that I nicked w/ a qtip in a drill, 3m headlight cleaner (to get rough parts) and then jb bore brite and then plastic lens polish

you can do it all w/ the latter, it just takes longer.

10

Bummer!!! I recently desoldered Q5 from aluminum plate with torch. Got plenty “cracks” as you said, “inside” dome.
I tossed it straihgt away …

11

I just watched christine. Kind of makes most recent films seem vapid aside from special effects...