My V1 KR1AA burned a hole in my pocket, so I enabled 1 minute AutoLock

LED Flashlights – General Info
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Today I experienced the first burned pocket of my flashlight career.

My KR1AA V1 melted a hole in my Nylon/Spandex hiking pants because I did not use Lockout while using LiIon.

The ceiling was set to 120/150 = 650 lm = 400°F. Turbo was disabled. Temperature and output testing details here.

KR1AA burn
KR1AA burn1920×898 322 KB

Safety Strategies Im experimenting with:

I am getting in the habit of using Manual Electronic lockout, and also using a

1 minute Auto lock.

In 7 Step Ramping, with

Step 4 of 7 Manual memory (56 lm), and

No temporary memory, so if I turn the light on when clipping to my pants the output will be too low to burn.

In Advanced UI, with ceilings 110/150 = about 516 lm = 360°F, for use with LiIon. This keeps the temperature below the 392°F melting point of my pants.

fwiw, With an Eneloop at 1.42V the highest output is 356 lm, iow, no risk of burn regardless of ceiling level.

More Details:

I dont know what output the light was on at, nor for how long. I had been sitting at my desk with the light clipped inside my right front pocket. My cat had been on my lap.

I dont know if she had pressed the button.
I then got undressed to take a shower and left the pants on my bed. I did not notice if the light was on.

When I got out of the shower and went to get dressed, I noticed the light was On in the pants pocket, but I did not check at how many lumens. I dont know if the light was ramped up to its ceiling or not. I wish I had checked the lumens before turning the light off. But it did not look very bright. I suspect thermal stepdown had reduced the output and prevented a more extensive burn.

There is a small hole melted into the grey mesh that lines the inside of the pocket, and also a small hole in the outside of the pants.

I had been carrying the light unlocked. I have now implemented a 5 minute auto lock, and have lowered the ceiling to 90/150 = 280 lumens. I dont know if that level can burn a hole in a pocket within that amount of time.

The pants are made of 96% nylon and 4% spandex.

I have started shopping for an O ring to mod the tailswitch for more resistance.

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Kr1AA vs. 1.5V LiIon
KR1AA beam is looking good
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phew…good thing you caught that…my olight s2 could melt a hole in a pc mouse on higher settings…that’s the curse of TIR with shorter focal lengths and some TIR in gemeral

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My KR1AA burned my pants too. Luckily, those exact jeans had been burned before by another light, I think one of my FW3As?

Was coming home after work, and my leg started burning. Instantly knew what’d happened. I’m guessing the button was activated somehow getting out of the vehicle.

My KR1AA has an o-ring inside the tailswitch silicone piece to increase button activation pressure a bit. It’s lighter than the button on an FW or TS10, but still much better feeling than a KR4 or similar.

So far, it’s the only light I have ever really used the auto-lock feature on. I’ve just gotten used to always 3C or 4H when I need to use it.

Off-topic: oh that raw KR1AA looks good. I definitely wish I could get one. Might get the D3AA version, or get another KR1AA to try to strip. I have the dark gray KR1AA V1, and I’ve found the anodization to be quite wear resistant compared to all my other Hank lights.

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And it’s fortunate that you caught it before it could have become a much worse problem. At least if you’re wearing the light, you’d feel it before it caught anything on fire.

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A few months ago HS21 did this to me on a bit larger scale :⁠-⁠). I was carrying stuff for the barbecue and to save myself walking, I stuffed the pockets with utensils and they somehow turned the headlamp on. I noticed when my pants started smoking :⁠-⁠)

This locking of the lights is no joke. For example IF19 has an annoying lock on a short timer, but it probably wouldn’t do that.

I dream of a headlamp with just dial(a) for modes/brightness and turning if off (like old radios or some good cameras) that you push in to lock and pull to unlock and turn.

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Thanks for that info.. it seems the O ring mod is not a complete solution to prevent accidental activation..

Physical Lockout seems like a good option. Or also the timed Electronic AutoLock, or Manual Electronic Lockout

Im using a 5 minute Auto Lock on my V1 that can not be physically locked out.

I can use Physical Lockout on my V2 with Clear Ano, but since it is a desk and nightstand light, I just keep it unlocked but with a low ceiling of 90/150.

We do have several good options.. they just require extra steps.. Auto Lockout beats a burn in the pants though..

At some point I would like to learn how many lumens are required to cause a burn. Apparently dark material is most vulnerable.. I may sacrifice a black T Shirt and do a few tests at different lumen levels..

For now, I lowered the ceilings to 90/150.. and am also using Lockout options when I pocket carry one of my KR1AA..

that is an interesting option
it might allow keeping the anodizing inside the tailcap, so physical lockout would still work..

please share your process and results if you decide to strip a KR1AA :wink:

It might be possible to buy a KR1AA from Hank UnAssembled, which would make stripping a bit less work.. Skipping the step of removing the electronics…

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tldnr:

I did some temperature tests in order to determine at what ceiling my pants would not melt.

Conclusion:

To avoid going over 392°F, at which temperature Spandex melts, on LiIon do not exceed Ceiling 110/150 = 519 lm = 360°F. So imo Lockout is not required when using LiIon with ceiling 110/150. With Turbo Disabled.

When using Eneloop there seems to be NoRisk of burn, at any ceiling, output stays below 500 lumens. So imo Lockout is not required when using Eneloop. With Turbo Disabled.

A note about using 1.5V LiIon. They trip protection at 110/150 ceiling, but work at 100/150 ceiling. This limits output to less than 400 lumens. Therefore there is no risk of burn when using 1.5V LiIon at ceiling 100/150. Turbo should be disabled because it will trip protection.

Safety Strategies Im experimenting with include Electronic Lockout on a V1, and Physical Lockout on a V2:

On my V1 KR1AA w 5000K LED, which I use for EDC, I am using a 1 minute Auto lock. Im using it in Advanced UI with ceilings 110/150 = about 510 lm = 360°F, for use with LiIon.

Testing details:

Temperature references:

Spandex melts at 392°F

Cotton fabric typically ignites and burns at temperatures above 410°F.

Nylon fabric generally melts at temperatures above 419°F, depending on the specific type.

Printer paper typically autoignites and burns at approximately 451°F a temperature famously referenced in Ray Bradbury’s novel Fahrenheit 451.

Initial Testing sequence:

I used a black sharpie to make a piece of printer paper black. Then did some tests at different ceiling levels.

Starting with the freshly applied black marker

at 80/150 = 170 lumens no smoke after 1 minute

at 90/150 = 270 lumens, paper started smoking within 5 seconds, I think this was the fresh black marker ink vaporizing, but the paper did not burn

at 100/150 = 375 lm, paper started smoking within 10 seconds, I think this was the fresh black marker ink vaporizing, but the paper did not burn

at 110/150 = 520 lm the paper started smoking after 10 sec, I think this was the black marker vaporizing but no actual paper burn

at 120/150 = 650 lm.. the paper started smoking immediately, I think this was the black marker vaporizing but no actual paper burn

After those tests, I did not add fresh black sharpie ink.. So the following tests used the same paper but after some or most of the fresh sharpie ink (or its carrier solvent) had evaporated or dried.

Second Round Test Data:

I restarted testing using my IR thermometer to check the temperature of the paper while it was on top of the light.

at 90/150 = 270 lm, no smoke after 1 minute … paper temp was 240°F

at 100/150 = 375 lm no smoke after 1 minute… paper temp was 275°F

at 110/150 = 519 lm after 20 sec paper temp was 360°F and no smoke. After 1 minute paper temp was 310°F and output was 480 lm (the light has started tripping thermal step down)

at 120/150 = 620 lm at 20 sec paper was 400°F, after 50 sec 390°F (the light has started tripping thermal step down). Note this was the ceiling the light was set to when it melted my Nylon pants that contain 4% Spandex

at 130/150 = 760 lm after 10 sec paper was at 460°F and the paper started turning brown and smoking

Caveats:

I dont know for a fact that the light was at ceiling when the Nylon/Spandex fabric melt happened..

There may be a difference in temperature of the fabric inside the pocket, as contrasted to the temperature of the paper sitting in open air on top of the light during the tests.

For these paper tests the battery had been partly depleted by the previous tests..

On a fresh charge level 120/150 reaches slightly over 650 lumens, but the paper test with dry ink was at 620 lumens

Speculation:

It is possible that my pants only melted a small amount because at ceiling 120/150 the light went into thermal step down. So the temperature that exceeded Spandex melting point was not sustained.

When light dimmed itself, the fabric stopped melting.

Max Safe Temp:

at ceiling 110/150 = ~510 lm the paper temp reached 360°F. This is slightly lower than the 392°F temp that google says Spandex can melt at.

Testing Setup Pic:

On left is the paper with fresh ink at start of test (ink on both sides of the paper):

Screen Shot 2026-03-31 at 11.54.43 AM
Screen Shot 2026-03-31 at 11.54.43 AM1920×697 163 KB

On right is the paper at end of test. Notice the paper has browned from using level 120/150, and some of the ink has evaporated or vaporized during testing (the light is On in the photo). When the light is Off the paper still looks black.

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And that’s why I waited for v2 with mechanical lockout

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eesh…hot enough to exceed the boiling point of water, you say…

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yes,
it appears that to stay below the temp of boiling water, you should limit ceiling to 80/150 = 170 lm.

Physical lockout with V2 is an excellent option. So is Electronic lockout.

For V1 we can use Electronic lockout, including the Auto lock timer if desired.

imo, Physical and or Electronic Lockout and or reduced ceilings are all viable safety strategies.

The main purpose of my test was to discover a safe ceiling Temperature level.

imo, limiting ceiling to 110/150 = ~510 lm = 360°F, or less, will keep temps below burning capability.

Using a relatively low last mode memory can also help minimize risk, but not as completely as using Lockout and or a lowered ceiling.

The O ring mod to the switch can also reduce risk, but not as completely as using Lockout, and or a lowered ceiling.

Notice that disabling Turbo without reducing ceilings does not protect against temperatures that are high enough to cause burns.

The default ceiling of 130/150 is capable of burning paper that has been colored black w a sharpie. (white paper stays much cooler and did not go over 120F at the same ceiling)

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Bad, BAD puddy tat! :wink:

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To be honest, I have not tried to install a different diameter o-ring in the tail, I’ve just left the same one in there. I’ve been carrying the KR1AA almost exclusively and only had that happen one time, and I was wearing black pants when it burned.

I’ve wanted to get more lights but have been quite financially challenged this year and all that. I have noticed a lot of people on Reddit saying they have problems with their KR1AA V2 and V2.5 or whichever.

I haven’t been on BLF in a while, but everyone that has problems with their light say it’s the version with a glued head and mechanical lockout. Edited: I’ve mostly been seeing the blinking error/wrong voltage detection on startup. It looks like he has put a wave washer type thing in the head in some of them. Maybe the inner tube length is wrong? I’m not terribly liking the idea of changing the battery through the tail on this type of light.

Again, my next one will definitely be 3000K SFT-70. I will get a raw/clear one if I can, but if not, I’ll try to strip one. I think the cyan ano might possibly be thinner than the black, looking at the wear on my other Hanks.

I have thought about asking him to ship one unassembled, since people have requested that before. I’ve already had mine taken apart once to swap the emitter, and it really wasn’t that bad. I’m also going to order some of the aux boards to try them in a TIR FW1A.

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I have noticed mine being on a few times in my pocket. It is easy to push the button when clipping it to a pants pocket.

Fortunately it has only been on at my memorized level of ~15/150. No burns…yet.

Sorry about the pants…

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That happened with both my V1 when changing the battery through the head, and with my V2 when changing the battery through the tail. With dirty lube.

I cleaned thoroughly and now change battery through the tail on both V1 and V2. I no longer get triple blink errors, as long as I dont let dirty lube accumulate on the contacts.

My takeaway from the pocket burn is that Spandex melts above 392°F. (Cotton burns at 410°F, and Paper burns at 451°F)

To stay below those temperatures, means setting the ceiling no higher than 110/150 = 510 lm = 360°F (and I disable Turbo). Or use Lockout.

agree
Lockout solves this.

fwiw,
my KR1AA V1 turns on at 20 ounces of switch pressure.
my TS10 V1 turns on at 26 ounces

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I have had multiple cotton pockets and nylon pouches burn. And one skin burn.
4 different flashlights with different UI’s.
For many years now I always try to remember to shut off all lights in the lowest mode they have. Whether I’m carrying them in pockets or pouches or anywhere in a vehicle or if they’re on the shelf at home. I don’t want lights coming on inadvertently in a high mode. Some do get tail caps loosened when I’m not using them. That has been working very good for me. Yes I still find my EDC lights on during the day or at the end of the day but it’s not a problem when it’s on at 1 lumen or less.

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My approach has always been:

  • 7 stepped levels

  • Manual Memory set to Level 4
    (easy 3 levels up or down for adjustment output)

  • Manual Memory Timer set to 1 Minute
    (gives me a substantial enough window to return to whatever output I last used, I find it very adequate 99% of the time)

  • Auto Lockout Timer set to 10 Minutes
    (if I’m not using the light for that long, I definitely want it to revert to my preferred, “all-purpose” level)

And that’s it - I haven’t had an Anduril light bite me in the pocket in probably 3 years, give or take… Several other non-Anduril lights, though, they get me pretty regularly.

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I happened to find a flashlight on the shelf was lit. Of course, I didn’t turn it on. I tried to turn it off by the mechanical tail switch (I’m not sure but it was Convoy S2+). But it didn’t work at all. I had to remove the battery. Simon told me to tighten the driver pill or switch retaining ring. And the problem was resolved. Since then, I use mechanical lock or remove battery even on the shelf.

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Sorry to hear that happened.

Would like to share that I own seven (7) NG KR1AAs. Three (3) of the original version. Four (4) of the next. Each torch has a different “click” from the others.

The only time I’ve had accidental activation was when wrestling the too tight clip bend radius on a pants pocket. This, of course, was entirely my fault.

Will admit, all the buttons are easy to press. It struck me that I could even readily use my chin; so I did so when I had winter gloves on.

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thanks.. not too bad all things considered.. the holes are small, and the edges are melted, not frayed..

I think the burn was small because the light stepped down, and the initial output was not too much higher than the minimum burn temperature of the material

It was a learning opportunity :wink:

thanks for sharing info.. congrats on your haul :wink:

Im debating trying to mod the switches with O rings, to increase the activation pressure.. it is pretty light, quite a bit lower than a TS10..

I measured my KR1AA switch at 20 oz pressure, my TS10SG switch requires 30oz pressure.. quite a big difference in absolute terms.. though it is not at all difficult to use the TS10SG switch in actual use.. it seems less prone to getting turned on accidentally..

In all my years of carrying a TS10, I have Never locked out.. The KR1AA is the first light to ever burn a pocket of mine.

and I agree a likely culprit to false activation is when pushing the light over a seam

I do like that that the KR1AA can use Eneloop.. they limit output to about 300 lumens, so burns are not possible anyway. I believe it takes over 600 lumens to cause fabric burns.

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'Sir, you are now a legit member of burned pocket society

#tacticalS21Bxhp70.26v5aturbo survivor
#close to the edge egg
Cheers :flashlight:

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