Hig pressure inside Fenix L2D?!

Hi all,
I was just doing a discharge duration test on my Fenix L2D (on high) with 2x2000mAh Uniross NiMh cells inside.
The light was tailstanding, and everything was normal for the first ~1 hour, the body was slightly warm as you'd expect. Then I went downstairs for 10 mins, came back upstairs and the light had fallen over! Picked it up, still working and still only slightly warm, but the tail switch had blown up like a balloon! I quickly unscrewed the head, and it hissed as the pressure was released. Now what I'm wondering is - did the cells vent, or is this caused simply by the air sealed inside the light expanding and having nowhere to go? Has anyone had this happen to them with this type of light?

some NIMH cells have been known to vent hydrogen during discharge, supposedly its not known to be a safety issue...but it does scare people, especially after reading lithium explosion threads.

Most likely you're batteries are venting.
https://www.candlepowerforums.com/threads/213293

That must have been it then, thanks for the reply

I guess it's not a safety issue by itself, but it could be a bit nasty if the hydrogen/oxygen inside the light was ignited by trying to switch the light off

Note to self, my custom flashlight will not only have a separate strobe switch, it will also feature a tiny one way pressure relieve valve like this:

http://www.agmcontainer.com/breather_valve/breather_valve_customvalves.htm



With the proper flow rate this design-in will prevent exploding flashlights and is immersion proof as well.

"The TA250-1 Immersion Proof Breather will withstand immersion in water to a depth of 1 meter for 2 hours without any water ingress. "
http://www.agmcontainer.com/immersion_breathers/immersion_breathers_ta250-1.htm


Could this work? (Patent pending)

Illum_the_nation said:

some NIMH cells have been known to vent hydrogen during discharge, supposedly its not known to be a safety issue...but it does scare people, especially after reading lithium explosion threads.

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Will eneloop have this problems?? just bought a pack of four and waiting for the batteries in my L2D Rebel100 to dry out before changing to eneloops..

ev13wt, i saw on your pictures description, it says clear annodized aluminum. im guessing its a typo

rockz4532 said:

ev13wt, i saw on your pictures description, it says clear annodized aluminum. im guessing its a typo

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I don't think it's a typo, but I presume it means the anodizing is clear, not the aluminium.

lumengeek said:

That must have been it then, thanks for the reply

I guess it's not a safety issue by itself, but it could be a bit nasty if the hydrogen/oxygen inside the light was ignited by trying to switch the light off

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That only happens if the concentrations are just so.

lumengeek said:

That must have been it then, thanks for the reply

I guess it's not a safety issue by itself, but it could be a bit nasty if the hydrogen/oxygen inside the light was ignited by trying to switch the light off

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The mixture ratio would be all wrong for any sort of ignition.

Zatoichi said:

I don't think it's a typo, but I presume it means the anodizing is clear, not the aluminium.

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Probably, but just FYI, I saw transparent aluminum just the other day. It actually quite surprised me that such a thing existed. It's not really suitable for structural components however.

http://science.howstuffworks.com/transparent-aluminum-armor3.htm

Hey that's pretty funny. I didn't know transparent aluminum really existed. When I read the posts above I immediately thought of the Star Trek 4 movie where they make a transparent aluminum wall to make an aquarium inside a Klingon Bird of Prey. The howstuffworks.com article linked to above has a reference to the movie. Since I saw the movie when it first came out I often thought about how cool it would be to make transparent metals. I did not know they actually made some already. Interesting.

Marduke said:

Probably, but just FYI, I saw transparent aluminum just the other day. It actually quite surprised me that such a thing existed. It's not really suitable for structural components however.

http://science.howstuffworks.com/transparent-aluminum-armor3.htm

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Wow! :huh: I've heard of it before, but only in Star Trek (The Voyage Home).

Marduke said:

Probably, but just FYI, I saw transparent aluminum just the other day. It actually quite surprised me that such a thing existed. It's not really suitable for structural components however.

http://science.howstuffworks.com/transparent-aluminum-armor3.htm

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I didn't know either. That is really cool! :thumbsup:

You think a valve makes sense?

Dude, I had the same pressure thing happen after reading this thread. I just got a new Nitecore D20 and I was using it to condition a set of Energizer 2500 mAh AA's. I fully charged the batteries and let them fully discharge in the light with it set at full brightness constantly. When I decided to take them out I noticed that I could not move the piston at all no matter how hard I pushed. Uh oh, must be a lot of pressure inside. I very slowly unscrewed the head to vent the pressure safely and got a sudden nasty hiss as the pressure vented and caused the o ring to bubble up like a balloon where the pressure vented. After this happened I removed the o ring that goes on the piston so that the light will hopefully no longer be air tight. I don't want this happening again.

Yep, it's a common problem with Fenix 2xAA lights. The lights are designed to work at full power at 1 volt, and, as such, they over-discharge batteries as a matter of course, and sometimes cause reverse charging.
Your light reverse charged a battery, causing it to vent. Throw out the battery - it's permanently damaged.

This topic is like a boomerang It was discussed here a couple of times...

Cells venting will never happen If you will use a matched pair of batteries. If one cell has more capacity than the other, then the weaker cell will discharge to zero and the stronger cell will start to charge it in reverse and that causes the venting.

Just use a good batteries and a charger that doesn't charge in pairs and you will be fine.

nutter said:

Yep, it's a common problem with Fenix 2xAA lights. The lights are designed to work at full power at 1 volt, and, as such, they over-discharge batteries as a matter of course, and sometimes cause reverse charging.
Your light reverse charged a battery, causing it to vent. Throw out the battery - it's permanently damaged.

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arpit??

So what's the final consensus on the L2D and NimH? Sounds like it won't cause damage so long as you turn it off as soon as you notice the light fall out of regulation.

This topic caught my eye because I just ordered a 2AA body to put an L1D head on. Maybe I'll use my already-worn-out NiMH for initial testing


Just for the record, hydrogen gas will ignite in air in a very broad range of concentrations. I forget the exact numbers, but it's something like from 15% to 90% hydrogen/air ratio. You could probably find the info on the NIST site or something like that if you're interested. (**EDIT: I found info from the "Praxair" company site. There's a PDF for the Hydrogen MSDS which states the following: FLAMMABLE LIMITS IN AIR, % by volume: LOWER: 4.0% UPPER: 75.0%")



Reason I bring it up is 'cause I've heard a lot of guys talking about building hydrogen gas generators for their cars (or something like that) basically producing lots of H2 through electrolysis. Hydrogen's nothing to screw around with, so let's be careful out there! :wave:

Stress_Test said:

So what's the final consensus on the L2D and NimH? Sounds like it won't cause damage so long as you turn it off as soon as you notice the light fall out of regulation.

This topic caught my eye because I just ordered a 2AA body to put an L1D head on. Maybe I'll use my already-worn-out NiMH for initial testing

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It's fine to use two cells. The light will not function at low enough voltages to permanently harm a quality NiMH cells.

However, I would recommend against using worn out NiMH cells. Those would be the ones to outgas at high loads. A quality light deserves quality cells, a.k.a. Eneloops or similar.

Marduke said:

Probably, but just FYI, I saw transparent aluminum just the other day. It actually quite surprised me that such a thing existed. It's not really suitable for structural components however.

http://science.howstuffworks.com/transparent-aluminum-armor3.htm

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woah... aluminum as bullet proof armor