A Little Accident. W/123's and a Peli. M6

[mike2004]

Re: A Little Accident. Enjoy.

[ QUOTE ]
Ray_of_Light said:
To measure flash-amps, set your DMM on 20 Amp scale, and measure the current flowing through the 123 cell.
Remember to keep the reading shorter than one or two seconds.

Anthony

[/ QUOTE ]


What reading will I get with a short?

What reading will I get without a short?

It takes my DMM 2-3 seconds to stabilize when taking current readings so what do I do then?

 

[Hans]

Re: A Little Accident. Enjoy.

[ QUOTE ]
Ray_of_Light said:
As morale, if you are scared from this story, the only precaution I advice is to flash-amp your cells. Cells with defective crimps, that can present the risk of water diffusion, show a short-circuit current, otherwise called flash-amp, of 1- 2 Amp.
Another valid suggestion is to buy only cells built from a ISO certified factory!

[/ QUOTE ]

If I understand your explanation correctly the sequence of events you described is only possible in a two cell light because the defective cell has to be reverse charged by a good cell. Is that correct? Because if it is there's another possibility to avoid this sort of thing happening - use only lights that work on one cell.

Is that line of reasoning sound?

Hans

 

[gadget_lover]

Re: A Little Accident. Enjoy.

OK, I'm a little confused....

It looks like there were bare cells in that box along with spare parts, bare wires, etc. A very bad way to store batteries.

Then there's the PM6 with what looks like soot all over. The PM6 is shown with the tailcap off, but the button plunger is not in the tailcap, nor is the battery contact. The plunger is to the right and the battery contact is to teh left of teh tailcap. The metal center contact plate is still in place. That would indicate the brass plunger (with a diameter around .704 inches) under the rubber cap was forced out through the .670 hole in the aluminum tail cap. That takes a lot of force.

I'm not sure why there would be any black soot between the metal center contact plate and the plunger.

If the tailcap was blown off, the button should have stayed in place. If the button was blown off, the battery contact should have stayed in place.

What does not make sense is what caused the black plastic inside battery contact holder to become unglued and unscrewed from the tailcap. The threads look OK. I had to boil mine to losen the locktite and even then it was a struggle due to the tight fit. Keep in mind the pressure would have pushed the plunger up against the metal plate that was still in the tailcap. I see no reason for the battery contact to be out of the tailcap.

The inside of a black PM6 is normally black, by the way.


My money is on one of the loose cells being shorted and starting a fire.

It' usually possible to determine the origin of a messy explosion by looking at the patterns of the residue, no? It looks like it may have come from the left rear of the box.

 

[beezaur]

Re: A Little Accident. Enjoy.

Let me see if I understand this. . .

Hypothetically:

One battery lost its volatiles from a leak; they were replaced by atmospheric water (or maybe just oxygen?). Kind of like ion exchange.

Then the bad battery was placed in series with current from the other battery running through it. I don't quite follow the electrochemistry, but this causes the thing to overheat and decompose the water -- BOOM.

Seems reasonable.

Now, we might all have "pipe bombs" or we might not. We can check by quickly measuring the short circuit current from each battery. They should be ~6-7 A new; 1-2 indicates a problem. (What would voltage be?) In no case should two lithium batteries with mismatched "flash-amps" be used in the same light at the same time.

Is that about right, and if so, is the procedure "bomb"-proof? /ubbthreads/images/graemlins/wink.gif

That sounds easy enough to do, even for me /ubbthreads/images/graemlins/smile.gif

Scott

 

[RY3]

Re: A Little Accident. Enjoy.

[ QUOTE ]
gadget_lover said:
OK, I'm a little confused....

[/ QUOTE ]

I am confuss on a few thing myself as well!!! For example, I still can not figure how the PM6 body get to where it was located.


[ QUOTE ]
It looks like there were bare cells in that box along with spare parts, bare wires, etc. A very bad way to store batteries.

[/ QUOTE ]

Yes. As I mentioned before, there were two 1/5A in the boxes and both showed no damage after the incidence. There should NOT be any bare wires. Can you point it out to me?

[ QUOTE ]
What does not make sense is what caused the black plastic inside battery contact holder to become unglued and unscrewed from the tailcap. The threads look OK. I had to boil mine to losen the locktite and even then it was a struggle due to the tight fit. Keep in mind the pressure would have pushed the plunger up against the metal plate that was still in the tailcap. I see no reason for the battery contact to be out of the tailcap.

[/ QUOTE ]

No idea how the tail cap got apart. But I took a close-up picture on the threads and the parts from the PM6. There was damage on the threads.

Also, as you can see from the pictures I posted before, the "bass plunger" was ended up behind box#1, the tail cap ended up in box#3; both the body and the negative contact part were found on the floor.

[ QUOTE ]
The inside of a black PM6 is normally black, by the way.

[/ QUOTE ]

I actually don't remember but it is definitely black now. Here is a close-up pic inside the PM6 while it was on the floor.

[ QUOTE ]
My money is on one of the loose cells being shorted and starting a fire.

[/ QUOTE ]

I am not sure about this. There were totally four 123 batteries in the boxes. Originally, I thought the DP and Duracell were lossely in the boxes but later my wife said she remember she used the UK-2L but it was dim, so she used the PM6 instead. If she remember correctly, this mean all the 123 cells were in the flashlights.

[ QUOTE ]
It' usually possible to determine the origin of a messy explosion by looking at the patterns of the residue, no? It looks like it may have come from the left rear of the box.

[/ QUOTE ]

I have to say I am not good at this. Beside, the box#1 was moved, so items might relocated. The box was on fire and it was put under running water in the sink to put the fire out.

Hope it clear some of the confussion.

By the way, I'm still trying get a full statement from my wife but she is not very cooperative!!

..

 

[BC0311]

Re: A Little Accident. Enjoy.

Excellent explanation, Ray.

This makes sense of what I observed in the incident with my defective Lisun (looks just like a DP) brand 123A cell.

If I don't need to keep lithium batteries in a light, I don't. I only use Duracell and Battery Station cells now. I've experience some quirkiness with a few Surefire cells, nothing major though.

Britt

 

[Lunal_Tic]

Re: A Little Accident. Enjoy.

Hmm, an uncooperative witness . . .the plot thickens. /ubbthreads/images/graemlins/popcorn.gif

 

[DaGeek]

Re: A Little Accident. Enjoy.

hmmmmmm

 

[enLIGHTenment]

Re: A Little Accident. Enjoy.

[ QUOTE ]
RY3 said:
I am not sure about this. There were totally four 123 batteries in the boxes. Originally, I thought the DP and Duracell were lossely in the boxes but later my wife said she remember she used the UK-2L but it was dim, so she used the PM6 instead. If she remember correctly, this mean all the 123 cells were in the flashlights.

[/ QUOTE ]

Correct me if I'm wrong here, but if all four batteries were in the lights, then both lights would have been loaded with mismatched cells. Bang.

Likely one of the lights cooked off and the other one (already in an unstable state due to mismatched cells) responded in sympathy due to the heat or blast.



chevrofreak: what's wrong with the M6 switch?

 

[gadget_lover]

Re: A Little Accident. Enjoy.

In picture P1020 (shows volt meter, charger and what appears to be a blasted cell in the lower left) there are all sorts of exposed metal. There are voltmeter probes, a power adapter, what looks like a coil of solder.....


I still have not figured out how an explosion would blow out the brass plunger and then still have enough presure built up to blow off the tailcap. The threads on the end of the light don't look great, but they don't look stripped. They look a lot like my PM6 incan's threads. Does the tailcap screw back on?

I suppose if there was enough pressure to force the button out through that hole, and then the black palstic of the battery cotact melted and sealed up the 1/4 inch hole in the plate it might have allowed pressure to build again. I would have thought that the melted plastic would just squirt through.

The threads on half the photos look shiny or metalic, on some others they are almost black. Is that an illusion or did some of the powder get spread around later?

Daniel

 

[Vrt]

Re: A Little Accident. Enjoy.

[ QUOTE ]
Ophiuchus said:
Lithium batteries discharge sulfur-dioxide gas. There is a slow industry trend toward a safer lithium-manganese composition. Many lithium batteries for modern military application are of lithium-manganese composition. Example;
http://www.ulbi.com/ and http://www.ulbi.com/market-display.asp?ID=7

[/ QUOTE ]

What type are popular CR123A cells ? Aren't they Li/MnO2 already ?

[ QUOTE ]
Ray_of_Light said:
This is because the electro-negativity of the lithium, used at the negative electrode is so high that it spontaneously decomposes the water into hydrogen and oxygen.

[/ QUOTE ]

As far as I know lithium doesn't decompose water into hydrogen and oxygen, it bonds with OH and hydrogen is released.
2Li + 2H2O -> 2LiOH + H2

[ QUOTE ]
Ray_of_Light said:
As morale, if you are scared from this story, the only precaution I advice is to flash-amp your cells. Cells with defective crimps, that can present the risk of water diffusion, show a short-circuit current, otherwise called flash-amp, of 1- 2 Amp.
Another valid suggestion is to buy only cells built from a ISO certified factory!

[/ QUOTE ]

Isn't short-circuit a cell dangerous ?

 

[Vrt]

Re: A Little Accident. Enjoy.

[ QUOTE ]
Hans said:
If I understand your explanation correctly the sequence of events you described is only possible in a two cell light because the defective cell has to be reverse charged by a good cell. Is that correct? Because if it is there's another possibility to avoid this sort of thing happening - use only lights that work on one cell.


[/ QUOTE ]

What is a reverse charging ?

 

[Lurker]

Re: A Little Accident. Enjoy.

[ QUOTE ]
gadget_lover said:
I still have not figured out how an explosion would blow out the brass plunger and then still have enough presure built up to blow off the tailcap.

[/ QUOTE ]

A possible explanation is that the explosion started in the cell that was farther from the tail cap. Maybe the explosion pushed the rear cell out like a bullet in a gun barrel. The "bullet" battery initially struck and forced the brass plunger out and after that, it struck the remainder of the tailcap and forced that off. The rear battery contained the pressure after the brass plunger left. This is obviously just speculation.

Another variable to consider in this story is that since the person who last used the lights is not being very forthcoming with details, maybe she did some strange things to the lights in an effort to make them work better. Things that she didn't want to admit after the explosion. Maybe she mixed up the batteries, banged the lights around, dropped one accidentally, left one on when she put it back, forced something, etc. It is still hard to see how that should cause an explosion, but it introduces more variables. She may have accidentally put a battery in backwards for all we know.

This thing has me worried and I would love to find out the real cause. It will certainly make me think twice before holding an M6 in my mouth.

 

[Lunal_Tic]

Re: A Little Accident. Enjoy.

While a thirst for knowledge may be good, it might be best to let "sleeping dogs lie" in this case. Pushing too hard for info might cause another type of explosion . . .

Everyone involved knows to be more careful now.

Just my 2yen.
-LT

 

[Lurker]

Re: A Little Accident. Enjoy.

[ QUOTE ]
Vrt said:
What is a reverse charging ?

[/ QUOTE ]
When you have two cells in series powering a light and one cell is dead while the other cell is still strong, the current will flow backwards through the dead cell. That is called reverse charging. It will also happen if you put a battery in a charger backwards.

 

[evan9162]

Re: A Little Accident. Enjoy.

[ QUOTE ]

When you have two cells in series powering a light and one cell is dead while the other cell is still strong, the current will flow backwards through the dead cell. That is called reverse charging. It will also happen if you put a battery in a charger backwards.



[/ QUOTE ]

Er, sort of.

The current still flows the same direction, but due to the chemistry inside the battery, instead of a positive voltage from - to +, you get a negative voltage from - to + ; in other words, the - terminal becomes the +, and the + becomes the -. The battery is no longer supplying energy, it is dissipating energy. Some in heat, some in causing chemical reactions to occurr. I'm not sure what the reactions are when a Li primary cell gets reverse charged, but it's certianly not what the manufacturer intended.

 

[Ray_of_Light]

Re: A Little Accident. Enjoy.

SOme clarifications.
Vrt correctly said that a simple reaction between Li and H2O produces LiOH and H. I oversimplified the reaction for sake of clarity, but the whole dynamics of chemistry is different with the presence of MnO2 at about 200 Celsius, togheter with many chlorinated organic compounds. Trust me on the fact that, at a certain point in time, you will have abundancy of hydrogen and oxygen. Oxygen is initially produced from the overheated MnO2, while some more will be produced from the dissociation of the -OH radical.

Please note that not all defectively crimped cells degrade in such destructive manner. The behavior of a lithium cell in presence of water contamination, depends on some specific physical properties of the MnO2, which varies from brand to brand. This involves the additives used, the purity of MnO2 and the preparation process. Some off-brand uses cheap hygroscopic additives, intended to improve the conductivity; based on the assumption that water should never get there.

Another point is the mechanics of the explosion. The expanding gases pushed the tailcap forward; while the gases are compressing, no cell pushes the other. After the tailcap has been pushed forward, then the gases shoot the cells outside the flashlight barrel, and the cells itself get disassembled by the expleting mechanical forces. Strange as it may appear, the flame front propagated from the slack of the barrel, INSIDE the battery, and then it waved back, shooting the tailcap forward, more or less as happen inside an ammunition round.

The black powder you see in the pictures is the MnO2.

Regards

Anthony

 

[Lurker]

Re: A Little Accident. Enjoy.

My chemistry is a little weak, but it sounds like Anthony knows what he is talking about and has a sound theory of what happened. I still don't see what ignited the hydrogen, but I could have missed something in all of that. In in any case, what exactly is the lesson to take from this? In the simplest terms possible. Would it be:

- Don't use cheap off brand lithium cells.
- Don't use a cell if the crimp looks defective or damaged in any way.

Or is it about venting your flashlight or avoiding the PM6 or is it something else? What should I be doing to avoid this? I like keeping at least one 2 x CR123 light loaded and ready, but i don't want to burn down my house or car.

 

[SilverFox]

Re: A Little Accident. Enjoy.

Hello Anthony,

I have speculated that the residue from a "rapid vent with flame" cell can be corrosive. Can you comment on that?

Tom

 

[RY3]

Re: A Little Accident. Enjoy.

[ QUOTE ]
There are voltmeter probes, a power adapter, what looks like a coil of solder.....

[/ QUOTE ]
The "coil of solder" look alike probably are the springs from the inside of the PM6 or UK-2L.
I don't have any bare wire or solder coil in the boxes. I agree I should and will store the batteries in a much safer manner.

[ QUOTE ]
The threads on the end of the light don't look great, but they don't look stripped. They
look a lot like my PM6 incan's threads. Does the tailcap screw back on?

[/ QUOTE ]
The picture didn't show it very clear but you can still see there is a piece of metal stuck in the threads. If you look at the photo, it is at the end and upper part of the thread. It is from the tailcap's threads.

[ QUOTE ]
The threads on half the photos look shiny or metalic, on some others they are almost black.
Is that an illusion or did some of the powder get spread around later?

[/ QUOTE ]
I believe it is just an illusion from the camera flash. The one with the PM6 on the floor was taken with a flash; it was taken the same day the accident happened. The other photo was taken yesterday with macro mode (no flash). I don't think there were any "black powder" got to it later but I do put all the parts together in a box after the accidence.

[ QUOTE ]
Correct me if I'm wrong here, but if all four batteries were in the lights, then both
lights would have been loaded with mismatched cells.

[/ QUOTE ]
As I can not identify one of the destroyed cell, I don't know. I really hope someone can id it from the photo.

[ QUOTE ]
A possible explanation is that the explosion started in the cell that was farther from the tail cap. Maybe the explosion pushed the rear cell out like a bullet in a gun barrel. The "bullet" battery initially struck and forced the brass plunger out and after that, it struck the remainder of the tailcap and forced that off. The rear battery contained the pressure after the brass plunger left. This is obviously just speculation.

[/ QUOTE ]
Another factor to consider is that some parts might not be disassembled by the explosion but rather by the impact on the cabinet door.

[ QUOTE ]
This thing has me worried and I would love to find out the real cause. It will certainly
make me think twice before holding an M6 in my mouth.

[/ QUOTE ]
Well, it was exactly how my wife held the PM6 when she clean out dog's ears. However, I do believe (and hope) there probably will have some indication if it happen while we are holding the flashlight.

[ QUOTE ]
While a thirst for knowledge may be good, it might be best to let "sleeping dogs lie" in
this case. Pushing too hard for info might cause another type of explosion...

[/ QUOTE ]
I really wish you gave me this warning earlier.

...