Very Loud Pop - Like a 22 pistol - But Should I worry NOW.

[Databyter]

Disclaimer: I am long winded.

My custom light based on the "torch" 623 bulb and 12 AA Nimh Elite 2000's made a loud pop last night.

What started it, and added to my confusion is that I was barely awake and was sitting in a chair in the living room and saw this HUGE long shadow scurrying across my floor. Thinking it was a cockroach or something I did not want breeding in my house I grabbed one of my tennis shoes I had taken off (I was barefoot) and my silver mag mod and I was off to save my home from pestilence.

I noticed right away that it was a VERY big centipede, which I had never seen before in my area. It kinda scared me since I had bare feet, and I was trying to use the light to herd it into an area where I could squash it. If I was more awake I would have probably tried to capture it because it was so rare looking and I want to know if it is poisonous.

At any rate I had the light pretty close to the damn thing and I felt kinda bad because I am not into torture, but I wanted it to move from behind a table leg, then BOOOM!

A loud pop that sounded like a rimfire pistol gunshot (I actually tried to make some normal sounds afterwards so my neighbors would not call the police at 2 a.m.). I forgot all about the centipede for a moment and had almost dropped the light.

After a few seconds in my groggy state I tried to work it out.

My first instinct was that the centipede had exploded, or that something else near the back of the table I couldn't see did.

I realized and remembered the power of the light I was holding (still on and still bright) and shut it off. When I shut it off I noticed that the plastic cap that usually covers the button was off and lying on the floor, I don't know if it was from pressure, or the fact that I almost dropped the light.

But at the time, the cap being popped off made me think that a cell had gone bad, reversed polarity or something and had an explosive vent. I am aware of the hazards of improperly used lithium, but I was sort of skeptical that a NiMH would be likely to reverse like that and need to look that up. Also I did not FEEL any vibration or concussion from my hand, turning the light off was just a safety afterthought.

The problem is that I of course removed the battery pack to check, and it looks perfect and no battery was even warm.

I put it aside to deal with this morning, and the voltage is 15.3 volts which means that each battery would have to be at 1.275 volts, or that if one batt. was bad, and simply still able to conduct thru, the rest would have to be at 1.39 V each, which I simply can't believe, It's not like I took the light off of the charger, it has been laying around for several weeks since the last charge at least.

The batt. tube is relatively clean except I did notice a white substance in two spots that were suspiciously about a battery length apart (head and tail), and would have been from a center battery because they were in the center of the tube. The white stuff was however dry and I could not swab any of it off with a qtip, so I wonder if it was always there or caused by something else. I did at one time sell this light to a guy who did not maintain it well, and had let the pack go very far south before he sold it back to me, and I restored it to greatness. (I had to sand and polish the contacts and replace all the cells).

Bottom line, if I was checking this batt pack off the shelf, I would give it a visual and voltage grade of A++ for holding a charge and operating my light effectively.

One theory I have now is that the centipede DID explode somehow, but, when I found it later (I did not stop my anti-centipede hunt after I shut the light off) it was still moving and was only a foot or so away from where I last had seen it. This doesn't seem likely, but, heck, this is a hot light, and bugs are wierd.

My other theory, that I am leaning towards but want Candlepower confirmation of, is that for whatever reason, one of my batteries, or all, simply decided to vent and the pressure was trapped by the mag body in the battery tube, until at some point it was able to expand and pop off the black plastic switch cover. But it was such a loud POP, or was it because I was near tile floor and it was 2 a.m. and was already fairly quiet in the world.

If it was a vent, should I worry about using this pack? it looks fine, I was planning on checking each battery individually this morning, until I measured the V and found it to be, if anything, impressive, after no charge and several uses.

Has anybody else had a switch cover pop off with a loud popping sound? Maybe that is all that it was, just a release of normal pressure from cells that are fine.

Should I just move on, it's not lithium, and I really just want to continue using these batt's if they appear to be ok.

Am I in danger to test them in the light, and then the charger?

My light.

Custom Quad Bored Silver 3D Mag Body
Aluminum Reflector
Borofloat Heat Resistant Lens
WA 64623 Bulb
12AA to 3D Batt. Pack (14.4V) (measures 15.3 day after event)
12 X Elite 2000 NiMH AA Batteries
AW Soft Start 3 Way Switch with strobe

ALSO, would it be brilliant to put a tiny pinhole (literally from a tiny pinprick near the edge of the cover) in the rubber cover to prevent this from happening again. It would still keep out rain for the most part, but would expand open under any instance of pressure.

I don't want to be scared of my favorite light, I used to be much better read in these areas, but have not been active in the hobby for a few years, beyond USING the lights. So my knowledge of what different types of batteries can do, and what is normal is a bit rusty. I can tell you that I always leaned towards NimH in certain builds BECAUSE I felt that they were more forgiving and had less potential for an unfortunate event.

[127.0.0.1]

small hydrogen gas buildup and explosion from the NiMH batteries venting over time

[Databyter]

small hydrogen gas buildup and explosion from the NiMH batteries venting over time

So there should be no issues with continuing to use the light I'm thinking?

I suppose I really should take the pack apart and individually inspect every cell end, I can only see the half of them that faces outward.

But I find it hard to believe that the voltage would still be normal and the pack still be functional, if there was a major flaw, not to mention, as I said, they were not hot.

Your theory makes sense. It may have been the fact that I picked it up, and heated it up, and had my hand on the button that made an already slow vent that had developed pressure find a way out.

The reason I have been resistant to take the batts out of the holder to inspect them, is that batts are not all the same length, and due to the design of this holder I need to arrange them so that each of the four columns of 3 batteries in series is the same length, because I have to squish them all equally regardless until the shortest column is as tight as the longest column and the contact is good.

I feel this puts a lot of stress on the batteries and that is why I bought a charger that I can charge as a pack vs squishing my batteries every few weeks. It also should theoretically ensure that they all charge equally and are conditioned the same.

Taking it apart would probably be fine, but those are the reasons I am leaning against it, when as you say this is probably just a case of a giant natural fart.

[Burgess]

Must admit . . . .


I would be Very Frightened by this occurrence,
and would NOT wanna' use that battery pack again.

EVER !



And Maybe . . . .

I wouldn't even want to use that FLASHLIGHT again !


But, of course, that's just me.


Good Luck to you, regardless of your decision.

[Burgess]

. . . . when as you say this is probably just a case of a giant natural fart.

A giant natural fart,


which IGNITED ! ! !





Edit to add --

Oops, i'm probably wrong about it actually Igniting !

Scratch that.

However, i will leave this posting intact, to (hopefully) avoid even MORE confusion.

_

[Illum]

A giant natural fart,

There was a thread some years back about first gen Eneloops doing this, as well as a couple odd cases of leakage. NIMHs stores alot of hydrogen actually, so much at at one point popular science came out an article when Hybrids were on the horizon the possibility of using the NIMH design to store hydrogen.

[Databyter]

A giant natural fart,


which IGNITED ! ! !



_

I'm not sure that it ignited, although it is possible. However I saw no residue of smoke. The inside of the tube and the switch area where the cover popped off is very clean. Of course hydrogen burns fairly clean, especially under pressure. How would it ignite though?

If the gas moved up by the bulb and ignited, would my lens and bulb actually survive? I doubt it.

I'm leaning towards the theory that I made the light to such tolerances that it was airtight, and when I had it on for a few minutes, for about the fifth time I've used it on this charge, the pressure became more than the rubber boot could keep in.

I don't use this light to start fires, it has three levels in my version, and I use it as a utility light that I keep handy by the door because it lights up my entire property like a floodlight, and I usually only need it for a minute or so at a time, max.

In this case I had it on for about 3 minutes when it popped.

I put the pack back in today, and perforated the button cover in a few places. For all practical purposes it is still waterproof, you can't even see the holes which I think only stretching would allow to open up, but should pressure develop again, I think those pinholes will start to whine and whistle and keep the cover from blowing off like a popped balloon, which now that I think of it, is exactly the sound that I heard. A loud POP.

I want to deplete the charge of the pack thru normal use, and then charge it, probably inside an iron pot, just to be safe.

I'm hoping Lux Luthor will respond to this thread when he sees it, he knows this area fairly well, and can advise me if I should worry or not, in the meantime I am cautiously optimistic, that at least, unlike a lithium battery, even if it fails, the worst it will do is scare the crap out of me, I do not believe it can injure me or get to a shrapnel level.

[Databyter]

There was a thread some years back about first gen Eneloops doing this, as well as a couple odd cases of leakage. NIMHs stores alot of hydrogen actually, so much at at one point popular science came out an article when Hybrids were on the horizon the possibility of using the NIMH design to store hydrogen.

Interesting. Assuming you aren't pulling my leg, and I don't think you are, it would be interesting to read about that.

[Burgess]

Oops !

Guess i was wrong to assume the Hydrogen gas actually * ignited *.





Your explanation sounds much more resonable.


I will amend my previous comment, so as not to confuse anyone else.

[Illum]

Interesting. Assuming you aren't pulling my leg, and I don't think you are, it would be interesting to read about that.

I really wish I kept my old magazines,
NIMH development actually started from researching on how to store hydrogen to operate Nickel hydrogen batteries. The PopSci article discussed how Hydrogen is stored in a solid state, and that it can be extracted through discharging. Gah, popular sciene's search engine sucks... I can't find it

[LuxLuthor]

Mike, not on here as much, but got your PM.

This was relatively common back when the Intellect Battery "IB" brand was being used from Cheap Battery Packs, still happened to some degree even with the newer, "better" yellow/orange "Elite" brand of 2/3 A 1500mAh cells.

I had this happen to three packs I had gotten from Ed (MadMaxabeam) who replaced them for me, and like you say it feels like a 22 or ladyfinger firecracker going off inside your light. When you open up the pack you don't see any apparent damage. My occasions did not blow out the side push button cover, split the shrink wrap, or do any damage elsewhere. It is obviously a rapid gas venting from what turns out to be a substandard, and/or weakened cell when heavy demand current drain is put through it as one in the series of 12-13 cells. After Ed disappeared from the scene in mid 2007, I got a spot wielder and began the learning process of making various battery packs, because one of his replacement packs popped again after several months. If it is hydrogen gas, there was no ignition as flames would have been obvious to see signs of. Again, not even the individual battery cell label was melted, but one of my popped cells was slightly bulged.

When I took the pack apart and tested each cell with voltmeter, it was obvious which one had a much lower voltage than the rest. When I selectively replaced that one cell, the pack was fine again. However, after many conversations with Mike at CheapBatteryPacks.com over this and how a number of his new Elite cells had either zero or < 0.9 volts on arrival, it became apparent that the Chinese cranked these out in their typical low quality manner. I had to charge & discharge all the cells several times to find those that were sub-par before making into a pack. Luckily I was buying enough quantity from Mike that he was generous with giving free replacements for the duds.

Now even if you got good cells (i.e. from a pack I made for you), over time these low resistance high performance NiMH cells wear down as the high drain rates just beat the crap out of them, and the weakest link cell in the chain will develop an internal short and when exposed to high current drain, do the vent explosion you noticed. In all my cases, the event was enough to damage the weak cell, break the battery series circuit, and no longer turned on the light. If your pack still turned on the light and/or had what looks like respectable total pack voltage, then the cell that vented did not completely short out, but likely will soon. It should still be detectable with individual cell testing.

In terms of worry....I would not worry from a safety standpoint, based on my experience...but you have a cell that has either failed or on its way to total failure and must be replaced. So your being able to consider it a reliable pack is no longer there. It may or may not "pop" again either during charging, but most likely during the high current discharging in the light. Let me know if this answers all your questions.

[Databyter]

Mike, not on here as much, but got your PM.

This was relatively common back when the Intellect Battery "IB" brand was being used from Cheap Battery Packs, still happened to some degree even with the newer, "better" yellow/orange "Elite" brand of 2/3 A 1500mAh cells.

I had this happen to three packs I had gotten from Ed (MadMaxabeam) who replaced them for me, and like you say it feels like a 22 or ladyfinger firecracker going off inside your light. When you open up the pack you don't see any apparent damage. My occasions did not blow out the side push button cover, split the shrink wrap, or do any damage elsewhere. It is obviously a rapid gas venting from what turns out to be a substandard, and/or weakened cell when heavy demand current drain is put through it as one in the series of 12-13 cells. After Ed disappeared from the scene in mid 2007, I got a spot wielder and began the learning process of making various battery packs, because one of his replacement packs popped again after several months. If it is hydrogen gas, there was no ignition as flames would have been obvious to see signs of. Again, not even the individual battery cell label was melted, but one of my popped cells was slightly bulged.

When I took the pack apart and tested each cell with voltmeter, it was obvious which one had a much lower voltage than the rest. When I selectively replaced that one cell, the pack was fine again. However, after many conversations with Mike at CheapBatteryPacks.com over this and how a number of his new Elite cells had either zero or < 0.9 volts on arrival, it became apparent that the Chinese cranked these out in their typical low quality manner. I had to charge & discharge all the cells several times to find those that were sub-par before making into a pack. Luckily I was buying enough quantity from Mike that he was generous with giving free replacements for the duds.

Now even if you got good cells (i.e. from a pack I made for you), over time these low resistance high performance NiMH cells wear down as the high drain rates just beat the crap out of them, and the weakest link cell in the chain will develop an internal short and when exposed to high current drain, do the vent explosion you noticed. In all my cases, the event was enough to damage the weak cell, break the battery series circuit, and no longer turned on the light. If your pack still turned on the light and/or had what looks like respectable total pack voltage, then the cell that vented did not completely short out, but likely will soon. It should still be detectable with individual cell testing.

In terms of worry....I would not worry from a safety standpoint, based on my experience...but you have a cell that has either failed or on its way to total failure and must be replaced. So your being able to consider it a reliable pack is no longer there. It may or may not "pop" again either during charging, but most likely during the high current discharging in the light. Let me know if this answers all your questions.

Thanks Lux, I knew you would know the answer.
And no, this was not part of one of your fine packs, it was something I made up with an FM holder, I guess I need to do some further culling of my batts, probably do some cycles of the ones that look ok, and then find one that matches them.
Probably just bad luck, because I have used quite a lot of similar cells in similar lights with no problems, on the other hand, maybe it was good luck, and I am just running into the inevitable.

I hate the feeling of anticipating the next loud pop, but I guess I will get over it.

Honestly I was more concerned about the neighbors calling the police for a gunshot than anything else. My windows were open and it was late, and the pop was very loud and distinctive. Sounded just like a small pistol. So I made sure to move around and make other normal noises. Anyhow, ..

Thanks again for responding, and explaining.

Data