TK Monster Explosion

[ejot]

Wow! I don't peruse this particular subforum often so I just now saw this thread. As many have said, I am so glad the injuries were minor. I'm sure it was a relief that the insurance will be covering the damages. Also sorry that you lost a beautiful light without getting any time to play with it.


As I'm sure this thread will be read to for years to come by many people, I feel obliged to comment on this reply:

dcaprilia: Don't worry about anhydrous hydrofluoric acid if your eyes didn't start burning and you didn't have trouble breathing right away your good to go.:thumbsup:

Especially regarding the "right away" part, this is not necessarily accurate, and is the really what makes HF such an insidious chemical. I don't know much about batteries or whether HF is or is not present when this particular chemistry vents, but I do know a lot about hydrofluoric acid. I work with it nearly every day and it truly is scary stuff.

Granted, HF vapors inhaled, or in your eyes will be immediately unpleasant. But under direct skin contact, it could potentially be hours before any pain whatsoever was noticed. This is particularly scary when you consider skin exposure of 50% acid to a 5"x5" patch will is typically fatal, and even a small drop in contact with skin can do some very serious damage. A deposit of anhydrous hydrogen fluoride anywhere, in any observable amount, is something that needs to be taken very seriously.

 

[HarryN]

...and that is why I carry a bag of CELOX in my attache. There are a few things in this world that, by the time you realize you need them, it is far too late to go get one. One of those things is hemostat -- if you have a torn or severed artery, you have about 5 minutes left to live, on a good day.

Thank you for pointing out this product - a good one to add to our family emergency kit, and perhaps even more places.

 

[New_World]

glad you dropped it when you did.

 

[mdocod]

Whew! Long thread here with a lot of long-winded responses to read through!

I'm very happy to hear that no-one was hurt. Also a sign of relief to hear that the insurance will be covering this.

A few thoughts:

The more I think about this issue of 4 of the cells being fully charged while the other 4 were basically reading 0V (assuming it had to be near 0V to not register anything on the ZTS), the more I lean towards the possibility of some sort of improper short in the battery adapter that could have been caused by either a user error where the adapter contacts were configured incorrectly (possibly by the previous owner) or a scenario where the adapter itself developed a short without any user-caused input. 4 cell abreast battery adapter designs are pretty complex to begin with, and trying to design them to be completely impervious to potential shorting is often very difficult. I wouldn't rule anything out at this point... Even the possibility that those 4 "dead" cells got that way the first time around via an intermittent short of sorts, which caused the wear-and-tear to lead to the venting on the next cycle.

Through most of this thread, people were assuming that the cells used here were unprotected lithium cobalt cells (considered "unsafe" chemistry). The cells that vented here technically fall into the "safe chemistry" category of "unprotected" cells but this incident shows that even "safe chemistry" can still be dangerous under the right circumstances. Had the cells in this flashlight been regular lithium cobalt or lithium manganese DIOXIDE primary cells, the explosion would likely have been multitudes more intense with powerful flames and far more toxic (hydrofluoric acid in large quantity) off-gassing.

Interesting to see so many people responding with great "surprise" at the concept of something powered by 8 x 18650 cells. I would like to point out, that most of the modern li-ion battery packs in power tools have anywhere from 10 to 16 x 18650 or larger cells involved. Most laptops have anywhere from 6 to 12 x 18650 or similar size cells. The difference is that, in those applications, the cells are wired up to a multi-channel protection circuit that keeps everything relatively safe. Also, most of those applications are not in a sealed container. If the same configurations of cells as used in this monster flashlight had vented in a more normal application, the results would be considered rather non-eventful. (some smoke/fumes, maybe a few audible bursts etc).

-Eric

 

[ejot]

Interesting to see so many people responding with great "surprise" at the concept of something powered by 8 x 18650 cells. I would like to point out, that most of the modern li-ion battery packs in power tools have anywhere from 10 to 16 x 18650 or larger cells involved. Most laptops have anywhere from 6 to 12 x 18650 or similar size cells. The difference is that, in those applications, the cells are wired up to a multi-channel protection circuit that keeps everything relatively safe. Also, most of those applications are not in a sealed container. If the same configurations of cells as used in this monster flashlight had vented in a more normal application, the results would be considered rather non-eventful. (some smoke/fumes, maybe a few audible bursts etc).

A more extreme example in the same vein would be the Tesla Roadster battery pack which must have around 6-7 thousand 18650's.

 

[bstrickler]

I think I'm not going to buy anything that uses more than 4 li-ion cells now. Thats scary as hell what 8 of them did! I'm glad to hear that the parts of the light hit the driveway glass, instead of a person!

This makes me even more afraid of Sony cells, especially after that massive fiasco with their defective cells exploding in laptops several years ago.

I do know that this may not necessarily be Sony's fault, but I personally find it hard to believe that the cells weren't probably somewhat defective in the first place, with their track history.

I really need to earn some money, so I can dispose of all my Sony cells & replace them with AW. Too many horror stories of their cells, and that is why they are stored in the garage, in a gutted helium tank, and charged inside another one.

I am glad to hear that you are okay for the most part

~Brian

 

[LuxLuthor]

When these batteries fail by venting gas at a high rate, like an automotive air bag device does, the gas needs to get out quickly. The fix is to provide for a pressure release. The TK Monster and many many other light designs are pressure chambers, capable of holding back extreme forces and therefor the buildup of extreme potential energy before the vessel fails and releases said energy.

My TK Monster is going to be drilled through the end cap. I recommend you all do the same to yours. Simply fill the hole with silicon glue. I suspect that a 1/4 hole in the battery cap would suffice but only testing would tell for sure, I am not testing mine!

My attention was recently drawn back to this thread which dcaprilia generously and graciously shared with all of us. Three points I see to make again.

1) Dave, I do not believe that a 1/4" tailcap hole would give adequate gas volume relief in the event of a multi-cell short generated gas venting. I think a 1" hole at a minimum. However, in either case, I believe what you have done is created a (gas) pressure driven "rocket light," and woe is he who is on the opposite end.

An example is when people let scuba (or any compressed gas) tanks fall over, breaking the neck-valve as it strikes a hard object or wall. The tanks will easily go flying through many walls and/or travel a great distance.
​

2) There is a reason that all 18650 lithium cells of any chemistry are made into spot welded packs, balance tap leads & protection circuits affixed, protective shrink surrounded, & usually the completed pack enclosed inside of a hard (plastic) case that is either glued, or held together with security head screws. Some people take these packs apart and use the cells like they are playing with tinker toys.

If you are going to give up the built in safety mechanisms, then you need to take your own steps to make sure you have put those same safety protections back into effect, or don't use such cannibalized cells.

I have at least a dozen "Elephant" wide body lights, including several of Modamag's Colossus which are beautiful creations. The key is learning how to use them safely, but despite your best intentions, "sheet happens." :tinfoil: The only guarantee in life is that you will die one day.

3) The other point to keep making is that any battery chemistry that is made to short/reverse charge can abruptly vent inside of a closed flashlight tube and cause the same damage as seen this example. This includes NiMH & Alkaline primaries.

I again point to the fact that dcaprilia's image of the recovered cell (label intact) and light in this post indicates there was not a thermal runaway...so for now I still regard these cells in the "safe" (notice the quotes) category of Lithium Ions--relative to Lithium Cobalt.


​

 

[eugeniuszluzar]

Indeed any battery is capable of venting. Look at these pics of an A123 cell that exploded on a charger that was turned off.
http://www.rcgroups.com/forums/showthread.php?t=709190

NiMH explosion:
https://www.candlepowerforums.com/threads/239520

Have read tales of nicad as well and don't even have to talk about sla.

I guess the size of the explosion safety is of course proportionate to the amount of stored energy, but this could have quite possibly happened with a 2 cell light as easily as an 8 cell light. Determining the cause, or at least a good a guess as possible is fine, but there is no need to point fingers, be it at the manufacturer, the previous owner or the OP.

This is terrible. My colleague had a similar case. Battery exploded in a mobile phone (model iPhone 6). Fortunately he didn't hold the phone in his pocket. Batteries are not safe.Technology becomes ever more dangerous.

 

[more_vampires]

This is a necrothread, but anyway...

The TLDR: Op did not have a matched set of cells. 4 live, 4 dead = not a matched set. The 4 dead got "vent with flame"-y in a reverse charge scenario.

No short or other explaination is required, the answer was in the original post.

Not trying to Monday Morning Quarterback 5 years after the fact, but running those cells on a battery analyzer should have revealed that.

Matching a set and keeping it matched is the very hardest part about large multicell lion lights.

As a former hazmat responder, all I can say is "glad it didn't happen indoors." When you hear your light sizzling, hit the switch and throw it away from living things.

This scenario happened to CPFer Subalpine, as well.
http://www.candlepowerforums.com/vb...orce-Explosion&highlight=solarforce+explosion

Flashlight pressure rupture overview here:
http://www.candlepowerforums.com/vb...n-flash-lights&highlight=solarforce+explosion

Please note that "explosion" is the wrong word. We all slip up and use it, but it's like "clip vs magazine on a gun forum."

 

[FRITZHID]

Lol, there's a reason I don't series lithiums. Just to Damn risky, espc when crammed into a sealed metal tube! I'll go the lithium pack with internal c/dc balance board. Safer, reliable and simple. Have one in my maxabeam and my personal Handsun HID. Yes I could fill the lights with 18650 or some other format but I'd rather play it safe than sorry.

 

[WarRaven]

Protected in series, cuts down risk a lot.

This was what, eight unprotected and unverified with DMM?

Big mess though, I imagine CA are clean and all friendly like too. 😲

 

[Monocrom]

This is terrible. My colleague had a similar case. Battery exploded in a mobile phone (model iPhone 6). Fortunately he didn't hold the phone in his pocket. Batteries are not safe.Technology becomes ever more dangerous.

Most likely.... counterfeit battery inside your buddy's phone. It has happened before.

 

[more_vampires]

Protected in series, cuts down risk a lot.

This was what, eight unprotected and unverified with DMM?

Big mess though, I imagine CA are clean and all friendly like too. 

Lots of lights choke on protected cells, such as my Noctigon M43. Can't use protected, won't power on. You have no choice but to match and maintain a set of unprotected 18650x4. That's a parallel lights, btw. CPF seems to think it's a touch safer than 4 up in series.

 

[WarRaven]

Lots of lights choke on protected cells, such as my Noctigon M43. Can't use protected, won't power on. You have no choice but to match and maintain a set of unprotected 18650x4. That's a parallel lights, btw. CPF seems to think it's a touch safer than 4 up in series.

Yes true.
Though some can eek out enough to work smoothly.
My M3XS being one, but it's not a lumen king though.

I'm OK with that. ☺

 

[Mark Hubbard]

Dear Mr. Caprilia,

I know this happened back in 2010, but I just wanted to thank you for posting about the explosion, the way you did so without being defensive or angry, and for all the follow-up pictures and reports you offered, never blaming the seller or even the manufacturer for the tragedy. You are a true gentleman (which is rare in our litigious society), and you may have saved my life and my home from fire. I never knew about the problems with multiple lithium cells or their potential for catastrophic failure. I used to be a fireman and EMT (long before Lithium-ion cells existed), so I consider myself reasonably safety-conscious, but I definitely need to change my behavior when it comes to buying, charging and using rechargeable batteries. I am an idiot for trusting my life to a $15 charger and leaving it unattended on the carpeted floor under a cluttered desk for days at a time.

With gratitude and very best wishes,

Mark H.
Eureka, California

 

[JasonJ]

Dear Mr. Caprilia,

I know this happened back in 2010, but I just wanted to thank you for posting about the explosion, the way you did so without being defensive or angry, and for all the follow-up pictures and reports you offered, never blaming the seller or even the manufacturer for the tragedy. You are a true gentleman (which is rare in our litigious society), and you may have saved my life and my home from fire. I never knew about the problems with multiple lithium cells or their potential for catastrophic failure. I used to be a fireman and EMT (long before Lithium-ion cells existed), so I consider myself reasonably safety-conscious, but I definitely need to change my behavior when it comes to buying, charging and using rechargeable batteries. I am an idiot for trusting my life to a $15 charger and leaving it unattended on the carpeted floor under a cluttered desk for days at a time.

With gratitude and very best wishes,

Mark H.
Eureka, California

+1; a digital voltmeter in this case would have made all the difference in the world.

 

[dcaprilia]

Happy new year Gentlemen!

Thank you for the kind words Mark. Sorry I haven't been on in a while and I only saw this message now. If I helped avoid even one accident for a member or anyone else then this post would have been worth it.

Over the years Ive joined a many of forums. Most of which I would only be a member for a few weeks then move on. This is the only forum that I still come back to occasionally because most if not all members are good and decent people.

Wishing you all the best!
Derrick

 

[KuanR]

Good to hear from you Derrick, hope to see you post more pictures of your amazing lights. I used to look at your threads and the flashlight groupies thread when I first joined

 

[325addict]

I just read this thread again, after many years, and it made me aware of the dangers of unprotected cells. We have moved on a lot in protected cell technology in 2023, for instance, the "R series" from Keeppower are able to hold up a discharge current of 15 Amps of CONTINUOUS(!) current. I have multiple lights where multiple 18650s are in some kind of series and/or parallel connection, the most brutal one (Elephant II by FiveMega) uses no less than TWELVE 18650s in a 3S/4P configuration. I make sure to only use high quality, protected cells in these, which are measured with a DMM after charging and resting, to be fairly EXACTLY the same in voltage. I have a lot of Wolf Eyes 18650 / 3400mAh cells I can use for this purpose. These cells have a DOUBLE wrapper and a very robust protection circuit that's designed to trip repeatedly from overcharging (that's the way the Wolf-Eyes chargers work, yikes, not my kind of stuff, but knowing the cells can take that is very reassuring). And: I make sure not to draw insane currents - there's a WA1166 in my Elephant, drawing just 1.97A from all these cells. That's hardly 500mA per cell. They won't even get luke warm from this load... and I have 7 hours of run time!