Author Topic: Deliberate Lithium cell overcharging  (Read 7645 times)

0 Members and 1 Guest are viewing this topic.

Offline ThinkingGrenadeTopic starter

  • Newbie
  • Posts: 5
  • Country: gb
Deliberate Lithium cell overcharging
« on: May 10, 2019, 05:12:11 pm »
I need to produce a overcharge condition in some typical 18650 cells (and large Lipo's) for training with our local fire and rescue service. i can pop 1 or 2 18650's with my bench power supply, but i need to do it with 8/10 (or more) cells at the same time. 

- a quick background - I live on the Isle of Man, every year the TT races are held here (google it) and for the last few we have had a race dedicated to Electric bikes (they aint slow) - some of which use a huge bank of 18650's. there was a fire last year that involved one of these packs, and the Fire service want to do some training with some new fire fighting mediums, specifically designed for battery fires

 

 I work for a company that provides fire equipment and i know how to make most things go boom, but im asking you guys, as my experience is limited with this kind of thing......
« Last Edit: May 10, 2019, 08:56:16 pm by ThinkingGrenade »
 

Online NiHaoMike

  • Super Contributor
  • ***
  • Posts: 9320
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
Re: Deliberate Lithium cell overcharging
« Reply #1 on: May 10, 2019, 05:48:16 pm »
Connect them all in parallel with a welder. Shouldn't take too long to get some flames.
Cryptocurrency has taught me to love math and at the same time be baffled by it.

Cryptocurrency lesson 0: Altcoins and Bitcoin are not the same thing.
 

Offline AG6QR

  • Frequent Contributor
  • **
  • Posts: 866
  • Country: us
    • AG6QR Blog
Re: Deliberate Lithium cell overcharging
« Reply #2 on: May 10, 2019, 05:49:57 pm »
It's not my area of expertise, but it sure sounds like fun!

My naive approach would be to first charge them fully with a proper charger to fill them with as much energy as practical.  Then, put three in series, and put them on a big charger intended for car batteries.  If you want to make more go off, wire up multiple parallel combinations of three in series.

Of course take appropriate safety precautions by keeping them far from humans and far from combustibles.

And have the cameras running!
 

Offline MagicSmoker

  • Super Contributor
  • ***
  • Posts: 1408
  • Country: us
Re: Deliberate Lithium cell overcharging
« Reply #3 on: May 10, 2019, 06:08:32 pm »
Overdischarge until at least one cell experiences voltage reversal reliably damages all lithium chemistries, but the real fireworks mainly occur during subsequent charging, particularly at currents >1C (e.g. - >4A for a 4Ah cell). However, the LiFePO4 is particularly tolerant of abuse and can take 4C charging in stride so wouldn't be the best choice if you actually want something bad to happen. Any of the Cobalt-containing chemistries should give you the kind of surprise you're looking for, but do make sure you have a blast shield of some sort if using 18650 or larger cells.

 

Offline KC0PPH

  • Supporter
  • ****
  • Posts: 117
  • Country: us
Re: Deliberate Lithium cell overcharging
« Reply #4 on: May 10, 2019, 06:13:33 pm »
Go buy an EDF RC airplane that runs off of 6S batteries. Fly the piss out of it for a few days fast charging each time, they should start puffing up pretty quickly (keep throttle wide open). Once they are puffed nicely then put them on a bench supply and charge with as fast of current as you can give em. They will make a spectacular show.

Batteries that are new tend to not be as entertaining to blow up, however well used ones with high IR tend to be exciting.
 

Offline Berni

  • Super Contributor
  • ***
  • Posts: 5050
  • Country: si
Re: Deliberate Lithium cell overcharging
« Reply #5 on: May 10, 2019, 06:14:22 pm »
Yep stick it across a big DC welder and off it goes

It's not even nececerry to overcharge the whole pack. These big battery pack fires are often started by a few bad cells. Once it starts going the batteries produce enough heat to cause the ones around it to explode and kick off a chain reaction that sets the whole pack on fire.

Another way to make them explode is to simply hammer a nail into the side of a cell.

But do take care because these cells can explode violently enough to launch them pretty far. Wouldn't want one flying off out of the training zone and setting something else on fire.Id say a 20m safety radius around the battery is a minimum.
 

Offline ThinkingGrenadeTopic starter

  • Newbie
  • Posts: 5
  • Country: gb
Re: Deliberate Lithium cell overcharging
« Reply #6 on: May 10, 2019, 08:37:28 pm »
Cheers folks.


It's not even nececerry to overcharge the whole pack. These big battery pack fires are often started by a few bad cells. Once it starts going the batteries produce enough heat to cause the ones around it to explode and kick off a chain reaction that sets the whole pack on fire.

Another way to make them explode is to simply hammer a nail into the side of a cell.

But do take care because these cells can explode violently enough to launch them pretty far. Wouldn't want one flying off out of the training zone and setting something else on fire.Id say a 20m safety radius around the battery is a minimum.

the few cells in the middle was the approach i was going to use, the hammer is the tertiary back up plan after the secondary blowtorch on a stick.

all this is going to be done at an actual fire training facility, with guys in full kit. ill be wearing a polo shirt/high vis vest and squinting heavily.  i have had experience with explodinating 7 and 8 cell lipo's and a few 18650/20700's  so i personally know how violent they can be

welder accross the pack seems to be the way to do it.  my next thought would be to use a couple of 12v car batteries.

Overdischarge until at least one cell experiences voltage reversal reliably damages all lithium chemistries, but the real fireworks mainly occur during subsequent charging, particularly at currents >1C (e.g. - >4A for a 4Ah cell). However, the LiFePO4 is particularly tolerant of abuse and can take 4C charging in stride so wouldn't be the best choice if you actually want something bad to happen. Any of the Cobalt-containing chemistries should give you the kind of surprise you're looking for, but do make sure you have a blast shield of some sort if using 18650 or larger cells.


 overdischarge might also be the way to go. i can easily achieve that too.  im gonna have a test and just short them to see how well it works.

I promise to film as much as i can of this BTW.
 

Offline MosherIV

  • Super Contributor
  • ***
  • Posts: 1530
  • Country: gb
Re: Deliberate Lithium cell overcharging
« Reply #7 on: May 10, 2019, 10:50:45 pm »
Hi

I work for a company designing and building lion packs for automotive.

One of the tests that must be done is to test what hapoens if one cell gasses and ignites.
To force a cell to ignite I was told that you just heat it gently.
It will eventually gas and ignite.

Hope that helps.
 
The following users thanked this post: ThinkingGrenade

Offline amyk

  • Super Contributor
  • ***
  • Posts: 8526
Re: Deliberate Lithium cell overcharging
« Reply #8 on: May 10, 2019, 11:42:44 pm »
How about a simpler option: straight across the mains.

18650s, especially the newer ones, are surprisingly tame when only "moderately" overcharged, since the safety standards require them to pass such tests:
Quote
9.1 Overcharge test
Test method: To charge with 20A-20V at 25℃ for 3hr.
Criteria: No fire, and no explosion.
9.2 External short-circuit test
Test method: To short-circuit the standard charged cell (or 50% discharged cell)
by connecting positive and negative terminal by 80mΩ wire for 10min.
Criteria: No fire, and no explosion.
Test method: To charge the standard charged cell with charge current 10A
By 0V for 2.5 hours.
Criteria: No fire, and no explosion.
Test method: To heat up the standard charged cell at heating rate 5℃ per minute up to
130℃ and keep the cell in oven for 10 minutes.
Criteria: No fire, and no explosion.
(From http://dalincom.ru/datasheet/SAMSUNG%20INR18650-25R.pdf )

You may get better "bang for your buck" with pouch cells, or if you insist on 18650, the cheapest ones from Aliexpress with "fire" in their name...
 

Offline Rerouter

  • Super Contributor
  • ***
  • Posts: 4705
  • Country: au
  • Question Everything... Except This Statement
Re: Deliberate Lithium cell overcharging
« Reply #9 on: May 11, 2019, 01:44:08 am »
If you want a proper hard to control fire, its either going to be a hard short with a non-tolerant chemistry, or for maximum effect excessive overcurrent to a higher voltage,

LiFe is too stable and wont be used in applications where every bit of power to weight matters, Li-Ion / Li-Poly (same thing in effect) will be used, but the li-poly pouches rarely have the over pressure disconnect that the 18650 cells have. If you do want to fail 18650's you need to heat them up to a destructive temperature before the gas pressure can build up, so the reaction continues

So take say an unprotected 3S pack with as many in parallel as you like, and hook it in parrellel to a truck battery with some jumper leads (truck side last to give you room to run), it should flame up in the next few minutes.
 

Offline 3roomlab

  • Frequent Contributor
  • **
  • Posts: 850
  • Country: 00
Re: Deliberate Lithium cell overcharging
« Reply #10 on: May 11, 2019, 01:58:30 am »
I happen to have read this
this DoD experiment, they made a fake cell which is a control cell with a heater inside used to heat a group of cells
maybe in your case, overheat to ignition. and it maynot even need to be a cell, just a heater
https://digitalcommons.unl.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1105&context=usnavyresearch

Novel 18650 lithium-ion battery surrogate cell design with anisot.pdf
(over 2mb doesnt upload in post)
 

Offline Siwastaja

  • Super Contributor
  • ***
  • Posts: 9327
  • Country: fi
Re: Deliberate Lithium cell overcharging
« Reply #11 on: May 11, 2019, 02:21:25 pm »
Proper 18650's tend to be fairly well protected with integrated PTC and CID devices. For demonstration, I have tried:
* Dead-shorting 18650's,
* Charging 18650 cells from a 30V, 10A lab supply, for hours -

and haven't been able to cause fire, explosion, smoke, or significant venting of electrolyte. Sony cell on a 30V,10A supply worked as a hysteretic PTC thermostat controlled heater, stabilized at around 100 degC IIRC.

Manufacturers often specify such test cases and guarantee* no fire. (* or, at least, that "no fire" is a typical result.)

For reliable demonstration, I'd suggest sourcing some low-quality cells (think about UltraFire etc. brands), and testing thoroughly before the big day.

Physical nail penetration might be the best, if it needs to demonstrate a typical cause. Otherwise, +1 for the in-battery cartridge heater! PTCs, CIDs etc. can protect against internal heat generation over the thermal runaway onset temperature, but using an external source, there's no limit. You should see things start going after your cells reach about 160 degC. (For LFP, that would be higher.)

If it needs to be external and electrical, long-term overcharging (or forcing negative voltage) would have best chances. Shorting a cell is almost a guaranteed demonstration failure - only the very crappiest cells would cause a fire during an external short.

Or, ramp up the voltage enough to arc through the PTC, CID and even the shutdown separator - a few hundred volts, maybe?

It sucks trying to demonstrate a li-ion fire. The chemistry itself is volatile, but they have significant load of safety features; they need to have, many BMS ICs on the market have a long tradition of having some dangerous failure modes, so the cell manufacturers have learned their lessons, their safety process is not completely relying on the pack designer staying within ratings. Yet, abusing a cell definitely increases the fire risk (which is why we do see fires related to, for example, overcharging after the management system failed), but not enough to provide a robust way to produce demonstrations easily (unless you are able to source a consistently very crappy cell).
« Last Edit: May 11, 2019, 02:30:56 pm by Siwastaja »
 

Offline Rerouter

  • Super Contributor
  • ***
  • Posts: 4705
  • Country: au
  • Question Everything... Except This Statement
Re: Deliberate Lithium cell overcharging
« Reply #12 on: May 11, 2019, 02:28:48 pm »
the 10A limit on your supply would probably be the limiting factor, you need to heat the contents to about 150C to cause the reaction to begin, I suppose for fire fighting test you could just use some nichrome wire to heat them up to this situation.
 

Offline Yansi

  • Super Contributor
  • ***
  • Posts: 3930
  • Country: 00
  • STM32, STM8, AVR, 8051
Re: Deliberate Lithium cell overcharging
« Reply #13 on: May 11, 2019, 02:29:52 pm »
To fight lithium battery fires - use water. A LOT OF IT.  The important thing is to cool them off as much as possible.
 

Offline Siwastaja

  • Super Contributor
  • ***
  • Posts: 9327
  • Country: fi
Re: Deliberate Lithium cell overcharging
« Reply #14 on: May 11, 2019, 02:35:13 pm »
the 10A limit on your supply would probably be the limiting factor, you need to heat the contents to about 150C to cause the reaction to begin, I suppose for fire fighting test you could just use some nichrome wire to heat them up to this situation.

Well, I have tested direct connection to a 12V lead acid battery as well. The result was similar to dead-shorting the cell itself - with little current limiting resistance, resulting in massive currents (>> 100A), almost no heating happens, as the PTC just reacts so quickly. In the end, less damaging charge (I*t) might go through the cell, compared to the current-limited lab supply test case.

I do agree that very large currents could cause localized heating within that short time, which could trigger thermal runaway, but I haven't been able to demonstrate that on brand cells, very likely because they use shutdown separators, melting and stopping ion transfer at the local hotspot before it can spread.

For any particular cell, either a very high current, or a more modest overcurrent, might do the trick, but the chances are that neither will.

External heating is indeed the only reliable way to start the thermal runaway.
« Last Edit: May 11, 2019, 02:39:37 pm by Siwastaja »
 

Offline Rerouter

  • Super Contributor
  • ***
  • Posts: 4705
  • Country: au
  • Question Everything... Except This Statement
Re: Deliberate Lithium cell overcharging
« Reply #15 on: May 11, 2019, 02:44:26 pm »
also to keep the water flowing well after the main event has settled down (can be low flow rate, water is very efficient at soaking up heat, and if its slow you may be able to see the steam if its about to reflare), when the batteries burst in to flame, generally there internal structure has been damaged enough to short out, so you initially extinguish the light show by cooling it down, but you need to maintain that cooling until every part of the pack is discharged,

Once the fire is out, you want to remove it from the vehicle, and Ideally leave it in a puddle of fresh water or similar to make sure its cold, you ideally would also want something like jumper leads with a bulb to discharge the pack reasonably slowly, When the battery is at 0V on all cells, then and only then can you turn your back on it and call it safe.

In a pinch Co2 extinguishers can chill packs quite quickly (dropping pressure on a gas causes a sub ambient cooling effect) however this is more for gaining time if your waiting on the water sources to come out.

the main thing I would say to avoid at all costs is ABE/ABC style extinguishers, the active components are salts, so if you combine that with a recently hosed down wet pack you end up with pockets of highly corrosive brine which will happily eat through most battery casings over a few weeks / months, possibly causing later issues if not all of the pack was drained.
 

Offline Yansi

  • Super Contributor
  • ***
  • Posts: 3930
  • Country: 00
  • STM32, STM8, AVR, 8051
Re: Deliberate Lithium cell overcharging
« Reply #16 on: May 11, 2019, 05:37:23 pm »
In a pinch Co2 extinguishers can chill packs quite quickly (dropping pressure on a gas causes a sub ambient cooling effect) however this is more for gaining time if your waiting on the water sources to come out.

In my personal experience, from an environment where rather large 5+ kWh packs were built, CO2 extinguishers are of not much use. Maybe only for small packs, but their cooling effect is very subtle and short-durating, compared to a full bucket of water.

DO NOT rely on CO2 extinguishers when handling large battery assemblies!
 

Offline amyk

  • Super Contributor
  • ***
  • Posts: 8526
Re: Deliberate Lithium cell overcharging
« Reply #17 on: May 11, 2019, 06:54:21 pm »
Physical nail penetration might be the best, if it needs to demonstrate a typical cause.
Even then, you might not get a fire. I can't find it now but there's a video on YouTube of someone driving a nail through a fully-charged 18650, and all it did was bubble electrolyte out, melt the wrapper, and then cool down boringly. I guess you need temperatures high enough to ignite the electrolyte in order to get anything more interesting to happen.
 

Offline ogden

  • Super Contributor
  • ***
  • Posts: 3731
  • Country: lv
Re: Deliberate Lithium cell overcharging
« Reply #18 on: May 11, 2019, 07:08:01 pm »
Better train your firefighters properly. Internet search gave many hits regarding EV fire training. Just one:

https://www.nfpa.org/Training-and-Events/By-topic/Alternative-Fuel-Vehicle-Safety-Training
 

Offline Marco

  • Super Contributor
  • ***
  • Posts: 7043
  • Country: nl
Re: Deliberate Lithium cell overcharging
« Reply #19 on: May 11, 2019, 07:19:22 pm »
I don't see how reproducing the exact way it catches fire is important for extinguishing it, as long as it only burns on its own accord when you start.

Wrap a cell in some magnesium ribbon to kick off the festivities?
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: Deliberate Lithium cell overcharging
« Reply #20 on: May 11, 2019, 08:05:22 pm »
There's no need to abuse the cells prior, lithium battery fires occur when cells are overcharged, or when they short circuit internally which is also what happens when they are overcharged. Worn out or abused packs tend to be more vulnerable because they can get out of balance but it's the overcharging that makes them burn.

That said, I don't really see what the point is here. The best way to fight a lithium battery fire is plain old fashioned water and lots of it. Take away the heat and the fire goes out.
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 20357
  • Country: gb
  • 0999
Re: Deliberate Lithium cell overcharging
« Reply #21 on: May 11, 2019, 08:05:41 pm »
Be careful. Lithium batteries are highly explosive. Photonicinduction did a couple of videos of them being abused.

Poking one with a skewer causes an explostion.


Fast forward to 6:00 for the lithium part. A small cell burns quite well when connected to AC.
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: Deliberate Lithium cell overcharging
« Reply #22 on: May 11, 2019, 09:32:44 pm »
They are not "highly explosive", or even moderately explosive, they contain flammable materials and a lot of stored energy so they can burn vigorously. That is not an explosion, it is a fire.

High explosives are things like nitroglycerine, dynamite, TNT, RDX, etc. No lithium battery behaves anything like this.
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 20357
  • Country: gb
  • 0999
Re: Deliberate Lithium cell overcharging
« Reply #23 on: May 11, 2019, 09:53:37 pm »
They are not "highly explosive", or even moderately explosive, they contain flammable materials and a lot of stored energy so they can burn vigorously. That is not an explosion, it is a fire.

High explosives are things like nitroglycerine, dynamite, TNT, RDX, etc. No lithium battery behaves anything like this.
The first video certainly does look like an explosion, rather than a fire, as there are no flames.

Where it actually is an explosion or not, the effect is the same: a big bang, along with lots of heat is produced.
 

Offline amyk

  • Super Contributor
  • ***
  • Posts: 8526
Re: Deliberate Lithium cell overcharging
« Reply #24 on: May 12, 2019, 12:01:44 am »
That was definitely not an explosion, there wasn't even a "big bang". If it was an explosion there would be a shockwave and shrapnel everywhere.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf