cautionary tale Lipo fire

[fidspeed]

Thanks for all the input fellas

i guess what we are learning from this is we all need to be a bit less complacent than we have been and maybe take a few more precautions

lipo accidents are maybe a bit more frequent than we thought and "airing" them here should help awareness

We dont need a debate on lipos/sack/bunkers/pouches and their various merits and shortcomings .

lets just be a bit more vigilant even watching our "pit neighbours "lipo charging while we happen to be racing or marshalling

regards dave

[SlowOne]

Originally Posted by Chris56

I have looked at them.

Slowone - for the record I am not advocating throwing the sack, just highlighting what somebody did when they saw the flames.

Sorry - it's always difficult to interpret what people say on a post! Yes, best advice is don't do that!

Originally Posted by Origineelreclamebord

Anyway, what's important to know is that water won't extinguish the fire (and may in fact fuel a stronger reaction), smothering helps but may not instantly stop the fire (because of oxides in the battery), and lowering the temperature will decrease the speed of the reaction. And of course lastly, if you can contain the fire inside something (an ammo box, safe or something else), you can give yourself time to get away or cool the container (to try and reduce the severity of the reaction).

The only extinguisher that will work on a LiPo fire is a copper powder one, but these are as rare as hens teeth. Excluding the oxygen is the key, and containing the shower of hot ashes. That is why sand is your friend.

Originally Posted by /tobys

So, whats the consensus on how to store Lipos? The realization that they can, in rare and unfortunate circumstances, spontaneously combust is enough for me to reconsider my current storage and handling.

Airtight, metal container for storage?
Where does this get stored, as we are told that they shouldn't be anywhere too cold (which rules out storing outside)?
Lipo pouch whenever connected to charger as a common sense approach to safety, rather than just to appease the race director (!)
Correct/Safest way to dispose of old lipos?
etc
etc

I think there is lots of good info/advice to be shared/discussed.

My suggestion would be to put the LiPos in a metal container, preferably steel, with vents to let the gases out so the lid doesn't come off as the gasses from the LiPo expand. If you are concerned about having that resting on a non-concrete floor, then put the container onto a large ceramic tile. Ceramic is a great insulator. HTH

(Also, check your charger. When disconnected and re-connected, does it default to the same charge settings you used last time? Some don't! Try every way of inadvertently disconnecting your charger, and then reconnect it and check the settings. If it doesn't go back to your usual LiPo settings, stick a big note on it saying CHECK SETTINGS to remind you.)

[andrewc]

My RC stuff currently lives in my garage; is there a recommended temp range for storage?

I never leave mine unattended when charging or discharging, but am a little surprised to hear one has burst just sitting in storage.

Am I correct that a FIRE can only occur during charge or discharge?

[Mike Haswell]

Originally Posted by andrewc

Am I correct that a FIRE can only occur during charge or discharge?

You would be incorrect on that - just because you aren't charging or discharging doesn't mean there isn't anything going on. A recent case at the Snowbirds saw a pack go up even though it had finished its discharge - was still hooked up to the charger though. Temperature fluctuations can make things happen too. I had a pack which had a slight bit of swelling and then one warm day I found that it had swelled further and popped the cause whilst not in use!

When we first started using lipos I read up on a few cases of lipo fires and one involved a bloke's plane going up in flames in his garage overnight. What they reckoned happened in that case was that the temperature had dropped overnight and that some condensation had caused the pack to short out.

[dale]

Originally Posted by andrewc

My RC stuff currently lives in my garage; is there a recommended temp range for storage?

I never leave mine unattended when charging or discharging, but am a little surprised to hear one has burst just sitting in storage.

Am I correct that a FIRE can only occur during charge or discharge?

Lipos don't like to be too hot or too cold, so the garage is pretty bad due to the temperature extremes and fluctuations. As Mike notes above a change in temperature can cause issues.

In the house in an ammo box is a safe storage solution while keeping the temperature stable.

[SlowOne]

Originally Posted by andrewc

My RC stuff currently lives in my garage; is there a recommended temp range for storage?

I never leave mine unattended when charging or discharging, but am a little surprised to hear one has burst just sitting in storage.

Am I correct that a FIRE can only occur during charge or discharge?

A fire is the unavoidable outcome of the pack fault allowing anode and cathode to touch each other creating a short circuit. It is more vigorous the higher the charge in the cell, but it is not something limited to it being on charge or discharge.

Above a range of 70°C to 90°C the Li-ion graphite anodes will start to self-heat. At about 130°C the separators will start to melt at which point the positive and negative electrodes will touch causing a short circuit. Now the temperature rises very quickly, the heat cannot be dissipated and the positive electrode burns releasing more oxygen that feeds the fire that results.

For fully charged cells, these temperatures can reach in excess of 600°C (1,110°F); case temperatures for lithium-iron phosphate cells are generally lower. The temperature rise is driven by reactions of the electrodes with electrolyte and release of stored energy.

Depending upon the environment around the cell, the cell vent gases may ignite. The gases are not “self-igniting.” There must be sufficient oxygen in the surrounding environment to sustain combustion of hydrocarbons and there must be a competent ignition source to ignite the vent gases. A burning cell would be a good ignition source.

The issue is that once something goes seriously wrong, the inevitable result is a thermal runaway. Cell puffing is also a cell failure, but it is non-energetic - nothing happens catastrophically.

I hope some information makes people more aware. This is not intended to scare anyone, just make people aware of the situation so they can take whatever action they need to for the risks they want to avoid. Judging by the posts above, peeps are aware and take steps to avoid risk. HTH

[maineyak]

Worrying about my lipo pack sat in me transmitter now.....

[beale]

You would be very unlucky if you had a problem at those levels of discharge, do you remove it to charge? And between events? I have had a lipo puff from being left fully charged for 2 weeks due to a DNF, that's when I started storing them storage charged in a lipo sack.
After reading this thread have bought a steel electrical cabinet as a home charge/storage bunker

[suparajicon]

Originally Posted by Neil Skull

Thanks for sharing Fidspeed,
I hope anyone thinking of leaving their lipo unattended will think twice!!
I don't leave any phone or laptop or anything on charge unsupervised! I wont even leave my phone on charge overnight! Thats wheter lipo or not! its just not worth the risk.

I agree with you.

[Danny]

Useful to be reminded that Lipos need a fairly large amount of respect with the way they are charged and stored. Someones already asked what the charger was and id be interested to know more bout the routines of these failed Lipos, like what kind of amps/C were they being charged at usually? What % was left in them during storage? And what approximate temperature were they stored at and for how long?

[beale]

Just been looking at the specs of the elangears Elan R used in the EOS pic, it isn't capable of rates I would of expected problems, but a highly discharged race cell then instantly put on a 15A charge could be.
Obviously there is component failure, poor connections ect to add as possible causes

[SlowOne]

Originally Posted by Danny

Useful to be reminded that Lipos need a fairly large amount of respect with the way they are charged and stored. Someones already asked what the charger was and id be interested to know more bout the routines of these failed Lipos, like what kind of amps/C were they being charged at usually? What % was left in them during storage? And what approximate temperature were they stored at and for how long?

In the two LiPo fires I have sat next to the charge rates were close to 1C. The issue with chargers is that some may default to an NiMh program when switched off, or disconnected inadvertently (power loss, fuse blown, etc.)

The temperature and storage state are not relevant to the issues. It is what has happened inside the cell that allows the anode and cathode the touch and short out. This can be caused by the growth of crystals known as dendrites. This is most common if a deep discharge happens, but age also comes into it. Dendrites are hard metal crystals that bridge the anode and cathode causing a short.

The most common fault is that during manufacturing the chemical parts of the manufacture are not easy to control. For any number of reasons there can be a fault inherent to the cell and there is nothing you can do about it. once the separators (about 70 microns thick, or half the thickness of a human hair) are hot and start to melt, there is nothing you can do to stop the inevitable.

In any given week over 1000 people are racing LiPo in the UK - it is probably five times that across the world? They charge their cells four times, say. That's 20,000 charges a week, over a million a year. I think I may be conservative on that, but if it's about right then we have maybe five or seven incidents factually recorded over three years - or about a one in 400,000 chance it might be you. I suspect the odds are longer than that.

Sensible precautions are the order of the day. Trying to find the exact conditions that lead to a failure is futile - the source of the faults that lead to catastrophic failure are seeded in the manufacturing process and you have no idea if they are there or not.

1C charge and discharge, store between 5C and 30C in a sack and/or metal container (steel is best) at the recommended storage charge - good advice to follow. HTH

[Danny]

Epic post SlowOne, cheers for clearing that one up!