Lipo fire

[Erfolg]

The debate needs to he more balanced than it has been to date.

I frankly feel there has been responded from a part of our community that has been less than controled and informative than I expect. Strong on what should be done, less strong on the bassis of the rational. Of course they could be right, although they cannot be certain, without understand ing both the science and the risks that follow from knowledge.

You are probably correct, a lot of the example's provided are illustrations of bad practice, or even irresponsible handling.

Then again the risks are there. I rember the period when Nicads were exploding almost every week, due to the wrong chargers or shorting. To me this illustrates the need for education based on fact, not supission. This could include charging bags etc

What is not needed is a safety initive based on prejudice, rather than facts and a proper assessment and understanding of the risk. Not some of the gut type reactions I have read from sources where I expect balance.

[Delta Foxtrot]

I can see the benefit potentially from a bag to contain a malfunctioning Lipo. I am not sure that a metal box and a Lipo are ideal. I can see the metal box potentially increasing the potential for increasing the risk.

My metal boxes are insulated on the inside by lining with depron or similar and are provided with vent holes. I do not see that this is in any way increasing the risk, but rather will limit the risk of a lipo fire spreading.

I don't think any one is claiming that lipos are unsafe unless they are damaged or improperly charged. I am sure that once these are correctly charged the risk of fires during storage are minute if nonexistent unless the cells get damaged. I certainly would not want to put any one off this great form of power for models, but it doesn't hurt to take a few precautions

[Erfolg]

David

I was certainly not specifically thinking about you. I was writing in a general sence.

The pont I am trying to make is that it is possible to increase the risk trying to do the right thing without real knowledge and understand ing the risks that come from the aforementioned.

I personally wouldn't advocate abuse. Although having from time to time witnessed practice's or actions which cause me to Blanche, Lipos are far more resilent than some suggest. Then again I personally would not advocate such actions.

If methanol or petrol were just new on the market I imagine that they would be subject to similar scare reaction and possiblely miss informed advice, all done with the best intention.

We really do need good sound advice based on science, not the best intentions and random observation, without understanding.

[Delta Foxtrot]

Erflog

no problem, I didn't take your comments personally, I just thought that it was worth mentioning that if ammo tins are used to stored batteries it is a good plan to insulate them.

i agree with you that actions based on a fundamental understanding of the physics and chemistry involved is the best approach. I would point newcomers to Andrew Gibbs guides on lipos and electric power as a good starting point.

cheers

dave

[Max50]

Have a look at " Batteries - a burning issue " in the latest BMFA News, page 49.

[Dave Miller]

Comparing Lipos with any other energy source is, I think, a waste of time. The simple facts are that they are inherently safe when used as recommended and charged in the correct way using the correct equipment. The relatively few problems that have been experienced with them result from the recommended procedures not having been followed, which includes using damaged cells.

[john stones 1 - Moderator]

agree with Dave

vast amounts being used, driving to field poses more danger

only thing i'd add is maybe carry a small extinguisher

[RichFR]

As said if ammo tins/fire safes are to be used I would put a lot of vent holes in them. The Lipo safe bag I have has vents at the top I feel comfortable keeping and carrying them in one.
You don't want to contain anything that may be explosive or vent gas.

Gun powders for example are fine stored in their plastic containers on a shelf but put them in a sealed metal box you have a bomb.

[Dave Miller]

Posted by john stones 1 on 19/01/2014 08:27:19:

agree with Dave

vast amounts being used, driving to field poses more danger

only thing i'd add is maybe carry a small extinguisher

But what sort of fire extinguisher would you carry? The only one that works as far as I know is sand.

[john stones 1 - Moderator]

for your car and models Dave

not going down road of extinguisher science

[Chuck Plains]

My Lipo storage.

2nd hand cash box from recycling centre plus a charging bag for each set of Lipos that I use regularly.

I leave the heavy box at home and transport the batteries in their respective bags to the flying site.

I do have one 2250 3s pack that got slightly mashed at one end after an, ahem, unexpected arrival. But it has shown no signs of retiring or firing. Yet.

[Dave Miller]

Posted by john stones 1 on 19/01/2014 10:24:46:

for your car and models Dave

not going down road of extinguisher science

Sorry, I though we were discussing Lipos. Good idea to carry one I think it's obligatory in most other countries.

[Capt Kremen]

Allied to our modelling concerns, anyone see that Japan Air are still having issues with their 'Dreamliner' fleet?

In the latest report, ('FlightAware', a Li battery 'discharged/vented' whilst engineers were servicing the a/c on the ground.

This after all the effort, monitoring and no doubt $$$$$s spent specifically on these items.

[Neil67]

Very interesting thread with lots of useful information, particularly around the issue of storing LiPos in steel containers and the need to vent any gasses should things go wrong. Being new to the electric flight I have stored my batteries in a steel box (well to be honest a quality street box - not great I agree) without insulation or vent holes, clearly something I will have to review. I also keep them in my garage which is underneath the main part of my house and can get relatively cold (down to a few degrees in the winter) as it is only heated if I am working in it. On a previous thread I was advised that batteries should be kept cold but brought up to room temperature prior to flying. Are there any risks associated with storage at very low temperatures in terms of battery deterioration and/or fire? Neil.

[john stones 1 - Moderator]

nothing to be sorry for Dave

I just agree with your comment , used correctly they are safe enough

loads are used at our club I've not seen one catch fire yet

most lads use lipo bags, charge out of model and don't leave em unattended

that does not seem too big a deal to me

[Simon Chaddock]

Nel67

The only real issue with temperature is the charge level. At low temperatures the maximum charge a LiPo can accept is reduced.

So fully charged warm (quite likely) they will be over charged at low temperatures and can be damaged.

At 'storage' charge level (about 40%) the normal range of temperatures will not cause a problem.

Also note that like most chemical batteries there performance is reduced if they are really cold.

[Erfolg]

Threads like this seem to cause me a lot anguish, having dreamt of lithium and my school days and chemistry class.

I seem to remember that lithium was one of those elements that we all played with in class, whilst investigating metals and other elements of the periodic table. Memory places it as part of the alkalide series of metals, very reactive, although looking up the series suggested that it is less reactive than other alkali metals.

I remember each member of class having a test tube with indivdual samples in test tubes, which were cut, put into flames etc. I am guessing that the lithium sample was stored in a small amount of oil to prevent it reacting with oxygen.

We really do need a chemist, as I suspect it needs oxygen to burn, either water, or some other source. If I am right a powder type extinguisher should do the trick.

But getting back to Simons point, the amount of lithium present in a Lipo is probably less than the sample we school kids played (ehm studied) with. If that is correct, the flame will be bright, but short on real energy. Certainly not the same as sodium metal, used in ton quantities in some nuclear reactors of the past.

I would also get back to the point that getting hold of anything really hot is not a good idea. I think the BMFA news item proves that. No one would be surprised if you got badly burnt if you grabbed hold of a burning can of methanol, or a red hot piece of steel.

I strongly believe that we do need a qualified experienced chemist to get a handle of the scale of the issue, what is actually happening, is it the lithium, the polymer wrapper or both that is the issue and how big an issue is it.

I feel that Lipos are an excellent source of electrical energy, pretty safe in most circumstances, as long as they are not abused. Can they be dangerous, well, yes, then again, so is methanol and petrol, particularly in the relative quantities typically used. I certainly do not see a doomsday weapon as some seem to which to paint Lipos.

We need facts, not scare stories.

Edited By Erfolg on 19/01/2014 15:30:05

[WolstonFlyer]

The Wikipedia entry for Lithium is very interesting, it has links to the different types of batteries **Link**

[John Privett]

I am not a chemist, though I do know that the Lithium in a LiPo battery is not in metallic form. So comparisons to the behaviour of metallic lithium are not necessarily valid.

Otherwise I think we'd be worried about pumping large quantities of a hydrogen compound through pipes into our homes. Or having a little container of sodium on our dinner tables and sprinkling it on our food...

[Erfolg]

I do take your general point John, and that is why we need a chemist, preferably with specific knowledge.

Some how though I do not expect that the lithium compound will be more reactive, or specifically more inclined to be more pyrophoric etc.

I do think we need to seriously consider Simons general point, the amount of Lithium present is extremely small, whatever the form. On that basis the energy release I would expect to be primarily of a electrical nature. I would be really surprised if lithium component of the fire was not either transient nature or low energy, sustaining a fire primarily of the other components.

I am not saying there is no fire risk, or a fire is trivial. I am querying where the latest assertion of "Lipo fires cannot be extinguished" comes from. To some extent, I am asking how great an inferno can you expect at the worst. Is a Lipo bag enough? I suspect if it is, perhaps the scale of the issue is overstated? I am asking for the scientific evidence. Not i know a friend etc. who may be in all innocence, reporting what they think or perceived was happening.

I guess what I really concerns me is advice on how to operate safely, based on, it seems to be a good idea, you can never be to safe etc. Our practises and guidance needs to be built on a sound understanding of all the issues. After all many hundreds of thousands of lipos and there derivatives are in regular use just in the UK, with no greater reported issues than many other artefacts we use.

[Peter Beeney]

I think that I’d consider any cell to be potentially dangerous, and that pun may be intentional, too! Generally they can release a lot of energy in a short time, and in the wrong circumstances this can have seriously unwanted effects. I know of one nickel receiver battery that could have easily burnt someone’s house down, and a very similar story was also related in the magazine some years ago. Likewise a very close call with the ubiquitous 7Ah monobloc SLA that inhabits many flight boxes; it was probably only due to the fact that the owner had a working smoke alarm and was on the spot at the time that a disaster was adverted. Over the years I suspect there have been many lead-acid cell/battery accidents, with many of them exploding and sending plastic/glass shrapnel and acid all over the place, especially where jump-starting cars are concerned. As always, though, most of this just goes unreported.

I’ve never seen a lipo burning so I’ve no experience of this, but it would appear from the evidence it is fairly dramatic and certainly some modellers have experienced this, for whatever reason. From the various reports it seems a lithium fire is very much self sustaining, and so cutting off it’s oxygen supply might not necessarily put it out.

One or two facts that I do know, however, having had some experience. Firstly the exploding nickel cells: I heard the stories, but I wasn’t really convinced, so I tried it. I actually found it quite difficult to do, but when I did succeed it just became the ultimate damp squib. The pressure built up relatively slowly inside and the the case spit open with a very subdued sigh. To be bomb like, I suspect you have to have a solid container, such as a fairly thick steel container, and a very rapid pressure build up inside. The cell has neither of these. The same thing happened to number that I tried. This was a long time ago, and probably not very important now anyway, but I’d consider it’s unlikely that any standard charger has enough poke to explode cells, the switching inverter is undoubtably a bit short in the grunt department. Also difficult to do on the discharge, I’ve seen them get hot enough to melt the heatshrink and burn it onto the cell, and I’ve personally burnt through the connections inside the cell, flying hotliners in the past, at discharge rates possibly in excess of 150C, but I’ve never seen one burst open.

More recently, in the lipo department, as I’ve related in other threads, we’ve successfully managed to force charge a few reluctant lipos into normal use, impossible to do with the standard charger. And relating to lipo overcharging I can say for certain sure that fairly recently a 3S 2.2Ah lipo was inadvertently charged to 14.7 volts, 2.1 volts over the upper limit. This was by accident and in the heat of the moment, of course, but it does amplify my first early thoughts about lipo charging, if you think you might get confused, use only a dedicated lipo charger for lipos, then there’s no chance of a mis-connection. By luck I happened to notice this, the battery seemed completely unfazed though, still stone cold and no signs of any swelling. I actually measured the voltage at 14.76V, then gently discharged to 12.6 and then down to 9. Still no adverse reaction, but it was also well over capacity, too, something that very sadly I omitted to make a note of. It’s now had a couple of cycles and still impeccably behaving itself, so the next trick is a gentle try in the air. It will interesting to compare how this behaves with it’s companions, in terms of longevity, it’s one of a gang of 9. So whilst this is definitely not any form of advice or instruction, do not try to replicate this, it does tend to suggest that not every lipo will instantly fail the moment the voltage goes over 4.2V/cell. If fact, it might even just tempt me into copping a couple of new packs and just experimenting ‘outside the box’ as it were. All entirely at my own risk, of course.

When they first stated tinkering with lithium cells it proved too dangerous, they just went on fire; but a change to lithium-ions, a funny sort lithium atom, I believe, improved things no end, and so we’ve got to where we are now. I did read once about the world’s demand for lithium, mostly for batteries, it’s going exponential, this must now therefore translate into many billions of cells, so overall, provided the operator can’t get at them to cock it all up, they must be considered to be pretty safe. Unless you own a Dreamliner, that is…

I personally treat lipos exactly as the lads do at the patch, similar to any other battery. With respect, of course, all cells can bite back without warning, but with no specialty precautions. If I thought they were likely to start going on fire without warning I wouldn’t use them, the risk would be too great. They certainly seem to come in a variety of standards of quality, from rubbish to excellent, for a start, but most seem pretty much up to scratch. So I reckon that the trick might be to use them fairly carefully but without to much in the way of nervous apprehension, and then make up your own mind on their strengths and weaknesses.

From the reports it seems that damaged cells can be vulnerable, and the resultant fire pretty spectacular, so I’m sure the ‘fierce fire’ stories are pretty kosher. Touch wood, so far we’ve not had any damaged batteries to have a little dabble with, but that might change any minute…

PB

Edited By Peter Beeney on 19/01/2014 22:59:39

[WolstonFlyer]

Just have a search on YouTube for 'Lipo fire', there are lots of examples to keep you scared or entertained.

Here is an example of one being deliberately over charged, it is quite spectacular

Edited By Pete B - Moderator on 19/01/2014 23:54:46

[Simon Chaddock]

It would appear than AA 'Lithium' batteries (non rechargeable) do contain a quantity of Lithium metal as this video shows.

If you could one of those to 'blow' you could end up with a true Lithium fire.

Edited By Simon Chaddock on 19/01/2014 23:20:27

[Erfolg]

Again Simon the video and what was seen needs placing into context.

It was interesting to see, perhaps some will be reminded, how quickly Lithium oxidises.

The second aspect is the shear mass of lithium that was present, many orders of magnitude greater than a Lipo, additionally significantly greater than school children get to characterise.

The second was how much energy was used to initiate the combustion process. I think we need again to consider how this relates to the real world. Most people are familiar with magnesium, and its reputation to catch fire and the hazard a fire produces. Yet in the 60s, magnesium was a relatively common material, used for VW gearbox casings, aircraft components, some car alloy wheels and also in industry. Todays generalist H&S gurus will now be saying totally irresponsible. Yet machining is not an issue, as long as fines and rubbing are not permitted and that the appropriate fire extinguisher is available, which again from memory was a powder type. It is a similar situation with metals in general, finely divided they can produce a fine, flaming display, iron fillings. Aluminium has been used as a fuel for large solid fuel rockets.

It is with these facts and others, in mind, that a balanced assessment, as to the true risks from Lipos should be discussed. There is far to much of this is what you should do, without the why, and the quantitive basis of this advice. There also appears to be the suggestion of outcomes, which could be a fact or based on supposition.

I do keep returning to my school days and can only assume that in the intervening years, that many less youths undertake chemistry. Not being familiar with for example alkali metals , cutting the material, noting what happens (seem to remember cuts very bright and shinny, rapidly dulling), setting the sample alight with a Bunsen burner. Attempts to make our own gunpowder, which was not part of the studies.

I accept there are some safety issues with Lipos. I can see the benefit of using a suitable bag. Is that enough. Is it necessary to charge outdoors?

But then again so many other batteries are potentially more hazardous if abused. Sometimes I get the impression some are trying to make a rod for our own backs, for no good reason.

If I were to suggest that methanol can cause blindness if ingested, that a methanol (pure) fire is very serious as it burns with no apparent flame, that it is potentially extremely explosive if in a confined space, with oxygen etc. I can imagine the response. All are true, but if placed in context, do they represent the situation as typically applied to modellers ?

[Chuck Plains]

Off topic. Magnesium. As always, the first thing that comes to my mind is the beautiful Bugatti Atlantic Aerolithe prototype and their GP cars of the 1930s with magnesium alloy bodies.