Lipo fire

[Chris Bott - Moderator]

I for one ALWAYS connect the balance lead when charging. There's a number of reasons:-

1) It's so easy - why not?
2) The "It's not a problem because it's never happened to me" arguments cut no ice at all. There's always a first time.
3) Because I balance charge every time, I never have any problems with longer charge times. If you do, it's very likely because your packs are going out of balance.
4) Connecting the balance lead gives the charger a chance to do an extra check that you've set it correctly. More than once I've perhaps been distracted slightly and have been "saved" by the charger.
5) See number 1 above!

[Bob Burton]

Pete - that manual is much more explicit than mine. Out of interest I have emailed the manufacturer of my charger with sparse information previously quoted (Overlander) asking for clarification.

I have long suspected that the firmware used in most '4 button' chargers is the same apart from the message shown on startup which would be easy to change. If this is not the case then several manufacturers have decided to use exactly the same menu structure and keypresses to access functions which seems unlikely in the extreme.

The only exception seems to be some chargers which are able to provide details of internal resistance of the Lipo. These must have different firmware and/or hardware in order to provide the functionality.

[Erfolg]

Has anyone else read Sturt's link?

I do think that it is worth the effort. Particularly for those who advice on lipo safety.

At first sight it may seem that there is cause for concern. Consideration of what is written in contect is different. I am not sure it supports those who argue that a lipo fire cannot be extinguished is supported. Nor that any significant amount of oxygen is generated. There is much, much more, such as gasses generated.

This source is much more convincing than say a uni safety doc. In that is original source document, not something put together as a general procedure for lavatory work, drawing on general saurses in compilation, for general labatory working.

I will be reading it again, as there is a lot to digest.k

[John Privett]

Posted by Erfolg on 23/01/2014 21:16:53:

This source is much more convincing than say a uni safety doc. In that is original source document, not something put together as a general procedure for lavatory work, drawing on ..

I'm not sure that's quite what you meant to type!

[Stuart C]

Two short videos of interest

Japanese Lipo manufacture www.teamorion.com/videos-en.html

Chinese Lipo manufacture www.haiyinstore.com/showvideo.asp

Both seem to use manual terminal soldering (not impressed by the condition of the chinese soldering iron).

"Weld spatter" (uk-solder spatter) on terminal connections is highlighted in the NFPA report as being one of the likely causes of contamination leading to early failure and possible consequential fire risk. Food for thought?

[Erfolg]

John

The problem seems to be a combination of three factors, the first is dumpy finger syndrome, the second is predictive text, the third seems to be an auto correction.

I am certainly not up to speed with Android and my tablet.

I also find that the tablet, although faster than using the PC, is showing even less on the screen, which I find is less conducive to reading, before posting.

Wow, that is my best excuse to date!

[Erfolg]

I am unable to view the second video, on my basis my comments are restricted to the first.

I am impressed with the production facilities, I am also impressed with the manufacturing plant. It certainly is not a rickety old shed as we in the west frequently prefer to envisage when discussing manufacturing plant and equipment.

As for soldering, is it a problem?

I have seen a video in the past which allegedly was Lipo manufacture, which was done in an inert cubicle, rolling out a billet, to foil like thickness. I am guessing that either this stage was omitted from the video of Stuart's, or the technique has been changed.

I do recognise that anything of value to competitors and the knowledgeable has been omitted. To me a layman, like me, the facilities are much better than much I have personally witnessed here in the UK.

[Erfolg]

Has anyone had the time to read Stuart's link?

I do believe it is the best source of relevant data, not hear say. Rather a quantified investigation, rather than personal impressions.

Chapter 6, appears to be very relevant, bearing in mind that the scenario is air freight of bulk Lipos. In bag type lipo, there is very small amounts of lithium. The flammable material is principally the electrolyte, which is changing with time. The venting gases are identified, apparently hydrogen and carbon.

The Max temperature is about 1400F, although transient for a single cell.

There is a suggestion that either water, sand/dry powders can be effective, although, residual heat can cause reignition. A lot is written on Halon gas, carbon dioxide type extinguishers.

There is a lot that is very relevant, even more that is not.

The big difference is the commercial type situations and scale.

The report does emphasis the rarity, the typical abuse necessary. Perhaps a greater concern is a suggestion that the danger period is after charging and shorting.

So is a lipo bag enough?

[Stuart C]

I come to the same conclusion. After a prang, all might look well, but the real damage manifests its self after the next charge - and not necessarilly immediately.

With the many millions of batteries being produced, it seems inevitable that duffers will enter the market. The risks are low but the hazzards are great. Wikipedia does warn about cheap lipos with agressive marketing names; something which is becoming quite prevalent these days.

Ps Chinese Lipo manufacture video, of my earlier posting, takes a while to load.

[Phil Claridge]

are halon extinguishers still used, they were all removed from trains years ago as the gas caused breathing problems in confined spaces

[Erfolg]

Phil

I do get the gist of your question.

I do think that the appropriate response for us modellers has not yet been outlined. In most cases we use a single lipo pack,rather than a large number gathered together.

In the scenario I have outlined the fire appears to have two separate stages. The first being the electrolyte, which is transient, although high temperature. The second is the wrapper and the material off construction.

This sequence is often complicated by multiple cells.

As an example, would sand suppress all stages if left until totally cold? It does appear that residual heat is a potential issue with multiple cells.

There seems a two part set of ssues,. A chemistry issue, needing the input from either a chemist or chemical engineer. Then a second part, probably best sorted by a fire expert or fighter

[Erfolg]

Phil

I do get the gist of your question.

I do think that the appropriate response for us modellers has not yet been outlined. In most cases we use a single lipo pack,rather than a large number gathered together.

In the scenario I have outlined the fire appears to have two separate stages. The first being the electrolyte, which is transient, although high temperature. The second is the wrapper and the material off construction.

This sequence is often complicated by multiple cells.

As an example, would sand suppress all stages if left until totally cold? It does appear that residual heat is a potential issue with multiple cells.

There seems a two part set of ssues,. A chemistry issue, needing the input from either a chemist or chemical engineer. Then a second part, probably best sorted by a fire expert or fighter

[Chuck Plains]

 

If anyone has more info, or corrections, please let me know or just add it.

L2 type dry powder extinguisher £196 plus shipping!

 

Researching how to extinguish a lithium fire has turned up some interesting info.

Nothing in life is simple!

It seems that what you need, if you want to stop a lithium fire, is a rather specific class D extinguisher. An ordinary ABC one will not work, and the DRY CHEMICAL TYPE WILL MAKE THE FIRE WORSE !

A lithium fire is not actually self perpetuating, it needs oxygen or nitrogen to keep itself alight. Exclude those and it will stop.

There seem to be three types of powder extingiusher that work on lithium, with the most

Copied from herobusinessblogspot.co.uk

* Copper based (Copper Powder Navy125S)-developed by the U.S. Navy in the 70s for hard to control lithium and lithium alloy fires. Powder smothers and acts as a heat sink to dissipate heat, but also forms a copper-lithium alloy on the surface which is non-combustible and cuts off the oxygen supply. Will cling to a vertical surface-lithium only.


* Graphite based (G-Plus, G-1, Lith-X, Pyromet or METAL.FIRE.XTNGSHR)-contains dry graphite that smothers burning metals. First type developed, designed for magnesium, works on other metals as well. Unlike sodium chloride powder extinguishers, the graphite powder fire extinguishers can be used on very hot burning metal fires such as lithium, but unlike copper powder extinguishers will not stick to and extinguish flowing or vertical lithium fires. Like copper extinguishers, the graphite powder acts as a heat sink as well as smothering the metal fire.

* Sodium carbonate based (Na-X)-used where stainless steel piping and equipment could be damaged by sodium chloride based agents to control sodium, potassium, and sodium-potassium alloy fires. NA-X agent is recommended wherever stress corrosion of stainless steel must be kept to an absolute minimum. Limited use on other metals. Smothers and forms a crust.

Most Class D extinguishers will have a special low velocity nozzle or discharge wand to gently apply the agent in large volumes to avoid disrupting any finely divided burning materials. Agents are also available in bulk and can be applied with a scoop or shovel.
------------------

Edited By Chuck Plains on 26/01/2014 12:10:47

[Chuck Plains]

Posted by Phil Claridge on 26/01/2014 09:55:07:

are halon extinguishers still used, they were all removed from trains years ago as the gas caused breathing problems in confined spaces

Halon will only put out the flames, but won't stop thermal runaway within the cells. Plus it's now going out of use due to it's ozone depleting effect.

Extinguishing In-Flight Laptop Fire - Lithium Battery Thermal Runaway.

[Erfolg]

Chuck

Both Stuarts and Simons references both indicate that the fire being primarily seen as a Lithium dominant fire is a misnomer with respect to our soft pouch type Lipos. The amount of Lithium present would appear to be infinitesimal, particularly when related to the continuants of the fire. The first part of the fire seems to be driven by the electrolyte gases, not the Lithium.

If this is so, we need it to be confirmed by someone with the necessary knowledge to confirm or contradict the proposition. A yes no answer would not be enough. or believe me I am an expert, or I decide these things.

If the fire were a lithium fire, it may still not necessarily be the dominant issue, as the early part of the fire is transient. It is probably the secondary stages, and the need to preferentially prevent the adjacent cells igniting, although this may not be possible. The other issue would be the products of combustion, are these harmful, if so, to what?

Again there appears to be two issues

1. In what, if anything should the lipo be charged
2. If there is a fire, how best to deal with it

It is very possible that charging is not the most critical issue with respect to igniting a cell, or a thermal runaway.

Stuart's report seems to indicate that thermal runaway is more frequently due to issues more frequently encountered than charging. Abuse, then accidents like shorting, and then accidental damage appear to lead the issues. Yet none of these automatically will lead to thermal runaway or fire, so it seems.

Edited By Erfolg on 26/01/2014 13:03:11

[Stuart C]

Dormant manufacturing flaws cannot be overlooked. With use (and abuse) these will have more effect on local cell impedance, and local thermal stability. Monitoring the individual cell states during charging might help in detecting these issues at an early stage. I've had 4S batteries that have consistently given equal voltage readings and never given a problem, but recently bought some cheapies and found cells out of balance after first charge. I'm thinking I ought to dump them (or the charger!). Lipo technology is really ripping away, and its quite scarey to see how far behind the safety issues are lagging.

[Stuart C]

Just as you thought it had all gone quiet and become a non-problem, the Beeb wades in with this www.bbc.co.uk/news/business-25733346

[Erfolg]

I saw the BBC report, there were some very encouraging aspects of the report, that is relative to comments re lipos on this site.

The first, an expert stated that the events were extremely rare,relative to the many millions in use.

The second was that the pictures seen required abuse to obtain the fire.

Perhaps most reassuring is that the fire on the aeroplane was extinguished with wet tea towels. No special fire extinguishers. Not a fire as some report that cannot be extinguished or similar unconstruuctiiive report.

Edited By Erfolg on 05/02/2014 18:09:25

Edited By Erfolg on 05/02/2014 18:12:22