Pub User:
Right! Professionals should confine themselves to reporting and discussing Rumors (& News), not starting them.
Now if you find a sensational tabloid rumor on the subject, I suppose you are free to report it and even quote it. :p

Pub User

I agree with you. Some people also seem to be using this forum to practice their comedian skills.

The improvements to the batteries and containment box seem to be addressing the safety requirements stipuated by the FAA. I felt depressed seeing all these great planes parked up when I flew out of Haneda last night. I am quietly optimistic it will be flying again in the next few weeks. If the 787 is on the schedule for any of the routes I take it will be my first choice.

"The battery is being so heavily modified it isn't the same battery any longer:"

What has not changed, as far as I know, is the cell chemistry. They're still Cobalt Oxide Batteries (COO2). The most volatile and also the most energy dense of all Lithium based battery chemistry's. No amount of shielding will change the chemical properties of that battery. In that sense, the battery remains identical.

What Boeing is doing in my uneducated view, is hazard mitigation, not cause elimination. Maybe charging and discharging them within a narrower band will make the battery more reliable. Maybe not. Until many have been operated for a statistically useful period, nobody will really know for sure. Even if the new shielding makes them safe, that does not speak to reliability.

Why they didn't switch to a different battery chemistry is really beyond me. What Boeing is doing seems too high risk to me.

Halon - oxygen depletion
 

Having once been involved in a very large fire whereby halon
was released, I can say that halon reduces fire by interfering
with the combustion process. In my case it was safe for humans
to be exposed to the halon atmosphere for in the order of hours.
That said surely halon might be useful in the boeing battery box.
If it is certain that there is no way for the contents of the box to
generate oxygen, then an inert atmosphere of any kind should
also work. If the batteries have a major short there still remains
the problem of the heat generated.

By the way, I looked up the battery rating of my ancient diesel's
12v lead acid battery and it is 920 amps for 30 seconds,
with a final voltage of at least 6 volts, and chemical recovery thereafter.
Still I suppose Boeing chose their particular li-ion
technology for some good reason. I see that many electric cars
use li-ion manganese. For the 'ZOE' the makers state that all
cells are monitored for condition, and charging is possible from any state of charge.

Lets be clear here. the FAA said the improvements to the battery were a step towards solving the safety issues with the 787.

The battery box is not a fix or solution to the problem according to the FAA.

No matter what Boeings PR depart claim, until the problem is identified and a solution provided, the 787 is not going to be flying commercially.

Boeing just might be able to lobby the FAA but I doubt the Japanese, Europeans or the NTSC will be so easily to push around.

Halon damages the liver and its unpleasant to breathe, the first time its used in a commercial aircraft would probably be the last, after the lawsuits.

Peter We

The JAL Boston and ANA Takamatsu incidents highlighted 2 issues:

1. The battery failure rate (thermal runaway) was considerably higher than expected.

2. The original battery box did not contain the fire which it is supposed to do in the rare instance that there is a battery failure. Special rulings were issued by the FAA during the 787 delvelopment on this. Sorry I have no time to go back through this thread to find this data.

The battery modifications such as the extra insulation between cells addresses issue 1. The stronger box addresses issue 2.

Underwriters' viewpoint ?
 

@ Cool Guys, re your point 2 : I can't see how the Stainless Steel casing has in any significant way changed the occurrence probability of 'Battery Unserviceable' as an EVENT; (refer to cockney steve in post # 1446) the present-day statistics show some 150 such events in 50,000 flight hours ... the question then comes : is this a 'no-go' event ? The next question is : what is the duration of 'change battery' as a line maintenance task ? (consider that henceforth the battery is to be encased in a sealed - explosion-proof - box, did you count the number of bolts/nuts = 52 ? - what about 'visual inspection' ?) Corollary : does this imply an aircraft change ? ... whence the possible concern of Underwriters : what exactly are we insuring, and for what premium ?

Did yesterday's flight use the new battery box or still the factory stock layout?

Frequent Traveller,

You are right, the box makes no differnce to the probability of a battery failure. The issue is the batteries will fail at some point. They are not 100% reliable, nothing is. The Li batteries have a high energy density so when whey do fail the fire etc must be contained.

Apparently most of these events were due to excessive discharge while on a ground. When an LI battery is discharged below its minimum level it should not be recharged up to normal levels again so it is replaced. I am not an expert on this but some smart people earlier in this thread explained this. This is not a safty issue.

I have no idea. I am sure it will be complete pain in the ar_e to service but this is not a safety issue.

I have no idea.

@ FlightPath OBN....Sorry, I didn't explain my thoughts very clearly....the box-flange is currently about an inch wide.....double it and add the thicknesss of the lid.....fold it back on itself, thus forming a slot...do that on 3 sides and the lid will slide into the slot....bolts (same relative position as the plastic-fronted "Demo" box)would only have tension if a pressure-event tried to force the lid upward....remember it's restrained by a 1" wide cpntinuous flange folded over 3 sides....If the top belly's it will try to pull out from the slot....the flange, being 2 thicknesses with a fold, is unlikely to bow outward anyway....but any bowing tendency would give shear on the bolts....lighter and stronger and cheaper to produce ehan what appears to be a cast /welded flange on the box as pictured....also the lid has nothing stiffening the edge-that's why the bolts have to be so close and so plentiful- to stop the tin-lid blowing between them.

As for maintenance- it's a sealed unit- uncouple the cables, uncouple the vent-pipe, heave out the "dead" box and shove in another....same as before, just a "bit" heavier and a drain to disconnect/reconnect.


@ Seth. Thanks for the correction :O Fascinating reading.

@Syseng. I agree with you , re Condensation....any present across the "live" bits would electrolyse and would "self-heal" anyway....bit of an old wives' tale, like the film-scenario of an electric-fire being chucked in a bath/swimming-pool and electrocuting the occupant(s).....fuse usually blows first!....pos-neg-earth about 5mm apart water, same resistance per linear distance, so victim more than 10 Cm away, is virtually insulated.

@ Mark in CA....Atomic Power Plants are normally occupied by professional engineers, who usually know what they're doing (unlike commercial Pax.)
When they foul up, you getCHERNOBYL ....Nuff said?

Halon (BCF) fire extinguishers are standard cabin equipment, and have been discharged many times in flight, in commercial aircraft. Their toxicity is the reason we are told to don a smokehood before use, if possible.

As far as I understood, excessive scharge will make the cells instable and lead to thermal runaway. With that respect, discharge is a safety issue. However, it seems to be perfectly prevented by the integrated logic, switching off the battery and making it unserviceable if it is discharged below a defined (still safe) threshold. So the overall Boeing design for this aspect worked perfectly for safety, but is a nightmare for maintenance cost / unscheduled removal.

Surely there's a very important Ops aspect to this. You can't ship Li on Pax A/C ! So is every outstation going to have have a huge stockpile?

Unfortunately, LiCoO2 reacts with the electrolyte above c. 130C and decomposes approaching 200C, giving off oxygen in the process. This becomes self-sustaining, i.e. thermal runaway. Halon will suppress naked flames by interfering with the chemistry but can't do much about what's happening inside the cell.

The total energy release from an electrical short and combustion of the materials that make up the battery is enough to raise the temperature by *thousands* of degrees. This would actually be made worse by insulation - disrupted cells get hot enough to melt steel... :eek:

From the FAA 787 "special conditions" for Li-ion:

Note that it doesn't say that it's okay if they are in a box, or if it only happens every now-and-then. LiCoO2 batteries are vulnerable to the above due to their chemical composition - whether it is triggered by over/under-charging, excessive current, manufacturing defects, cosmic rays or a change in interest rates, doesn't really matter. So far, there has been no (public) confirmation of *why* these failures occurred, so pushing a solution seems ever so slightly premature.

I do wonder how they're going to get round this provision: either the FAA will have to retract the offending paragraph or Boeing will have to use a different type of battery. I suppose the third way will be to argue "we don't know what caused it but we've changed lots of things so it's OK now"; depends on how much spine the regulator has that morning, I suppose...

Or perhaps a compromise could be reached for the FAA to say OK so you have done some substantial changes to the battery and given that if it should fail the box will prevent it from setting fire to the aircraft, we will give you a CofA but with a temporary restriction of 180mins ETOPS only, (ie the same as for a non functioning APU.) if after 12 months there have been no more incidents then we will lift this restriction. They could also demand that any batteries swapped out and returned to the manufactures are opened in the presence of an inspector from the Japanese regulators.

They will have to be shipped out by freighter aircraft. I believe that UPS have experience with shipping this type of cargo, notably around Dubai ..........

Boeing is watching what's happening on the old continent ...
 

Airbus has installed on the first flight-test A350 XWB its two flight-ready Rolls-Royce Trent XWB engines and is also installing the new Honeywell HGT1700 APU.

"With the installation of its engines and also the APU, the A350 XWB MSN001 becomes essentially a ‘completed’ aircraft. Following the ongoing ground tests, other preparations and also painting in the coming weeks, MSN001 will then be handed over to the Airbus Flight Test team to commence preparations for ground runs and maiden flight in the summer."
.

Following FullWings's post
 

My understanding is that any oxygen recombines with the anode material as it is produced, with heat and non-combustible byproducts; if the anode is graphite, which I conjecture is the case, that would be CO2 for a large part.

Any good sources on the exact chemistry in the battery, and how it degenerates in case of thermal runaway ?

Also, independently
This is from http://www.gpo.gov/fdsys/pkg/FR-2007...df/E7-8186.pdf

Any advise on how this could be worked around by Boeing from a legal standpoint? Especially since the design of the cells remains apparently unchanged (only their testing is), and experience has proved that self-sustaining uncontrolled increase in temperature is a real possibility.

Edit: Perhaps uncontrolled is a solution: now that there is the fire box/enclosure, any self-sustaining increase in temperature or pressure is arguably controlled. Or perhaps Boeing can waive the special conditions and re-certify according to general rules.

fgrieu:Lithium Battery Failures gives a good overview.

http://www-scf.usc.edu/~rzhao/LFP_study.pdf gives a deeper look at the normal chemistry of Lithium ion batteries.

Types of Lithium-ion Batteries compares different variations on the Lithium ion chemistry.

http://www.kta-ev.com/v/vspfiles/ass...chnologies.pdf gives another overview of alternative Lithium chemistries, including some safety information and includes the useful point: I found a very good scholarly analysis of the exact anode, cathode, and electrode reactions involved in thermal runaway, but I don't have the URL handy at the moment. Possibly later.

"Surely there's a very important Ops aspect to this. You can't ship Li on Pax A/C ! So is every outstation going to have have a huge stockpile? "

I assume you cannot ship them because of the potentail risk involved?

So how can it be say to fly around an aircraft with two highly rated LI units bolted to the airframe, I assume I am missing something here.



Pax Brit , but not on a 787 any time soon