Problems with the Dreamliner battery

nsaspook

This is a complete WAG but maybe we are seeing the effects of strong EM fields on the metal foils that are in tight coils inside each cell when operated at high energy combined with high density levels. Looking at the length of the foils from the Dreamliner cells they would seem to have a fairly large inductance. Rapid current changes from loads or from being charged at high variable rates could be causing some sort of voltage or current non-uniformity inside the cells from the magnetic field effects.

AlephZero

... from http://www.ft.com/cms/s/0/79906f2e-6...#axzz2JV7ZNnGX

I'm sticking with my original "best guess": there won't be a quick fix for this.

An interestng choice of words in the FT article: Boeing is "assuming" (not "forecasting"!) no significant financial impact from all this. Elsewhere, I've seen an estimate that a grounding to the end of 2013 would knock about $7bn off their 2013 earnings, plus knock-on effects on cancelled orders and other future business.

EDIT: Those 10 battery incidents at ANA were on a fleet of just 17 aircraft

jim hardy

Batteries have a ripple current rating, just like capacitors. Manufacturers caution about ripple in the charger output.

http://www.artec-ingenieria.com/pdf/...uide_en_LR.pdf

Clearly, high crest factor waveform has more heating value than sinewave.
And high frequency would shift that load to the foil nearest the terminals for reason you stated.

I once had to tame some loads - we had SCR style inverters modulating 135 volt 1000 AH batteries to the tune of 100 volt spikes. Their currrent draw was not constant, they drew it in huge gulps. We added one microfarad per milliamp across inverter inputs to calm the battery bus.

So what you suggest is possible.
Ripple and its heating can come either from charger or load.
I'd wager the charger is well behaved,
but the loads are a wag for me, too. In fact an Un-Scientific one, USWAG.

Dotini

http://seattletimes.com/html/busines...urcingxml.html

The latest in a series of Seattle Times aerospace reporter articles into the 787 electrical woes.

As an off-and-on employee of The Boeing Company from 1968 to 2005, in various positions on all commercial airplane programs, I can relate to the sentiments expressed in the article. The Company may indeed be embroiled in something of a fiasco, but I deeply hope and believe it has the ability and time it needs to recover. My pension may depend upon it!

Respectfully submitted,
Steve

nsaspook

This seems more related to the current problem.

http://seattletimes.com/html/busines...mid=obinsource

nsaspook

http://www.thestate.com/2013/02/05/2...l#.URGs-uDlAW0

http://mainichi.jp/english/english/n...dm001000c.html

AlephZero

The problem is, they are doing the CT scans etc after a lot of secondary damage occurred. The hard part is figuring out what was the primary cause.

To use a different example, this

looks impressive, but was not very relevant to the investigation compared with looking at what actually broke (or half of it, to be pedantic):


... from http://online.wsj.com/article/SB1000...368343774.html

Having apparently got nowhere after a month of ground testing, Boeing have asked the FAA to approve some 787 flight tests to try to diagnose the problem. Flgiht testing to certify a fix is one thing. Flgiht testing to reproduce an on-board fire hazard is something else. I wonder that the FAA will make of the request

nsaspook

The failure modes in these cases seem almost identical, a chemically driven positive temperature feedback loop that once started seems to be impossible to stop by all present electronic control measures and so far there seems to be little data on the precursors that start it from all the monitoring data on the system. That leads me to believe the problem is related to what Elon Musk describes (large cells in close contact, thermal and/or electromagnetic effects).

AlephZero

A (lack of) progress report from the NTSB investigation: http://www.bbc.co.uk/news/business-21373593
I guess somebody in Boeing is saying "ouch", after those comments.

Re the "test flights", The FAA has granted Boeing permisson for one flight to return a 787 from a "paint job" in Texas back to Everett (i.e. not a test flight as such, though there are conditions imposed on monitoring the batteries while in flight).

Other news: the Europoean air safety agency (EASA) has been invited to join the US investigations. And Polish airline LOT, which has a 787 grounded in Chicago, is applying to the FAA via the EASA, for permission to fly it back home (presumably the fuel cost is less than the long term parking charges!)

AlephZero

FAA approval for 787 test flights: http://www.faa.gov/news/press_releas...m?newsId=14295

Ptero

The person I consider to have the best investigative performance to date on this issue is Celina Mikolajczak.

Lithium-Ion Batteries Hazard and Use Assessment
Final Report Prepared by:
Celina Mikolajczak, PE
Michael Kahn, PhD
Kevin White, PhD
Richard Thomas Long, PE
Exponent Failure Analysis Associates, Inc.
© July 2011 Fire Protection Research Foundation
http://www.nfpa.org/assets/files/PDF...riesHazard.pdf

I will be glad to provide my opinions on what is contained in this rather damning document, but I am most interested in yours. It is clear to me that this technology is not mature enough in manufacture to be allowed in commercial aircraft. The absolute inability to identify point shorts and dendrite growth, or to prevent Li plating on the anode, the concerns with aging increasing liklihood of shorting, the acceptance of flammable electrolyte, the outgassing of flammable gas and the impossibility of extinguishing electrolyte fires with halon, the cascading effects of thermal runaway events and the inadequate "solution" of boxing this ticking timebomb of a battery in a titanium box vented to the slipstream screams not just of engineering incompetence but of another political mandate gone sour. I do not know if that last bit is true, but I do see Steven Chu scrambling for the exit as Airbus reconsiders Li-Ion deployment.

A kludge (or kluge) is a workaround, a quick-and-dirty solution, a clumsy, inelegant, difficult to extend, hard to maintain yet effective and quick solution to a problem, and a rough synonym to the terms "jury rig", "Jugaad" or "jerry rig". -- Wikipedia

Photos of Japan Airlines January 7 incident, battery pack and cell damage
-- Slide #13: NOTE THE SHORTING DAMAGE THROUGH THE TITANIUM CONTAINMENT! The failure of NTSB's mandated kludge may have been the strongest reason to ground the B-787 fleet. (The melting point of titanium is 3000 F.)
NTSB PDF February 7, 2013
http://www.ntsb.gov/investigations/2...787_2-7-13.pdf

jim hardy

Thanks Ptero i forwarded that nfpa paper to a friend at Boeing.

Disasters are always a string of small things stacked up, they topple like Dominoes. That was Ernie Gann's premise in "Fate is the Hunter".
I saw same principle at work in nuclear industry.

In my opinion that is a significant domino.

OmCheeto

What's this? No one has quoted wiki yet?

Groundings
bolding mine

Interesting. But I understand how contracts go. Something better comes along, but we've signed a contract to buy the inherently more dangerous battery.

I changed one of the reference links[193 original ref link], as the original was in some incomprehensible language(Norsk I think). My link points to the following image:



hmmm.... What was the name of that guy who was so enthralled with LiFePO batteries, that he lost a small fortune investing in a company that made them? What was his name?



----------------------------
Ok to delete, as I am aware that I'm being a, "told you so", kind of smart***

AlephZero

That last page of the NFPA paper says it is a literature survey about transportation and storage of Li batteries, not about their actual use.

This may be more relevant in showing how faults develop can during use - e.g Fig 5 showing that heat release was delayed for 20 hours after the simulated fault was created.
http://www.evdl.org/docs/li_fault_detection.pdf

If something "goes bang" when you poke it with a sharp stick, there's a fair chance you will speculate there could be a cause and effect mechanism. If it goes bang a day later, for no apparent reason, that's not so easy to understand.

OmCheeto

TLDR. But yes, bang, is not a pleasant sound.



Not that their manganese based LIOH battery was that bad. Didn't that Volt catch fire 2 weeks after it had been crash tested?

AlephZero

At which point, one of my engineering mentors would repeat his favorite "development engineering is hard" parable:

Ug the caveman set off to the woods to pick some nuts and berries, but found the path blocked by a large dinosaur, asleep in the sun.

Shouting at the dinosaur had no effect, so Ug went back to his cave, found a sharp stick, and poked the dinosaur in the posterior.

Nothing happened for a couple of hours. Then, the dinosaur got up, took two steps backwards, and sat down on top of Ug, crushing him to death.

Now, the moral of this story is this: the dinosaur did not attack Ug because of the poke from the sharp stick. It was actually responding to a tap on the nose that somebody had given it three weeks earlier.

Ptero

"Didn't that Volt catch fire 2 weeks after it had been crash tested?"

In this instance, the battery pack had sustained damage and the battery coolant had drained out. The fire occurred, I think, as you state, two weeks later and was blamed by all investigators on a mechanically-damaged cell that initiated the thermal runaway, likely due to a combination of physical damage and a lack of coolant. GM subsequently retrofitted the battery armor on the Volt, beefing it up, and the US DOT accepted this as an effective fix and cancelled the investigation. Personally, I do not consider this anything but a kludge based in inadequate investigation. But this was the accident where GM and the NHTSA learned that these battery packs could not be left to sit idle after an accident like their conventional kin, so I am inclined to cut them some slack as a giant and ponderous organization, despite the fact that they failed to listen to some of their more knowledgeable people. However, I am also not satisfied that the entire truth has been told - because of politics - yet there have been no more fires, and no deaths or injuries that I know of, so perhaps I am being too skeptical in regard to magnesium-type Li-Ion, irregardless of the fact that it, too, contains flammable electrolyte. Gasoline, diesel, ethanol, propane, natural gas and hydrogen, after all, are also flammable and can ignite in accidents. But spontaneous ignition and thermal runaway, as has occurred in smaller consumer cells and in aviation cargo, or ignition during charging or discharging, or most dramatically with the thermal runaways of Cobalt Li-Ion that resulted in the B-787 fleet grounding, should not be acceptable, imo. Cobalt Li-Ion remains a unique and frightening story. There are serious and unresolved physics problems here - perhaps even fundamental physics barriers that cannot be overcome and extend across the gamut of Li-Ion (this is my personal belief - what do you think?). I do not understand why Cobalt Li-Ion was not entirely abandoned by the aviation industry when the currently insurmountable problems came to light, unless politics played a role. In commercial transport history, it has become de rigueur that virtually all latent design threats to aircraft operations have been immediately addressed and resolved. The implementation of design features with known dangerous faults is unusual in the extreme. That said, I remain suspicious of undetectable dendrite formation in all (flammable electrolyte) Li-Ion battery types so I am keeping a close eye on pure EV as well as hybrid batteries as they age.