787 Batteries and Chargers - Part 2

[john_tullamarine]

Thread Part 1 starts here (http://www.pprune.org/tech-log/505695-787-batteries-chargers.html).

[inetdog]

Welcome to Part II.


Machaca:
It is my understanding both transcripts and videos of all the sessions will be available next week on the NTSB website.
But that will be without the totally hilarious captioning/transcription errors you got from the "live" feed.

Line 375:
YOU WILL NOTICE IN MY PRESENTATION, WHEN YOU SEE IT ON THE DOCKET, THAT I HAVE INFORMATION FOR BOTH LIVE IN MY AUNT AND METAL BATTERIES. -- FOR BOTH LITHIUM AND METAL BATTERIES.
Actually "For both Lithium-ion and metal batteries."

There is also some good stuff, like this, which pretty well lays to rest all of the speculation about the effect of electrolyte combustion and the contribution of the oxygen liberated within the battery electrode (which is small enough to combust only a very small fraction of the electrolyte):

WHICH THEN GOES BACK TO DR. CHIANG'S POINT. IF YOU ENGINEER A SYSTEM THAT HAS NO OTHER AVAILABLE OXYGEN, YOU TAKE AWAY THAT HEAT SOURCE, THAT ENERGY SOURCE, WHICH IS ROUGHLY, IN A GIVEN CELL, THE COMBUSTION ENERGY OF THE ELECTROLYTE IS 1 TO 2 TIMES THE ENERGY THAT IS CONTAINABLE IN THE CELL. IT IS NOT A SMALL AMOUNT. THOSE ARE MY TWO COMMENTS.
So the firebox will reduce the worst case catastrophic energy release by a factor of two or three, in addition to containing it.

Also, a very nice sequence on the choice of Li chemistry:
(ITALIC text is my insertion.)
Starting at 319:
>> UNDERSTANDING THAT EVERYTHING THAT WE DO HAS SOME RISK IN IT, ARE THERE CERTAIN LITHIUM-ION CHEMISTRIES THAT HAVE BEEN DETERMINED TO BE UNSUITABLE FOR CERTAIN APPLICATIONS AS FAR AS RISK LEVEL?

>> I DON'T THINK THAT QUESTION LEADS TO A PRODUCTIVE RESULT. TO BAN A CERTAIN TYPE OF THEM ASTRAY. -- TYPE OF CHEMISTRY.

>> NOT NECESSARILY BANNING. CHOICES PEOPLE HAVE MADE FOR A CERTAIN ENVIRONMENT. FOR EXAMPLE, ON A SUBMARINE, ON AN AIRCRAFT CARRIER, OUT ON A SATELLITE, ARE THERE CERTAIN CHEMISTRIES THAT HAVE BEEN RULED OUT THE CAUSE OF THEIR RISK?

>> WHEN WE WERE TESTING MODULES, WE WOULD IT MODULES WITH A " SAFER CHEMISTRY" AND ONES WITH A MORE DANGEROUS CHEMISTRY IN THE CELLS. THE PERFORMANCE OF THE MODULES DIDN'T FOLLOW. THE CELLS THAT WERE DEEMED SAFER AT THE MODULE LEVEL PERFORMED WORSE. SO I WOULD ADVISE A COMPREHENSIVE AND THOUGHTFUL TESTING PROGRAM AND NOT WORRY ABOUT WHAT THE CHEMISTRY OF THE CELL IS.

>> I WOULD COMPLETELY AGREE. I THINK THE IMPORTANT REASON TO SAY THAT IS I CAN BUILD A COBALT, A HIGH CHARGED COBALT CELL INTO A MODEL THAT MAY NOT FAIL AND COULD WEIGH A TON. SO I CAN MAKE THAT BATTERY IN PHOSPHATE AND IT MIGHT WEIGH FIVE POUNDS. SO THE SAFETY REQUIREMENT OF THE APPLICATION, WE WILL HAVE TO GIVE YOU THE LIGHTEST, MOST COST-EFFECTIVE SOLUTION. BUT YOU, THE USER, CAN SAY I WILL NOT TOLERATE THIS. I CANNOT ACCEPT THAT. THIS IS A FAILURE. THE NAVY PROGRAM HAS DEVELOPED A VERY CLEAR YOU CANNOT PUT THIS ON OUR SUBMARINE IF IT DOES THESE THINGS. THAT WILL DRIVE US TO CHOOSE THE SYSTEM DESIGN, INCLUDING CHEMISTRY AND EVERYTHING, TO DELIVER WHAT THEY WANT. BUT TO DECIDE THAT A CHEMISTRY CANNOT WE USED IS LIKE TRYING TO SOLVE A PROBLEM WITH THE FIRST GRAIN OF SAND.

>> WITH RESPECT TO APPLICATIONS, THE CHEMISTRY IS IMPORTANT IF YOU WANT A VERY HIGH RATE APPLICATION. WE WOULD CERTAINLY GO WITH LIKE A SPINNER (spinel?) OR A PHOSPHATE TYPE OF CHEMISTRY. IF YOU ARE NOT LOOKING FOR HYBRID (higher?) PERFORMANCE, THEN WE WOULD GO WITH SO I THINK WE WOULD GO WITH THAT MORE THAN THE SAFETY OF THE CHEMISTRY.

>> LIKE WISE. I THINK THE SAME WESTERN ([I]question) -- ARE THERE SITUATIONS WHERE BATTERIES HAVE BEEN REPLACED BECAUSE OF THE FAILURE RISK BEING TOO GREAT? HE YOU HAVE AN ANSWER TO THAT?

>> NOT WITH RESPECT TO LITHIUM- ION. BUT WE HAVE REPLACED CHEMISTRIES LIKE LITHIUM PCX. WE DID NOT HAVE A GOOD REFLECTION OF WHAT THE ACTUAL ENVIRONMENT WOULD BE. FOR INSTANCE, IN THE ARBITER (orbiter), WE WANTED TO PUT IMPACT SENSORS ON THE WING SO WE COULD UNDERSTAND WHAT WAS GOING ON. AND IF AN IMPACT OCCURRED. SINCE WE DID NOT UNDERSTAND THE ALIGNMENT OF THE TEMPERATURES, WE ACTUALLY REFUSED TO ALLOW THEM TO USE THE BCX CELL BECAUSE OF IT BEING EXPLOSIVE. SO, YES, BUT NOT WITH RESPECT TO LITHIUM-ION.

[archae86]

Arguably this is more relevant to the 787 grounding issue than specifically to the batteries and chargers issue, but I noticed on FlightAware several reported flights reported as 787 flights operating under the ID BOE5 out of San Bernardino International in the last few days.

The FlightAware link for BOE5 is:

Boeing #5 Flight Tracker ? FlightAware (http://flightaware.com/live/flight/BOE5)

While I've seen seeing a small number of apparently spurious taggings of flights as 787 flights for weeks (mostly presumably false data-entry on ANA Frankfurt-Haneda operations) these KSBD flights seem plausible.

In BOE5 flights listed as of the moment of my posting, there appears to have been a positioning flight from Boeing Field to San Bernardino on April 13, with subsequent daily or more flights out over the ocean in a generally SSW direction. The tracking data seem erratic, possibly partly because of the over-ocean positions.

My guess is that these are real 787 flights. Does anyone know more?

[FlightPathOBN]

Arch,

Made a few inquiries on BOE05...

ZA005 is in San Bernardino conducting testing to demonstrate the performance of engine improvements provided by General Electric.
GE’s second package of upgrades for the 787’s GEnx-1B engine was certificated by the FAA on April 12. That’s engine-only certification.
This week’s San Bernardino flight tests are working toward the certification of the upgraded engine and plane together.

[FlightPathOBN]

The NTSB just released the agenda for the April 23/24 hearing on the 787 Battery.

Investigative Hearing Agenda Japan Airlines, JA829J Boeing 787 Battery Fire (http://www.ntsb.gov/news/events/2013/B787_hearing/B787%20Battery%20Fire%20Investigative%20Hearing%20Agenda.pdf )
April 23-24, 2013

It seems odd that the press is currently reported that the FAA will sign-off on the battery fix today...

[Kiskaloo]

Press Release – FAA Approves Boeing 787 Battery System Design Changes

Press Release ? FAA Approves Boeing 787 Battery System Design Changes (http://www.faa.gov/news/press_releases/news_story.cfm?newsId=14554)

The FAA will publish next week the final directive that will allow UA to resume operations of the 787. It is expected other regulatory agencies will follow shortly to allow the 787 to resume services worldwide.

[FlightPathOBN]

Well, this will certainly make some some entertaining conversations at the hearings next week...

[Kerosene Kraut]

So how reliable is the modified battery expected to be now if there is still no root cause detected?

[Speed of Sound]

More reliable than the previous design but how much more reliable will only be revealed after some time in in operation has passed.

Some of this increase in reliability will unfortunately be masked by better working practices on the ground, which seems to have been a major cause of batteries going 'low' and having to be replaced.

SoS

[EEngr]

Speed of Sound (http://www.pprune.org/members/55017-speed-of-sound)

More reliable than the previous design but how much more reliable will only be revealed after some time in in operation has passed.Unfortunately, that's not going to do any good. Reliability numbers out around one event per billion flight hours aren't generated by service history. Or we'd all still be flying Wright Flyers. These are based upon analysis of first principles of the physics and engineering involved together with studies of how defects or tolerance errors do or do not lead to subsequent failures.

Unfortunately, a bit of service history can do wonders to :mad: up that original analysis. And waiting for statistical samples to set those numbers right again just isn't in the cards economically.

Boeing (Thales, GS Yuasa, etc.) are going to have to trace these failures back to that mysterious root cause and put in place a plan and process to eliminate it. Only then do they get to go back to a clean sheet of paper, reliability wise.

Yes, there will be an overhaul of the manufacturing process to eliminate contaminants, for example. But until the presence of contaminants in statistically significant samples of existing production runs can be shown, that's just guessing at the cause and the efficacy of the fix.

[FlightPathOBN]

Well, the hearing is currently ongoing...

from the FAA:

"THERE WAS A REQUIREMENT TO TEST THE BATTERY TO INDUCE THAT CATASTROPHIC THERMAL RUNAWAY FROM MR. SINNETT DESCRIBED TO SEE WHAT HAPPENS. WELL, AN ALTERNATIVE APPROACH, RATHER THAN TO SEE WHAT HAPPENS, IS JUST DECIDE, IT IS CATASTROPHIC, WE MUST PREVENT IT. THERE IS NO NEED TO TEST A CATASTROPHIC CONDITION. YOU ALREADY HAVE ASSUMED IT'S CATASTROPHIC. YOU JUST PREVENT IT."

In a nutshell, it appears that the FAA doesnt care about testing, thermal runaway, or the cause..they assume that all of that is a catastrophic failure, so you dont even really need to test for any of this.
The catastrophic failure simply needs to be contained, hence the lifting of the flight restriction with a better box.

Both the FAA and Boeing said that neither event had an effect on the aircraft...

The venting of the EE bay was an odd response from Boeing. The system has to detect the smoke first (or in their explanation, the 'odor') then the system has to re-configure to vent to the outside, and this takes time to do, so there will be 'odor' into the aircraft.

[FlightPathOBN]

I know, I know...there was never any fire, there is never any smoke. :suspect:

[Intruder]

Airplanes have outflow valves, sink drains, and various other holes that already vent to the outside. All another vent will do is allow the outflow valves to close a bit more...

[Bye]

Just out of interest, whilst carrying out some research on Li-ion cells for EV's last year, i had a couple of occurrences of thermal incidents.

i actually found the root cause to be back EMF spikes from the electronics i was using, and that it could set up a frequency resonance making the cells "pant" until internally breaking down and letting the "odour" out.

Just thought i'd share that with you.

GB.

[FlightPathOBN]

Bye,

That is interesting because the last speaker was saying that the continued focus on the event would be on the grounding system of the aircraft, how it is isolated and related.

Another good question to Thales was why is the system meant to protect the battery, the BMU, located inside the case with the battery cells themselves.

[Machaca]

Query to GS Yuasa:

>> OKAY, THANKS. JUST FOLLOW UP ON THAT. HAVE YOU HAD IN THESE PARTICULAR DESIGNS, HAVE YOU SEEN ANY EVIDENCE PRIOR TO THE INCIDENT OF ANY INTERNALLY SHORTED CELLS?

>> NO.

>> THANK YOU.

[Kiskaloo]

When asked about the BMU's location, Thales responded that the closer the BMU is to the cells it is monitoring, the better.

When asked if there was any benefit to having the BMU external to the containment vessel, Thales responded that the BMU is isolated somewhat from the cells themselves in the containment vessel (even more so, now, in the new design) and they felt that having the BMU inside the containment box was the logical way to proceed because it prevented a failure risk due to connection problems.

The decision to place the BMU in the containment box was made by Thales and GS Yuasa.

EDIT: Thales is recapping their statement and noted that the BMU has thermal disconnects so it sounds like even if the cells enter thermal runaway and damage the BMU, these disconnects would trip and kills electricity flow to and from the cells in the battery pack.

[FlightPathOBN]

52 bolts for the lid, 51 more to go..take one down, pass it around...

http://boeingblogs.com/randy/images/AOG-story-2.jpg

EDIT: Dont know about you guys...but since one uses the bolt head to tighten (and measure torque), not the nut...that hes got the bolts in bassackwards....(the ones on the bottom are really going to suk trying to tighten....)

[PickyPerkins]

I think there may be a typo in the article "NTSB hearing on 787 batteries reveals Boeing shift on testing", by Stephen Trimble Washington DC, linked below:
NTSB hearing on 787 batteries reveals Boeing shift on testing (http://www.flightglobal.com/news/articles/ntsb-hearing-on-787-batteries-reveals-boeing-shift-on-testing-385038/)

Where the article says, "In neither incident did the battery failure prevent a risk to the overall aircraft, ...", I think it should say,"In neither incident did the battery failure present a risk to the overall aircraft, ..."

[I see that this typo has now been corrected.]

[Kiskaloo]

I watched the entire proceedings and indeed on multiple occasions testimony was given, including by Mr. Bahrami, that neither NH692 nor JL8 was at risk of hull loss so yes, that is a typo.

[archae86]

I've been looking at FlightAware for 787 flights several times a day lately, expecting to see a flurry of the Boeing aircraft caught on the ground before customer delivery going up for B-1 flights and such. But, aside from the engine testing flights ending last week under the ID BOE5, I've not been shown any in flight so far (the aircraft type method only detects aircraft in flight--though with a flight number you can see history as well).

Instead, today, I saw a flight under a 4-digit United flight number listed as a 787 flying from Los Angeles International to Lackland AFB.

While this could just be a mis-attribution, I'm inclined to guess it was real. LAX was listed as the location where one of the United 787s was stranded, and I believe that some kinds of 787 work get done at Lackland. The past history of the flight number did not show other KLAX to KSKF operations under that ID recently.

If it was real, then either someone gave special dispensation for the flight to be operated without the battery fix, or this is a bird that got the fix in already.

Can anyone here correct, expand, confirm, or deny?

[FlightPathOBN]

I can check it out, do you have the designator?

Edit: got it 6850

[archae86]

This link will allow detail to be seen for the next few days for the FlightAware listing of interest. (assuming PPRUNE forum software does not corrupt it).

The line of interest is for a flight from KLAX to LSKF departing KLAX at 11:19 a.m. PDT on 4/23/2013.

UA 6850 on flightaware (http://flightaware.com/live/flight/UAL6850/history/20130423/1900Z/KLAX/KSKF)

UAL 6850
(edit: you got the answer before I replied, but I'll leave the link up in case it might interest someone else)

[FlightPathOBN]

CHICAGO (AP) — United Airlines says it flew one of its 787s to a Boeing facility in San Antonio on Tuesday for the battery fix it needs to resume flying.
United has six of the planes. They've been grounded worldwide for three months because two of them had smoldering batteries. Boeing's proposed fix has been approved by the Federal Aviation Administration. Last week the FAA approved non-passenger flights for the 787 like the United flight that left from Los Angeles.
United Continental Holdings Inc. says Boeing Co. workers will install the fix, with help from United mechanics. Boeing has said the battery system modifications will take about five days per plane to install.
United has 787s in its schedule for May 31, but it has said that flights might resume earlier.

[kenneth house]

In the airworthiness factual report there appears to be an error on page 16 concerning the JAL APU start power consumption.

The Flight Data Recorder report shows measurement DCBus_APU_Battery_Current (A) in figure B-12 on page 10B-13 only discharging an average of about 20 amps for the APU start with a momentary spike up to 30 amps during the 35-second discharge.

This would only be 640 watts average with the spike at 960 watts, not the 9.6 kW (32V x 300A) mentioned in the airworthiness report. Some of the other power figures in that paragraph appear incorrect also and should be re-checked.

In addition I wanted to point out that same FDR current data also shows that the APU battery was constantly being overcharged by trickle-charging at 1 to 2 amps during the 14 minutes between Last Engine Shut Down and the APU Shuts Down event.

The Securaplane battery charging patent #5,780,994 is based upon a Ni-Cd battery charging profile and assumes a trickle-charging phase of indefinite length following the fast-charge phase.

GS Yuasa does not include trickle-charging in the CC/CV charging procedure found in the LVP10-66.pdf data sheet for the cells, nor does any other manufacturer of Lithium chemistry batteries.

The CT Scan report also provides evidence of overcharging in the scans of the "normal undamaged" Main battery. The cell walls are clearly seen to be bulging outward and there may be cell-to-cell wall contact. This swelling of the cells is also seen in the CT scans shown in the JTSB reports for the "undamaged" APU battery of the ANA aircraft.

I have a mechanical load analysis which shows that only a couple of psi delta-pressure is necessary to deform the 0.031" stainless steel material used as the cell case. A deformed cell case would likely cause internal short-circuit contact of the current collector bars to the case leading to cell thermal runaway such as was experienced in both battery incidents.

The source of the pressure delta could be internal due to overcharging, and/or external due to operation at reduced atmospheric pressure such as in high altitudes (e.g. 6000 ft).

[awblain]

There was a single United 787 parked out in the open at the south of the western maintenance area at LAX about 2 weeks ago. Is it still there?

[DType]

When I said in post #742 (thread 1) that there is:-

No powered plane without fire
Aeroplanes have been living with fire (in their engines) for over 100 years. This COULD be a precedent for permitting (inadvertent) fires in another power source, the batteries, provided it was as well contained as the engine combustion???

I did not seriously think that they WOULD do it.

PS I accepted the correction that there are some powered aircraft without fire.

[kenneth house]

In the new set of documents that was just released on the NTSB Docket site. On docket # SA-536, exhibit # 17-A, Airworthiness Excerpts from Boeing Battery Specification Control Drawing:

page 89, section 3.2.4.13, Charging Requirements
The fully charged battery shall accept continuous overcharge at _ V without explosion or damage to the battery case.

The blanked out voltage was redacted due to proprietary concerns.

So it looks like Boeing wrote a requirement on the battery that might be fine for Pb or Ni-Cd but violates the fundamental law of Lithium battery chemistry...

[TURIN]

Something I heard the other day.
The battery vent indicator burst-disc keeps blowing off in flight. The fix is to place the disc at the other end of the vent tube. IE. at the battery containment box.
It is a weekly check item to ensure this disc is intact.
The only way to check it is to remove the 52 bolts from the lid and do an internal inspection.
Takes about 3 hours apparently.
This may well be a load of BS as I haven't had it confirmed yet.


Posted from Pprune.org App for Android

[FlightPathOBN]

Yesterday, the guy from Boeing stated that if there are any issues with the battery, there is an alert to the crew, and that any battery alert prevents dispatch.

It should be interesting to see how that plays out...

edit: awblaine...note post#24 above.

[archae86]

the battery vent indicator burst-disc keeps blowing off in flight.
While I love to get inside information here, there seems to me a little problem with this account: the very small number of flights to date of the revised system.

Famously there was just one in the certification plan for the revised battery system. Also, I think, a handful under flight number BOE5 handling certification for an engine upgrade (mostly last week). Other than that, the reported recent flights (UAL ex Los Angeles, Qatar ex London) seem to have been relocations still carrying the old system.

My doubt on the runup to the situation does not address the possible truth of the weekly inspection requirement, which would be an unwelcome addition for several reasons. Still, 3 hours seems rather a lot unless the paperwork enormously outweighs the inspection work.

Please advise if you get updates on any aspect of this.

[TURIN]

Yes, I took it with a pinch of salt but I just thought I would throw it out there just to get a confirmation. 3 hrs seemed a bit excessive to me too.


Posted from Pprune.org App for Android

[FlightPathOBN]

Well, look at set up, then unscrewing 52 bolts...doing what you have to do, then placing and tightening 52 bolts...(at Union scale)

Given the picture, one could easily see 60 seconds per bolt sequence...

[kenneth house]

and never had an internal short-- according to the GS Yuasa representative in today's hearing. These are the industrial cells of the same construction as the 787 cells, but using a different chemistry.

[mm43]

So it looks like Boeing wrote a requirement on the battery that might be fine for Pb or Ni-Cd but violates the fundamental law of Lithium battery chemistry...Having reviewed parts of the Day 1 NTSB hearing, and looked at the rough transcription; it seems that no one has questioned the over-voltage charging regime, nor the CV trickle charging.

The transcription mentions the cell OCV as 4.55V, then a little later reconfirms this figure by stating that for the battery -We also do a test where we charge at 36 volts for a long timeSo, it would appear that the 36V [36.4] figure has been redacted from the Airworthiness Excerpts now released.

[archae86]

Michael Mecham posted on Aviation Week's Things with Wings blogs a comment attributed to Boeing Chairman and CEO McNerney that the fixes "were installed" in "10 fleet aircraft and 9 production aircraft". That sounds like "all done".

Mecham battery progress post (http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:7a78f54e-b3dd-4fa6-ae6e-dff2ffd7bdbb&plckPostId=Blog:7a78f54e-b3dd-4fa6-ae6e-dff2ffd7bdbbPost:31b522e5-add6-40d7-93da-e7e19b95eec3)

However, a Boeing VP posting in his own voice on his own blog, VP Marketing for Boeing Commercial Airplanes, describes it as "We’ve started installation on 10 787s already in the customer fleet, as well as nine production airplanes. The bulk of the fleet retrofits should be wrapped up by mid-May. 787 deliveries are expected to resume in early May."

Tinseth blog (http://www.boeingblogs.com/randy/) (look for the second paragraph of the entry which first mentions the quarterly earnings report. It is the top entry at the moment I am posting, but will move down).

I don't usually expect the Marketing channel to have the more accurate story, but in this case my bet is on Randy, not on McNerney as quoted by Mecham. Boeing has elsewhere described the installation as taking about 5 elapsed days on an airframe, and I think they did not start customer fixes nor most in-process birds until the approval came through. I'm talking about bending and cutting metal and composite--not about pre-positioning people and materials, which clearly happened. Randy comments in his post that he was in Ethiopia at the time of writing. I'd guess that may hint that the widespread story that Ethiopian may be the first airline flying seems more likely than some may have thought.

[FlightPathOBN]

It is interesting the amount of detail that has been shown for the box in the rear bay. I bet it is a real bitch getting that thing installed in the fwd EE bay....

[saptzae]

@mm43

Having reviewed parts of the Day 1 NTSB hearing, and looked at the rough transcription; it seems that no one has questioned the over-voltage charging regime, nor the CV trickle charging.

The transcription mentions the cell OCV as 4.55V, then a little later reconfirms this figure by stating that for the battery - Quote:
We also do a test where we charge at 36 volts for a long time
So, it would appear that the 36V [36.4] figure has been redacted from the Airworthiness Excerpts now released. I doubt they production test at 4.55V Per cell, as it would do irreparable damage and set cells up for failure within a short time - seconds - thereafter.

Actually, FDR at BOS shows charging after the first cell beginning to short - up to 4.57V for the remaining 7 cells - 32 / 7.

[kenneth house]

According to Thales in the Battery Acceptance Test Procedure general ambient conditions for all tests were performed with atmospheric pressure from 84 to 107 kPa, temperature at 25 +/-10 C.

The Thales Climatic Environmental Qual Test Report has altitude, decompression and overpressure testing, but all the values are redacted.

If cabin pressure is held at that of 6000 ft altitude and also maintained all the way into the Main and Aft E/E compartments, then the delta-pressure across the cell walls is on the order of -2.9 psi, which will cause the cell cases to swell and bulge out such as is seen in the CT scans of the exemplar batteries from both Boston and the ANA battery events.

[inetdog]

The online NTSB document access system (http://dms.ntsb.gov/pubdms/search/document.cfm?docID=390299&docketID=54251&mkey=85973) just had 36 new documents added to it, most relating to new certification. Have not had time to read any yet.

[FlightPathOBN]

dog,

During the hearing, there was quite a bit of information that was asked for by the NTSB and others.

[nitpicker330]

You guys have probably already seen this BBC report?

BBC News - Boeing 787 Dreamliner returns to service in Ethiopia flight (http://www.bbc.co.uk/news/business-22315317)

Ethiopian already back in the air :ok:

[green granite]

The original cells were 75Ah, limiting the lowest discharge level reduced them to 65Ah, according to that Boeing engineer they have reduced the top charged level voltage and increased the lowest discharge level voltage, does anyone here have a figure for the new capacity?

[kenneth house]

rated at 65 Ahr, but the state of charge (SOC) and the depth of discharge (DoD) may now be different. One of the documents mentioned that the battery pack would lock up (open the contactor) and become non-functional requiring change out and return to Yuasa if discharged more than 15% (i.e. below 85% SOC), or basically after using only 10 Ahrs of the rated 65. From that it would appear that they are barely using the capacity of the cells.

The cells would last a very very long time and never need containment if they would only charge them to 90% and never discharge below 10%. This would provide 80% of useful energy from the rated 65 AHr, or 52 Ahrs, and every bit of it useful for starting APUs.

[PickyPerkins]

"Never" is a long time. Any battery can burst, even ordinary AA cells occasionally burst.
Did you know AA alkaline batteries could explode? | Procrastiblog (http://procrastiblog.com/2007/06/01/did-you-know-aa-alkaline-batteries-could-explode/)
Given the large energy content, these batteries need a box.

I do not know what the new charging range is.

The Boeing SCD for the APU battery calls for it provide three successive APU starts, nominally needing 18kW x 45 seconds x 3 = 0.675 kWh.

If we take a worst case of the battery providing only 22V, this only requires a battery capacity of 30.7Ah (and less if the voltage is higher), so it seems to me that capacity is not likely to be a problem even with a restricted charging range applied to a nominal 65Ah battery.

If cabin pressure is held at that of 6000 ft altitude and also maintained all the way into the Main and Aft E/E compartments, then the delta-pressure across the cell walls is on the order of -2.9 psi, which will cause the cell cases to swell and bulge out such as is seen in the CT scans of the exemplar batteries from both Boston and the ANA battery events.

I have difficulty following the logic here. The new battery enclosure consists of a steel box, an exhaust pipe, and a pressure relief diaphragm.

It is a sealed system in which its internal pressure will not change with cabin pressure. The air pressure in the system will change with temperature, but not with altitude. So the delta-pressure across the battery cell walls (if any) will not change with altitude. And any increase in temperature will increase the pressure and thus tend to inhibit swelling.

In any case, if the cells contain only solid material and electrolyte (no gas) then bulging can only occur if the pressure differential is great enough to vaporize the electrolyte or to release dissolved gases, and -2.9 psi is probably not enough to do this. If the cells contain free gas then bulging could occur much more easily, but I expect them to be gas-free.

Normal charging of LiCoO2 cells has been reported to cause 11% swelling:
http://www.pprune.org/7693607-post689.html

[Kiskaloo]

The electrolyte in the battery is in the form of a paste-like substance, PickyPerkins. It only becomes a liquid when exposed to high temperatures (as what happened when the cells entered thermal runaway and vented).

[kenneth house]

@PickyPerkins
i would think that the pressure in the Aft E/E is actually lower than cabin pressure since there is airflow into the EE from the cabin, so the delta P in the event configuration may have been -3 to -4 psi. The cell case dimensions are a little over 2x5x7 inches, with surface area ~120 sq inch, and the bulging force at -3 psi delta is about 360 lbs acting on the 0.031 inch thick stainless steel walls. It results in large deformation of 304 stainless in computer stimulations.

Now add some of that 11% swelling due to normal wear and tear charging to the delta P bulging--and you have found the root cause of the internal cell short circuiting that resulted in the venting and smoke events at Narita and Boston. Add some Ni-Cd profile trickle overcharging to a Lithium battery and you have a ticking timeb0mb in a blue box--lithiums can cook off at anytime once the cumulative damage has been done.

The cells are not produced in a vacuum chamber and have quite a bit of air volume internally. We know this because Yuasa stated at the NTSB hearing that they use a loosely-compacted roll technique in order to not cause short circuits from excessive compaction penetrating the (20 micron?) separators. They also said that they have never seen an internal short circuit in any of their industrial cells numbering over 14,000 since 2001.

Not all the cells vented, for example cells 4 and 5 at Narita. The CT scans showed that the internal current collector bars for those cells were intact and not broken, whereas the cells that vented all had broken collector bars. Yuasa showed a chart that overcharging could cause a cell to swell and deform, which could break an internal current collector bar and cause short circuiting.

Now about that new configuration: If you can get the dimensions and material thickness of the vault we can run a delta P load case for how much it will swell if unvented. At what pressure does the vent open? If/once the vent opens there will be a huge delta P on the blue box and the cell cases depending upon altitude.

[inetdog]

kenneth house:
Now about that new configuration: If you can get the dimensions and material thickness of the vault we can run a delta P load case for how much it will swell if unvented. At what pressure does the vent open? If/once the vent opens there will be a huge delta P on the blue box and the cell cases depending upon altitude.

The information I have seen indicates that for reliability the vent is simply a rupture disk.
If we assume that it has to be able to tolerate more than the pressure differential between pressurization altitude and maximum flight altitude, you can get a lower limit on the overpressure required at low altitude to rupture the disk.
What I would like to know is whether there is also some sort of very restricted air bleed to allow for a slow equalization of internal pressure over the normal time between maintenance openings of the box.

[PickyPerkins]

@inetdog

If we assume that it has to be able to tolerate more than the pressure differential between pressurization altitude and maximum flight altitude, you can get a lower limit on the overpressure required at low altitude to rupture the disk.



Maybe the lower limit on the overpressure required to rupture the disk has to be higher than you are suggesting.

Initially the air pressure in the sealed system will be whatever the atmospheric pressure was at the place and time that the system was closed. If at a later time the system and its battery is hotter then the pressure in the system will be higher. So the lower limit on the overpressure required to rupture the vent disk maybe ought to be the difference between this higher-than-atmospheric-pressure and the pressure at maximum flight altitude (plus a good margin). This is a higher limit than you suggested.

I was interested to see that a presentation at one of the NTSB hearings (by a manufacturer who seems not to be involved with the 787) mentioned an example of a burst disk operating pressure of a cell (not a battery and not a sealed enclosure) of 200psi.
http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Visco%20Quallion%20Presentation%20-%20Battery%20Forum.pdf


What I would like to know is whether there is also some sort of very restricted air bleed to allow for a slow equalization of internal pressure over the normal time between maintenance openings of the box.
　
I hope not. A “a very restricted air bleed” is how moisture can accumulate inside a system, something Boeing has already found in testing.
http://www.pprune.org/tech-log/505695-787-batteries-chargers-part-1-a-53.html#post7759373 (http://www.pprune.org/tech-log/505695-787-batteries-chargers-part-1-a-53.html)

[TURIN]

i would think that the pressure in the Aft E/E is actually lower than cabin pressure since there is airflow into the EE from the cabin, so the delta P in the event configuration may have been -3 to -4 psi.

The aft EE bay is within the pressurised fuselage area. Same pressure as cabin pressure.

[kenneth house]

@ Turin

On page 53 of the Airworthiness report is a figure showing the E/E compartment being just upstream of the overboard exhaust valve. The pressure in the cabin will be higher than in the EE compartment--there has to be a pressure drop otherwise there will be no air flow.

Where is the cabin altitude pressure sensor located? That is the feedback control point for the ECS and all downstream pressures from there will be lower than at that location.

[toffeez]

The US National Transportation Safety Board (NTSB) is conducting an urgent new round of testing on the Boeing 787 (http://www.flightglobal.com/landingpage/Boeing%20787.html)'s lithium-ion batteries in hopes of finding a root cause before most airlines resume routine commercial flights next month.

A solicitation issued on 3 May by the NSTB uses the "urgency" of the tests to justify bypassing federal regulations that require calling for multiple bids and instead award the work to a contractor based close to the agency's headquarters in Washington DC.

The computed tomography (CT) scans of eight lithium-ion battery cells "must also be completed within the shortest timeframe possible to provide the fastest possible receipt of this information to avoid potential future accidents involving this type of aircraft battery", the NTSB says. "Since the [Federal Aviation Administration] has recently approved a plan intended to result in the Boeing (http://www.flightglobal.com/landingpage/Boeing.html) 787 (http://www.flightglobal.com/landingpage/Boeing%20787.html) being approved for a return to service, the information from these tests is needed as soon as possible," the agency adds.

[EEngr]

Interesting. Do you have a link to their proposed test plan?

At this point, many of us suspect that the 787 battery problems are a 'systems' problem (integration of battery, charger, loads, etc.). It will be interesting to see how far the NTSB is planning to go in simulating these interactions.
:8

[Ian W]

At this point, many of us suspect that the 787 battery problems are a 'systems' problem (integration of battery, charger, loads, etc.). It will be interesting to see how far the NTSB is planning to go in simulating these interactions.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/nerd.gif

There may also be SOP issues as well. Where there could be unexpected ways of handling the aircraft systems perhaps after flight, like nav lights on for longer than expected or braking when towing. I would hope that the multiple fixes that have been instituted - not only the armored box - will have closed the potential for systemic or procedure issues.

[ozaub]

FWIW from data dump at #40, particularly http://dms.ntsb.gov/public%2F54000-54499%2F54251%2F524338.pdf and testimony at NTSB hearings I wrote an account of whole sorry saga. Published yesterday in Canberra Times at Dreamliner's nightmare run (http://www.canberratimes.com.au/comment/dreamliners-nightmare-run-20130509-2jb30.html). Sorry for tabloid journalism and any over simplifications. There seem to be few overviews and best I’ve read elsewhere is at FAA, Boeing Grilled About Battery Certification (http://www.aviationweek.com/Article.aspx?id=/article-xml/AW_04_29_2013_p24-573413.xml)

[Kiskaloo]

toffeez noted:
The US National Transportation Safety Board (NTSB) is conducting an urgent new round of testing on the Boeing 787's lithium-ion batteries in hopes of finding a root cause before most airlines resume routine commercial flights next month.

The NTSB subsequently issued a follow-up statement noting that this was “contracting language” meant to quickly secure funding for the work and was not meant to imply an acceleration of efforts to find the root cause of 787 battery problems.

The Board noted they would be correcting the language in the request and added that there was no new information on the investigation.

[mm43]

NTSB press release follows:-

WASHINGTON – The investigative work into the Jan. 7, 2013, fire aboard a Japan Airlines Boeing 787 at Logan International Airport in Boston, is estimated to be completed by the end of March, the National Transportation Safety Board said today. The analytical and report writing phase of the investigation will follow the completion of the investigative activities. The final report is expected to be presented to the Board at a public meeting in Washington in the fall.

Members of the investigative team have been conducting work in the United States, Japan, France, and Taiwan. As the investigation has progressed, the NTSB has been working closely with Boeing, the Federal Aviation Administration, the Japan Transport Safety Bureau, the French BEA, and technical advisors from Japan and France.

Some of the investigative activities include:

- Completed disassembly and documentation of the individual cells of the incident battery.

- Completed examinations of exemplar batteries and battery cells for baseline reference and comparison to the incident battery. These examinations were conducted at NTSB and independent laboratories and included computed tomography scans, non-destructive soft short testing, and destructive evaluation and analysis of the batteries and cells.

- Awarded a contract to Underwriter’s Laboratories to assist the NTSB in defining and performing system-level tests of the Boeing 787 battery and charging system. The testing includes characterization of the thermal and electrochemical properties of the battery and oscillatory testing and is expected to be completed in February.

- Radiographic studies, which included over 200,000 CT scan images, were conducted to examine and document the internal configuration of individual cells from the incident and exemplar batteries.

- Conducted interviews with FAA, Boeing, Thales, and GS Yuasa personnel to review and document key steps, personnel roles and responsibilities, data and information flow, design artifacts, and approvals in the certification process for the battery and charging system.

- Evaluated and documented the process for the battery system safety assessment, including a review of the supporting tests and analysis performed and the safety analysis standards relevant for lithium-ion batteries.

- Conducted on-site survey of battery manufacturing facility in Japan including a review of design, engineering, and production documentation, as well as manufacturing processes, procedures, and training for personnel involved in the manufacture of the battery.

The date of the Board meeting at which the findings of the investigation will be released, including the probable cause of the battery fire, will be announced later in the year.

All of the information and resources the NTSB has released for this investigation can be accessed from the following page:-

Accident Investigations - Boeing 787 (http://go.usa.gov/4K4J)

[airman1900]

From Flightglobal news article today Jan. 8, 2014

One year later, no issues for Boeing 787 battery redesign (http://www.flightglobal.com/news/articles/one-year-later-no-issues-for-boeing-787-battery-redesign-394664/)

"Since the certification of the improved battery system and the return-to-service for the 787 Dreamliner (http://www.flightglobal.com/landingpage/Boeing%20787.html) fleet, there have been no battery cell failures,” Boeing says in a statement to Flightglobal.

[airman1900]

From Flightglobal news article today Jan. 14, 2014 titled:

Boeing confirms new 787 battery problem in Tokyo

http://www.flightglobal.com/news/articles/boeing-confirms-new-787-battery-problem-in-tokyo-394831/ (http://www.flightglobal.com/news/articles/one-year-later-no-issues-for-boeing-787-battery-redesign-394664/)


Boeing (http://www.flightglobal.com/landingpage/Boeing.html) has confirmed that a single cell of a Japan Airlines (http://www.flightglobal.com/landingpage/Japan%20Airlines.html) 787 (http://www.flightglobal.com/landingpage/Boeing%20787.html) lithium-ion battery overheated with the aircraft parked at Tokyo Narita International (http://www.flightglobal.com/landingpage/Tokyo%20Narita%20International.html) airport on 14 January.

“The issue occurred during scheduled maintenance activities with no passengers on board,” Boeing says in a statement. “The improvements made to the 787 battery system last year appear to have worked as designed.”

Boeing shares fell 4% immediately following a published report about the latest 787 lithium ion battery failure.

Within an hour the company’s shares had recovered to nearly $140 each, but that was still below the $142 price per share prior to the report.

According to a Reuters story, Japan Airlines says maintenance workers found smoke coming from the main battery of the 787.

The workers also found an unidentified liquid coming from the battery, the report says.

[Dubaian]

This was the lead story on BBC World News (TV) this morning. Reasonably sensible reporting (as far as I can judge) and pretty much in line with the above linked article. They said one of eight batteries had melted but the box did contain the problem.

BBC web site article and video BBC News - Boeing 787 aircraft grounded after battery problem in Japan (http://www.bbc.co.uk/news/business-25737515)

[mm43]

NTSB PARTICIPATING IN JAPAN’S INVESTIGATION OF B-787 BATTERY SMOKE EVENT

January 15, 2014
WASHINGTON – The National Transportation Safety Board will participate in the investigation of a smoke event involving the main battery of a Japan Airlines B-787 that occurred while the aircraft was parked at Tokyo’s Narita Airport on Jan. 14.

The investigation is being led by the Japan Civil Aviation Bureau. NTSB aircraft systems investigator Mike Bauer will travel to Japan to assist with the investigation.

All information regarding the investigation will be released by the JCAB.

Latest press release.

[inetdog]

airman1900: Your post had the correct text form of the link, but the URL behind the text pointed to the previously posted article.
For those who are less agile with their browsers, here is the correct link:
Boeing confirms new 787 battery problem in Tokyo - 1/14/2014 - Flight Global (http://www.flightglobal.com/news/articles/boeing-confirms-new-787-battery-problem-in-tokyo-394831/)

[RR_NDB]

Hi,

Recent incident suggest:

1) Continued problems with battery charging "method"

2) Failure of thermal monitoring of individual cells (was implemented?)

3) Probable failure of voltage monitoring of individual cells (is implemented?)

4) Delay of monitoring. AFAIK smoke was visible BEFORE electronic alarms.

Smoking occur after cell abuse, mostly during charging.

A decent System can ABSOLUTELY avoid cell abuse.

The BAD Thales original design seems still present. "Murphy" is around the corner. :}

Parallel charging was not implemented? IMHO, would be the best option MAIN/APU Li batt. for airliners.

[RR_NDB]

Is a Contained Problem a Solved Problem?

Boeing 787 Dreamliner: Ready for Takeoff...Again? (http://petergreenberg.com/2013/04/30/boeing-787-dreamliner-ready-for-takeoff-again/)


"But should you rush out to buy a ticket on a Dreamliner? Boeing admits that three months of rigorous testing failed to discover the source of the earlier battery fires. Is containing a problem the same thing as eliminating it?"

[RCav8or]

Since no battery technology is 100% failure proof, I would have to say that mitigating the potential issues of fire, or damage to other systems in the electronics bay is a big step to making a Li-on battery failure on a 787 a manageable event.
Hopefully, more information as to what exactly the failure mode with this individual cell was in this event, will lead to future improvements in the battery and charging system.

Now I have a question for those with more in depth knowledge of the 787 electrical system. My limited understanding suggests that if the main battery on a 787 were to become unusable, the APU battery can be switched to the 28Vdc bus, providing a backup to the 787's main battery. I'm also under the impression that the APU battery is only used to start the APU on the ground when no other power source is available, and that an APU start when at least one of the main engines is running is done with power from the main engine generators. Am I correct in this thinking?

[TURIN]

No.
The APU battery starts the APU and supplies power to some external lights when towing on bat only.
It cannot connect to any DC bus.

[RR_NDB]

Indeed, the fix was an overkill. But we must learn thoroughly the issue and kill the causes, not just the consequences.

Certainly something improved in the charging/management of the batteries. The failure rate shows. And the "container" was not necessary. Til this case:
Question: Undetected parameter (electrical and/or thermal and suddenly, smoke and spill?

This sound as an indication of cell abuse. Certailnly when charging the battery.

Very suspicious of additional "room for improvement"

I strongly suspect now:

1) Lack of per cell thermal monitoring

2) Lack of per cell voltage adequate "processing".

My experience with these cells shows they are much more critical than other chemistries. Abuse notably during charging is unacceptable. What kind of?
Not proper thermal and voltage in a "per cell" basis.

[RR_NDB]

TURIN,

Did you learn what kind of miswiring was detected?

Considering the lights you mentioned could be drive by the busses a miswiring could charge the APU batt bypassing the it´s dedicated charger.

The damage to the battery was impressive. Actually i "modeled" the equivalent circuit and posted the analysis.

I didn´t learn on findings in that case.

Like the Tokyo in the APU batt.

[phiggsbroadband]

As every aero-modeller will confirm, when you discharge a Lithium Ion cell in minutes as opposed to hours, ( i.e. at a rate higher than 1xC ) it will get warm. The same applies for fast charging.


As the outside vent from the sealed box is sealed with a rupture plug, Is it true that the whole box has no natural or forced cooling air-flow? I have not been able to find any reference to a cooling system.

[Pub User]

The 787 Batteries have no cooling system.

[DType]

My mobile phone stopped working up the hill today because of sub zero temperature, so I put it inside my jacket until it warmed up. Which made me wonder about possible transient temperature effects on the 787.
Now Li-ion is much less degraded by low temperatures than other chemistries, but it must still be temperature dependent to some extent. Assuming (!!) the charging voltage is adjusted down as the temperature drops, then it would also be adjusted back up as the temperature recovers on descent and landing. But not every area of every cell will be at the same (transient) temperature as the relevant sensor at all times. If this temperature discrepancy exceeded the built in "safety" margins, then over voltage could be applied in some local area(s), leading to damage, and failure becoming apparent after landing.
Of course, the reverse temperature changes occur on take off and climb, but maybe the margins are deliberately greater in that phase, to minimise the probability of an in flight problem.
And I know that I don't know what I'm talking about, so it is more of a question than a suggestion.

[Volume]

We discussed already some time ago the temperature range recommended by the cell manufacturer compared to the temperature range an aircraft operates in. It looks like nobody has reliable data about the temperature in the electronics bay of a transport aircraft. Especially no data about the regularly experienced temperature cahnges, the extremes when parked in Sibiria overnight or in Dubai on the tarmax at noon with all electronics running is quite predictable, but the temperature range in the electronics bay during a typical moderate climate to moderate climate (via frosty stratosphere) flight seems to be widely unknown.

The 787 Batteries have no cooling system. Which is strange, as other high performance battery applications even have full temperature control (cooling and heating), for example the Antares motorglider or hybrid cars. Typically the energy used for heating is smaller than the increase in battery capacity with temperature, so you win available energy by spending some on temperature control. KISS can sometimes make you keep something too simple...

[Machaca]

The JTSB has issued their Final Report on the ANA JA804A (http://www.mlit.go.jp/jtsb/eng-air_report/JA804A.pdf) battery incident.