787 Batteries and Chargers - Part 2
You guys have probably already seen this BBC report?
BBC News - Boeing 787 Dreamliner returns to service in Ethiopia flight
Ethiopian already back in the air
BBC News - Boeing 787 Dreamliner returns to service in Ethiopia flight
Ethiopian already back in the air
More bang for your buck
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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?
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The cell and pack capacity is still the same
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.
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.
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The cells would .... never need containment .....
"Never" is a long time. Any battery can burst, even ordinary AA cells occasionally burst.
Did you know AA alkaline batteries could explode? | Procrastiblog
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.
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
Did you know AA alkaline batteries could explode? | Procrastiblog
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.
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
Last edited by PickyPerkins; 30th Apr 2013 at 21:40. Reason: spelling, and to remove the word "liquid".
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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).
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That delta P was looking at the Root Cause, not at the vault...
@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.
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.
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kenneth house:
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.
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.
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.
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@inetdog
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...ry%20Forum.pdf
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
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.
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...ry%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
Last edited by Jetdriver; 8th Jan 2014 at 18:58.
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.
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It's all 'Nominally' at cabin pressure, but varies along the path.
@ 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.
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.
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NTSB conducting urgent new round of testing on the 787's batteries
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.
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 787 being approved for a return to service, the information from these tests is needed as soon as possible," the agency adds.
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 787 being approved for a return to service, the information from these tests is needed as soon as possible," the agency adds.
RE: NTSB conducting urgent new round of testing on the 787's batteries
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.
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.
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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.
FWIW from data dump at #40, particularly http://dms.ntsb.gov/public%2F54000-5...1%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. 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
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toffeez noted:
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.
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 Board noted they would be correcting the language in the request and added that there was no new information on the investigation.
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NTSB Update on Investigation
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
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
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From Flightglobal news article today Jan. 8, 2014
One year later, no issues for Boeing 787 battery redesign
One year later, no issues for Boeing 787 battery redesign
"Since the certification of the improved battery system and the return-to-service for the 787 Dreamliner fleet, there have been no battery cell failures,” Boeing says in a statement to Flightglobal.
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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/
Boeing confirms new 787 battery problem in Tokyo
http://www.flightglobal.com/news/articles/boeing-confirms-new-787-battery-problem-in-tokyo-394831/
Boeing has confirmed that a single cell of a Japan Airlines 787 lithium-ion battery overheated with the aircraft parked at Tokyo Narita International 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.
“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.
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On BBC
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
BBC web site article and video BBC News - Boeing 787 aircraft grounded after battery problem in Japan
Last edited by Dubaian; 15th Jan 2014 at 06:09.