787 Batteries and Chargers - Part 1
Join Date: Feb 2011
Location: Nearby SBBR and SDAM
Posts: 875
Likes: 0
Received 0 Likes
on
0 Posts
Something went terribly wrong in dealing with 2 simple but important parts
Hi,
Sadly Boeing is suffering a serious setback. What´s important now:
787 Back in the skies with batteries within “aviation standards”
Considering it could take long to precisely know what caused one or both incidents and above all, timing is very important for all players, the best path seems to return ASAP to the current “standard”: Ni Cd´s. A third case is inconceivable.
Any implication like weight penalties, etc. IMO are "becoming small" compared to prolonged grounding. So the business could not wait too much.
It seems wiser to start again the effort to adopt these wonderful but dangerous items in airliners. The 787 program is paying a high price. Even the use of them in the A380 emergency lighting would require a closer look. Not to mention the A350 and other. (Mil not included here)
Despite the current use of electronics “inside the case” of the Thales used in 787, a battery is a simple device. A Lead Acid or Ni Cd may have just cells to work properly. You may “protect” any battery internally, externally or in both ways.
A charger is also a simple device even for Lithium. In the later the operation just requires monitoring and control of each cell voltage and temperature to keep the cells inside the envelope. (Monitoring the individual cell temperature adds extra safety to properly manage the cells and monitor the unit.) The circuitry required to accomplish this is also “simple”. (a closed loop system). And with the protections ideally derating the battery for airliners application, the advantages of Lithium versus Ni Cd will certainly be reduced.
I am a technician, love high performance items but the management of the crisis demands a sound managerial decision making.
With safety first, looking to the people and the business involved.
Mac
bsieker:
Easily affordable, IMO.
Sadly Boeing is suffering a serious setback. What´s important now:
787 Back in the skies with batteries within “aviation standards”
Considering it could take long to precisely know what caused one or both incidents and above all, timing is very important for all players, the best path seems to return ASAP to the current “standard”: Ni Cd´s. A third case is inconceivable.
Any implication like weight penalties, etc. IMO are "becoming small" compared to prolonged grounding. So the business could not wait too much.
It seems wiser to start again the effort to adopt these wonderful but dangerous items in airliners. The 787 program is paying a high price. Even the use of them in the A380 emergency lighting would require a closer look. Not to mention the A350 and other. (Mil not included here)
Despite the current use of electronics “inside the case” of the Thales used in 787, a battery is a simple device. A Lead Acid or Ni Cd may have just cells to work properly. You may “protect” any battery internally, externally or in both ways.
A charger is also a simple device even for Lithium. In the later the operation just requires monitoring and control of each cell voltage and temperature to keep the cells inside the envelope. (Monitoring the individual cell temperature adds extra safety to properly manage the cells and monitor the unit.) The circuitry required to accomplish this is also “simple”. (a closed loop system). And with the protections ideally derating the battery for airliners application, the advantages of Lithium versus Ni Cd will certainly be reduced.
I am a technician, love high performance items but the management of the crisis demands a sound managerial decision making.
With safety first, looking to the people and the business involved.
Mac
bsieker:
...with all the redesign that requires.
Easily affordable, IMO.
Last edited by RR_NDB; 23rd Jan 2013 at 00:53. Reason: Add link
Join Date: Mar 2009
Location: USA
Posts: 70
Likes: 0
Received 0 Likes
on
0 Posts
No doubt that the Li-ion batteries have a greater power/density/weight capability than some of the not-so-old batteries like the nickel-metal-hydride ones. Funny, but Toyota sticks with those nickel ones for their Prius.
You might want to do a little research.
ALL Prius vicheles sold outside of North America feature Li-Ion batteries.
The US "pluck-in" version also featurs Li-Ion.
Join Date: Jun 2009
Location: somewhere
Posts: 451
Likes: 0
Received 0 Likes
on
0 Posts
Even the use of them in the A380 emergency lighting would require a closer look. Not to mention the A350 and other.
In the later the operation just requires monitoring and control of each cell voltage and temperature to keep the cells inside the envelope. (Monitoring the individual cell temperature adds extra safety to properly manage the cells and monitor the unit.)
The charging, monitoring, and protection functions are integrated in each battery.
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
MurphyWasRight,
The only thing I found on this is that the APU battery is designed for two consecutive start attempts, after which a 5 minute cooling period must be observed before a third starting attempt. I don't know if that means 5 minutes from then on after every start attempt, or if a maximum of 3 attempts is permitted, and if the limiting factor is only the battery or perhaps also the starter motor. (Starting from other sources, the starter motor used can be alternated, but the APU battery can only power the right starter motor.)
RR_NDB,
I agree that a redesign for Ni-Cd would almost certainly be cheaper than another (serious) incident or accident.
Bernd
For example what % of the APU battery charge is used by a single start cycle? How long does it take to "top off" after that and how many start attempts must be avaialable in non-nominal flight?
RR_NDB,
I agree that a redesign for Ni-Cd would almost certainly be cheaper than another (serious) incident or accident.
Bernd
Quotes from bsieker:
(1) “The only thing I found on this is that the APU battery is designed for two consecutive start attempts, after which a 5 minute cooling period must be observed before a third starting attempt. I don't know if that means 5 minutes from then on after every start attempt, or if a maximum of 3 attempts is permitted, and if the limiting factor is only the battery or perhaps also the starter motor.”
It sounds a very familiar, conventional limitation, typical of APU starting limitations since the 1960s, where the batteries have been lead-acid or NiCd. My understanding was always that it was to stop the starter overheating, and/or time for unburned (sorry, pun not intended!) fuel to drain away. But within these factors, an unwritten battery-protection measure may have been contained, as you seem to be suggesting might be the case with these Li-Ion ones.
As you know better than I, the peak battery load on starter engagement is massive (just as it is on a car battery during engine start). The A320 uses its 2 main (NiCd) batteries for APU start if no external power is available. In the 1990s, when starting the APU using external power, I was able to monitor the two TR loads. Initially, they would be off-scale but, IIRC, they reappeared as the current was falling through 350 amps (each). So the peak current delivered by the TRs was in excess of 700 amps. But the main (NiCd) battery was also contributing, so this suggests a peak starter load of the order of 1000 amps.
(When the A320 entered service, it only employed one TR for APU start. This led to an embarrassing incident on a demonstration flight for the French President, during which the relevant TR failed during APU start, resulting in considerable DC load-shedding.)
(2) “(Starting from other sources, the starter motor used can be alternated, but the APU battery can only power the right starter motor.)”
I’ve never used an APU that had more than one starter motor, AFAIK. When you say the “right” starter motor, do you mean “R/H” or “correct”? (The English word “right” can be ambiguous, which is why many of us old pilots replace it with “starb’d”.) Are there two APU starter motors on the B787?
(1) “The only thing I found on this is that the APU battery is designed for two consecutive start attempts, after which a 5 minute cooling period must be observed before a third starting attempt. I don't know if that means 5 minutes from then on after every start attempt, or if a maximum of 3 attempts is permitted, and if the limiting factor is only the battery or perhaps also the starter motor.”
It sounds a very familiar, conventional limitation, typical of APU starting limitations since the 1960s, where the batteries have been lead-acid or NiCd. My understanding was always that it was to stop the starter overheating, and/or time for unburned (sorry, pun not intended!) fuel to drain away. But within these factors, an unwritten battery-protection measure may have been contained, as you seem to be suggesting might be the case with these Li-Ion ones.
As you know better than I, the peak battery load on starter engagement is massive (just as it is on a car battery during engine start). The A320 uses its 2 main (NiCd) batteries for APU start if no external power is available. In the 1990s, when starting the APU using external power, I was able to monitor the two TR loads. Initially, they would be off-scale but, IIRC, they reappeared as the current was falling through 350 amps (each). So the peak current delivered by the TRs was in excess of 700 amps. But the main (NiCd) battery was also contributing, so this suggests a peak starter load of the order of 1000 amps.
(When the A320 entered service, it only employed one TR for APU start. This led to an embarrassing incident on a demonstration flight for the French President, during which the relevant TR failed during APU start, resulting in considerable DC load-shedding.)
(2) “(Starting from other sources, the starter motor used can be alternated, but the APU battery can only power the right starter motor.)”
I’ve never used an APU that had more than one starter motor, AFAIK. When you say the “right” starter motor, do you mean “R/H” or “correct”? (The English word “right” can be ambiguous, which is why many of us old pilots replace it with “starb’d”.) Are there two APU starter motors on the B787?
OLD RED DAMASK
Join Date: Apr 2004
Location: Lancashire born. In Cebu now
Age: 70
Posts: 368
Likes: 0
Received 0 Likes
on
0 Posts
You'd think even a giant like Boeing would have heeded a warning in 2011 when Cessna CJ4's were grounded by the FAA.
"In 2011, the Federal Aviation Administration temporarily grounded the CJ4 and issued an airworthiness directive because of battery fires in the Lithium-Ion original equipment:
We are adopting a new airworthiness directive (AD) for certain Cessna Aircraft Company (Cessna) Model 525C airplanes. This emergency AD was sent previously to all known U.S. owners and operators of these airplanes. This AD requires replacing certain lithium-ion batteries installed as the main aircraft battery with either a Ni-Cad or a lead acid battery. This AD was prompted by a report of a battery fire that resulted after an energized ground power unit was connected to one of the affected airplanes equipped with a lithium-ion battery as the main aircraft battery. We are issuing this AD to correct the unsafe condition on these products."
"In 2011, the Federal Aviation Administration temporarily grounded the CJ4 and issued an airworthiness directive because of battery fires in the Lithium-Ion original equipment:
We are adopting a new airworthiness directive (AD) for certain Cessna Aircraft Company (Cessna) Model 525C airplanes. This emergency AD was sent previously to all known U.S. owners and operators of these airplanes. This AD requires replacing certain lithium-ion batteries installed as the main aircraft battery with either a Ni-Cad or a lead acid battery. This AD was prompted by a report of a battery fire that resulted after an energized ground power unit was connected to one of the affected airplanes equipped with a lithium-ion battery as the main aircraft battery. We are issuing this AD to correct the unsafe condition on these products."
Last edited by lasernigel; 23rd Jan 2013 at 09:54.
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
Chris Scott,
yes, I meant "right hand". I was aware of the ambiguity when I sent it, but decided to leave it like that, because that is the wording used.
On the Dreamliner, being the "more electric plane", both main engines and the APU each have two starter/generators. The APU's SGs are designated "left" and "right".
A single dedicated starter would probably suffice, but since they are starter/generators, and two generators are installed for redundancy, one ends up with two starters as well.
Bernd
yes, I meant "right hand". I was aware of the ambiguity when I sent it, but decided to leave it like that, because that is the wording used.
On the Dreamliner, being the "more electric plane", both main engines and the APU each have two starter/generators. The APU's SGs are designated "left" and "right".
A single dedicated starter would probably suffice, but since they are starter/generators, and two generators are installed for redundancy, one ends up with two starters as well.
Bernd
Quote from bsieker:
“...both main engines and the APU each have two starter/generators. The APU's SGs are designated "left" and "right".
A single dedicated starter would probably suffice, but since they are starter/generators, and two generators are installed for redundancy, one ends up with two starters as well.”
Thanks for the clarification, Bernd, and for reminding me that they are starter/generators. I’m disappointed with Boeing’s left/right terminology in this instance.
The twin starter/generator configuration is shown in the only document that I have seen, entitled “B787 Systems and Performance”, which dates from 2005. In addition to being at least six years ahead of actual entry into service, it has the look more of a publicity document than a technical overview, so I’ve been taking its contents with a large pinch of salt. The fact that it schedules certification and delivery in 2008 does little to inspire confidence in the currency of its information.
The document also shows both APU gennies, together with the 4 ED gennies, supplying a common, nebulous “230Vac Distribution”. I presume you must have a more detailed, authoritative source?
Somewhere in the multitude of PPRuNe threads (is it 5?) started since the APU battery failure in Boston earlier this month, I’ve picked up the idea that the APU battery can only be charged by energy from its dedicated APU charge circuit; not by the main electrical system. So, bearing in mind what you have said, I tentatively conclude that the R/H starter/generator feeds the APU battery charge circuit, while the L/H starter/generator feeds the main 230Vac system. Is that correct?
The APU battery and the Main battery seem to be identical in themselves, each rated at only 65Ah. Unlike the B777, it seems there is only one Main battery unit. There has been speculation on whether the separate APU and Main battery failures were similar or not, and whether they were under charge or under load. It seems unlikely that the ANA aircraft’s Main battery would have been subject to a high load, although the same cannot be said for the APU battery in the JAL case. If the failures were from a common cause, it would probably be the chargingsystem?
Chris
“...both main engines and the APU each have two starter/generators. The APU's SGs are designated "left" and "right".
A single dedicated starter would probably suffice, but since they are starter/generators, and two generators are installed for redundancy, one ends up with two starters as well.”
Thanks for the clarification, Bernd, and for reminding me that they are starter/generators. I’m disappointed with Boeing’s left/right terminology in this instance.
The twin starter/generator configuration is shown in the only document that I have seen, entitled “B787 Systems and Performance”, which dates from 2005. In addition to being at least six years ahead of actual entry into service, it has the look more of a publicity document than a technical overview, so I’ve been taking its contents with a large pinch of salt. The fact that it schedules certification and delivery in 2008 does little to inspire confidence in the currency of its information.
The document also shows both APU gennies, together with the 4 ED gennies, supplying a common, nebulous “230Vac Distribution”. I presume you must have a more detailed, authoritative source?
Somewhere in the multitude of PPRuNe threads (is it 5?) started since the APU battery failure in Boston earlier this month, I’ve picked up the idea that the APU battery can only be charged by energy from its dedicated APU charge circuit; not by the main electrical system. So, bearing in mind what you have said, I tentatively conclude that the R/H starter/generator feeds the APU battery charge circuit, while the L/H starter/generator feeds the main 230Vac system. Is that correct?
The APU battery and the Main battery seem to be identical in themselves, each rated at only 65Ah. Unlike the B777, it seems there is only one Main battery unit. There has been speculation on whether the separate APU and Main battery failures were similar or not, and whether they were under charge or under load. It seems unlikely that the ANA aircraft’s Main battery would have been subject to a high load, although the same cannot be said for the APU battery in the JAL case. If the failures were from a common cause, it would probably be the chargingsystem?
Chris
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,074
Likes: 0
Received 0 Likes
on
0 Posts
I am viewing what I think is the same source as Chris Scott re: schematic. So let me display a risk of appearing thick...
Aren't the SG's on all the turbines AC? Simply from a weight standpoint, how could they be DC? Obviously the APUBATT is 28vDC?
I 've peeped the APU, and it seems a bit massive for its DC power (EMER) source?
So how is APUBATT integrated to the APU/start? Inverter, or separate (dedicated) and DC SG?
layman
Aren't the SG's on all the turbines AC? Simply from a weight standpoint, how could they be DC? Obviously the APUBATT is 28vDC?
I 've peeped the APU, and it seems a bit massive for its DC power (EMER) source?
So how is APUBATT integrated to the APU/start? Inverter, or separate (dedicated) and DC SG?
layman
Last edited by Lyman; 23rd Jan 2013 at 13:10.
Join Date: May 2009
Location: sfo
Age: 70
Posts: 309
Likes: 0
Received 0 Likes
on
0 Posts
Lyman
From the study guide, circa 2010:
The Start Power Unit (SPU) takes 28v dc from the battery and changes it to 115v ac. The 115v ac is sent to the R2 Autotransformer Rectifier Unit (ATRU) where it is changed to +/- 135v dc and then sent to the Common Motor Start Controller (CMSC) which then changes it back to 115v ac (!) to start the APU if 4 or so other things have happened in the meantime.
As I understand it, 115v ac is used to turn the ASG (which normally puts out 230v ac) and the generator neutral relay must be open.
The right-hand ASG is used to start from battery power. From ship or ground power, they alternate.
The Start Power Unit (SPU) takes 28v dc from the battery and changes it to 115v ac. The 115v ac is sent to the R2 Autotransformer Rectifier Unit (ATRU) where it is changed to +/- 135v dc and then sent to the Common Motor Start Controller (CMSC) which then changes it back to 115v ac (!) to start the APU if 4 or so other things have happened in the meantime.
As I understand it, 115v ac is used to turn the ASG (which normally puts out 230v ac) and the generator neutral relay must be open.
The right-hand ASG is used to start from battery power. From ship or ground power, they alternate.
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,074
Likes: 0
Received 0 Likes
on
0 Posts
Dangit, that is just the thing...
Thanks sfo
My very first a/c was a 1966 J model Cessna 182. I obviously am weak in the technoELEC.
Having noticed an architecture in the 787 that mimics fifty (sixty?) year old technology, as to back up systems, how behind the times are regs, and FAA?
For all the flak Boeing are taking, it must be grating to put a battery in their electric jet.
Aside. LiH is what makes the Hydrogen bomb go boom, no?
For my money, a sufficient amount of compressed air and a small turbine would be safer and more dependable than Lithium, imo. At least to start the APU.
thanks, Bernd
Thanks sfo
My very first a/c was a 1966 J model Cessna 182. I obviously am weak in the technoELEC.
Having noticed an architecture in the 787 that mimics fifty (sixty?) year old technology, as to back up systems, how behind the times are regs, and FAA?
For all the flak Boeing are taking, it must be grating to put a battery in their electric jet.
Aside. LiH is what makes the Hydrogen bomb go boom, no?
For my money, a sufficient amount of compressed air and a small turbine would be safer and more dependable than Lithium, imo. At least to start the APU.
thanks, Bernd
Last edited by Lyman; 23rd Jan 2013 at 14:48.
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
Chris, Lyman,
The "235 V AC distribution" consists of 4 buses, L1, L2, R1, R2. Normally each is powered by one main engine generator, but there seems to be some crossbar switching, so if generators fail, the associated buses are powered from other buses.
The APU can power all four buses, or those buses not powered by main engine generators. As far as I can see, in practice, the buses can be switched onto different generators dynamically, as load and available generation requires.
They are all variable frequency AC, depending on generator rpm, so I guess it's not a good idea to try to power one bus from two different sources at the same time.
(I don't know how authoritative my source is. It says "do not use for flight" and appears to be from 2010.)
Bernd
The "235 V AC distribution" consists of 4 buses, L1, L2, R1, R2. Normally each is powered by one main engine generator, but there seems to be some crossbar switching, so if generators fail, the associated buses are powered from other buses.
The APU can power all four buses, or those buses not powered by main engine generators. As far as I can see, in practice, the buses can be switched onto different generators dynamically, as load and available generation requires.
They are all variable frequency AC, depending on generator rpm, so I guess it's not a good idea to try to power one bus from two different sources at the same time.
(I don't know how authoritative my source is. It says "do not use for flight" and appears to be from 2010.)
Bernd
Last edited by bsieker; 23rd Jan 2013 at 14:37.
Join Date: Feb 2011
Location: Nearby SBBR and SDAM
Posts: 875
Likes: 0
Received 0 Likes
on
0 Posts
Charging her is just one concern. There are other dangerous issues
Hi,
The battery has ~ 1/1000 of the mentioned ~ "1.5 MW" plane design. I´ve heard of a diode in the main battery circuitry. We will be able to understand the approach used.
A very low internal resistance together a highly critical battery in a bus (i am looking for the main battery) is another concern. You naturally have "discharge spikes" to batteries in buses. Lead acid and Ni Cd´s are much more tolerant.
I hope transient loading (a design parameter of the electric circuit) to the main battery allows Boeing to replace to Ni Cd without further considerations. (A battery in a bus also acts as a "capacitor" reducing the ripple in the DC level).
In APU battery fire (BOS) we may say this was not a factor. It started the APU and being recharged as we imagine.
IMO what saved the day in TAK was just how fast the crew landed. I also think Machaca put a "lighter" scenario on Japan incident.
Question: The battery case cover is flat or has the geometry showed in the picture of destroyed main battery?
Mac
The battery has ~ 1/1000 of the mentioned ~ "1.5 MW" plane design. I´ve heard of a diode in the main battery circuitry. We will be able to understand the approach used.
A very low internal resistance together a highly critical battery in a bus (i am looking for the main battery) is another concern. You naturally have "discharge spikes" to batteries in buses. Lead acid and Ni Cd´s are much more tolerant.
I hope transient loading (a design parameter of the electric circuit) to the main battery allows Boeing to replace to Ni Cd without further considerations. (A battery in a bus also acts as a "capacitor" reducing the ripple in the DC level).
In APU battery fire (BOS) we may say this was not a factor. It started the APU and being recharged as we imagine.
IMO what saved the day in TAK was just how fast the crew landed. I also think Machaca put a "lighter" scenario on Japan incident.
Question: The battery case cover is flat or has the geometry showed in the picture of destroyed main battery?
Mac
Last edited by RR_NDB; 24th Jan 2013 at 00:38. Reason: Text improvement
Join Date: Jan 2008
Location: Denmark
Age: 79
Posts: 158
Likes: 0
Received 0 Likes
on
0 Posts
RR_NDB,
I also agree 100% with your post#81.
As you say: A third case is inconceivable - so right and BOEING knows that!
Therefore I think they will have to go back to the "old" battery technology as the best option for getting this very important project on track again.
In any case before the type will be allowed to fly again, BOEING "must demonstrate to the FAA that the battery system is safe" - not an easy job with the current system, bearing in mind the many known causes of Lithium-ion battery failures.
I also agree 100% with your post#81.
As you say: A third case is inconceivable - so right and BOEING knows that!
Therefore I think they will have to go back to the "old" battery technology as the best option for getting this very important project on track again.
In any case before the type will be allowed to fly again, BOEING "must demonstrate to the FAA that the battery system is safe" - not an easy job with the current system, bearing in mind the many known causes of Lithium-ion battery failures.
Join Date: Feb 2011
Location: Nearby SBBR and SDAM
Posts: 875
Likes: 0
Received 0 Likes
on
0 Posts
A33Zab,
It seems not feasible/possible integrate an effective protection inside the battery.
It allows even remove the battery from the bus?
I could limit the discharge spikes current?
This sounds "marketing talk".
Will comment on that in subsequent posts. And also your first question.
Mac
I´m posting using the mobile between meetings.
It seems not feasible/possible integrate an effective protection inside the battery.
It allows even remove the battery from the bus?
I could limit the discharge spikes current?
This sounds "marketing talk".
Will comment on that in subsequent posts. And also your first question.
Mac
I´m posting using the mobile between meetings.
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,074
Likes: 0
Received 0 Likes
on
0 Posts
The image Machaca posted from ANA shows top cover attached, and exhibiting the results of "rapid expansion" of contents. It is higher resolution, but does not show as extensive display of dripping electrolytes on front cover.
The JAL (APU) BATT shows evidence of a pry tool to remove damaged top cover.
(Anyone able to report on the health and whereabouts of the injured firefighter?)
From RR_NDB....
"I think Machaca put a "lighter" scenario on Japan incident. Question: The battery case cover is flat or has the geometry showed in the picture of destroyed main battery?"
Another thank you to Machaca for such helpful imagery...
The JAL (APU) BATT shows evidence of a pry tool to remove damaged top cover.
(Anyone able to report on the health and whereabouts of the injured firefighter?)
From RR_NDB....
"I think Machaca put a "lighter" scenario on Japan incident. Question: The battery case cover is flat or has the geometry showed in the picture of destroyed main battery?"
Another thank you to Machaca for such helpful imagery...
Last edited by Lyman; 23rd Jan 2013 at 17:38.
Join Date: Jun 2009
Location: somewhere
Posts: 451
Likes: 0
Received 0 Likes
on
0 Posts
@RR_NDB:
"marketing talk".
Withholding information is also a 'marketing strategy'.
You are seriously worried about A380 emergency lighting?
What about the installed but - not mentioned - approx. 40! wireless emergency lighting Li-Ion batteries, 2 Li-Ion Flight Control BackUp batteries and the 2 Li-Ion indepent power supplies to the recorders in B787?
Last edited by A33Zab; 23rd Jan 2013 at 18:32.
Thread Starter
Join Date: Jul 2007
Location: My Stringy Brane
Posts: 377
Likes: 0
Received 0 Likes
on
0 Posts
The Chicago Tribune reports:
Japan: overcharging unlikely cause of Dreamliner woes
TOKYO/WASHINGTON (Reuters) - Japanese regulators have joined their U.S. counterparts in all but ruling out overcharged batteries as the cause of recent fires on the Boeing Co 787 Dreamliner, which has now been grounded for a week worldwide.
TOKYO/WASHINGTON (Reuters) - Japanese regulators have joined their U.S. counterparts in all but ruling out overcharged batteries as the cause of recent fires on the Boeing Co 787 Dreamliner, which has now been grounded for a week worldwide.
Solving the battery issue has become the primary focus of the investigation, but with excess voltage more or less off the table, investigators are still hunting for a possible cause.
Last weekend the U.S. National Transportation Safety Board said the fire on a Japan Airlines Co Ltd 787 in Boston was not due to excess voltage, and on Wednesday, Japanese officials all but ruled it out for the incident on an All Nippon Airways Co Ltd plane there.
"On the surface, it appears there was no overcharging," said Norihiro Goto, chairman of the Japan Transport Safety Board, at a media briefing.