Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

787 Batteries and Chargers - Part 1

Tech Log The very best in practical technical discussion on the web

787 Batteries and Chargers - Part 1

Old 27th Feb 2013, 01:54
  #821 (permalink)  
 
Join Date: Mar 2011
Location: engineer at large
Posts: 1,409
from Boeing Land...

Reports of Boeing 787 test flights "completely inaccurate": FAA

SEATTLE (Reuters) - The Federal Aviation Administration said it is not close to approving test flights of Boeing's 787 Dreamliner with a proposed fix for the plane's troubled batteries, denying news reports that such tests could start as early as next week.
"Reports that we are close to allowing 787 test flights are completely inaccurate," spokeswoman Laura Brown said on Tuesday in an email to Reuters.


http://finance.yahoo.com/news/report...w_default=true
FlightPathOBN is offline  
Old 27th Feb 2013, 04:23
  #822 (permalink)  
 
Join Date: Nov 2009
Location: flying by night
Posts: 504
Here's an excellent overview of triggers of thermal runaway, mechanisms of internal shorting, and implications for managing field failures (particularly page 5 onwards, "Triggers for Li-Ion thermal runaway" from the annotated book facsimile) :

Lattice Energy LLC- Field Failures and LENRs in Lithium-based Batte...

I would be surprised if the 787 battery incidents were triggered by external "abuse", ie the batteries were operated outside limits, although it is not unthinkable. If this was the case, the investigation should be able to find out sooner rather than later.

It seems clear that cascading was an issue - due to inadequate spacing/thermal insulation, a failed cell would release heat to neighbouring cells. This will be adressed with the proposed new design (but as many have already pointed out, it won't prevent the battery from failing, it will just fail with less smoldering).

Boeing states that clean room technology is used to manufacture the cells. This is to minimize contaminations which could later trigger an internal short (such contaminations can not yet be detected with cell screening). I would speculate that cleanliness and manufacturing QC are well managed and not an issue (it shouldn't at least , and if it is, the investigations should be able to find out).

According to Boeing, the 2.2 Million cell hours before January 2013 were without incidents. If the 787 incidents, or one of them, are true "field failures", as described in the book, neither triggered by external influence, nor triggered by contamination introduced during manufacturing, the investigations will never be able to know with certainty what exactly happened.

Now if Boeing wants to contain the fire, and hope it's a 1:1'000'000 thing, this leads me to believe they're leaning towards field failure as a probable cause?

Last edited by deptrai; 27th Feb 2013 at 05:12.
deptrai is offline  
Old 27th Feb 2013, 05:30
  #823 (permalink)  
 
Join Date: Aug 2011
Location: hong kong
Age: 59
Posts: 93
LiCoO2 is mature technology. These cells are derated to 4.025V EOC and ultra reliable.

There is too much damage to the cells. It is improbable, that the cause of the Primary failure can be conclusively established by forensics.

Further analysis of the electrical system and of reported wiring errors will provide clues.

Now if Boeing wants to contain the fire, and hope it's a 1:1'000'000 thing, this leads me to believe they're leaning towards field failure as a probable cause?
I doubt that. They just want to make sure.
saptzae is offline  
Old 27th Feb 2013, 06:18
  #824 (permalink)  
 
Join Date: Nov 2009
Location: flying by night
Posts: 504
LiCoO2 is mature technology. These cells are derated to 4.025V EOC and ultra reliable.
Agreed, the cells should be very reliable. According to GS Yuasa Technologies,

"[GYT] fixed their chemical design at 1999 and did not change. GYT large Li-ion cells [...] have never showed internal short accident through more than 10 years production. (>5000 cells)"

(from a sales pitch to NASA https://batteryworkshop.msfc.nasa.go...Ion_TInoue.pdf - which also shows the differences between "aerospace-grade" and typical "commercial" Sony cells. These GS Yuasa cells are certainly well engineered).

Last edited by deptrai; 27th Feb 2013 at 06:24.
deptrai is offline  
Old 27th Feb 2013, 16:11
  #825 (permalink)  
 
Join Date: Mar 2011
Location: engineer at large
Posts: 1,409
"The battery, made by Japan’s GS Yuasa, was Boeing’s choice for the 787’s design in 2005, which Laslau says is unfortunate because its cathode was based on cobalt oxide. “The cobalt oxide chemistry that Boeing chose has a fantastic energy density, but it’s not the safest. Lithium iron phosphate would be safer,” he says. But the iron phosphate alternative wasn’t well developed seven years ago."


Boeing Battery Blues

edit...

I still feel that a circular wind is needed..the thermal expansion would be radial and transferred along the length. Hopefully, they would be smart enough to wind it with the proper thermal spacing.
With a square wind, you have the ability to create a bend during manufacture, but even if you dont, the thermal expansion will keep hitting the corners and eventually may degrade the winding.
There is also the compression/decomp of normal aircraft ops on the battery itself

Last edited by FlightPathOBN; 27th Feb 2013 at 19:21.
FlightPathOBN is offline  
Old 27th Feb 2013, 23:33
  #826 (permalink)  
 
Join Date: Mar 2011
Location: engineer at large
Posts: 1,409
From Boeing land..

Battery maker GS Yuasa believes the fix for the battery should include a voltage regulator that could stop electricity from entering the battery, the Journal said.

Boeing proposed its fix to the FAA on Friday, but on Thursday, Yuasa told the FAA that its laboratory tests indicated that a power surge outside the battery, or other external problem, started the failures on two batteries, according to the newspaper.

Boeing, battery maker at odds over 787 fix - WSJ | Reuters
FlightPathOBN is offline  
Old 27th Feb 2013, 23:53
  #827 (permalink)  
 
Join Date: Feb 2013
Location: Placerville, CA
Posts: 71
From the Reuters article:

Boeing spokesman Marc Birtel said that the investigation has not showed that overcharging was a factor and that the 787 had quadruple-redundant protection against overcharging in any case.
The admitted wiring error or component failure that allowed the APU battery to power loads that should only have been on the bus from the main battery leads me to conjecture that in the ANA case the quadruply redundant protection may have been at most singly or doubly redundant.

Last edited by inetdog; 27th Feb 2013 at 23:54.
inetdog is offline  
Old 28th Feb 2013, 00:08
  #828 (permalink)  
 
Join Date: Jan 2013
Location: BRISBANE
Posts: 13
B787 battery

There has never been any sense in keeping voltage across a Li-Ion battery when 100% SOC. It is like trying to overfill a fuel tank. But this is only one hole in the swiss cheese model.

Regards
bill good is offline  
Old 28th Feb 2013, 00:20
  #829 (permalink)  
 
Join Date: Feb 2013
Location: Placerville, CA
Posts: 71
bill good said:
There has never been any sense in keeping voltage across a Li-Ion battery when 100% SOC. It is like trying to overfill a fuel tank. But this is only one hole in the swiss cheese model.
Not the same Li chemistry, but I believe that at least some plug-in EV manufacturers recommend that for maximum life their battery should not be left idle for long periods with an SOC above 80%. They advise to top off the charge shortly before using it if full range is needed.
Since under expected usage, the 787 batteries will be sitting without loads almost all of their lives, this could be an issue.
inetdog is offline  
Old 28th Feb 2013, 05:59
  #830 (permalink)  
 
Join Date: Aug 2011
Location: hong kong
Age: 59
Posts: 93
Derated

Cells are derated to 4.025V EOC, or about 70%-80% of max charge at 4.2V.

Consumer or EV batteries will charge to 4.1 - 4.2V.

The difference in reliability is huge. 0.1V reduction quintuples cell life.

Last edited by saptzae; 28th Feb 2013 at 05:59.
saptzae is offline  
Old 2nd Mar 2013, 19:27
  #831 (permalink)  
 
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,123
ANA: Dreamliner Battery Solution

Last edited by Lyman; 2nd Mar 2013 at 19:29.
Lyman is offline  
Old 2nd Mar 2013, 21:58
  #832 (permalink)  
 
Join Date: Mar 2011
Location: engineer at large
Posts: 1,409
"A Boeing presentation in February described "baking the battery to induce overheating, crush testing and puncturing a cell with nail to induce short circuit."

At the same time the FAA approved the special conditions in 2007, FAA staff and the aircraft manufacturing industry, including Boeing, were devising lithium-ion battery tests that included all the details the special conditions lacked.

Published in 2008 and adopted by the FAA three years later, the standard known as RTCA DO-311 gave precise instructions for tests. The worst-case-scenario test required turning off all failsafe electronics, short-circuiting the battery and watching for flames for three hours.

Boeing did not run those tests. "The RTCA standards were not designed for the 787," and Boeing provided extensive testing to show the 787 met the special conditions, spokesman Marc Birtel said.

The FAA acknowledged the batteries were potentially flammable in the special conditions approved. Said former Inspector General Schiavo, "They knew they had problems. They just said 'OK.'""

Insight: Will Dreamliner drama affect industry self-inspection? | Reuters
FlightPathOBN is offline  
Old 6th Mar 2013, 20:41
  #833 (permalink)  
 
Join Date: Mar 2011
Location: engineer at large
Posts: 1,409
ANA says it had Dreamliner power distribution panel trouble three times

ANA says it had Dreamliner power distribution panel trouble three times - Yahoo! News

Japanese union uneasy with 787 electrical power panels | Business & Technology | The Seattle Times

At least the circuit panels are made in Mexico, not Japan...

Last edited by FlightPathOBN; 6th Mar 2013 at 20:45.
FlightPathOBN is offline  
Old 7th Mar 2013, 06:53
  #834 (permalink)  
 
Join Date: Apr 2008
Location: back of beyond
Posts: 98
I think we might be getting closer to the root cause of the battery problems. Anyone have any idea how solid state isolators and diodes (and lithium batteries!) react to conditions that burn out circuit boards? Even if described by Boeing as "a low energy arc that lasted milliseconds, very small", what happens to the bus voltage during the incident? How does the battery isolation/charging circuitry react? Has this been tested for on the bench?
fizz57 is offline  
Old 7th Mar 2013, 08:19
  #835 (permalink)  
 
Join Date: Oct 2012
Location: toofaraway
Posts: 224
P100 Power Distribution Panel after Laredo emergency landing

“The risk to the company is not this battery, even though this is really bad right now,” said one 787 electrical
engineer, who asked not to be identified. “The real problem is the power panels." Unlike earlier Boeing jets, he said,
the innards of the 787 power distribution panels — which control the flow of electricity to the plane’s many
systems — are “like Radio Shack,” with parts that are “cheap, plastic and prone to failure.”
Seattle Times.


Last edited by toffeez; 7th Mar 2013 at 08:43.
toffeez is offline  
Old 7th Mar 2013, 08:26
  #836 (permalink)  
 
Join Date: Dec 2001
Location: England
Posts: 1,387
Anyone have any idea how solid state isolators and diodes (and lithium batteries!) react to conditions that burn out circuit boards?
I'm an electronics engineer. There is nothing like enough information in those articles to comment on how one part of the system might respond to a fault in another. Common sense at the design stage would require each system to isolate itself from others in the event of an internal fault (eg breakers/fuses used so that a short circuit doesn't have consequences outside that part of the system). I've not seen any reports that the aircraft that had power panel fauts was the same aircraft that had battery faults.
cwatters is offline  
Old 7th Mar 2013, 09:24
  #837 (permalink)  
 
Join Date: Apr 2008
Location: back of beyond
Posts: 98
Agree 100%. My only point is that this new information about failing panels does indicate that something in the 787's electrical systems is not behaving as intended, with collateral effects that may not be limited to shorting distribution panels.

I don't buy the argument that the panels themselves (or the batteries, or the chargers) are under-engineered. Today's components may have more silicon than copper but are just as robust. And in any case bench testing will have shown up any obvious shortcomings.

Funny how this information about line failures is leaking out slowly (and not from Boeing). First the battery replacements, now this. What's going to be next?
fizz57 is offline  
Old 7th Mar 2013, 15:22
  #838 (permalink)  
 
Join Date: Mar 2011
Location: engineer at large
Posts: 1,409
cwatters, fizz,

Exactly...

As noted in the voluminous amount of article(s), most of these issues were not reported. The 150 batteries, the panels, and who knows what else...we only find out in small controlled batches of disconnected information. I cant really believe that there have been 150 batteries returned for a single issue with the battery alone. There arent that many aircraft flying, and only what, 16 batteries per ac...

The articles note that everyone is deliberately vague, and in all cases, wont identify the aircraft the issue was found on.

Like many other directives, inspections will be ordered on all aircraft, so you may see many other aircraft with these issues, once people start looking.

Last edited by FlightPathOBN; 7th Mar 2013 at 15:23.
FlightPathOBN is offline  
Old 7th Mar 2013, 15:45
  #839 (permalink)  
 
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,123
Shall we at least try to determine these "circuit boards" problems are NOT the printed circuit boards in the battery case?

Power Panels could easily be confused with "circuit boards".

Perhaps the 150 battery replacements had to do with failures in the battery's own "circuit boards"?

BLOOMBERG is reporting ANA leaks as "circuit boards".

Flight Path.... are you on board with the "Eight Battery" Battery? Not the "Eight Cell" "Battery"?

Boeing used the "Eight Cell" concept to inflate their line experience.

Eight Batteries, in series. IMO.

Last edited by Lyman; 7th Mar 2013 at 15:51.
Lyman is offline  
Old 7th Mar 2013, 17:25
  #840 (permalink)  
 
Join Date: Jan 2008
Location: Blighty (Nth. Downs)
Age: 73
Posts: 2,052
It's time for another statement from Boeing/FAA/NTSB. This rumour mill is getting out of hand. Surely the customer airlines cannot be expected to do it. The credibility of the joint world-leader in airliner manufacture is slowly bleeding. Not a prettty sight.

Lyman

Quote:
.... are you on board with the "Eight Battery" Battery? Not the "Eight Cell" "Battery"?
(unquote)

I presume you, like me, have at least one conventional automobile, using recent - but not cutting-edge - technology. They each have a 12V DC electrical system, whose en-route power supply is some kind of engine-driven generator, backed up by a battery to cater for short-term contigencies. However, the main task of that battery is to provide a very high current for a few seconds to turn the engine's starter motor. (With me so far?)

In most cases, the 12V battery will be of the lead-acid type, consisting of eight 1.5V cells in series.

Are you telling me now that my car has 8 batteries? If not, please explain the difference in plain, simple English, if that's possible.

Quote:
Boeing used the "Eight Cell" concept to inflate their line experience.
(unquote)

Can you decode that for me?
Chris Scott is offline  

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.