Boeing lithium batteries

[[email protected]]

It's dead easy- we do it in some airborne battery systems (not Li) to

prevent thermal runaway from cascading, but it costs some size and

weight.

Looks like Cessna is on the right track here:
http://www.asme.org/kb/yellowbrix-a...8e13-49b4-9faf-c190dd738c57&storyid=181747960

 

[josephkk]

Follow articles in Aviation Week, The Wall Street Journal, and The New
York Times. Eventually there will be a comprehensive report from the
FAA and/or the NTSB.

The article in WSJ this morning said that the cause was traced to a
battery cell shorting itself. Why the cell shorted is not yet known,
but my guess is that vibration and bumps on landing are involved, mainly
because most test labs do not fly, so flying is what's new.

While test labs do not fly they certainly have vibration, shock, altitude,
vacuum test facilities, and some have combined altitude/vacuum with shock
and vibration facilities. So now the question is did they specify such
testing? Failing to specify both extensive shock and vibration testing
would clearly be an engineering slip-up at a minimum, more likely a
management foul-up for not understanding the importance of these rather
expensive tests for this application.

 

[josephkk]

Richard Henry wrote:


Well, it is pretty obvious they took some shortcuts on this system.
Either they contracted with Thales to torture-test this battery system,
or they should have done it themselves. That would mean thermal
cycling, vibration simulating flight plus takeoff/landing cycles, and
charge/discharge cycles. They also should have done failure insertion
tests to the charge/discharge control systems to deliberately cause
over/undercharge situations that would damage the batteries and see
how they fared.

So, either they didn't do the torture tests, or they didn't do them
for enough cycles. Since some of these planes were delivered in 2011,
it is possible they did quite a bit of due diligence, but just hadn't
accumulated enough hours to bring on the failures. They have racked up
quite a number of flight hours on the just 50 aircraft delivered so far.
It would be VERY interesting to know the actual number of hours and
flight cycles on the specific batteries that failed! I would almost guess
they are among the older units deployed, and if they kept the fleet flying
they would have developed more battery failures pretty soon.

Jon

Sounds like you have done some test engineering or at least been close
enough to understand. I did 13 years of test at Hughes once upon a time.

?-)

 

[josephkk]

On 2013-02-11 21:56, [email protected] wrote:

On Monday, February 11, 2013 3:25:00 PM UTC-5, Jon Elson wrote:

[email protected] wrote:

[Lots of double spaced junk deleted...]



Right, for the Boston JAL incident NTSB determined the runaway

originated in cell 6 and only cell 3 went into sympathetic

combustion. The cells were arranged in two columns of four where 3

and 6 were in separate columns next to one another. There are

insulator materials can handle temperatures way higher than the 500oC

heat of this fire and are quite thin. I'm pretty sure Boeing knows

quite a bit about fire containment, just not corrosive electrolyte

containment. But then again this fire was extinguished and not

allowed to run its course.





How do they deal with Li fires anyway? Water or CO2 don't cut it.



Jeroen Belleman

The Logan FD is reported to have used Halon.

IIRC the electrolyte acts as an oxidizer in a fire. So halon
wouldn't have done much until the oxidizer was depleted. This means
the only way to extinguish a fire in these is to get rid of the heat
-f

Yep, the fire extinguisher of choice is liquid Argon or liquid Neon. Also
for Magnesium fires and Thermite. It takes a lot in either case.

?-)

 

[josephkk]

Test labs do have vibe tables, though, and airplane designers do specify
vibe and shock standards for avionics. Everything is expected to not
only be designed for shock and vibe, but to be thoroughly tested.

Perhaps the difference is that they didn't shake things for 10 hours to
simulate a trans-Pacific flight. I dunno. But you can bet they were
specified, designed, and tested for vibe.


Again, this is a known phenomenon in avionics, and you design your boxes
to withstand such, then test the hell out of them before you ship. If
your customer is smart, they review your results, too.


The FAA tends to have a "blame the victim" mentality. If you go flying
and you crash because you did something, it's pilot error. If you go
flying and you crash because your equipment broke, then unless your
mechanic seriously pulled the wool over your eyes it's pilot error
because you took off with faulty equipment. If you go flying and you
crash because of bad weather, it's your fault because you didn't pay
attention to the weather. "Shit happens" is not a phrase to be found in
the FAA dictionary.

Obviously, if Boeing did a safety analysis that said the batteries were
OK, and they failed anyway, then ipso facto (by FAA logic) Boeing's
safety analysis was clearly deficient. Heaven knows -- the FAA may even
be right.

One thing is clear as he**, the general public will never get a clear
accounting of the cause. I doubt that even forensic engineers other than
the investigative team will ever get adequate information.

?-)

 

[Jeroen Belleman]

In a recent paper I did read Navy uses water vapour,
as that cools the cells down.
From:
Lithium-Ion Batteries Hazard
and Use Assessment
pdf is on the internet, google,

<quote from page 112 (of 126)>
The FAA studied suppression of lithium-ion batteries with water and Halon 1211, as these are
typically available in hand extinguishers aboard commercial aircraft.172 As a first choice, the
FAA recommends the use of water to suppress fires involving notebook computers, because
water will both extinguish flames and suppress thermal runaway propagation. As a second
choice, the FAA recommends using Halon 1211 to knock down flames, followed by deluge from
available water sources (such as bottles of drinking water). Halon 1211 alone will not prevent
<end quote>

Water is a strong oxidizer for Li. Pouring water on Li metal will
ignite it, not extinguish it!

As someone else in this thread pointed out, it's not even necessary
to add any oxidizer. In a charged battery, fuel and oxidizer are
conveniently close together in a single little package. While in less
efficient battery technologies, thermal mass and presence of inert
materials was sufficient to prevent fires, modern batteries have
energy densities that are high enough to ignite if breached.

I believe that to make them safe in this respect, oxidizer and
fuel should be stored apart.

Jeroen Belleman

 

[[email protected]]

While test labs do not fly they certainly have vibration, shock, altitude,

vacuum test facilities, and some have combined altitude/vacuum with shock

and vibration facilities. So now the question is did they specify such

testing? Failing to specify both extensive shock and vibration testing

would clearly be an engineering slip-up at a minimum, more likely a

management foul-up for not understanding the importance of these rather

expensive tests for this application.

If anything they did too much testing. There are general aviation requirements for lithium battery test from several organizations, electrical, mechanical, and environmental, many called out on a per battery basis, that for years have been suspected of introducing inchoate defects that eventually grow into full blown failures. In other news, the UN is pushing through emergency regulation by the ICAO to limit lithium batteries carried in passengerplane cargo to 11 lbs, down from the 77 lbs they were allowed prior to the787 fiasco.

 

[[email protected]]

[email protected] wrote:







Halon-type materials are designed to put out carbon fuel fires, such

as wood, paper, hydrocarbon fuels, plastics and things like circuit boards.

There are not supposed to be effective on metal fires and fires which

provide their own oxygen source. But, by the time they got there, all

of those other materials were probably involved in the mess.



Jon

A story supposedly leaked to CBS news was that the airframe damage was severe enough that had it occurred in flight the tail section would have broken loose of the fuselage.

 

[Martin Riddle]

Does anyone have a pointer to a good technical discussion of the
Dreamliner batteries?

Latest theory is Dendrites. I have heard of dendrites in lead acid
batteries (from Eagle Picher) but not in LI-Ion.

Here's a video that shows the dendrites forming.

<http://lithiumbatteryresearch.com/Dendrites-and-Fracture.php>


Cheers

 

[Cydrome Leader]

Looks like Cessna is on the right track here:
http://www.asme.org/kb/yellowbrix-a...8e13-49b4-9faf-c190dd738c57&storyid=181747960

I think you mean cessna never strayed from good design in the first place.

european electronics is always skethy stuff.

 

[Cydrome Leader]

That is not the only problem,
they have had a cracked window in the passengers compartment,
and a cracked windscreen at the pilot's.
This points to stresses in the composite? body.
Anybody remember 'comet'?
In that time they also tried to make things thinner and lighter,
a bit too thin, and like a comet it fell..
http://en.wikipedia.org/wiki/BOAC_Flight_781

And Airbus has also problems with cracks in the wings,

and the tails falling off.

 

[[email protected]]

I think you mean cessna never strayed from good design in the first place.



european electronics is always skethy stuff.

They had a LiFePO4 catch fire a few years ago and FAA issued an emergency airworthiness directive in 2011 ordering them to remove it and replace it with a NiCd.

 

[[email protected]]

Latest theory is Dendrites. I have heard of dendrites in lead acid

batteries (from Eagle Picher) but not in LI-Ion.



Here's a video that shows the dendrites forming.



<http://lithiumbatteryresearch.com/Dendrites-and-Fracture.php>





Cheers

They've known about dendrite formation for over a decade now.