At 02:13 AM 26/02/2013, you wrote:
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Its interesting that billions of consumer
devices can use Lithium-xxx batteries safely
(maybe one per 100 million catching fire) while
Boeing with the help of FAA regulations
manages to fry two out of fifty aircraft
The Monster has become very well at running the
daily business (almost no more crashes in big,
commercial aviation), but completely incapable of even minor innovation.
Only my personal, uninformed, subjective, (somewhat outsider) observation
Urs
Here's some good information:
http://www.mpoweruk.com/lithium_failures.htm
There's lots of other good information there too.
There are in fact a fair number of fires in
commercial aircraft usually caused by personal
electronic devices failing. Of course you never
know how the devices or batteries have been
treated. I'd worry about dropping on to hard
surfaces causing internal damage leading to
internal shorts in the cells. This can apply to
all battery chemistries of course including
sealed lead acid and even vented lead acid batteries like car batteries.
I've heard of two crashes, one recent in the
Middle east where a 747 freighter went down after
a fire in the cargo where there it was known that
Li ion batteries were on board. Another South
African 747 disappeared over the Indian Ocean
about 10 years ago or so and a cargo of lithium
batteries was suspected. Check the FAA battery fire database.
There are still crashes in large commercial
aviation (Air France 447, the Turkish 737 that
landed short at Schiphol and others) mostly where
the monkeys up front don't seem to be paying
attention or channelise their attention so they
miss the big picture. It requires basic stick and
rudder skills and the ability to think, neither
of which feature much in their daily operations.
There seems to be a trend, not only in aviation,
to de-skill most jobs and substitute procedure
which is fine until something goes wrong or is out of the ordinary.
A Boeing spokesman recently said they were
modifying the battery in the 787 to put it in a
titanium box, add a vent system to outside in the
event of fire and actually monitor the temperature and voltage of each cell.
Yikes! I'd have thought that would have been in
the original design. At least the last bit. How
did that get past certification?
Seems Thales got the overall battery power
design, Securaplane(Meggitt) got the supervisory
electronics and Yuasa built the battery cells.
Securaplane had a fire some years ago that burned
down one of their buildings - where they were
running failure tests in lithium batteries. Hmmmm.
Note LiFePO4 are lithium ION batteries. Just the
chemistry is different. See the link. That
chemistry apparently is considerably safer than
some others. Note that the Airbus A380 uses
lithium batteries and the first A350 will be
lithium battery equipped as they want to fly and
test first. It would not surprise me to see
lithium in production A350s after the present
kerfuffle dies down. Should take about 3 months.
Now about those electric gliders with all those
incendiary grenades packed alongside the spar or
in the middle of the fuselage. High discharge
current on very high capacity cells.
I think LiFePO4 is safe enough to use for
avionics and some other functions in gliders but
I'd want to monitor each cell voltage at least in
operation, use a proper automatic charger with a
cell balance feature and remove the battery from
the glider when charging (don't use as starter in
motorgliders where there is a generator). In
short, properly engineer the installation. Don't
charge in the hangar or leave unattended. A nice
steel box with nothing up against it that can catch fire would be good.
Mike
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