All battery systems pose a potential fire risk especially if short
circuited, this is why it is essential to provide a suitable fuse as close
to the battery terminal as possible.
Due to their potential to provide high amounts of discharge current Lithium
batteries will generate a great deal of heat if shorted and certainly become
a major fire or even explosion risk. If a cell or the battery develops an
internal short (before the terminals) then no amount protection in the way
of external fuses or circuit breakers will be effective.
All new battery technology seems to go through this problem, I can well
remember major similar issues with Nickel Metal Hydride batteries a couple
of decades ago.
I believe in the long term Lithium technology especially some of the newer
Lithium Phosphate variants will replace the >150 year old lead acid
technology completely (much in the same way as LED lighting is rapidly
replacing both incandescent and fluorescent lighting).
If you consider the huge amount of lithium batteries in use in mobile
devices ranging from portable tools through to laptops, phones tablet PC's
and now electric cars, and the relatively rare event of fires caused by
these devices then I think it puts the situation into better perspective.
One of the major differences in battery usage in a commercial airliner as
opposed to a glider (apart from the obvious size of the batteries!) is that
the airliners systems are designed to charge the batteries in flight. We
would generally charge our batteries in the hanger (unless you have solar
panels on the fuselage), And as far as I understand the charging process is
where a significant amount of the overheating problems have occurred.
I think Airbus is being justifiably prudent given the recent incident with
the Boeing 787. However I think with pressure from the aviation industry
that battery manufacturers will rapidly further develop their manufacturing
processes and fine tune the chemistry, and Lithium technology will win out.
As far as our own pastime is concerned, I have been evaluating Lithium
Phosphate Batteries manufactured by Shorai in Japan. These are marketed as a
replacement 12Volt motorcycle battery. I have conducted discharge tests at
fixed current rates (generally 2 Amps) using a commercially designed
computer based battery testing system, whilst the manufactures stated A/H
capacity is somewhat overstated, the ability of the battery to provide a
constant voltage throughout the discharge period (>12V) is significantly
better than that of its lead acid counterpart. Couple this with the reduced
weight and expected longer life then this becomes an interesting option as a
Glider battery.
By the way throughout the testing I have at no stage found any evidence of
abnormal heating of the battery.
I have personally used the Shorai battery in flight several times, but given
the concerns of the aviation industry in general have held off recommending
that our club converts its fleet to this technology in the short term. I
believe that it will only be a couple of years before this technology full
acceptance in the aviation industry.
John Parncutt
From: aus-soaring-boun...@lists.internode.on.net
[mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Craig
Vinall
Sent: Monday, 25 February 2013 9:04 PM
To: aus-soaring@lists.internode.on.net
Subject: [Aus-soaring] AIRBUS has abandoned its plans to use lithium-ion
batteries for its new A350 airplanes
Thought this may be of interest. I know that these batteries are becoming
popular in gliders; what do others think? Is there a potential fire risk?
AIRBUS has abandoned its plans to use lithium-ion batteries for its new A350
airplanes.
The European aerospace group said Thursday it would revert to conventional
nickel-cadmium batteries for the A350 due to the uncertainty surrounding the
technology following the grounding of Boeing's 787 Dreamliner. The A350 is a
wide-body long-range jet rival to the 787 and is expected to make its first
flight around the middle of the year.
Airbus says it does not expect the battery switch to delay the A350's
schedule.
Lithium batteries are lighter and can store more energy than other types of
batteries of an equivalent size, and manufacturers view them as an important
way to save on fuel costs. But the batteries are also more likely to short
circuit and start a fire than other batteries if they are damaged, if there
is a manufacturing flaw or if they are exposed to excessive heat.
Federal officials grounded the 787 last month because of problems with its
lithium-ion batteries that caused one fire and forced another plane to make
an emergency landing.
"Airbus considers this to be the most appropriate way forward in the
interest of program execution and A350 XWB reliability," spokeswoman Mary
Anne Greczyn said.
Airbus noted the A350 uses batteries in a different setup than the 787,
making it unlikely that it would face the same problems. Its A350
flight-test program would still go forward with lithium-ion batteries.
But because the causes of the problems with the 787 batteries remain
unclear, Airbus decided to make the switch "to optimise program certainty,"
Ms Greczyn said. Airbus is a unit of Netherlands-based EADS NV.
The Wall Street Journal first reported on Airbus' decision to drop the
lithium-ion batteries, noting the incidents with the 787 have led to
industry uncertainty about future safety standards for the technology.
Regards
Craig Vinall
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