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July 18, 2006, 6:48 pm
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batteries with exposed terminals that shorted]
WASHINGTON Did laptop batteries aboard a UPS cargo plane ignite,=20
causing the aircraft to catch fire?
The National Transportation Safety Board began looking into the question =
at a hearing Wednesday.
All three crew members on the plane were treated for minor injuries=20
after it made an emergency landing shortly after midnight Feb. 8 at=20
Philadelphia International Airport.
Several other incidents have occurred in recent years in which lithium=20
batteries _ used in laptops and cell phones _ have caught fire aboard=20
Less than two months ago in Chicago, a spare laptop battery packed in a=20
bag stored in an overhead bin started emitting smoke, chief crash=20
investigator Frank Hilldrup of the NTSB testified Wednesday.
A flight attendant used an extinguisher and the bag was removed, but the =
bag caught fire on a ramp, Hilldrup said.
Investigators in the Philadelphia fire found that several computer=20
laptop batteries were on board the plane, and that in many cases=20
portions of the laptop batteries had burned, he said.
"It is not known at this time the role these batteries may have played=20
in the fire," Hilldrup said.
Lithium ion batteries are sometimes referred to as "rechargeable" or=20
"secondary" lithium batteries. They, along with primary or=20
"non-rechargeable" lithium batteries, can present fire hazards because=20
of the heat often generated when they are damaged or suffer a short circu=
It is expected to take several months for the NTSB to reach a conclusion =
about the cause of the fire in Philadelphia, although several hazardous=20
materials on board the plane have been determined not to be the cause.=20
The NTSB is also examining other related issues, such as what can be=20
done to make cargo flights safer and the overall emergency response to=20
In 1999, a shipment of lithium batteries ignited after it was unloaded=20
from a passenger jet at Los Angeles International Airport. Another=20
shipment erupted into flames in Memphis in 2004 when it was being loaded =
onto a FedEx plane bound for Paris.
In the case of the UPS cargo plane, the crew declared an emergency on=20
approach into Philadelphia. Fire and rescue crews met the four-engine=20
jet, a DC-8 that originated in Atlanta, when it touched down shortly=20
Firefighters said the blaze was under control about four hours later,=20
although the charred plane smoldered for hours.
Re: NTSB Probes Laptop Batteries in Jet Fire
If that were the case, you could ship as many batteries as it is possible to
fit in the aeroplane - because Lithium-ion batteries which have not been
abused contain no metallic Lithium whatsoever. The lithium is held in a
chemical compound and is entirely safe in this form. The flammable part of
the battery is the electrolyte, but as long as that is kept within the
battery, it does not normally pose a problem.
The 4 pricipal dangers with these batteries are:
(1) Puncturing of the cells which exposes the electrolyte to the air
whereupon it ignites (though the Lithium-ion-polymer construction has
improved this considerably).
(2) Overcharging or which causes the lithium to be deposited as metal but
also liberates oxygen from the chemistry. The lithium ignites in turn
igniting the electrolyte. The charge monitor circuit should prevent this.
(3) Discharging at excessive current (or short circuit) causes the same
effect as 2. The maximum discharge was 0.5C several years ago, but
Lithium-ion technology has improved over the years. Cells should contain a
PTC device to minimize this.
(4) Overdischarging (i.e. discharging to below 3.0 volts per cell (2.5 volts
for some early constructions)). This causes metallic copper to be plated on
the internal structure of the cell. This provides an alternative discharge
path (see scenario 3 for the next stage). It should be noted that the
plated out copper bypasses the cell's normal PTC protective devices. The
charge monitor should dis-allow charging cells in the condition, but there
is always someone who attempts to recover such a cell. A little knowledge
here can be a very dangerous thing.
It should also be noted that as the cell generates its own oxygen, a burning
cell is quite impossible to extinguish. Fire fighting should be restricted
to the surrounding material. The fireball from a burning cell can be as
much as a metre in diameter, and flames can be projected much further than
This is by no means an exhaustive discussion of the subject.