Audi 2010 Annual Report Download - page 105

The temperature inside a lithium-ion battery should always
be between 25 and 55 degrees Celsius. If it is too cold, the
cells’ internal resistance increases rapidly – by as much as a
factor of ten. Battery output plummets. Heat, on the other
hand, greatly accelerates the aging of the cells.
Audi engineers are therefore investing particularly large
amounts of expertise into optimal temperature manage-
ment. This is also essential elsewhere, as the human body
must likewise maintain its temperature within a narrow
normal range at all times in order to survive.
Caution: chain reaction!
Chain reactions, such as when overcharging destroys a cell,
represent a major risk for an electric car’s battery block.
“The overall functionality of a battery is determined by its
weakest cell,” warns Kötz. Safety intervals and good heat
dissipation are therefore used in addition to charge status
monitoring to protect the battery against secondary damage.
After all, slight damage should not result in the failure of the
overall system. The human body uses new blood vessels to
bypass a blood clot for similar reasons.
Lithium-ion batteries are a still relatively young tech-
nology and unlike humans do not require millions of years
to achieve gains in effi ciency. Audi uses a trick to speed up
their “evolution.” The development engineers subject test
batteries to permanent charge and discharge cycles on bat-
tery test rigs. This accelerated aging helps them to quickly
develop new high-voltage batteries with greater energy
capacities while maintaining a constant level of safety and
extending service life. Such fast-paced generational changes
mean that even reluctant people can overcome their nerves
and partake in the electric mobility of the future. O
FALKO BLASK
103
Route 3
Range –
the ultimate goal
Route 2
Range with normal driving behavior
Prudence and eff ective technology already enable good
ranges today. Recuperation allows energy to be recovered,
adjustments to torque save electricity when starting off ,
and economical use of electrical consumers enables electric
vehicles to cover longer distances.
The evolution of battery tech-
nology is still in its infancy.
Greater capacities and improved
battery management will increase
the range of electric vehicles
substantially. Lower-weight cells
and vehicles as well as progress
in drive technology are alleviating
people’s fear of running out of
energy and replacing it with pure
driving enjoyment.
An audio version of this article is available at:
www.audi.com/ar2010/battery
Weight reduction
Thermal insulation
Optimized cooling
coo g
Improved steering
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Optimized battery electronics
oni
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Improved drive technology