Audi R8 2008 Service Training Manual page 50

Electrical
Battery
In the Audi R8, the battery is located at the front
in the luggage compartment, behind the luggage
compartment cover. The battery terminals are
accessible by removing the battery compartment cover.
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To remove the battery, it is necessary to remove the
luggage compartment well cover and then the luggage
compartment well itself. The R8 does not have any
special jump start points.