Hello DREW-- The battery in the Audi A8 is located in the trunk on the passenger side.  That design is meant to protect you from battery acid burns in the event of a front end collision.  It happened to me in 1973 in a minor collision (my fault.)  I hit the other guy at such an angle that my battery exploded and covered my legs with the battery acid.  It ruined a perfectly good pair of double-knit bell bottoms.   Good luck from Bovan.

Trunk, passenger's side. And it is there as there is no room under the V8's hood for it, NOT because it may explode...GEEZ!