As a car battery ages, it becomes less capable of supplying the power needed to crank the Audi A6 and run its electronic components. If your battery can no longer hold enough of a charge to start your vehicle or run its electronics, chances are you will need to replace it. In order to install a new battery, you must remove the old battery from its location against the firewall, near the centre of the car. Removing the battery from the A6 should take no more than 15 to 20 minutes in ideal conditions.
Open the bonnet and locate the plastic dust tray near the windshield. The battery is located underneath the tray near the passenger side of the car. You will have to be remove the tray in order to gain access to the battery.
Remove the rubber seal from the edge of the plastic tray. Grab the tray with both hands and lift upward, then outward away from the windshield.
Remove the plastic passenger windshield cover. This cover is held down by three Phillips screws and one 8mm bolt. Remove all three screws and the single bolt, then pull the cover outward away from the windshield.
Disconnect the negative and positive battery cables with a 10mm wrench. Remove the retaining bolt at the base of the battery on the passenger side with a 13mm ratchet socket. Disconnect the battery drain hose from the battery.
Lift the battery out of the engine compartment. The battery is very heavy, so take caution and have a firm grip when lifting it out.
If the original equipment manufacturer (OEM) battery installed in your Audi cannot hold a charge, you may only need to refill the battery with distilled water instead of replacing it. Re-fill the battery and try recharging it. If it still can't hold a charge, you will have to replace it.
Have your Audi's radio code on hand when removing the battery, in case the radio needs to be reprogrammed after replacing the battery. Always wear protective gloves when handling a battery, in case of any spills or acid residue.