The battery in the 1999 Audi A4 supplies the electrical charge to start your car's engine; it also provides the electricity to operate some of the mechanical devices in your car, such as the radio and the windows. In time, the battery will discharge and require replacement. Though the replacement of many car parts require the assistance of a mechanic, you can save money and replace the battery in your Audi A4 yourself.
Open the hood of the Audi A4.
Unsnap the black battery cover to expose the battery.
Loosen the negative battery cable, using the 10-mm wrench, and pull the cable off of the battery terminal. The negative battery terminal has a "-" symbol next to it.
Remove the positive battery cable by loosening the nut with the 10-mm wrench, and pull it off of the terminal. The positive battery cable has a "+" symbol next to it.
Unscrew the retaining bolt at the bottom of the battery holder and lift out the battery.
Place the replacement battery in the holder and tighten the retaining bolt.
Attach the positive battery cable to the positive battery terminal and tighten it with the 10-mm wrench.
Slide the negative battery cable onto the negative battery terminal and tighten the cable with the 10-mm wrench.
Close the battery cover by snapping it into place.
