The BMW Z4 is a rear-wheel-drive sports car that replaced the Z3 in 2002. Its battery is housed in the boot to make for a shorter, sportier front. You can easily replace it yourself.
Place the Z4 in park and turn the engine off. Allow it to cool for a half hour.
Open the boot. Pull up the removable carpet and flooring. You will now have access to the battery, on the right side seated in a bracket.
Remove the bracket with a screwdriver. There are a total of three screws, two on the bracket and one securing it.
Remove the positive cable from the battery using a socket. Place the cable to the side. Remove the negative cable in the same manner. Pull the wall out.
Lift the battery out of the vehicle. Batteries can weigh up to 31.8 Kilogram, so get some help.
Place the replacement into the bracket. Replace the three screws to secure the bracket to the battery. Connect the positive battery cable and tighten it. Repeat the same process for the negative.