If your BMW car battery is dead, you'll need to charge it. Charging the battery on a BMW is relatively straightforward. However, unlike most vehicles, BMW placed their battery in the boot instead of under the hood in the front of the vehicle. This means that you must access the battery through the boot. In most BMWs, the battery sits on the right-hand side of the vehicle underneath the luggage compartment's carpet and floor. There are actually two compartments--the spare tire compartment and the battery compartment.
Open the boot and pull up the luggage compartment carpet and floor using the small black looped handle to expose the spare tire and battery compartments.
Turn the locknuts on the battery compartment cover 1/4 turn counter-clockwise. The battery compartment is on the right side of the boot.
Lift the battery cover off the battery to expose the battery terminals.
Before you plug the charger in, connect the red (positive) alligator clamp on the battery charger to the positive terminal on the battery. Connect the black (negative) alligator clamp to the negative terminal of the battery. Then plug the charger in. Following this sequence reduces sparking and the chance of and explosion.
Turn the battery charger on and set the charger to charge the BMW's battery over a period of 12 hours if the battery was completely dead before the charge.