How to Disconnect the Battery on a BMW 325Xi

1. Park your BMW 325Xi and turn the engine off. Depress the trunk release button in the handle recess above the license plate and lift the trunk lid up.
2. Put on a pair of safety glasses and leather gloves for protection.
3. Lift up on the trunk floor panel removal ring to remove the floor panel. Set it aside.
4. Locate the battery cover panel on the right side of the trunk. Twist the two release screws counterclockwise with your hand and pull the cover off the battery.
5. Unscrew the bolt securing the negative (black) battery cable to the battery terminal, using a 10mm wrench.
6. Pull the negative battery cable directly off the battery terminal and push it aside, so that there is no chance it will contact the battery terminal while you remove the positive cable.
7. Unscrew the bolt securing the positive (red) battery cable to the battery terminal using a 10mm wrench.
8. Pull the positive battery cable directly off the battery terminal and push it aside so that there is no chance it will contact the battery terminal.
9. Remove the battery mounting bolt by turning the long metal screw in the left corner of the battery counterclockwise with a Phillips screwdriver. Pull up to remove the battery mounting bolt. Slide the battery backward slightly, then lift up on the battery to remove it.
10. Replace the battery, if necessary. Install the new battery following the removal procedure in reverse. Note that you should connect the positive battery cable first when reconnecting battery cables.