When your battery goes dead on your BMW 325xi and it won't stay charged, you will need to get a new battery and replace the old one. The BMW 325xi's battery placement is unique: It is in the trunk, on the passenger side. The battery is wired to the engine, though, the same way other car batteries are.
Open your BMW 325xi's trunk.
Turn the knob holding the panel over the battery on the right side of the trunk. Remove the panel.
Loosen and remove the clamp holding the black cable to the battery's negative post. Loosen and remove the clamp holding the red cable to the battery's positive post.
Twist off the knob holding the center bracket over the battery. Pull up the bracket and remove the old battery. Put the new battery in place and tighten the bracket over it.
Tighten the clamp on the red cable over the positive post on the 12 volt battery. Tighten the clamp on the black cable over the negative post on the 12 volt battery.
Screw the panel back on over the battery. Close the trunk.
