When replacing the car battery in your BMW, you should keep a few things in mind. Factors include the size of the battery, whether you want a sealed or unsealed battery, and if you need side posts or top posts. Some questions, such as whether to use a top- or side-mount post, can be answered by looking at the old battery. To determine the size of the battery, refer to your owner's manual or check the battery guide at your local automotive center. Whether to get a sealed or unsealed battery is a matter of personal preference. Some owners do not want to deal with checking the battery's water level, so they opt for a sealed battery. If you want to have access to the water level, choose an unsealed battery.
Locate the battery of your BMW in the trunk of the car on the right-hand side under the carpeting. Pull the carpeting back so you can work freely.
Detach the positive and negative battery cables from the old battery with a crescent wrench and open-end wrench, starting with the negative. Lift the cables off the terminal posts and move them out of the way. Be careful that the two cable ends do not touch one another; you could cause a short in your car's electrical system.
Unfasten the bolts holding the battery to the battery pan with a socket wrench, and remove the clips from the sides of your battery.
Locate the handle strap on the side of your battery, and lift the battery out of the battery well. If your battery does not have straps, cover it with an old towel or rag on each side before lifting it out.
Place the new battery in the battery well the same way the old battery came out. Verify that the posts are in the same direction.
Attach the clips to the sides of your battery to hold it in place.
Attach the red cable to the positive post and the black cable to the negative post.
Return the carpeting to the top of the battery well.
Start the BMW to test the battery.
