How to Replace a Battery in a BMW Trunk

by Leonardo R. Grabkowski

BMW has a reputation for building high-quality sporty vehicles. Most BMW models have a trunk-mounted battery, rather than a traditional engine-bay-mounted battery. This is due to limited engine bay space (large engine in a small area) and the desire to keep the weight balance as close to 50/50 as possible. Other than the location, not much is different about changing a BMW battery than any other battery.

Step 1

Check your owner's manual or contact your dealer to determine what type of battery you need. Different BMW models, such as the 3-Series or 5-Series, require different types of batteries.

Step 2

Open your trunk and remove the trunk liner and carpeting. Depending on your model, you may also have to remove the spare tire and cross brace (BMW X5 only).

Step 3

Locate the battery compartment (passenger side on most models). Use the screwdriver or pliers to remove the battery access cover.

Step 4

Lift the protective covering away from the negative (-) battery cable (usually black). Use the pliers to loosen the nut securing the cable to the battery terminal. Carefully lift the cable from the terminal, and then move on to the positive (+) battery cable (usually red).

Step 5

Use the socket wrench to remove the bolts securing the battery to the battery compartment. Some BMW batteries are attached by a mounting bolt on top, others are attached by bolts on the bottom. You may need an extension to reach it.

Step 6

Lift the old battery from the compartment using the battery handle. The handle is usually folded down onto one side when installed. Wear gloves to protect your hands.

Step 7

Mount the new battery and replace the mounting bolts. Attach the positive (+) battery cable first and tighten the nut. Once the positive cable is attached, reattach the negative battery cable.

Step 8

Replace the battery cover and the trunk liner. Start your BMW to make sure everything is working correctly.

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