The battery in your vehicle can be mounted in a variety of locations depending on the model, engine or chassis style, convertible or hardtop. The battery is mounted in the engine compartment on the right side on the E30 series vehicles. On E36 series vehicles the battery is located in the luggage compartment. The 3 Series' battery is mounted in the trunk on the right side, under the trunk liner. On Z3 models, the battery is centrally located under the floor mat and may have an additional cover secured by two nuts that must be removed to access the battery.