In a 2007 BMW 328i, the main 12-volt battery is located in the trunk, not in the engine bay. It sits on the right-hand side of the cargo area beneath a removable cover.
Finding the trunk-mounted battery
The battery in this model is housed inside the trunk on the passenger side (the right side when facing the rear of the car). To access it, you must remove the trunk floor cover and lift the plastic battery shield or cover that sits above the battery. Once exposed, you’ll see the battery in a tray with the red positive terminal clearly marked and a black negative terminal nearby.
Below is a practical step-by-step guide to locating and accessing the battery in the trunk.
- Open the trunk and lift the floor panel or remove the carpeted mat to expose the trunk floor.
- On the right side of the trunk, locate the removable plastic cover or panel that conceals the battery.
- Remove the cover to reveal the battery, terminals, and any venting components.
- Confirm the battery type and check for corrosion, loose connections, or a damaged vent tube before proceeding with maintenance or replacement.
Concluding note: Accessing the battery through the trunk panel is the standard procedure for this model, and taking care to disconnect power safely helps prevent shorts or sparks.
Jump-starting and safety considerations
If you need to jump-start the car or use a battery charger, follow these safety-focused guidelines. Some E90s provide a dedicated jump-start point in the engine bay; if yours has one, you can use that instead of the trunk battery terminal. If not, you’ll connect to the trunk-mounted battery as described below.
Before attempting any jump-start, ensure both vehicles are off, the parking brakes are engaged, and the cables are in good condition. If you’re unsure, consult the owner’s manual or a professional technician for assistance.
- Position the donor vehicle close enough to reach both batteries with jumper cables, and ensure both engines are off.
- Connect the red jumper clamp to the positive terminal of the donor battery. If your car has a dedicated engine-bay jump-start terminal, you may use that instead of the trunk battery’s positive terminal.
- Connect the other red clamp to the positive terminal on the BMW’s trunk-mounted battery (if accessible via the trunk) or to the appropriate jump-start point in the engine bay if provided by your model.
- Connect the black jumper clamp to a solid, unpainted metal ground on the donor vehicle. Attach the other black clamp to a clean metal ground point on the BMW away from the battery area to minimize sparking near the battery.
- Start the donor vehicle and let it run for a few minutes, then attempt to start the BMW. If it doesn’t start, wait a few more minutes and try again.
- Once the BMW starts, remove the cables in reverse order: black from the BMW, black from the donor vehicle, red from the BMW, then red from the donor vehicle.
Note: If your BMW has a dedicated engine-bay jump-start point, follow the same order but attach the red clamp first to that point and the black clamp to a suitable engine-ground point. Always avoid connecting the clamps to the same post on both cars and keep cables clear of moving parts and hot surfaces.
Summary
The 2007 BMW 328i stores its main battery in the trunk on the right side behind a removable cover, separate from the engine bay. Access involves lifting the trunk floor panel and removing the battery cover. For starting assistance, use jumper cables with careful attention to the correct polarity and grounding, and consider using any engine-bay jump-start terminal if your vehicle is equipped with one. When in doubt, consult the owner’s manual or a professional technician for guidance.