Where to Find the Battery on a 2009 BMW 328i

The battery on a 2009 BMW 328i is located in the trunk, on the right-hand (passenger) side, beneath a removable trim panel near the rear taillight. Unlike many older cars where the battery sits under the hood, BMW places the main battery in the rear for weight distribution and packaging reasons.

Why the Battery Isn’t Under the Hood

The 2009 BMW 328i, part of the E90/E91/E92/E93 3 Series generation, is designed with performance balance and safety in mind. To improve handling, BMW moves heavy components like the battery closer to the rear axle. As a result, if you pop the hood expecting to see a conventional battery, you will instead find only jump-start terminals while the actual battery lives in the trunk.

Exact Battery Location in the Trunk

On all standard 2009 328i models (sedan, wagon, coupe, and convertible), the battery is located in the trunk, tucked behind trim on the right side. Access requires lifting or removing some trunk linings, but no special tools are usually needed.

Step-by-Step: How to Access the Battery

The following steps explain how to locate and reach the battery safely in a 2009 BMW 328i, from opening the trunk to fully exposing the battery compartment.

1. Open the trunk: Use the key fob, trunk release button, or interior trunk switch to open the trunk lid.
2. Clear the trunk floor: Remove any cargo, floor mats, or trunk organizers so you have full access to the bare trunk floor.
3. Locate the right-side panel: Look to the right (passenger side) rear corner of the trunk, near the taillight area. You will see a fabric or plastic trim panel or cover.
4. Remove the trim panel: Gently pull back or unclip the right-side trunk lining. On many models, there’s a small access door or panel that swings open; others may require you to lift or pop out part of the trim.
5. Identify the battery: Behind this trim, you will see the rectangular 12‑volt battery secured in place, often with a hold-down bracket and covered partially by a plastic protective cover.
6. Check for vent tube and wiring: Most BMW trunk-mounted batteries have a small vent tube attached (to vent gases outside the car) and several cables connected to the terminals and distribution block.

Once the trim panel is removed, the battery is clearly visible and accessible for inspection, testing, or replacement without needing to work under the vehicle or remove major components.

Jump-Starting vs. Direct Battery Access

BMW expects owners to use under-hood terminals for jump-starting instead of attaching clamps directly to the trunk battery. This design reduces risk of sparks near the battery and makes it easier to assist or receive a jump.

Under-Hood Jump-Start Terminals

While the battery lives in the trunk, you can still provide or receive a jump from the engine bay. BMW provides clearly marked jump-start posts under the hood for this purpose.

Use the following guide to find these front terminals on a 2009 BMW 328i.

1. Open the hood: Pull the hood release twice from the driver’s footwell (BMW’s double-pull system), then lift the hood from the front.
2. Locate the positive terminal: Look on the passenger side or near the firewall (exact position can vary slightly by body style). You will see a red plastic cover or cap marked with a plus sign (+). Flip this cover open to expose the positive post.
3. Locate the negative/ground point: Find the designated ground post or a clearly marked metal stud or bracket with a minus sign (−) symbol. Do not clamp directly to painted surfaces or small brackets not meant for ground.
4. Attach jumper cables or booster safely: Connect positive to positive, negative to the BMW ground point, and follow standard jump-start procedure as outlined in the owner’s manual.

By using the front jump-start terminals, you avoid disturbing the trunk trim or directly accessing the battery unless you are diagnosing or replacing it.

Special Considerations When Replacing the Battery

Finding the battery is only the first step; modern BMWs, including the 2009 328i, treat the battery as part of an intelligent charging system. Incorrect replacement can shorten battery life or cause electrical issues.

Registration and Coding Requirements

When you install a new battery in a 2009 BMW 328i, the car’s computer (DME/ECU) should be told that a new battery has been fitted—a process known as “battery registration.”

The main points below outline what’s involved when replacing the battery in this model.

• Battery registration is recommended: The car needs to know the battery is new so it can adjust charging behavior and monitor battery condition correctly.
• Use appropriate battery type: Most 2009 328i models use an AGM or high-quality lead-acid battery with specific capacity (e.g., 70–90 Ah). Matching the original specifications is important.
• Coding may be required if capacity/type changes: If you change from, say, 70 Ah to 90 Ah, or from lead-acid to AGM (or vice versa), coding with a diagnostic tool may be needed to update the vehicle’s stored configuration.
• Professional tools or shop visit: Many independent BMW shops and dealerships use tools like BMW ISTA, Autologic, or advanced OBD scanners to perform registration and, if needed, coding.
• DIY possible with the right equipment: Some consumer-level OBD tools and apps support BMW battery registration, but you must confirm compatibility for E90/E92 3 Series before attempting it yourself.

Taking these extra steps after physically accessing the trunk-mounted battery helps maintain proper charging and extends the lifespan of the new unit.

Common Misconceptions About the 2009 328i Battery Location

Owners unfamiliar with BMW’s design often assume the battery must be under the hood or hidden under a seat. In the 2009 328i, however, the answer is consistent across body styles.

The following clarifications address frequent misunderstandings regarding where the battery might be.

• Not under the hood: The visible power posts under the hood are for jump-starting, not the physical battery itself.
• Not under the front seats: Unlike some other brands or BMW models from different eras, the 2009 3 Series battery is not mounted beneath a seat.
• Same basic location across trims: Whether you drive a 328i sedan (E90), wagon (E91), coupe (E92), or convertible (E93), the main battery is trunk-mounted on the right side.
• No secondary 12V battery for standard models: The non-hybrid 2009 328i typically uses a single main 12‑volt battery rather than multiple batteries.

Understanding these points helps narrow your search to the trunk and prevents confusion when inspecting or servicing the car’s electrical system.

Safety Tips for Accessing the Trunk-Mounted Battery

Working around any 12‑volt automotive battery requires basic precautions. In a trunk-mounted setup like the 2009 BMW 328i’s, space is tight and there are additional cables and electronic modules nearby.

Keep the following safety practices in mind before touching or removing the battery.

1. Switch everything off: Ensure the ignition is off, lights are off, and the key fob is away from the vehicle before disconnecting terminals.
2. Disconnect negative first: When removing the battery, loosen and remove the negative (−) terminal first to reduce risk of short circuits.
3. Reconnect negative last: When installing a new battery, connect the positive (+) terminal first, then the negative (−) terminal.
4. Avoid sparks and metal tools touching both terminals: Be careful with wrenches and sockets; shorting across terminals or to bodywork can cause arcing.
5. Mind the vent tube: Ensure the battery’s vent tube remains attached and correctly routed to the exterior to avoid gas buildup in the trunk.
6. Secure the battery firmly: Always reinstall the hold-down bracket to keep the battery from moving during driving, braking, or impacts.

Following these steps not only shields you from injury but also protects the BMW’s sensitive electronics from damage caused by accidental shorts or loose connections.

Summary

On a 2009 BMW 328i, the 12‑volt battery is located in the trunk on the right (passenger) side, hidden behind a trim panel near the rear taillight. Accessing it involves opening the trunk, removing or swinging aside the right-side interior panel, and exposing the battery and its mounting bracket. For jump-starting, BMW provides dedicated positive and negative terminals under the hood, so you rarely need direct battery access unless you are replacing or inspecting it. When replacement is necessary, BMW recommends registering the new battery with the vehicle’s computer and, if specifications change, performing coding to ensure correct charging behavior and long-term reliability.

Where is the battery on a 2009 328i BMW?

So your battery is actually located back here in the trunk. So we’re going to come back. Here. Open our trunk. Okay and now twist that little button right there. Right there is your battery. Voila.

Where to jump start a BMW?

To jump-start a BMW, open the hood and use the positive terminal under the red cap and the negative ground point on the engine block or chassis. Do not connect directly to the battery, which is typically in the trunk, as this can damage the vehicle’s electronics. 
This video demonstrates how to locate and use the jump-start terminals in a BMW engine bay: 57sCarLubeTvYouTube · Dec 19, 2021
Before you begin

• Park the working car close enough to the dead BMW so the jumper cables can reach. 
• Turn off both cars, open the hood, and locate the jump terminals in the BMW’s engine bay. 
• Remove the metal key from the key fob and have it in the car. 

Connecting the jumper cables

1. Attach the red (positive) clamp: to the positive terminal on the dead BMW. This is a red cap with a “+” sign under which is the positive terminal. 
2. Attach the other red (positive) clamp: to the positive terminal of the working car’s battery. 
3. Attach the black (negative) clamp: to the negative terminal of the working car’s battery. 
4. Attach the other black (negative) clamp: to a solid, unpainted metal part of the BMW’s chassis or engine block, away from the battery. 
5. If the battery is completely dead, you may need to activate manual mode on your jump starter. Check your jump starter’s manual for instructions, which often involves holding down two buttons for a few seconds. 

This video shows the proper procedure for connecting the jumper cables to a BMW: 50sYOUCANICYouTube · Sep 17, 2020
Starting the engine

1. Start the engine of the working car. 
2. Press the brake pedal in the BMW. 
3. Attempt to start the BMW’s engine. 
4. If it doesn’t start, wait a few minutes with the cables connected and try again. 
5. If the BMW starts, carefully disconnect the cables in the reverse order of how you connected them. 
6. Allow the BMW to run for a while to charge the battery, or drive it to charge the battery sufficiently. 

What battery for 2009 BMW 328i?

Duralast Group Size 94R H7 Battery H7-DL.

Where is the BMW 3 series battery located?

The BMW 3 Series battery is located in the trunk, under the floor on the right-hand side (passenger side). To access it, you will need to lift the trunk floor and remove the trim panel or cover on that side.
 
This video shows how to access the battery in the trunk of a BMW 3 Series: 1mDaringBeefcakeYouTube · Aug 25, 2021
Step-by-step access guide

1. Open the trunk.
2. Lift the trunk floor mat and locate the panel on the right-hand side. 
3. You may need to remove clips or turn a small dial to get the panel out. 
4. Once the panel is removed, you will see the battery behind it. 

You can watch this video for a detailed guide on removing the battery from a BMW 3 Series: 48sAutoMobile Battery & AccessoriesYouTube · Mar 27, 2025