Changing your car battery might seem daunting, but with the right guidance, it’s a task you can confidently undertake, even on your Audi A4 B8 model. One of the first hurdles is often simply locating the battery. Unlike some vehicles where the battery is conveniently placed under the hood, the Audi A4 B8 has opted for a less conventional location. This guide will walk you through each step to easily access and change the battery in your Audi A4 2009 (B8) model. Remember, this is for informational purposes and should be used as a reference. Always prioritize safety and consult a professional if you are unsure at any point.
Step 1: Accessing the Trunk and the Battery Compartment
The battery in your Audi A4 B8 is located in the trunk, under the spare tire compartment. To begin, open your trunk as you normally would. Once open, locate the trunk floor cover. You’ll find a latch or handle that allows you to lift this cover and access the spare tire area.
Step 2: Removing the Spare Tire
After opening the trunk floor cover, you’ll see the spare tire. To access the battery, the spare tire needs to be removed. Typically, the spare tire is secured with a screw or bolt in the center. Unscrew this fastener to loosen and remove the spare tire from the trunk. Carefully lift out the spare tire and set it aside in a safe place.
Step 3: Taking Out the Plastic Cover
With the spare tire removed, you will now see a plastic cover that further protects the battery compartment. This plastic cover needs to be removed to get to the battery. Usually, this cover is held in place by simple clips or pressure fittings. Carefully lift and remove this plastic cover. It may require a bit of gentle maneuvering to detach it completely.
Step 4: Removing the Tool Holder and Tools
Often, Audi includes a tool holder with your vehicle, which might be located within the battery compartment area. Before proceeding further, remove the tool holder and any tools that are stored there. This will provide you with more space and prevent any tools from getting in the way while you access the battery.
Step 5: Detaching the Spare Wheel Holder
Beneath the tool holder, you’ll likely find a spare wheel holder. This holder is typically bolted down and needs to be removed to fully expose the battery. Using a 13mm socket wrench, locate the bolts securing the spare wheel holder. Unscrew these bolts and remove the spare wheel holder from the compartment.
Step 6: Removing the Battery Holder
Now you are getting closer to the battery! You should see a battery holder, which is another bracket securing the battery in place. Similar to the spare wheel holder, this is also typically attached with bolts. Use your 13mm socket wrench again to unscrew the bolts holding the battery holder. Remove this holder to free the battery for removal.
Step 7: Maintaining Power During Battery Change (Optional but Recommended)
Modern cars, including the Audi A4, can sometimes experience memory loss or require radio code re-entry when the battery is disconnected. To prevent this, you can use an auxiliary power source to maintain power to the car’s electrical system while changing the battery. Important Safety Note: As shown in the image, one method (use with extreme caution and at your own risk) is to connect an aux battery to the positive terminal in the engine bay. However, this method is not recommended due to safety risks. A safer approach is to use a dedicated memory saver device that plugs into the OBD-II port or cigarette lighter. Always ensure the positive terminal of any connected battery does not touch the car body when the main battery is disconnected, as it will remain live.
Step 8: Removing the Battery Cover
The battery itself might have a protective cover. This cover is usually clipped on and easily removable. Inspect the battery for any clips on the sides or bottom of the cover. Unclip these to remove the battery cover and fully expose the battery terminals.
Step 9: Loosening the Battery Terminal Connectors
Now you are ready to disconnect the battery terminals. Using a 10mm socket wrench, loosen the nut on both the negative and positive battery terminal clamps. Loosen them enough so you can remove the clamps, but don’t remove the nuts completely yet.
Step 10: Disconnecting the Vent Hose from the Negative Terminal
Audi batteries often have a vent hose connected to the negative terminal. This hose vents battery gases outside of the vehicle. Before fully disconnecting the negative terminal, locate this black hose and gently detach it from the negative battery terminal.
Step 11: Disconnecting the Battery Terminals
With the terminal clamps loosened and the vent hose detached, you can now disconnect the battery terminals. Start by removing the negative terminal first, followed by the positive terminal. Carefully lift the terminal clamps off the battery posts. Ensure that the disconnected positive terminal does not touch any metal part of the car body to prevent short circuits. Secure the terminals out of the way.
If your Audi A4 requires battery coding (which may not be necessary in all cases, especially for a like-for-like battery replacement), the serial number is typically engraved on the battery itself, and the battery brand might be on a sticker on top. Note these down if needed for coding purposes with a diagnostic tool like VAG-COM.
Step 12: Installing the New Battery and Reassembly
Now, carefully lift out the old battery. Install the new battery in its place, ensuring it’s the correct type and specification for your Audi A4 B8. Reconnect the battery terminals in reverse order: positive first, then negative. Reattach the vent hose to the negative terminal. Tighten the terminal clamps securely. Reinstall the battery holder, spare wheel holder, tool holder, plastic cover, spare tire, and trunk floor cover in reverse order of removal.
After installation, if you used an auxiliary power source, disconnect it. Start your car. It’s a good idea to drive for a short while to allow the car’s systems to adapt to the new battery. In some cases, you might need to use a diagnostic tool like VAG-COM to clear any low voltage error codes that may have appeared.
While this guide covers the main steps for locating and changing the battery in your Audi A4 B8, always refer to your vehicle’s owner’s manual and consult a professional mechanic if you have any doubts or encounter difficulties.
