2009–2016 Audi A4

2009-2016 Audi A4 - Battery Replacement

By Tom Becker ✓ Certified Mechanic · Published Sep 21, 2026 · Updated Oct 22, 2026

🔧🔧 Moderate 45–60 minutes $140 DIY

Save $175 by doing it yourself! Shop cost: $315

Quick answer: Battery Replacement on a 2009–2016 Audi A4 is rated Moderate and takes about 45–60 minutes. You'll need 5 tools for this job, and parts cost about $140. This guide walks you through the full job step by step, including the mistakes to avoid.

Quick Video Tutorial

Parts You Need

Total Cost

$140.00

Part Name	Part Number	Price	Buy
Correct group-size battery	—	$140.00	Amazon
Terminal cleaner Optional	—	$8.00	Amazon
Terminal protectant Optional	—	$7.00	Amazon

About prices: shown prices are typical retail averages and change frequently; cheaper alternatives may be available. Confirm the current price before buying.

💡 Pro tip: Order all parts at once to save on shipping

Step-by-Step Instructions

Follow these steps carefully

Prepare the vehicle and find the trunk battery

Park on a level surface, set the parking brake, and switch the ignition fully off. Open the trunk, clear it out, and put on safety glasses and gloves. Have your phone handy: you'll want to photograph the battery's top label before removing it.

Remove the spare tire and note the BEM code

Lift the trunk floor carpet to expose the spare-tire area. Remove the tool tray and lift out the spare tire so the battery is fully accessible.

🔧 Mechanic's note — Tom Becker

Write down that BEM code before the old battery comes out — it's two serial numbers plus a vendor identifier, and you need it when the new battery gets coded. Photograph the label; 'I think it was...' isn't good enough.

Disconnect the vent hose and both cables

Pull the vent (vacuum) hose off the side of the battery — this hose routes gases outside the car and must go back on the new battery. Using a 10mm socket, loosen the clamp on the negative (black) battery cable a few turns and pull the clamp off the post. Move the cable where it cannot accidentally swing back onto the terminal. Do the same for the positive (red) cable, opening its terminal cover first if one is fitted.

Remove both battery hold-down brackets

Remove both bolts and lift the brackets clear. Once both brackets are off, confirm that both cables and the vent hose are fully detached before you attempt to lift.

Lift out the old battery

It weighs 40 to 50 pounds, so keep your back straight, lift with your legs, and set it down gently on the ground — never drop it or tip it on its side.

Install the new battery and reconnect

Push the vent hose firmly onto the new battery's vent port. Reconnect the POSITIVE battery cable first and tighten its clamp, then connect the NEGATIVE cable last. Reinstall both hold-down brackets and tighten the 13mm bolts so the battery cannot move at all.

Reassemble, test, and code the battery

The clock and one-touch window functions may need resetting, and radio presets may be lost — check your owner's manual for the exact reset steps for this car. Start the engine and confirm it cranks strongly; check the lights, windows, and infotainment.

🔧 Mechanic's note — Ray Delgado

I get the battery coded to the car — without it the B8 runs in a low-power charging mode and quietly kills the new battery early. It still drives fine, which is exactly why people skip it and pay later.

All Done!

Test your repair before closing everything up. If something doesn't work right, double-check your steps.

⚠️ Common Mistakes to Avoid

• Assuming the battery is under the hood — on the 2009–2016 A4 (B8) it is in the trunk, under the spare tire beneath the trunk floor.
• Leaving the vent/vacuum hose disconnected from the side of the battery, which lets hydrogen gas collect inside the trunk.
• Throwing away the old battery before writing down its BEM code — the code is printed on the battery top and is needed if the new battery gets coded to the car.
• Removing only the top bracket and then yanking at the battery, not realizing a second, smaller bracket at the base still holds it.

Tools You'll Need

10mm socket 13mm socket ratchet with extension battery terminal brush safety glasses gloves battery terminal protector spray (optional) phone camera (to record the BEM code)

Related Trouble Codes

P0562 System Voltage Low

Torque Specifications

Critical specs — don't skip these!

Bolt	Nm	ft-lbs
Battery hold-down	11	8

Important: Use a calibrated torque wrench. Over-tightening can strip threads. Under-tightening can loosen parts.

⚠️ Safety First!

• Disconnect the negative terminal first and reconnect it last; keep tools from touching both terminals at once to avoid sparks and short circuits.
• Batteries contain sulfuric acid — wear safety glasses and gloves, and rinse skin or eyes with plenty of water if acid contacts them.
• The battery is heavy; lift with your legs out of the deep trunk well and get help if needed rather than dropping it.