How to Replace the 12V Battery in a Mercedes GLS (4th Generation, 2019–Current)

If your Mercedes GLS (4th Generation, 2019–current) is showing battery warning messages or struggling to start, it may be time to replace the 12V battery. While the process is straightforward, it's important to follow the correct steps to protect your vehicle's electrical system.

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Tools You'll Need

• Replacement 12V battery compatible with your Mercedes GLS

• 10mm and 13mm socket or wrench

• Ratchet with extension

• Safety gloves and eye protection

Step 1: Prepare the Vehicle

Park the vehicle on a level surface, switch off the engine, remove the key, and engage the parking brake. Open the rear tailgate to access the battery compartment.

Step 2: Locate the 12V Battery

The main 12V battery is typically located beneath the luggage compartment floor in the rear of the vehicle. Remove the cargo floor panel and any covers to expose the battery.

Step 3: Disconnect the Negative Terminal

Using a 10mm wrench, loosen the negative (-) battery terminal and remove the cable. Position it away from the battery to prevent accidental contact.

Step 4: Disconnect the Positive Terminal

Loosen and remove the positive (+) terminal. Avoid allowing metal tools to bridge the battery terminals.

Step 5: Remove the Battery Hold-Down Clamp

Remove the retaining bracket or hold-down clamp securing the battery. Carefully lift the old battery out, keeping it upright as it can be heavy.

Step 6: Install the New Battery

Place the new battery into the battery tray in the same orientation as the original. Reinstall and tighten the hold-down clamp to keep the battery securely in place.

Step 7: Reconnect the Battery

Reconnect the positive (+) terminal first, followed by the negative (-) terminal. Tighten both connections securely without over-tightening.

Step 8: Test the Vehicle

Start the engine and confirm the battery warning light is no longer displayed. Reset the clock and any saved settings if necessary, and verify all electrical systems are operating correctly.

Final Thoughts

Replacing the 12V battery in a 2019-current Mercedes GLS is a manageable DIY maintenance task with the right tools and a compatible replacement battery. Following these step-by-step instructions can help restore reliable starting performance and keep your SUV's electrical systems operating as intended. If your vehicle continues to display battery-related warnings after installation, have the charging system and battery registration checked by a qualified technician.