Mercedes-Benz W205 Auxiliary Battery Replacement DIY (Mercedes-Benz C300, S63 AMG, C63 AMG, & More)

Introduction

This tutorial provides a step-by-step guide for replacing the auxiliary battery in a Mercedes-Benz W205, which includes models like the C300, S63 AMG, and C63 AMG. The auxiliary battery, also known as the voltage converter, is crucial for vehicles with electronic gear selectors and eco start-stop functions. If you encounter error messages related to the auxiliary battery, this guide will help you through the replacement process, ensuring your vehicle runs smoothly.

Step 1: Gather Tools and Materials

Before starting the replacement, make sure you have the following tools and materials:

• Flathead screwdriver
• Phillips screwdriver
• Trim removal tool
• New auxiliary battery (voltage converter)
• Safety gloves
• Safety goggles

Step 2: Remove Carpet, Trim, and Kick Panel

1. Remove the Carpet:

   • Locate the carpet covering the battery area.
   • Gently pull back the carpet to expose the trim and battery compartment.

2. Remove the Trim:

   • Use the trim removal tool to carefully detach any plastic trim pieces.
   • Ensure not to damage the clips or the trim itself.

3. Remove the Kick Panel:

   • Unscrew any screws holding the kick panel in place using a Phillips screwdriver.
   • Carefully pull the kick panel away to reveal the battery compartment.

Step 3: Inspect and Remove the Auxiliary Battery

1. Inspect the Auxiliary Battery:

   • Check for any obvious signs of damage, such as corrosion or leaks.
   • If you see any signs of failure, proceed with removal.

2. Disconnect the Battery:

   • Locate the battery terminals.
   • Use the appropriate screwdriver to loosen and remove the negative (-) terminal first, followed by the positive (+) terminal.

3. Remove the Battery:

   • Carefully lift the auxiliary battery out of its compartment.
   • Place it in a safe location for disposal or recycling.

Step 4: Install the New Auxiliary Battery

1. Position the New Battery:

   • Take your new auxiliary battery and position it in the compartment where the old battery was located.

2. Reconnect the Battery:

   • First, connect the positive (+) terminal and tighten it securely.
   • Next, connect the negative (-) terminal and tighten it.

Step 5: Reinstall Kick Panel, Trim, and Carpet

1. Reattach the Kick Panel:

   • Align the kick panel back into its original position.
   • Screw it back in using the Phillips screwdriver.

2. Reattach the Trim:

   • Snap the trim pieces back into place carefully.
   • Ensure all clips are seated properly.

3. Replace the Carpet:

   • Lay the carpet back down and ensure it is smooth without any wrinkles.

Step 6: Inspect Fuses

1. Check Fuses:
   • Locate the fuse box and inspect any fuses related to the auxiliary battery.
   • Replace any blown fuses to ensure the electrical system functions properly.

Conclusion

Replacing the auxiliary battery in your Mercedes-Benz W205 is a straightforward process that can improve your vehicle's performance and reliability. By following these steps, you can successfully replace the battery and address any associated error messages. After the installation, consider monitoring your vehicle's performance and checking for any further issues. If you encounter persistent problems, it may be wise to consult a professional mechanic.