How to Replace the Batteries in a Mercedes Key Fob. Replacing the batteries in your Mercedes key fob is a straightforward process, but the steps vary depending on the type of key fob you have. Mercedes uses three main types of key fobs: New Chrome Keys, Old Chrome Keys, and Smart Keys. Here’s a detailed guide for each type.
Method 1: Chrome Keys Made After 2017
Step 1: Identify the Key Type
New Chrome Keys feature a sleek, silver casing and lack a large red panic button.
Step 2: Remove the Spare Key
- Flip the key fob over.
- Press the silver button on the back to release the spare key.
Step 3: Open the Key Casing
- Use the spare key tip to press the button on the back and slide off the casing. How to Replace the Batteries in a Mercedes Key Fob
- For S-Class models, push the spare key into the slot where the key was stored to pry off the back cover.
Step 4: Remove the Battery Compartment
- Push the spare key into the side slot or notch along the edge of the key to slide out the battery compartment.
- For S-Class models, locate a circular seam and notch on the back and use the spare key to remove the battery cover.
Step 5: Replace the Battery
- Remove the old CR2032 battery.
- Insert a new CR2032 battery:
- Positive side facing down for most models.
- Positive side facing up for S-Class models.
Step 6: Reassemble and Test
- Slide the battery compartment back in and reattach the back casing.
- Insert the spare key and test the key fob by locking/unlocking your car.
Method 2: Chrome Keys Prior to 2017
Step 1: Identify the Key Type
Older Chrome Keys have a square piece at the top with either a triangular panic button (1 battery) or circular panic button (2 batteries).
Step 2: Remove the Spare Key
- Slide the small tab at the bottom of the key to release the spare key.
Step 3: Open the Back Cover
- Push the spare key into the narrow slot above the tab to loosen the back cover.
- Slide off the back casing.
Step 4: Replace the Battery/Batteries
- Remove the old CR2025 batteries.
- Insert new batteries:
- For triangular panic buttons: Use 1 CR2025 battery.
- For circular panic buttons: Use 2 CR2025 batteries.
- Ensure the positive side of the batteries is facing up.
Step 5: Reassemble and Test
- Snap the back cover into place.
- Insert the spare key and test the key fob.
Method 3: Smart Keys
Step 1: Identify the Key Type
Smart Keys are made of black plastic and require 2 CR2025 batteries. They may or may not have a red panic button.
Step 2: Remove the Spare Key
- Slide the square latch at the bottom of the fob to release the spare key.
Step 3: Open the Battery Compartment
- Push the spare key horizontally into the narrow slot above the latch to loosen the battery compartment.
- Pull the compartment out.
Step 4: Replace the Batteries
- Remove the old CR2025 batteries.
- Insert 2 new CR2025 batteries with the positive side facing up.
Step 5: Reassemble and Test
- Slide the battery compartment back in.
- Insert the spare key and test the key fob.
Key Maintenance Tips
- Protect Your Key: Use a silicone or durable key case to protect it from damage.
- Use Lithium Batteries: Lithium batteries last longer than alkaline batteries and offer better performance.
- Use a Tracker: Attach a tracking device like Tile, AirTag, or Chipolo to prevent losing your key fob.
- Replace When Necessary: Replace batteries when the signal weakens or every 2–3 years.
If the replacement process doesn’t resolve the issue, visit a Mercedes dealership to purchase a new key fob or seek professional assistance.
