Mercedes-Benz key fobs, like any other electronic devices, rely on batteries to power their various functions such as locking and unlocking the vehicle, opening the trunk, and even starting the engine. Over time, these batteries tend to wear down and need to be replaced. While it’s always an option to take your Mercedes to a dealership or automotive shop for battery replacement, it’s actually a fairly simple task that you can do yourself with the right tools and a bit of know-how. In this guide, we’ll walk you through the step-by-step process of changing the key battery on your Mercedes.
Before you begin, you’ll need to gather a few tools. You’ll need a small Phillips head screwdriver, a new CR2025 battery, and a soft cloth. Once you have your tools, follow these steps to change the key battery on your Mercedes:
1. Locate the small screw on the back of the key fob. This screw is usually located near the bottom of the fob. Use the Phillips head screwdriver to carefully remove the screw.
2. Once the screw is removed, gently pry open the back of the key fob. The back of the fob should come off easily.
3. Locate the old battery inside the key fob. The battery will be a small, round, silver-colored coin-shaped battery. Use your fingernail or a small tool to gently remove the old battery.
4. Insert the new CR2025 battery into the key fob. Make sure that the positive (+) side of the battery is facing up.
Gather Necessary Materials and Tools
Gather the Required Materials and Tools:
Before embarking on the task of replacing your Mercedes key battery, it is crucial to assemble the necessary materials and tools. This will ensure a smooth and efficient battery replacement process.
Materials:
| Material | Quantity |
|---|---|
| CR2025 Battery | 1 |
Tools:
- Small Phillips-head Screwdriver or Torx Wrench (size T8 or T10, depending on the key model)
- Small Flat-head Screwdriver or Pry Tool
- Clean Cotton Swab or Soft Cloth
Additional Tools (Optional):
- Flashlight (for improved illumination if necessary)
- Magnifying Glass (for enhanced visibility of small components)
It is advisable to purchase a high-quality CR2025 battery from a reputable supplier to ensure optimal battery life and performance.
Locate the Key Battery Compartment
The key battery compartment on a Mercedes is typically concealed within the key fob itself. Here’s a detailed guide on how to locate it:
- Identify the Release Button: Most Mercedes key fobs have a small button or lever that, when pressed or slid, releases the battery compartment cover.
- Locate the Cover: Once you’ve identified the release button, locate the battery compartment cover. It’s usually a small, rectangular panel on the side or back of the key fob.
- Pry Open the Cover: Using a small, flat-head screwdriver or your fingernail, gently pry open the battery compartment cover. Be careful not to damage the cover or the key fob.
Identifying the Battery Type
Once you’ve located the battery compartment, you’ll need to identify the type of battery it uses. Mercedes keys typically use CR2025 batteries, which are small, round lithium coin batteries. However, some older models may use CR2032 batteries, which are slightly larger.
| Battery Type | Dimensions |
|---|---|
| CR2025 | 25 mm (diameter) x 2.5 mm (thickness) |
| CR2032 | 32 mm (diameter) x 3.2 mm (thickness) |
Remove the Old Battery
Once you’ve located the battery, it’s time to remove it. Here are the detailed steps:
Step 1: Disconnect the Terminals
Start by disconnecting the negative (black) terminal. Use a wrench or a pair of pliers to carefully loosen the nut holding the terminal in place. Once it’s loose, lift the terminal off the battery post.
Step 2: Remove the Positive Terminal
Next, disconnect the positive (red) terminal. Follow the same procedure as for the negative terminal. Be extra cautious when working with the positive terminal, as it can spark if it comes into contact with any metal surfaces.
Step 3: Remove the Battery Clamps
Now it’s time to remove the battery clamps. These are usually located at the top and bottom of the battery and are secured with bolts or screws. Use a wrench or a screwdriver to loosen the bolts or screws and lift the clamps away from the battery.
Step 4: Lift Out the Battery
With the clamps removed, you can now lift the battery out of the compartment. Be careful not to drop it, as it can be heavy. If the battery is stuck, gently rock it back and forth until it loosens.
Here’s a table summarizing the steps for removing the old battery:
| Step | Action |
|---|---|
| 1 | Disconnect the negative terminal |
| 2 | Disconnect the positive terminal |
| 3 | Remove the battery clamps |
| 4 | Lift out the battery |
Insert the New Battery
Step 1: Orient the Battery Correctly
Grip the new battery with the positive (+) terminal facing up. Align it with the corresponding terminal on the key.
Step 2: Insert the Positive Terminal
Carefully slide the positive terminal of the battery into the corresponding slot on the key. Ensure it fits snugly.
Step 3: Secure the Negative Terminal
With the positive terminal in place, gently push the negative (-) terminal of the battery into the remaining slot on the key.
Step 4: Confirm Battery Placement
Once both terminals are inserted, check that the battery is firmly seated and not loose within the key. If it wiggles or feels unstable, re-orient and re-insert the battery to ensure a secure connection.
| Tip: |
|---|
| For optimal performance, use a new, high-quality battery of the same type and voltage as the original. |
Step 5: Replace the Key Cover
Once the battery is securely in place, align the key cover with the slots on the key and press firmly until it snaps shut.
Replace the Key Battery Compartment Cover
Locate the key battery compartment cover on the back of the key fob. It’s usually a small, rectangular plastic cover with a groove or notch along the edge.
Use a small flathead screwdriver or a key to insert into the groove or notch and gently pry open the cover.
Once the cover is open, you’ll see a small metal battery inside. This is the key battery that needs to be replaced.
Carefully remove the old key battery and insert a new one of the same type in its place. Make sure the “+” and “-” terminals of the battery are aligned correctly.
Replace the cover by sliding it back into place until it clicks into place, ensuring that it’s securely closed.
Verify the Functionality of the Key
Confirm that the key is indeed malfunctioning before proceeding with battery replacement. Test the following functions:
– Unlocking and locking doors: Attempt to unlock and lock the vehicle using the key. If neither action works, the battery may be the culprit.
– Trunk release: Press the trunk release button to see if the trunk opens.
– Remote start (if equipped): If the key provides remote start functionality, attempt to start the vehicle from a distance.
| Symptom | Possible Cause |
|---|---|
| Key does not unlock/lock doors | Battery depletion |
| Trunk release not working | Battery depletion or trunk release button malfunction |
| Remote start not functioning | Battery depletion or remote start system failure |
If multiple functions are not working, there is a higher likelihood that the battery needs to be replaced.
Required Tools:
1. New key battery (size CR2025)
2. Small flathead screwdriver or key extractor tool
Step-by-Step Guide:
1. Locate the key release button on your Mercedes key fob. It’s usually located on the side or bottom.
2. Press the release button and pull the metal key out of the fob.
3. Use a small flathead screwdriver or key extractor tool to gently pry open the back cover of the fob.
4. Remove the old battery and insert the new one, positive side up.
5. Replace the back cover and snap it into place.
6. Reinsert the metal key into the fob.
7. Test the key fob to ensure it’s working properly before locking your vehicle.
Additional Tips for Changing Key Battery:
– If you have trouble prying open the back cover, try using a thin plastic tool or a credit card to avoid damaging the fob.
– When inserting the new battery, make sure it’s firmly pressed into place to ensure good contact.
– After changing the battery, check the key fob’s functionality by pressing all the buttons and trying to unlock your car.
– If the key fob still doesn’t work, try resetting it by removing the battery and holding down the unlock button for 10 seconds.
– If you’re still experiencing issues, you may need to contact a Mercedes dealership or automotive locksmith for assistance.
Safety Precautions to Consider
Before you begin, it’s crucial to take these safety precautions:
Wear Gloves
To prevent skin irritation, wear disposable gloves while handling the battery and key components.
Park Safely
Park your Mercedes in a well-lit and secure area to ensure safety.
Turn Off the Engine
Turn off the engine to prevent any electrical accidents during the battery replacement process.
Open the Key
Locate the small button or lever on the key and press or slide it to open the housing.
Remove the Battery
Carefully remove the old battery using a small tool or your fingers. Ensure not to touch the battery terminals with bare hands.
Clean the Contacts
Use a clean cloth to gently clean the battery contacts on both the key and the battery itself.
Insert the New Battery
Place the new battery into the key, ensuring the positive (+) and negative (-) terminals align correctly. Do not overtighten.
Test the Key
Reassemble the key and test it to ensure it works properly by locking and unlocking the vehicle.
Dispose of the Old Battery
Dispose of the old battery responsibly at designated recycling centers to avoid environmental pollution.
Troubleshooting Common Issues
1. Remote Won’t Respond After Battery Replacement
Ensure the key has been paired to the vehicle. Refer to your vehicle’s user manual for pairing instructions.
2. Error Message on Dashboard
Check the battery terminal contacts for corrosion or damage. Clean them if necessary.
3. Key Battery Drains Quickly
Excessive key usage can drain the battery. Reduce key usage by using the vehicle’s keyless entry system whenever possible.
4. Key Doesn’t Lock/Unlock Doors
Verify that the key is in range of the vehicle. Replace the battery again if the issue persists.
5. Side Buttons Not Working
Clean the side button contacts with a cotton swab and rubbing alcohol. Ensure the buttons are not jammed or obstructed.
6. Difficulty Inserting Battery
Check the battery orientation. It should be inserted with the positive (+) terminal facing up.
7. Key Remote Malfunctions
Consider replacing the key remote itself if the issue persists after troubleshooting other causes.
8. Key Fob Buttons Sticking
Clean the buttons with a cotton swab and rubbing alcohol. If the issue persists, the buttons may need to be replaced.
9. Extensive Battery Lifetime
Conserve battery life by:
| Factor | Recommendation |
|---|---|
| Regular Key Use | Use keyless entry system as much as possible. |
| Battery Type | Use high-quality batteries specifically designed for key fobs. |
| Extreme Temperatures | Avoid exposing the key to extreme heat or cold. |
| Signal Strength | Minimize key usage in areas with weak signal reception. |
Replacing the Key Battery in a Mercedes
Replacing the battery in a Mercedes key is a relatively simple process that can be performed with a few basic tools. Here are the steps on how to do it:
- Gather your materials: You will need a small screwdriver or key removal tool, a new battery for your key, and a clean work surface.
- Remove the old battery: Use the screwdriver to remove the screw that holds the key together. Then, carefully pry open the key and remove the old battery.
- Insert the new battery: Make sure that the positive (+) side of the battery is facing up. Then, carefully insert the new battery into place.
- Close the key: Press the two halves of the key back together and tighten the screw.
- Test the key: Check to make sure that your key is working properly by pressing the buttons on the key.
Professional Assistance When Needed
If you are having trouble replacing the battery in your Mercedes key, you may need to seek professional assistance. A locksmith can help you replace or repair the key, and they can also provide you with a new key if necessary.
Additional Tips
- Make sure that you have the correct battery for your key. The type of battery required will vary depending on the model of your car.
- Be careful when removing the old battery. If you damage the battery, it may leak acid.
- Dispose of the old battery properly. Batteries can contain hazardous materials, so it is important to dispose of them properly.
| Mercedes-Benz Key Battery Types | |
|---|---|
| CR2025 | CR2032 |
If you are still having trouble replacing the battery in your Mercedes key, please refer to your car’s owner’s manual for specific instructions.
How to Change the Key Battery in a Mercedes
Replacing the battery in your Mercedes key is a simple process that can be completed in a few minutes. Here are the steps on how to do it:
- Locate the key release button on the back of the key fob. Press the button and pull the key out of the fob.
- Flip the key over and locate the small screw on the back. Use a small Phillips head screwdriver to remove the screw.
- Carefully pry open the back of the key fob using a thin object like a flathead screwdriver or a butter knife. Be careful not to damage the key fob.
- Locate the battery inside the key fob. It will be a small, round battery. Use a pair of tweezers to carefully remove the battery.
- Insert the new battery into the key fob, making sure that the positive side of the battery is facing up.
- Close the back of the key fob and tighten the screw.
- Insert the key back into the key fob and test it to make sure it is working properly.
People Also Ask
How often should I change the battery in my Mercedes key?
The battery in your Mercedes key should be changed every 2-3 years.
What type of battery does my Mercedes key use?
The type of battery used in Mercedes keys varies depending on the model of the car. However, most Mercedes keys use a CR2025 or CR2032 battery.
Can I change the battery in my Mercedes key myself?
Yes, you can change the battery in your Mercedes key yourself. Follow the steps outlined above to replace the battery.
