Battery Equivalents and Replacements

How to Change Mercedes Key Fob Battery

Mercedes-Benz vehicles represent a blend of luxury, performance, and cutting-edge technology. A critical component of this technology is the key fob, which offers convenience and security through features like keyless entry, push-button start, and more.

Like all battery-powered devices, the key fob requires occasional battery replacement to maintain its functionality. Recognizing the signs of a weak battery, knowing which battery to use, and understanding how to change it are essential skills for any Mercedes owner.

Published: April 4, 2024.

mercedes 1

First Signs of Weak Mercedes Key Fob Battery

Several indicators suggest the battery in your Mercedes key fob is weakening:

  • Reduced Range: If you notice that you have to be closer to your vehicle than usual for the key fob to work, it’s likely that the battery is dying.
  • Inconsistent Functionality: When the key fob becomes unreliable, failing to unlock the doors or start the car on the first try, it's a sign the battery is low.
  • Dashboard Warning: Many Mercedes models will display a warning message on the dashboard indicating that the key fob battery is low.

Addressing these signs early can prevent you from being locked out of your vehicle or unable to start it.

Most Common Mercedes Key Fob Batteries

Mercedes key fobs generally use one of the following batteries, depending on the model and year of the vehicle:

  • CR2025: A 3-volt lithium coin battery, used in many compact key fobs.
  • CR2032: Slightly thicker than the CR2025, this 3-volt lithium coin battery is also commonly used in Mercedes key fobs.

Always refer to your vehicle’s owner's manual or the existing battery in your key fob to confirm the correct type.

Popular Mercedes Models and Their Key Fob Batteries

Mercedes-Benz, a brand synonymous with luxury and precision engineering, offers a wide range of vehicles that cater to various tastes and needs. Each model comes with a key fob designed for convenience, allowing for keyless entry, push-to-start functionality, and more.

The key fob battery is a critical component that requires occasional replacement to ensure continuous operation.

Below is a list of popular Mercedes models and the typical batteries their key fobs use, helping you keep your Mercedes in top working condition.

Sedans, Coupes, and Convertibles

  • Mercedes-Benz C-Class (including C300, C350, and AMG variants): Most C-Class models use a CR2025 or CR2032 battery for their key fobs, depending on the year and specific key fob design.
  • Mercedes-Benz E-Class (including E350, E400, and AMG variants): The E-Class key fobs typically require a CR2025 or CR2032 battery, reflecting the model's blend of luxury and technology.
  • Mercedes-Benz S-Class (including S550, S63 AMG, and S65 AMG): Key fobs for the flagship S-Class luxury sedan usually need a CR2025 or CR2032 battery, ensuring the keyless entry and ignition system's smooth operation.

SUVs and Crossovers

  • Mercedes-Benz GLA-Class: The compact SUV from Mercedes often uses a CR2032 battery in its key fob, providing access to its agility and innovation.
  • Mercedes-Benz GLC-Class (including GLC 300, GLC 350e, and AMG variants): The GLC-Class models usually require a CR2025 or CR2032 battery for their key fobs, accommodating the needs of luxury crossover enthusiasts.
  • Mercedes-Benz GLE-Class (including GLE 350, GLE 450, and AMG variants): GLE-Class vehicles typically use a CR2025 or CR2032 battery in their key fobs, matching their sophistication and versatility.
  • Mercedes-Benz GLS-Class: For the full-size luxury SUV, the key fob often requires a CR2025 or CR2032 battery, ensuring the convenience of its advanced features.

Roadsters and Sports Cars

  • Mercedes-Benz SL-Class: This iconic roadster's key fobs generally need a CR2025 or CR2032 battery, reflecting its blend of performance and luxury.
  • Mercedes-Benz AMG GT: The high-performance sports car from Mercedes, the AMG GT's key fobs typically use a CR2025 or CR2032 battery, ensuring the responsiveness of its advanced features.

mercedes key fob

How to Change Your Mercedes Key Fob Battery

Changing the battery in a Mercedes key fob is a straightforward process. Here are the general steps, which may vary slightly depending on your specific model:

  • Identify Your Key Fob Type: Mercedes uses several key fob designs, so first, identify whether you have a newer “Smart Key” or an older style fob.
  • Opening the Key Fob:

For Older Models: Slide the latch at the back of the key fob to release the mechanical key. Use this key or a flathead screwdriver to pry open the key fob case.

For Newer “Smart Key” Models: Push the small tab or slide the switch to remove the mechanical key, then use it to pry open the battery compartment.

  • Replace the Battery: Once open, remove the old battery. Note its orientation so you can insert the new battery correctly. Avoid touching the new battery's contacts with your fingers as much as possible to prevent corrosion.
  • Reassemble the Key Fob: Carefully snap the key fob case back together. Make sure it’s securely closed.
  • Test the Key Fob: After replacing the battery, test the key fob to ensure it’s functioning correctly by locking and unlocking your vehicle.

Additional Tips

  • Battery Handling: Ensure the new battery is handled carefully. The oil from your skin can affect its lifespan and performance.
  • Recycling the Old Battery: Be environmentally responsible by recycling the old battery properly.
  • Seek Professional Help if Needed: If you encounter difficulties or the key fob does not work after the battery change, consult with a Mercedes dealership or a professional for assistance.

Do You Have To Reprogram the Mercedes Key Fob After the Battery Replacement

No, typically you do not need to reprogram your Mercedes key fob after replacing the battery. Mercedes key fobs are designed to retain their programming even when the battery is removed or replaced.

Once the new battery is installed, the key fob should continue to work with your vehicle as it did before, without the need for any additional steps or reprogramming.

However, if you find that the key fob is not functioning correctly after you've changed the battery, there may be a few reasons for this:

  • Battery Installation: Ensure that the new battery is installed correctly, with the positive side facing the correct direction, and that the battery compartment is securely closed.
  • Battery Type: Double-check that you've used the correct type of battery (CR2025 or CR2032 are most common) and that the battery is fresh. A battery that has been sitting on a shelf for a long time may not have full voltage.
  • Key Fob Reset: In some instances, although rare, the key fob may require a simple reset to properly communicate with your vehicle again. This can usually be done by removing and reinserting the battery or by following a specific procedure outlined in your vehicle's owner manual.
  • Vehicle's Receiver Issue: If the key fob is still not working, the issue might be with the vehicle's receiver rather than the key fob itself. In this case, consulting with a Mercedes-Benz dealer or a qualified automotive locksmith is advisable.
  • Damaged Key Fob: If the key fob was dropped or damaged, there might be an internal issue preventing it from working. Professional assessment might be necessary.

If after checking these factors your key fob still isn’t functioning correctly, it may be necessary to visit a Mercedes-Benz dealership or a professional who can diagnose the problem accurately and provide a solution, whether it be reprogramming or repairing the key fob.

mercedes 2

How to Start Mercedes With Dead Key Fob Battery?

Starting a Mercedes-Benz with a dead key fob battery can seem challenging, but Mercedes designs its vehicles with alternative entry and ignition methods to ensure you're not left stranded.

Here's how you can start your Mercedes even when the key fob battery is completely dead:

Accessing the Vehicle

  • Manual Key Access: Most Mercedes key fobs contain a manual, metallic key blade concealed inside them. You can usually release this key by pressing a small button or sliding a latch on the key fob. Use this metallic key to manually unlock the driver's door. It's important to note that some models might have a cap covering the keyhole on the door handle. This cap can often be removed by prying it off gently, revealing the keyhole beneath.

Starting the Engine

  • After gaining access to your vehicle, the process to start the engine depends on whether your Mercedes-Benz model has a traditional ignition slot or a push-button start system.

For Models with an Ignition Slot

  • Insert the Metal Key: If your vehicle has a traditional ignition slot, insert the manual key into it and turn to start the vehicle as you would with a regular key.

For Models with Push-Button Start

  • Key Fob to Push-Button: For models equipped with push-button start but no place to insert a key, hold the key fob directly against the push-button start or the designated area for key recognition (often marked on the steering column or the center console). This area acts as a backup RFID reader that can detect the key fob even if its battery is dead.
  • Press the Start Button: While holding the key fob against the button or designated area, press the brake pedal (or clutch pedal in manual transmission vehicles) and push the start button. The vehicle should recognize the key fob through this direct contact and allow you to start the engine.

Tips for Dealing with a Dead Key Fob Battery

  • Battery Replacement: To avoid future inconveniences, replace the key fob battery as soon as possible. Key fob batteries are usually cheap and can be easily replaced by following the instructions in your vehicle's manual or key fob documentation.
  • Spare Battery: Keeping a spare key fob battery in your vehicle can save you from being stranded in the future.
  • Mercedes-Benz Assistance: If you're unable to start your vehicle due to issues with the key fob or its battery, consider contacting Mercedes-Benz roadside assistance or visiting a dealership for support.

Knowing how to start your Mercedes-Benz with a dead key fob battery ensures you can still use your vehicle even in situations where the key fob has lost power.

It’s a handy piece of knowledge that can help you avoid the stress and inconvenience of being unable to start your car.