How to Change the Battery in Mercedes Key Fobs

How to Change Mercedes Key Fob Battery

How Long Before You Should Change the Battery in the Mercedes Key

Signs You Need to Change the Mercedes Key Battery

Accessing Your Car with a Dead Key Fob

To change the battery in your Mercedes-Benz key fob, you first need to determine what kind of key you have. The series of steps you have to follow will depend on what type of key you own.

When your key is not working, replacing it looks like the easiest option, but it is the more expensive option. The replacement cost may reach $400 or more. Meanwhile, replacing the key’s battery may cost less than $5.

Learning how to change your car’s key fob batteries should only take a moment, and performing it shouldn’t be difficult enough to frustrate you. In this article, we’ll teach you how to change the battery in your Mercedes’ key fob and discuss other relevant topics that can help you.

How to Change a Mercedes Key Battery

If you plan to change your Mercedes key fob’s battery, you need to find out what kind of model you have. Mercedes-Benz currently has two popular key fob models:

  • Smart Key: This type of key fob was made for older Mercedes-Benz models and is entirely constructed from tough plastic. Whether you have an old or new version of the Smart Key, it will require two CR 2025 batteries.
  • Chrome Key: This type of key fob is made for the newer models of Mercedes-Benz and comes in a metal casing. The newer version of Chrome Keys need two CR 2025 batteries while the old one requires only one.

If you’re unsure what version of Chrome Key you have, the best way to find out is by checking the panic button on the key. The old version has a circle-shaped panic button. The new version has a triangular panic button.

If you want to double-check what type of key fob you have or what version of Chrome Key you possess, refer to the car’s manual for details. Once you’ve determined what key fob you have, you may proceed with changing the batteries by following these steps:

Smart Key

  1. While holding the key, pull the latch at the end of the holder.
  2. Retrieve the emergency key that shows up.
  3. Insert the emergency key into the open slot at a horizontal position.
  4. This should allow you to lift out the battery compartment.
  5. Insert two new CR 2025 batteries in the proper orientation.
  6. Put every component back into place and you should be done.

Chrome Key

  1. Find a square-shaped silver tab on the bottom of the key fob.
  2. Gently pull out this bottom tab until a key is released from the key fob.
  3. Get the key and a small gap should show right after.
  4. Insert the key into the gap and the cover should pop off.
  5. Remove the cover and the old battery underneath.
  6. Place one or two batteries, depending on the version of Chrome Key you have.
  7. Place everything back together and you’re done.

The process of changing the battery in your Mercedes-Benz key fob should take no more than a few minutes. If some parts of the key fob appear jammed or damaged, you can take it to a reliable auto service center. They should be able to replace the batteries or fix the key fob if necessary.

When used regularly, these batteries can last for three to four years before needing replacement.

woman holding car keys

How Long Before You Should Change the Battery in a Mercedes Key?

Key fobs generally use one or two CR 2025 batteries to operate. When used regularly, these batteries can last for three to four years before being replaced. However, their longevity will still depend on how often the key fobs are used.

If your current key fob is already past its third year, consider replacing the batteries even if there are no problems with your key. A severely depleted key fob battery can die out any time, which can be very inconvenient if you’re in the middle of an important trip.

Signs You Need to Change Your Mercedes Key Battery

Your Mercedes-Benz car key fob may look like it’s working properly, but there could be subtle irregularities that indicate the batteries are close to running out. The following are some of the common signs that your key fob needs a battery change:

1. It’s taking multiple clicks to unlock doors

A working key fob should be able to unlock the car doors with a single press of the button. On rare occasions, it might take a click or two before the doors respond. If you’ve been regularly putting in more effort to unlock the car doors with the key fob, it’s a sign that the batteries are on their last leg.

When you’re experiencing this issue and you realize that it’s been a while since you started using the key fob, consider replacing the batteries immediately. This is especially true if your key fob is required for your car’s push-to-start engines. The last thing you want is to not be able to start the engine when you need to.

2. There’s a delayed response

The good thing about key fobs is that every time you press them, your vehicle automatically responds. Whether opening doors or starting the engine, there shouldn’t be any significant delays between the button press and the response.

If your car’s response ranges from 3 to 5 seconds every time you press on the key fob, chances are the batteries are struggling to provide enough power. Unless you notice any loose or jammed buttons on the key fob, replacing the batteries should resolve the issue.

3. The signal range is lower

Most modern car key fobs like those from Mercedes-Benz have a signal range of around 50 feet. As the key fob’s battery wears out, the signal range decreases to a point that you need to be extremely close to your car for it to respond.

While a signal range of 30 to 40 feet can still be considered passable, any distance below that range should indicate that you need to change the batteries.

4. “Key Fob Battery Low” warning light is lit up

Most cars manufactured by Mercedes-Benz typically have a “Key Fob Battery Low” warning light present on the dashboard. What it does is monitor the output voltage that your key fob sends out every time you use it.

At some point, this system will be able to detect if your key fob’s battery is starting to wear out and the “Key Fob Battery Low” light will turn on. This light indicator will remain on unless a fully recharged key fob interacts with it again.

When this light indicator lights up, make sure to replace the key fob’s batteries as soon as possible to avoid future complications.

If you happen to have multiple key fobs, take note of which one was last used to interact with the car. Most light indicators are not permanently linked to a key fob. Using a different one can overwrite the previous record the indicator detected.

The precise steps needed to access and start your car with a dead key fob can be found in your car’s manual.

car keys

Accessing Your Car with a Dead Key Fob

You might find yourself in the unfortunate situation of being locked out of the car because of a dead key fob. While it looks like a hopeless situation, there are a few ways you can unlock and start the car using a dead key fob.

Unlocking the car door

  1. While holding the key fob, take the physical key by prying open the cover securing it. This could be a simple button press in the back of the key fob or by applying a sliding motion.
  1. With the physical key in your hand, approach the car door and look for a small slit somewhere around the handle. The location of the slit varies depending on the car model, but it’s almost always the part of the door handle that can’t be pulled.
  1. Once you find the small slit, insert the physical key in it. When the entire key is inside the slit, pull it up, and that section of the door handle will pop off. Underneath it is a keyhole.
  1. Insert the physical key into the keyhole, turn it, and you should hear a clicking sound. This action unlocks the door and you can open it normally.
  1. Please take note that in newer car models that use a Chrome Key, the alarm will automatically go off. This is part of its security protocol and will only turn off when you start the car.

Starting the engines

If your car requires the key fob to initiate the push-to-start engine, there’s still a way to ignite it. However, the steps differ according to the type of key you own.

  • Smart Key: To ignite the engines using a dead smart key, look for the push-to-start button first. That particular button is usually elevated an inch or so from the dashboard. This will allow you to pry off the button from the dashboard, revealing a keyhole underneath. Insert your Smart Key on the keyhole and the car should start automatically.
  • Chrome Key: Unlike the Smart Key, the backup keyhole is hidden from plain view in a Chrome Key-activated car. However, most Mercedes-Benz models have their backup keyholes located in front of the cup holders. It is marked with a key symbol. Simply slide the key fob in. After a few seconds, the car should automatically start.

The precise steps needed to access and start your car with a dead key fob can be found in your car’s manual. It’s highly recommended that you take the time to familiarize yourself with the steps so it could serve you during emergencies.

man in his car

Bottom Line

The last thing you want to happen is a dead key fob preventing you from accessing your car when you need it the most. That’s why you must be able to both notice the signs of a bad key fob battery and how to replace them properly.

If you still doubt your ability to change the key fob batteries yourself, there’s no harm in reaching out to your trusted car care expert to help you out.

Auto Works of Brandon offers complete auto care services like professional tune-ups and battery replacement. If you’re having trouble with your car or key fob’s batteries, feel free to set an appointment with us today. Our team will be happy to help you get those batteries replaced.


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