How to Replace the Batteries in a Mercedes Key Fob

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Simple steps for changing Chrome & Smart Keys

Co-authored by Shawn Fago and Devin McSween

Last Updated: August 29, 2024 Fact Checked

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New Chrome Keys

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Old Chrome Keys

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Smart Keys

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Key Care

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How Do You Replace The Battery In a Car Key Fob?

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If your key fob isn’t unlocking your Mercedes or starting the engine right away, dead batteries might be the culprit. We're here to walk you through the process for all 3 types of Mercedes key fobs. Silver Chrome keys made after 2017 take 1 CR2032 battery, older Chrome keys with triangular or circular panic buttons use 1 to 2 CR2025 batteries, and plastic Smart Keys require 2 CR2025 batteries. Let's get to it.

Things You Should Know

On new Chrome keys, remove the spare key and hold the back button to open the key casing. Pull out the battery compartment and insert a new CR2032 battery.
On older Chrome keys, take out the spare key and push it into the slot at the bottom of the key fob. Slide off the casing and insert 1 to 2 new CR2025 batteries.
On Smart Keys, remove the spare key and press it into the slot at the end of the fob. Slide out the battery compartment and add 2 new CR2025 batteries.

Method 1

Method 1 of 4:

Chrome Keys Made After 2017

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Unlike older models, Mercedes keys made after 2017 models don’t have a square piece at the top of the key with a large, red panic button. Newer Chrome keys use 1 CR2032 battery.^{[1]
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Flip over your key and look for the silver button towards the bottom. Simply press down on the button and pull out the spare key inside your fob.^{[2]
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Hold the tip of the key on the button and slide off the back casing. Use the tip of the spare key to press down on the silver button. While holding it down, use your other hand to push back on the casing and slide off the back cover.^{[3]
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- For S-Class models: Push the key into the cavity where the spare key was to pry off the back cover.^{[4]
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Push the key inside the side slot to remove the battery compartment. Look for 2 gray tabs and a small notch along the edge of the exposed key back. Then, push the tip of the key into the notch and slide the battery compartment out of the key.^{[5]
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- For S-Class models: Look for the circular seam on the back of the fob and a small notch above it. Then, push the tip of the spare key into the slot to remove the cover over the battery.^{[6]
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Remove the battery and add a new CR2032 battery. Lift the old battery out of the compartment with your fingers. Then, take a new CR2032 battery and place the positive side, or the side with writing on it, face down in the compartment.^{[7]
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- For S-Class models: Place the positive side of the CR2032 battery face up.^{[8]
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Reassemble the key and test it to make sure it works. Push the battery compartment back inside the key, slide on the back casing, and insert the spare key. Then, click the buttons to unlock and lock your car to ensure it works.^{[9]
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- If your key still isn’t working, you may have inserted the battery the wrong way. Just take apart the key again and flip over the battery.

Method 2

Method 2 of 4:

Chrome Keys Prior to 2017

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Most Chrome keys made before 2017 have a square piece at the top of the fob with either a triangular or circular panic button. Chrome keys made after 2013 typically have triangular panic buttons and only need 1 CR2025 battery, while older chrome keys with a circular panic button require 2 CR2025 batteries.^{[10]
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Look for a small, square silver or black tab at the bottom of your key fob. Then, simply pull the tab back to release the spare key and take it out of the fob.^{[11]
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Removing the spare key exposes a small, narrow slot above the tab you just pulled at the bottom of the fob. Just push the tip of your key into the slot to loosen the back cover from the fob.^{[12]
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Remove the back cover and take out the old battery or batteries. With the back cover off, simply flip the fob over and gently smack it to remove the old battery or batteries. Set the old batteries aside to discard them safely at your local recycling center.^{[13]
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- Chrome keys with triangular panic buttons have 1 battery while keys with a circular button have 2.
5
Insert 1 or 2 new CR2025 batteries, depending on your key model. On most Chrome keys, insert the new battery (or batteries) with the positive side, or the side with writing, face up. Just add 1 battery if you have a key with a triangular panic button, or 2 batteries if it has a circular panic button. Then, simply snap the back cover on and place the spare key back into the key holder.^{[14]
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- Test your key to make sure it unlocks and locks your car.
- If the fob isn’t working, you might have inserted the batteries the wrong way. Simply take apart the key again and flip over the batteries.

Method 3

Method 3 of 4:

Smart Keys

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1
Look for black, plastic casing on Smart Keys. Unlike Chrome keys that are made out of metal, new and older Smart Keys are made out of plastic. These keys also require 2 CR2025 batteries.^{[15]
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- Current Smart Key models have a red panic button identical to older Chrome keys, while Smart Keys prior to 1999 do not.
Look for a black, square latch at the bottom end of your key fob. Then, slide the latch to loosen the spare key from the fob and pull it out.^{[16]
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After you remove the spare key, look for a narrow slot above the latch you just pulled. Then, turn the key fob sideways and push the spare key into the slot.^{[17]
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Pushing the spare key into the slot triggers the battery compartment to loosen and jut out of the fob. Just grab the end of the compartment and pull it out of the fob.^{[18]
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Remove the old batteries and replace them with 2 CR2025 batteries. Lift out the old batteries from the compartment with your fingers or your spare key. Then, insert 2 new batteries in the old slots with the positive side of the battery, or the side with writing on it, face up. Slide the battery compartment back into the key holder and then push your spare key back into the slot at the bottom of the fob.^{[19]
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- Unlock and lock your car to ensure your key works.
- If your fob doesn’t work, you may have placed the batteries in the wrong way. Just open the battery compartment back up and flip over the batteries.

Method 4

Method 4 of 4:

Taking Care of Your Mercedes Keys

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1
Use a key case to protect your Mercedes keys. Some Mercedes keys, especially old models, can be fragile and easily damaged if you drop or scratch them. So, cover your keys with a key case to protect them from unexpected falls and other damage.^{[20]
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- For the most durable protection, opt for a silicone key case.
Lithium batteries typically last much longer than alkaline and other types of batteries. While lithium CR2025 and CR2032 batteries tend to be more expensive than alkaline batteries, you don’t have to charge them as often which means they’re a better bang for your buck.^{[21]
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Use a tracking device to keep track of your keys. To prevent yourself from losing your precious Mercedes keys, attach a tracker to the fob or your keychain. Most trackers come with a corresponding app that allows you to locate your keys if you misplace them. Some popular key tracking devices are:
- Tile
- AirTag
- Chipolo One
- Cube
4
Change the batteries when you notice the key signal is weak. If your car doesn’t unlock on the first click, it’s probably time to replace your key’s batteries. Changing the batteries as soon as they start declining prevents you from being stuck with a key fob that doesn’t work at all.
- How often you change your key batteries depends on the type of batteries you use and how often you use your keys.
5
Purchase new keys from a Mercedes dealership, if necessary. Unfortunately, Mercedes keys aren’t invincible and after a few years, they might not work even after you change the batteries. If your keys aren’t unlocking your car after a battery switch, simply visit your local Mercedes dealership and tell them you need a new set of keys.^{[22]
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- Most Mercedes dealerships sell new keys to customers even if they did not initially purchase their car from the dealership.
- A replacement key from a dealership can cost $200 or more.
- Replace your Mercedes key every 2 to 3 years, or when your key no longer works.

How Do You Replace The Battery In a Car Key Fob?

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Question

I have two batteries in my remote. How do I put the new ones in? Piggyback?

Community Answer

On the little remote, just above the buttons, and under the circle where the laser is sent out of, there is a white arrow (if you don't have one, that is fine). Pull the top of the lower section of it, and the top should come off. You will see the batteries. Just pull them out and put new ones in. Put the top back on and it's ready to use.

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Tips

Check your car insurance or car warranty before you switch out your key batteries. Some car dealerships or insurance companies provide free or inexpensive key battery replacements to their customers.

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