How to Change a Mercedes Key Battery

Co-authored by wikiHow Staff

Last Updated: October 21, 2021 References

A Mercedes key with dead batteries is no laughing matter. Until you replace them, you may not be able to remotely unlock your car or trigger the car's panic mode in case of emergency. Although all Mercedes keys require the same type of battery (CR 2025), how many you will need or the method you use to change the battery will depend on which model you have. Compare your key to other models before you attempt changing its batteries to avoid damaging your keys or accidentally following the wrong instructions.

Part 1

Part 1 of 4:

Determining Which Mercedes Key Model You Have

1
Distinguish between a Chrome or Smart Key. Chrome and Smart Keys look similar, but Chrome Keys belong to newer Mercedes cars. Chrome Keys have a metal casing, but Smart Keys are generally made of plastic. Although Chrome and Smart Keys operate in a similar way, their batteries are changed in different ways.
2
Spot the latest Chrome model by its red triangular button. The current Chrome key model has a red triangle for its panic button. The words "panic" should be written on this button in capital letters. If you have the latest Chrome key, purchase one CR 2025 battery before you open its case.^{[1]
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3
Look for a circular panic button on older Chrome keys. All Chrome key batteries are changed in the same way, but older models need 2 CR 2025 batteries instead of one. Unlike newer models, older Chrome keys have a circular panic button with the word "panic" inscribed in white letters.^{[2]
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4
Check for a plastic casing on Smart Keys. Newer and older Smart Keys will have a black plastic casing. Although all Smart Key batteries are changed in the same way, newer Smart Keys have a red panic button identical to older Chrome keys while first model Smart Keys do not.^{[3]
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- Smart Keys need 2 CR 2025 batteries.
- The first Smart Key model does not have a panic button.

Part 2

Part 2 of 4:

Changing Chrome Keys

1
Pull on the tab at the bottom of the Chrome key. The tab should be small and square with a silver coating. Pull the key back to release the key, which should fall out of its slot once the tab is moved.^{[4]
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2
Push the key into the narrow end of the slot. When your key is removed, it should leave a narrow gap on the bottom end of the key holder. One end has a dip while the other end is flat and narrow. Push your key into the narrow end to unlatch and loosen the cover.^{[5]
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3
Remove the loose cover from the side of the key holder. If you have pushed the key in far enough, the cover should snap off of the key holder without using force. The battery (or batteries, depending on your model) will be exposed once the cover is off. Remove both old batteries and discard them safely.^{[6]
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- Push the key further into the slot if your cover cannot be pried loose.
4
Replace the CR 2025 battery or batteries. Inspect the battery slots carefully to make sure you are placing them in the right end and position. Once one or both are secure in their designated slots, snap the cover back on and place the key back into the key holder.
- Place the key back into its holder right away to avoid losing it.

Part 3

Part 3 of 4:

Changing Smart Keys

1
Pull the latch at the end of the key holder down. The latch should be black, square, and located at the bottom end of the key holder. Your Mercedes key will fall out of its holder. Hold out your other hand to catch it as you pull the latch to avoid losing it.^{[7]
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2
Stick your key horizontally into the open slot. After you remove the key, you should notice an empty slot around the bottom end of the key holder. Turn your key holder sideways and push your key into the slot. Push the key entirely in, until you cannot push it further, to open the battery compartment.^{[8]
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3
Lift the battery compartment up and out of the key holder bottom. When your key has triggered the latch, the top of the battery compartment will jut out slightly. Grab it by the end and pull it slowly out of the key holder. Once pulled out, you should notice 2 exposed battery slots.^{[9]
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4
Remove and replace your CR 2025 batteries. Take out your 2 old batteries and replace them with 2 new ones in the designated slots. Slide the battery compartment back into the key holder until you hear a click. Put your key back into the slot vertically until it is secure as well.

Part 4

Part 4 of 4:

Taking Care of Your Mercedes Keys

1
Purchase a key case to protect your Mercedes keys. Some Mercedes keys, especially old models, are fragile and may not work if they have been dropped or damaged. Use a case to protect your keys from unexpected falls or scratches.
- Silicone key cases are recommended because they are more durable.^{[10]
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2
Use lithium batteries when changing your key batteries. Batteries come in a variety of metals, depending on their expense. While some battery types might be less expensive, lithium CR 2025 batteries last longest and are often cheaper than other options in the long-term.^{[11]
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- Choose lithium batteries if you would prefer not to change your key batteries often.
3
Use a tracking app to find lost keys. Mercedes keys can be expensive to replace. To avoid this mishap, attach a tracker to your keys or keychain and download its corresponding app. Popular key tracking devices include:^{[12]
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- BiKN
- Button TrackR
- Cobra Tag
- HipKey
- Hone
- iFi
- Kensington Proximo
- Stick'n'Find
- Tile
- Zomm
4
Change your batteries whenever you notice weakened efficiency. How often you change your battery depends on the metal type and the frequency that you use your keys. As a rule of thumb, your batteries need replacement if they stop responding when you press the buttons or if they respond infrequently.
- Replace your batteries as soon as you notice diminished efficiency to avoid emergencies or further inconveniences.
5
Purchase new keys from a Mercedes dealership if necessary. After a few years, your Mercedes keys may not work even after you change the batteries. Replace your Mercedes key every 2-3 years or when your key no longer works, even with new batteries.
- Most Mercedes dealerships will sell new keys to customers even if they did not initially purchase their car from the dealership.

Community Q&A

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.