UniEnergy Technologies Battery » How To Replace Key Battery Mercedes? (Step-By-Step Guide)

How To Replace Key Battery Mercedes? (Step-By-Step Guide)

Mercedes is one of the most prominent, well-respected car brands worldwide. But no matter how fast, comfortable, and impressive your wheels are, they’re pretty useless if you can’t get into your car to turn it on.

Battery problems can be a real headache for many car owners. Replacing the battery for your Mercedes could cost a small fortune.

But what if we told you there’s a simple, quick, and easy way to solve your problem? By yourself, and with no skills required!

This article will guide you through a tried and tested approach to replacing the battery inside your keys. With our help, you can drive your prized Mercedes in no time!

Step-by-step guide on replacing the key battery of your Mercedes car

You can replace the battery in your key fob in just five easy steps. You will only need your new lithium batteries for this task, which can be easily bought online or in a local hardware store.

But before you begin, there’s just one thing you must examine; what type of key type you have. There are two tied to Mercedes, both of which demand a slightly different setup:

Mercedes-Benz Chrome key

Chrome keys are tied with newer versions and models of Mercedes cars; as their name implies, they have a metal casing.

There are two slight variations of Chrome keys, each demanding a different number of batteries. You can tell which you have by examining the panic button on your fob.

Newer Chrome keys will have a triangle-shaped panic alarm button and only require one CR 2025 lithium battery. Older Chrome keys will have a circular panic button and require two batteries instead.

How to change your Chrome key battery:

  1. Simply pull down the tab at the end of the key holder until the key releases itself from the casing.
  2. Move the key to the narrow end of the open slot. This will unlatch the fob’s casing, making it easier to remove.
  3. Next, remove the covering to expose the battery. Inspect the area for corrosion or damage, and gently remove the old batteries.
  4. Carefully place the new battery inside, ensuring it is facing correctly.
  5. Snap the casing back on, and move your key back into the correct position to finish.
Mercedes-Benz SmartKey
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Mercedes-Benz SmartKey

SmartKeyscan is easy to spot because of its plastic casing. They are often linked with older Mercedes-Benz models, requiring two batteries to power on.

Similar to Chrome keys, there are both new and old versions of Smartkeys. The older variations will not have a panic button, while newer Smart keys have a circular one like their Chrome counterparts.

How to change your Smart key battery

  1. Simply pull down the latch on the end of the fob. This will cause the key to fall out – be ready to catch it.
  2. Push your key fully into the narrow, empty slot at the bottom of the fob. A small gap will open up to reveal the battery compartment.
  3. Lift this compartment out to expose the two battery slots.
  4. Replace both batteries simultaneously, and examine the surrounding area to ensure everything is healthy. Slide the compartment back into the fob until you hear a “clicking” sound.
  5. Place the key cover and your key back into the fob to secure it in place.
Expert Tips
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Expert Tips

Below are some simple but effective tips to keep in mind when changing batteries and keeping your car key safe:

  • An excellent way to diagnose the health and charge of your battery is using distance – see how powerful your fob is at various distances. If it only works close to the car, the battery is underperforming.
  • Always replace batteries away from drains, pipes, toilets, or holes. Keys can drop from the fob and may become lost otherwise!
  • Depending on the make of your Mercedes, your dashboard can also send a warning light to signal the fob is malfunctioning.
  • Always use this opportunity to examine your fob’s health and condition. Signs of corrosion suggest the casing may have sprung a leak.
  • Try to change your batteries at the earliest time possible. Warning signs it is beginning to fail are a weakened signal or delayed response time.
  • Buy the right batteries for your fob – while there are many choices, lithium types offer the longest-lasting service. They’re often cheaper too!
  • The key may become damaged at some point, and the fob will not work despite changing batteries. At this time, you need to visit your local Mercedes dealership to get a new key cut.
  • Check your car insurance and local service center – sometimes, a free battery replacement is offered under your coverage.


Because of its power, efficiency, and high cost, many people are afraid to tamper too much with their Mercedes key fob. But as our article has shown, five simple steps are all it takes to change the battery yourself and get back on the road!

The most important consideration is ensuring the key doesn’t slip out and become lost. Otherwise, you should have trouble opening the casing, accessing the batteries, and replacing them without a fuss.

But if you still have questions on how best to replace the battery or want to share your expert tips, please comment below.

In short, remember:

  • Chrome keys usually come with newer Mercedes-Benz models made of metal. They usually only require one battery.
  • Smart keys usually come with older Mercedes-Benz vehicles, are usually made of plastic, and require two batteries to power on.
  • Lithium batteries are the recommended type, as they are long-lasting and cheaper.

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