How to Replace the Battery in Your Car's Keyless Remote

Man's hand holding a remote next to closed car door

 PhotoAlto/Odilon Dimier / Getty Images

Nearly every car built in the past few years uses a keyless remote to lock and unlock the vehicle. These are handy to use, but if the battery dies you may find yourself locked out of your car. This guide will show you how to change the battery in your car's remote key entry fob.

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Check the Battery Type

The Honda keyless remote has an easy access battery cover, Mercedes does not.


Most manufacturers, like Honda, make it fairly easy to find out what kind of battery your key fob uses. The battery number should be embossed on the back side of the remote. Look for a four-digit number like 2025. 

If you drive an older vehicle, the battery type may not be indicated. Check your owner's manual or the manufacturer's website, or call a local dealer if you don't know what kind of battery you need. Don't just pry open the remote; you could break it and end up having to pay for a pricey replacement.

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Remove the Battery Cover

Use a coin to remove the battery cover.


Turn the keyless remote over (that's the side with no buttons on it). There might be a circle in the back that is actually a battery cover. If you do have such luck, you'll also see an easy way to get this cover off, usually in the shape of a slot that fits a coin. Find a coin that closely fits the slot. Insert the coin and use it as a screwdriver to get the cover off. Other remotes use tiny screws or must be pried open. If you're unsure, consult your owner's manual first.

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Replace the Battery

Check the battery type and placement before you go on.


You now have your battery cover removed. Before you remove the dead battery, take a look at how it's in there so that you know how to put the new battery in correctly. Most battery compartments in remotes use a plus sign (+) to indicate where the positive end of the battery should go.

Some luxury-car makers like Mercedes make changing the keyless remote battery much more difficult. The next slides show you how to change a battery in just a few steps.

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If You Own a Luxury Vehicle

Slide the lever sideways and pop out the emergency key.


This procedure covers Mercedes remotes, but the steps are similar for many higher-end makes and models. If you own a vehicle like this, the first step in the process is to remove the metal backup key from the remote unit. You can do this by sliding its locking mechanism to the side and then pulling the key out.

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Disassemble the Remote

Use the emergency key to depress the small button inside.


Look for a second locking mechanism just inside the unit. Using the metal key you extracted, slide that locking mechanism sideways. You should be able to see a clear notch for the key end.

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Expose the Batteries

With the button depressed, separate the halves of the remote, exposing the batteries.


With the latch pushed aside, separate the top and bottom of the remote. You may have to remove an access cover or slide the entire processor out of the keyless remote housing. Remember to do this gently, as you don't want to snag anything fragile or break off any little plastic tabs.

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Check and Replace

The battery holder slides out of the bottom part of the key.


From here, the battery replacement process is the same as it is for a Honda-style keyless remote. Remember to examine the battery and chamber for any signs of corrosion. Sometimes, dead batteries can rupture or leak caustic chemicals. If you do see evidence of corrosion, carefully clean out the battery compartment and then install the new batteries. If your remote doesn't work, it may have been damaged by the dead battery.