Car Key Battery Replacement 101: An Informative Guide for Easy Fob Maintenance

by | Mar 13, 2024 | Article

Dead car key fob? In our Car Key Battery Replacement 101, we’ll take you through the tell-tale signs your battery’s dwindling power, identify the kind of key fob you own, and demonstrate how to switch out the old battery for a new one. All the essential steps you need to stay on-top of your keyless entry. Take a read to resurrect your fob’s responsiveness with ease.

Key Points To Remember

  • Symptoms like increased clicking distance or inconsistent response and a dim or unlit LED indicate the need for car key battery replacement.

  • Car keys come in different types, such as standard keys with separate remote fobs, static blade remote keys, remote flip keys, and smart/proximity keys, each requiring their respective batteries and handling procedures for replacement.

  • For effective battery replacement, gather the proper tools, carefully open the key fob, replace the battery while ensuring correct orientation, and reassemble the fob finally checking its functionality.

Recognising the Need for a Car Key Battery Replacement

Car Key In Hand

Is your car key fob not responding as it used to? This could be an early sign that your car key battery needs to be replaced. Some symptoms to look out for include increased clicking distance or inconsistent response, such as needing multiple button presses. These signal that the car key battery is weakening.

If the LED light on your key fob is faint or doesn’t illuminate when buttons are pressed, or you notice a decreased signal range, it can be a subtle indication of a dying battery. No response or considerable delay when attempting to unlock the vehicle, is a clear sign that the car key battery likely needs to be replaced.

Identifying Your Car Key Type

Different types of car keys

Before we dive into the battery replacement process, it’s crucial to identify your car key type. Car keys come in a variety of forms, each with specific battery needs and features that need to be considered during replacement. By accurately determining your key type, you can ensure you choose the appropriate battery.

The most common size for many car key battery’s is the CR2032, this you can find in many supermarkets. The next most common sizes are Cr2016 found in many Nissan Keys for example, and Cr 1620 found in many older style Peugeot/Citroen, Renault and Honda Keys. The Cr2025 is found in Mercedes Keys and modern VW Keys and Cr2450 found in BMW keys.

Let’s explore the four common types of car keys: standard keys, static blade remote keys, remote flip keys, and smart/proximity keys.

Standard Keys

Standard car keys are the traditional type that most of us are familiar with. These keys are symmetrical and may have grooves on both sides or channel track cut into the middle.

Standard Car Key With Separate Remote Fob

Standard keys on their own lack the ability to open and close the vehicle from a distance. They are often found as they are but can be accompanied by a separate remote fob attached to the key ring.

These keys can:

  • Open car doors via the door lock

  • Start the ignition if containing an RFID Transponder Chip

  • Open the glove compartment

  • Sometimes even open the trunk if there is a trunk lock available

Non Flip Remote Keys

Non-Flip Remote Car Key

Unlike their flip counterparts, these keys maintain a static form, with the key blade and electronic components encased in a durable shell. They offer the convenience of having more room in your pocket or bag by removing the extra chunkiness caused from requiring two separate elements to your car key.

The absence of moving parts, as seen in flip keys, minimises wear and tear, potentially increasing the longevity of the key. the main downside to non flip is the blade is susceptible to snapping which is what the flip key aims to solve.

Remote Flip Keys

Remote flip keys combine the traditional key and modern convenience of remote access in a compact design. With a press of a button, the key blade flips out, ready for use and integrated into the key body buttons for remote locking and unlocking. They’re particularly useful for quick access and offer a modern solution to car security without complicating the user experience.

The battery type commonly found in remote flip keys is the CR2032, other models. If there is uncertainty about the correct battery type, consulting with a dealership or auto locksmith can ensure the correct battery is purchased.

Proximity Keys & Smart Keys

Proximity Smart Key

So, what exactly are smart keys? They are technologically advanced keys that enhance convenience by allowing drivers to keep the key fob pocketed for unlocking, locking, and even starting the vehicle. This is made possible by antennas in the vehicle’s bodywork and a radio pulse generator in the key.

Vehicles equipped with smart keys can disengage the immobiliser and activate the ignition via a push button or a twist switch, eliminating the need for inserting a key. Smart keys provide user customisation by adjusting preferences like seat positions, steering wheel position, and temperature settings when unlocking the vehicle. It’s essential to consult the owner’s manual for specific details on how to operate and customise your smart key system.

Gathering Necessary Tools for Battery Replacement

Tools for car key battery replacement

Now that we know the type of key we’re dealing with, let’s gather the necessary tools for the battery replacement. Depending on the design of your key fob, you will need a couple of sizes of a small flat-head screwdrivers. If the car key contains a small screw, a suitable small Phillips-head screwdriver may be necessary to remove it. For Stiff to open cases with a click on back cover a small set of long nose pliers may come in handy to apply the little bit of extra force required. If you wish to get super fancy you could use a pair of circlip pliers.

For individuals without a small flathead screwdriver, a small plastic pry tool, or even just their fingers, may suffice for opening the key fob without damaging it.

Accessing the Car Key Battery

Opening car key fob

Once you’ve gathered your tools, the next step is to access the car key battery. If you have a non-flip key or a separate fob, begin by unscrewing the key fob’s back using a small Philips screwdriver to access the battery compartment. If you have a flip key the bottom section should split off and you should be able to gently prise the key shell in half around the seem.

If you have a smart key key you will need to remove the emergency key blade first which may reveal a notch or pressure tab and then you will be able to split the key.
If you are ever unsure google your manufacture name and car model followed by key battery replacement to find many videos for example:

Once the key fob is open, check the existing battery type and specifications in order to match the replacement car key batteries exactly, using a slightly different size will not work.

It’s vital to handle your car key and its components gently throughout the battery replacement process to avoid damage.

Seam or Notch Location

To open the fob, you need to:

  1. Locate the seam or notch.

  2. Remove any physical key from the fob if applicable.

  3. Inspect the edges of the fob, potentially in the cavity where a removable key resides, or along the top, bottom, or sides.

  4. Some key fobs may require the use of a special tool or the key itself to release a clip for the fob to open.

Gently Prying Open the Fob

After locating the seam or notch, it’s time to gently pry open the fob. Use a plastic pry tool or a flathead screwdriver to twist and separate the halves. Be gentle and lift at different points to fully separate the halves without causing damage.

Carefully prying the two halves of the case apart will help you gain confidence in separating them without causing harm.

Replacing the Old Battery with the New One

Replacing car key battery

With the key fob open, it’s now time to replace the old battery with the new one. Car key batteries, including key fob batteries, come in various sizes as per the few examples stated above, they are denoted by a series of numbers, and it’s important to match the right size for your key.

Here is a list of some of the many Button Cell Battery types

  • CR2032

  • CR2025

  • CR2016

  • CR1620

  • CR1220

  • CR2450

  • CR2430

Removing the Old Battery

Before attempting to remove the old battery, observe whether it is held in place by a retaining clip or if it simply rests inside the battery compartment. If the old battery is secured with a retaining clip or a small metal tab, carefully release it to avoid damaging any components of the key fob.

Gently use fingers or a non-metallic tool to lift the old battery out of its compartment, ensuring not to apply excessive force that could damage the key fob housing or the internal components.

Inserting the New Battery

Now, it’s time to insert the new battery. Follow these steps:

  1. Check that the new battery is free from any packaging or protective films before insertion to ensure proper electrical contact. If you have used a Duracell battery be extra certain you have removed the child safe sticker from the negative terminal.

  2. Slide the new battery into the slot ensuring the correct orientation.

  3. Press firmly to secure it in place so it sits flat within the battery compartment.

After inserting the new battery, follow these steps to complete the reassembly process:

  1. Align the cover of the battery compartment.

  2. Press the cover back into position, making sure it is securely in place.

  3. Use screws, if necessary, to further secure the battery compartment.

  4. Test the key fob functionality to ensure the battery is working correctly.

  5. Once you have confirmed that the key fob is functioning properly, the reassembly process is complete.

Tips for Prolonging Your Car Key Battery’s Life

Congratulations – you’ve successfully replaced your car key battery! But wouldn’t it be great if you could prolong the life of your car key battery? Here are some tips that can help you extend your car key battery’s life.

Temperature Control

The life of your car key battery can be significantly affected by the temperatures it is exposed to. Avoiding extreme temperatures is essential to extend the life of your car key battery.

Do not leave the car key fob in direct sunlight or in places like a car dashboard where it can get hot, as this can lead to faster battery drainage.

Minimising Clicks

Did you know that the more you click, the faster your battery drains? Therefore, it’s advisable to avoid playing with the car key fob or using it as a stress-relief toy to minimize battery wear caused by unnecessary clicks.

Visit your local store to find a suitable bag or purse with a dedicated compartment for storing the car key fob securely, reducing the likelihood of accidental presses.

Regular Check-Ups

Just like any other device, your car key fob requires regular check-ups to ensure it remains free from damage and functions properly. A car key fob battery typically lasts between two to three years under normal conditions, but smart key fobs usually have a shorter battery lifespan, ranging from one to two years, due to more frequent communication with the vehicle.

There are a few battery brands available we found this battery guide which list the different types and which brands are the strongest.

Troubleshooting Car Key Battery Issues

Even with the best care and maintenance, you may still encounter some issues with your car key battery. Regular check-ups for a car key battery should include measuring the voltage with a millimetre while the key fob is transmitting to ensure it is operating effectively. A more accurate assessment of a car key battery’s health can be obtained by using a cheap battery tester that applies a load on the battery while measuring the voltage.

However, if you find your car key quickly using up batteries or if you receive an incorrect ‘Key ID Incorrect’ message, it’s advisable to consult a specialist auto locksmith as a new fob may be needed. Physical damage to key fobs, including cracked casings or water exposure, often necessitates professional repair or seeking a car key replacement service.

Seeking Professional Help

While it’s great to be able to replace your car key battery yourself, there are times when professional help is necessary. If your key fob exhibits persistent weak or inconsistent signal strength that doesn’t improve with a new battery, or if its buttons remain unresponsive even after attempts at cleaning or battery replacement, it’s time to seek professional help.

Professional auto locksmiths are equipped with the tools and knowledge to repair or replace a car key, including faulty key fobs, and reprogram them, ensuring functionality with the vehicle’s electronic systems. They can also offer car key replacement and key duplication services, which are almost always a more cost-effective solution compared to getting services from dealerships, especially in case of lost or seriously damaged car keys that are beyond repair.


Throughout this guide, we’ve covered everything from recognizing the need for a car key battery replacement to prolonging its life and troubleshooting common issues. Proper maintenance of your car key battery is crucial to ensure a hassle-free driving experience. Remember, a little effort can go a long way in extending the lifespan of your car key battery.

Frequently Asked Questions

Can you replace car key battery yourself?

Yes, you can replace a car key battery yourself at home as it doesn’t require specialist skills and can be done quickly and cheaply. Just ensure you purchase the correct battery for your specific car key.

What to do when car key battery is low?

To replace a low car key battery, start by ensuring you have the right type of battery for your key. Then, open the key fob, remove the old battery, replace it with a new one, and test the fob button for functionality.

How do I start my car when my key battery runs out?

You can start your car by placing the key fob near the start button or by using the backup slot for physically inserting the key fob. This will help you get going even if the key battery is running out.

Do I need to reprogram my car after key battery replacement?

No, you do not need to reprogram your car after replacing the key battery; the key fob’s programming is stored in non-volatile memory and will not be affected by a battery replacement. This means that the key fob will retain its programming even if power is lost. However in some instances if the car key battery has been dead for a long duration of time, more than a few months, on older vehicles the key fob may lose its sync and position on the the rolling code list.

How often should I replace my car key battery?

You should replace your car key fob battery every one to two years for smart key fobs, and every three to four years for regular key fobs. Regular maintenance helps ensure your key fob operates smoothly.