How to Replace a Car Key Battery?

A modern car key is a sophisticated technical device equipped with electronic functions that require power, which is provided by a battery. When the battery charge runs low, the system stops responding to the immobiliser signals, alerting the user that the key is no longer synchronised with the car.

Most chip keys in modern vehicles have a nearly identical structure. These keys are becoming increasingly complex and functional. However, they all operate using ordinary batteries. Naturally, the battery’s lifespan comes to an end over time. When this happens, many car owners may not immediately realise it’s due to the battery and instead check the alarm system or other functions. In reality, identifying when the battery needs replacement is quite straightforward.

To begin, let’s learn how to recognise that the battery needs replacing.

The main sign is, of course, the car alarm no longer working and being unable to start the car. In this case, you will need to use the mechanical key to unlock the car and then investigate further.

Can I Replace the Key Fob Battery Myself?

Replacing a car key battery can be done on your own. You just need to know how to change the battery in the key, which is usually quite simple for most cars.

In modern foreign cars, diagnosing the problem is often as easy as checking the dashboard. There is typically an indicator that shows whether the car key is paired with the vehicle system. If the indicator flashes, it means the connection has been lost—something that usually happens when the battery is dead.

However, you’ll need to open the car first to confirm this. This is easy to do if there’s a mechanical key. However, some brands manufacture cars without a visible keyhole. These vehicles usually include a hidden emergency key that allows you to not only unlock the car but also start the engine, enabling you to drive to a service centre. Such systems are commonly found in premium brands (e.g., Mercedes). Their chip keys are too complex for a car owner to repair independently.

In more affordable models, you can use a regular key to unlock the car. However, it’s best to avoid waiting until the battery is completely dead. Signs that the battery is running low include:

  • Reduced range of the remote control.
  • A warning signal appearing on the dashboard.
  • Delayed response from the car when the key is used.

How Much Does It Cost to Replace a Key Fob Battery?

If you are not confident about replacing the car key battery yourself, we recommend consulting a professional. This can be done by a car mechanic or a car locksmith. The usual cost for replacement ranges from £5-10.

Alternatively, you can visit your nearest Timpson store, where they can replace the battery in just a few minutes.

What Kind of Battery Does My Key Fob Use?

The main types of batteries used in car keys are:

  • CR2025
  • CR2032
  • CR2016
  • CR2450
  • CR1616
  • CR1620
  • CR1632

The most commonly used type is the CR2032. However, to replace the car ignition key battery, it’s essential to determine the exact type. This is very easy—just check the label on your old battery.

What Happens If a Key Fob Runs Out of Battery?

If you don’t replace the key fob battery, the following issues may arise:

  • Reduced range: The key fob will stop working at distances it previously functioned at.
  • Difficulty locking and unlocking: The key fob may take longer to unlock or lock car doors, or stop responding altogether.
  • Weaker signals: The indicator light on the fob may flash dimly or not at all.
  • Emergency alarms: A dead battery could trigger unexpected alarms or cause other unusual behaviour in the fob.

Additionally, if the battery isn’t replaced in time, the key may “unpair” from the car’s system, meaning the remote will lose connection with the vehicle’s power unit, and they will no longer work together.

It is recommended to check the battery’s condition and replace it at the first signs of discharge or malfunction.

If replacing the battery doesn’t resolve the issue, there may be another underlying problem. In such cases, the best solution is to contact a qualified professional, such as an automotive locksmith.

If you’re looking for a specialist who values convenience and professionalism, contact us at Phoenix Car Keys. We’ll resolve your issue promptly.

Our mobile car locksmith can come to you, diagnose the key’s problem, and determine whether it can be repaired or if a car key replacement is necessary.
To book a service or receive more information, please contact us anytime. We are always happy to help.