How to change a car key battery?|How to adjust a car headlight?

A keyless entry key fob is a small remote-control device that is able to control the remote keyless entry system. An important question here is “How do you change a car key battery?”. Upon pressing the unlock button on the key fob, a confirmation chirp is sounded from the car’s unlocking mechanism. However, there is a lot more to key fob technology than meets the eye.

A keyless entry key fob is one of those devices that we use constantly but don’t know much about. The technology used in these tiny hand-held devices is revolutionary in the development of remote keyless entry systems for cars and other automobiles. It just takes a few minutes of losing a keyless entry key fob that you realize how important and convenient it is.

Let’s look more deeply into the question of “what is a key fob” and “how do you replace a car key battery”. There could be many aspects of a key fob that you may not know. We’ll ask the question “Why are key fob cases an important part of the keyless entry system” and “How to choose the right one”.

These are the basic principles of a key fob regarding their design, manufacture and use:

  1. A key fob is a remote control with a radio frequency ID (RFID)chip and an antenna. The key fob uses radio frequencies to send signals to another radio frequency ID reader device inside the car that controls the locking mechanism. Each key fob transmits a specific RFID information tag that can be read by the reader device inside the car.
  2. When the button on the key fob is pressed, the key fob will transmit a radio frequency ID message to the receiving device inside the car. If the radio frequency that is transmitted from the key fob corresponds to the receiver mechanism that is programmed to accept it, the unlocking mechanism will open the door lock.
  3. Radio frequency ID key fobs are very versatile and can be programmed for various purposes. The functions such as unlocking a specific door or firing up the engine can be programmed into the keyless system. In most of the cases, the key fob unit has multiple functions assigned to it using different buttons.
  4. Usually, the key fob will be contained in a plastic enclosure that is small enough to fit in your hand. Some key fobs don’t have any buttons, instead they have proximity sensors that work when passed in front of the receiver electronic lock/unlock mechanism. Other types of key fob systems use buttons to transmit a radio frequency that is specific to the lock/unlock mechanism. Each button on the key fob performs a certain function – like unlocking the vehicle, locking it or starting the engine and even opening the trunk lid.
  5. RFID key fobs are the most commonly used keyless entry systems used for vehicles today. The technology used in key fobs has much wider applications than just for locking/unlocking a vehicle.
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How to change a car key battery

The battery in a car key fob can die just like any other device that requires a battery. Often, they fail when we most need them which can be quite frustrating at times. Fortunately, the batteries are easy to replace.

Modern cars come with some sort of key fob, either attached to the keyring with buttons to communicate with the locking/unlocking mechanism. These key fobs send an RFID signal wirelessly to the car, and they operate under the power of a battery. Batteries in the key fob commonly last for between 2 and 5 years. If during this time, the battery in the car fob is weak, the remote device may stop working and you may not be able to get into the car or perform any keyless functions. However, replacing the battery in a car key fob is relatively simple. Below is a guide on how to change the battery in a car key fob.

  1. 1. Check for the battery type in the plastic housing

    On certain key fobs, the battery type is visible from the outside. It is easy to purchase the same type and size of battery from the store before even opening up the key fob. Popular brands of key fob batteries are Panasonic, Energizer and Duracell.
  2. 2. Look for the part where the key fob seams come together

    Key fobs open up in a clam shell, with 2 halves snapping together. This is the part that can be split into 2 halves. There is sometimes a notch in the seam that makes prying the key fob into two easier. If the car requires the key to be inserted into the ignition to start it, don’t hang anything else from the keyring other than the fob. This is to prevent the ignition cylinder from wearing down under the weight of the keyring.
  3. 3. Gently take apart the key fob

    Use a small, flat blade screwdriver to pry the 2 seams of the key fob apart. Even a fingernail will suffice here. Take apart the key fob from the seams and gently open the casing down the middle. Modern cars with key fobs and RFID keys will not allow you to lock your keys inside the car. Taking apart the key fob is a very simple task.
  4. 4. Check the battery terminals – positive and negative ends

    The battery looks like a small coin. It will have the battery size and a plus sign and minus sign embossed on it. Carefully slot in the battery in the correct orientation. It will need to go in the same way as the old battery was inserted.
  5. 5. Remove the old battery and replace it with the new one

    The battery will usually pop out of place due to the inbuilt spring. If it doesn’t come out, gently pry it out with the flat bladed screwdriver. Replace the old battery with the new one in the same plus and minus orientation as the old one.
  6. 6. Put the key fob back together

    Assemble the key fob the reverse way of disassembling it. Snap the two pieces of the key fob back together and check if the buttons are working. The key fob should work as good as new.

Advantages of using a key fob

Using a key fob has several advantages, whether for an automobile or for a different purpose. The main advantages are:


Duplicate keys don’t work sometimes especially if they have been made using cheaper materials or with substandard equipment. A remote keyless entry key fob is a reliable option and will last a long time providing years of convenience.


Physical keys are easily lost and could be copied to gain access. A lost key fob can be deactivated remotely.


key fobs can be easily reprogrammed when the key fob is lost. Replacing a physical lock and key can be expensive and is a hassle.


Using key fobs, the vehicle can be locked and unlocked in a matter of seconds which is incredibly fast. Even people with disabilities find that using a key fob is much more convenient than using a physical key.


Key-fobs with multiple buttons fulfil numerous functions into a highly portable and small package.


Key fobs can be programmed to provide access to only certain parts of areas. This makes them excellent for applications with restricted access.


Some key fobs don’t need a battery because they are powered by the energy transmitted between the receiver and the antenna. Those key fobs that do use batteries last a long time, typically between 2 and 5 years depending of usage.

Key fob uses

Key fobs gained more prominence in the late 80’s and early 90’s when they became widely available in cars. Early types of keyless entry systems made use of infrared waves, but these were not very helpful because they required a line of sight to work. RFID key fobs became the preferred technology thereafter due to their reliability and security.

Keyless entry systems now include many advanced functions and features. Some key fobs are designed to open the rear hatch which is perfect for people carrying their heavy shopping. Other RFID key fobs can start a car’s engine, which is helpful for warming up an engine before a short ride.

Secure key fobs

Manufacturers of wireless remote keyless systems must take steps to make the device secure. Of course, wireless key fobs are more secure than physical keys, it is possible for thieves to exploit the system when not properly secured. These vulnerabilities must be eliminated from the RFID keyless entry systems.

Modern keyless entries prevent their signals by being intercepted by other devices. Many key fob transmitters use a coded signal that changes every time it is used, yet the receiver is capable of using that signal to lock/unlock the vehicle doors.

Frequently asked questions

Q1. When do you change the car key battery?

Ans. When the remote’s battery gets weak, its range is greatly reduced so that the key fob will not work from a distance. It will have a decreased signal range and will only start functioning when you are close to the car. Typically, it should have a range of about 30 to 60 feet. Another sign is that clicks are inconsistent and you have to click several times to lock and unlock your car. The functions can even get delayed with a weak battery. After pressing the button, there is a delay of about 2 seconds before the car is unlocked. Usually, key fob batteries should be replaced every 3 to 5 years.

Q2. Where do you replace the car key battery?

Ans. The batteries used in car key batteries are the common cell type like CR2025 or CR2032 and they can be found in any general store, home improvement store or auto parts store. Popular brands of car key batteries are Duracell, Energizer and Panasonic. Car accessory shops will usually have various kinds of car key batteries in stock along with different car key battery types and brands.

Q3. How do you change the car key battery yourself?

Ans. First check the battery type in the plastic housing. Then pry open the 2 halves of the key fob. Check the battery terminal’s positive and negative ends. Remove the old battery and discard it. Place the new battery in the correct position at the correct terminals. Assemble the key fob in the same way you had disassembled it.

Q4. How much does it cost to change a car key battery?

Ans. The car key battery that is used in most key fobs is widely available and costs between Rs.300 -Rs.400. They can be obtained easily from a car accessory store. Popular brands of car key batteries are Philips, Duracell, Energizer and Panasonic.

Q5. Do different car brands have different kinds of car key fobs and batteries?

Ans. Different manufacturers and models have different types of key fobs and different kinds of batteries used in them. But the process to change them is generally the same, and the car key batteries can be obtained from any car accessory shop as they usually stock the different types of batteries.

Q6. How often do you change the car key battery?

Ans. The battery life in most car keys is around 3 to 4 years. It also depends on the amount of usage. Also, the key fob should not be kept inside the car or near the car on a hook when the car is parked. This is because the car key fob will continuously be sending signals to the receiver and will shorten the battery life.


It doesn’t really matter what kind of car key fob you have, replacing the car key battery is a simple task that can be completed in a couple of minutes. The techniques used to pry open the casing and change the battery are generally the same for most models. Once the battery has been replaced, your car key fob should work as good as new and give you years of convenience at your fingertips.

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