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How to replace the CMOS battery?

How to replace the CMOS battery?

The CMOS battery, commonly known as the RTC (real-time clock), is a tiny battery installed on your computer's motherboard. When the computer is shut off, this battery maintains the BIOS settings and keeps the computer's clock running. The CMOS battery will eventually run out of power, which could interfere with the clock and BIOS settings. The significance of the CMOS battery, warning indications that it might need to be changed, and instructions for doing so will all be covered in this article.

Why is a CMOS battery important?

The Basic Input/Output System, or BIOS, is a set of instructions that regulates the exchange of data between the hardware and software of the computer. The BIOS settings would be lost each time the computer was switched off without the CMOS battery, which keeps the machine's clock accurate.

The CMOS battery is important because it ensures that the computer can maintain its accurate time and date even when turned off. This is necessary to keep file timestamps accurate and the computer's clock in sync with network time servers, among other things. The CMOS battery also ensures that the BIOS settings are not lost when the computer is turned off, which can help avoid problems like boot difficulties and system crashes.

The CMOS battery must be replaced since it ultimately loses its charge, just like all batteries. Your computer's clock might not be keeping accurate time, or the BIOS settings might have been reset if the CMOS battery malfunctioned.

Additionally, a low CMOS battery can interfere with the computer's ability to boot up, making it challenging to turn on the machine. These problems can be solved by changing the battery.

Note: Although the CMOS battery is small and reasonably priced, it is crucial to a computer's correct operation. Your computer will function more smoothly if the CMOS battery is regularly checked and replaced. This can help prevent problems with the clock and BIOS settings.

Why should I replace my CMOS battery?

  1. The time or date settings on my computer keep changing: When the computer is turned off, the CMOS battery maintains the BIOS settings and keeps the computer's clock running. The CMOS battery will eventually run out of power, which could interfere with the clock and BIOS settings. It is possible that the CMOS battery has to be changed if you discover that the computer clock is not keeping accurate time.
  2. When the computer boots, the following error or alert message is displayed: The subsequent messages could be a sign that the CMOS battery needs to be changed:
    • CMOS Read Error
    • CMOS Checksum Error
    • CMOS Battery Failure
    • The system battery voltage is low

These messages can mean that the CMOS battery is dying or low. If any of these messages appear, the CMOS battery must be replaced when the computer boots.

Tools and materials required for replacing the CMOS battery

You will need a few basic tools and materials to replace the CMOS battery. These are the items you will require:

How to replace the CMOS battery?
  • A new CMOS battery: it is usually available at an electronics store or online. As various motherboards use various types of batteries, be careful you purchase the appropriate battery for your motherboard.
  • A small Phillips-head screwdriver: This will be used to remove the screws that hold the computer's chassis together.
  • A plastic or flat-head screwdriver: The battery will be removed from its socket using this gently.
  • An anti-static wrist strap: This is an optional but recommended accessory that helps to protect the computer from static energy.
  • A flashlight: Some motherboards include a battery in a difficult-to-find location, so a flashlight might help you find it.
  • A small brush: A small brush is excellent for cleaning the contact points of the battery socket and the fresh battery.

Note: To prevent any potential harm to the computer caused by static electricity, you should unplug it from the power source and remove the battery (if there is one) before you start working on it. Additionally, it's always a good idea to look for precise instructions and advice on replacing the CMOS battery on your motherboard in the manual or on the manufacturer's website.

Replacing the CMOS battery

  • To protect the computer from potential static electricity harm, unplug it from the power source and remove the battery (if it has one).
  • Remove the computer's case by unscrewing the screws that hold it together. You will then have access to the motherboard.
  • On the motherboard, find the CMOS battery. Usually, it will look like a tiny, round battery with a "+" and "-" sign on it. Note its orientation to ensure that the battery is replaced in the same orientation. Most computers use a coin cell CMOS battery such as the CR2032.
    How to replace the CMOS battery?
  • Clean the battery socket's contact points with a tiny brush to ensure the new battery makes excellent contact.
  • Screws must be tightened after replacing the computer's case.
  • To check that the clock and BIOS settings are correct, connect the computer to a power supply and turn it on.

Note: If you're having difficulties finding the battery on a motherboard because it's hidden somewhere difficult to see, try using a flashlight to guide you. Additionally, some motherboards might feature a little button or switch to reset the BIOS; the manufacturer will note this in the handbook or website.

Resetting the BIOS settings:

The BIOS (Basic Input/Output System) manages a computer's fundamental operations, including system settings and booting. The BIOS settings might be restored to their default positions when the CMOS battery is changed.


  • When the machine starts up, use the BIOS setup tool to configure it.
  • Locate the "Load default configuration" or "Reset to default" option. Usually, the "Exit" or "Maintenance" menus contain this option.
How to replace the CMOS battery?

Note: any customized settings, such as overclocking options or custom boot priorities, will be lost if the BIOS is reset. Before resetting the BIOS, the user should ensure that they have a backup of any crucial settings.

  • The user should save the modifications and close the BIOS setup application after resetting the BIOS settings.
  • The modified settings will then go into effect after the computer restarts.
  • After changing the CMOS battery, verify the date and time in the BIOS setup tool because they might have been reset to the default values.


For detailed instructions on resetting the BIOS settings, it is always a good idea to consult the computer's or motherboard's instructions or get in touch with the manufacturer.

Tips for properly handling and disposing of the old battery

How to replace the CMOS battery?

It's necessary to take specific care when handling and to dispose of old batteries to prevent potential risks. Here are some guidelines for managing and discarding the used CMOS battery safely:

  • Handle the old battery with caution: old batteries can be deadly if not handled properly. They risk leaking, overheating, or even explosion if not handled properly. Always use gloves and treat the battery gently.
  • Keep the old battery in a safe place: After removing the old battery from your computer, keep it in a safe place away from children and pets.
  • Dispose of the old battery properly: Do not throw away the old battery. Batteries have chemicals that, if not disposed of appropriately, can harm the environment. The majority of cities and towns have battery recycling facilities. Information on properly recycling batteries can be found by contacting your neighborhood's waste management organization or electronics retailer.
  • Do not open or disassemble the battery: Opening or disassembling the battery might be risky and unleash toxic chemicals.
  • Check with the manufacturer for proper disposal instructions: If you're unsure how to get rid of the old battery, ask the manufacturer for the right procedures.

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