May 21, 2024


Unlimited Technology

Is Your Computer Battery Dead? How to Fix and Replace Your CMOS Battery

All computers, including desktops and laptops, have a small battery inside the motherboard that provides power to the CMOS (Complementary Metal Oxide Semiconductor). This battery is known as a CMOS battery.

The CMOS on your computer is responsible for remembering hardware settings, system time and date, and some primary parameters required during booting. The CMOS battery provides power to the CMOS chip even when a system is off, saving your settings, but it will revert to the original factory settings if it doesn’t receive power.

Read on to learn how to spot a dead CMOS battery and what you can do to fix it.

What Is a CMOS Battery?

This battery is an essential part of the motherboard and can also be called the backup power for a motherboard. Installed for basic hardware settings, it retains the stored information and is used by:

  • Digital Logic Circuits
  • Microcontrollers
  • Microprocessors
  • Static RAM (SRAM)

What Happens When the CMOS Battery Dies?

CMOS battery is inside the motherboard

Unsplash/Michael Dziedzic

A failed CMOS battery will cause the following problems:

  • The computer will give an incorrect date and time.
  • BIOS passwords will be reset.
  • Some drivers may be missing or may not work properly.
  • The computer will throw a boot error.
  • You may not be able to visit certain websites or access services due to the wrong date and time.
  • You may hear a constant beeping sound, indicating a low or dead CMOS battery.
  • Sometimes, computer peripherals like the keyboard or mouse fail or malfunction when the CMOS battery is dead.

Although your internet connection doesn’t depend on the correct date and time of a PC, as it is connected via Ethernet, USB dongle, or Wi-Fi, you may find it difficult to connect to certain sites, as many programs use date and time as an essential part of security check.

The computer maintains its own date and time and uses it to secure files, documents, and reminders. An incorrect time may lead to lost files, missed appointments, and other issues.

Related: How to Extend Laptop Battery Life With Custom Windows Power Plans

What Does a CMOS Battery Look Like? How Long Does It Last?

CMOS Battery

Image Credits: Raimond Spekking

Learning more about the CMOS battery can help users replace it in case it dies.

  • The CMOS battery is a lithium cell battery that looks like a coin and is located in the motherboard of the computers.
  • It has a low static power consumption.
  • This battery has a lifespan of around 3-4 years. Some batteries are even designed to last for around 10 years.
  • The battery is not rechargeable.
  • Failure of the battery can cause a blank, blue, or black screen.
  • Most CMOS batteries are 3V. However, some computers may require a 5V battery.
  • CMOS batteries are compatible with all computers.

New age CMOS batteries last a motherboard’s lifetime and go up to ten years but sometimes may be required to replace earlier.

Related: Should I Remove My Laptop Battery To Increase its Life?

Can a Computer Run Without a CMOS Battery?

Yes, you can run your PC without the CMOS battery. This battery does not provide power to the entire computer but powers the CMOS when the computer is powered off.

However, without the CMOS battery, you will be required to reset the clock every time you turn your computer on. The BIOS may also reset to its original factory settings each time you boot and shut down the computer. Your computer will function, but everything in your BIOS like boot order, time and date, and other functions will be reset.

How to Replace the CMOS Battery in Your Laptop

Replace your CMOS battery


Replacing this battery is simple and requires only a few minutes.

  1. Choose a suitable place: Remember that a laptop component can get damaged by an electrostatic discharge. So, it is advisable to avoid working on a carpeted surface. A flat and conductive foam pad is best to work on when replacing CMOS batteries. Also, rub your hands thoroughly against a separate metallic object to remove any static charge. You could also consider using an anti-static wrist strap.
  2. Remove power and other cords: Shut down your laptop and disconnect it from the power source. Also, make sure to remove all cables and attachments from the laptop, including peripherals.
  3. Unscrew the laptop’s casing: Flip the laptop over and use a star-head screwdriver to remove all the screws. Carefully remove the casing and look for the shiny metallic coin-shaped lithium battery.
  4. Locate and take out the CMOS battery: Remove the battery from the holding socket. Be careful while handling the motherboard, as it is the most important part of your laptop. Before removing the battery, make sure to note the battery’s orientation so that you don’t place the new battery into the wrong poles.
  5. Insert the new battery: Now, place the new battery in the empty socket. Check and confirm once again that you have placed the battery in the same orientation as the older one.
  6. Rescrew the laptop casing: Re-screw all the screws of the laptop casings. Tighten them with just enough force that you don’t damage the plastic casing.
  7. Final testing: Plug the laptop into the power source and switch on the laptop. You may find BIOS default back to the original settings, so you will have to set the date and time again.

Be cautious while changing a CMOS battery, as it is situated inside the motherboard, which is the heart of a laptop; a little carelessness may result in serious damage.

How to Replace the CMOS Battery from a Desktop Computer

The CMOS battery on the motherboard can be replaced by following these steps:

  1. Remove cables: Remove all cables except for the power cord. Remember to note down the location of each cable to be able to correctly connect them later.
  2. Unplug power: Now, unplug the power cable and press the power button of the PC. This step ensures the removal of any flow of current in the components of the PC.
  3. Unscrew and remove: Unscrew all the screws at the rear end of the PC securing the side panel. Gently hold the side panel and pull it outwards to slide it off.
  4. Locate the battery: Find the battery on the motherboard, and remove it with the help of a screwdriver. Note and remember the direction of the battery placed.
  5. Replace the CMOS battery: Get a new battery with the same ratings as the older one and replace it in the socket. Ensure that you install the new battery in the same orientation as the older one. Replace the side panel and secure it with screws as before.
  6. Reconnect your power: Finally, connect all cables and turn on the power. You will be required to set the current time and date of your PC as the final step.

Related: How to Fix a Windows 10 Laptop With Wrong Battery Percentage

Prevent the Loss of Your Settings, Replace Your CMOS Battery

The CMOS battery powers the BIOS firmware and is responsible for booting up the system. Replacing this battery is a simple process and anyone can do it while taking some extra precautions. It is a simple DIY process and could save you money in labor costs.

It is also common to remove the battery and return a system to factory settings with flash-back CMOS settings when a system encounters a configuration problem.

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