When a computer is powered on, the CMOS battery on the motherboard provides the necessary power to the CMOS chip, which stores important system settings such as the system clock and BIOS configuration.
Without a CMOS battery, the computer will not be able to retain these settings and may not function properly.
What is a CMOS battery?
A CMOS battery, also known as a RTC (Real Time Clock) battery, is a small battery that provides power to the CMOS (Complementary Metal-Oxide-Semiconductor) chip on the motherboard of a computer.
The CMOS chip stores important system settings such as the system clock, BIOS settings, and other configuration information.
Without a CMOS battery, the computer will not be able to retain these settings, which can cause the computer to function improperly or not at all.
Symptoms of a dead CMOS battery
There are several symptoms that may indicate that the CMOS battery on a computer’s motherboard is dead or failing.
These include:
- Incorrect date and time displayed on the computer
- BIOS settings resetting to default after the computer is powered off
- Computer not booting up or unable to enter the BIOS
- Error messages related to the CMOS or RTC battery
If you experience any of these symptoms, it is likely that the CMOS battery on your motherboard needs to be replaced.

How to replace a CMOS battery
Replacing a CMOS battery is a relatively simple process that can usually be done by anyone with basic computer knowledge and a screwdriver.
Here are the steps to follow:
- Turn off the computer and unplug it from the power source.
- Remove the computer’s case to access the motherboard. Refer to your computer’s manual or online documentation for instructions on how to do this.
- Locate the CMOS battery on the motherboard. It is typically a small, circular battery with a “+” symbol on one side.
- Use a screwdriver to remove the battery from its holder.
- Replace the old battery with a new one of the same type and size. Make sure to match the “+” symbol on the new battery with the “+” symbol on the motherboard.
- Reassemble the computer and plug it back in to the power source.
- Turn on the computer and check the date and time settings to make sure they are correct.
Should a CMOS Battery Be Replaced In The Motherboard?
Yes, if the CMOS battery on a computer’s motherboard is dead or failing, it should be replaced.
The CMOS battery provides power to the CMOS chip, which stores important system settings such as the system clock and BIOS configuration. Without a functioning CMOS battery, the computer may not be able to retain these settings and may not function properly.
It is generally a simple and inexpensive process to replace the CMOS battery, and doing so can prevent potential problems with the computer’s operation.
How To Find A Good CMOS Battery For The Motherboard
To find a good CMOS battery for your computer’s motherboard, you will need to know the type and size of battery that is compatible with your motherboard. The type and size of the CMOS battery is usually specified in the motherboard’s manual or online documentation.
You can also refer to the old battery that you are replacing, as it will have this information printed on it. Once you know the type and size of the CMOS battery you need, you can purchase a new one from a computer store or electronics retailer.
It is important to make sure that you get a high-quality battery from a reputable manufacturer to ensure that it will provide reliable power to the CMOS chip on your motherboard.

Causes Of A Dead CMOS Battery
There are several potential causes of a dead CMOS battery.
The most common cause is simply the battery reaching the end of its lifespan and losing its ability to hold a charge. CMOS batteries typically last for several years, but their lifespan can vary depending on factors such as the type of battery, the quality of the battery, and the amount of use the computer receives.
Other potential causes of a dead CMOS battery include physical damage to the battery, such as puncturing or crushing, or exposure to extreme temperatures.
In some cases, a dead CMOS battery may be caused by a problem with the motherboard or other hardware components in the computer.
Final Thoughts
A CMOS battery is an essential component of a computer’s motherboard, providing power to the CMOS chip and allowing the computer to retain important system settings.
Without a functioning CMOS battery, a computer may not function properly or at all.
If you suspect that the CMOS battery on your computer’s motherboard is dead or failing, replacing it is a simple process that can usually be done by anyone with basic computer knowledge and a screwdriver.