Why CMOS Battery is Used in Motherboard

Why CMOS Battery is Used in Motherboard

The Real Time Clock (RTC) chip on the motherboard requires a backup power source; this is where the CMOS battery comes in. The RTC chip keeps track of the time and date for the computer, even when the power is out. Unless a CMOS battery is present, the time and date will need to be manually adjusted each time the computer is turned on.

The boot sequence and any passwords configured in the BIOS are also powered by the CMOS battery. The CMOS battery ensures that the BIOS settings are preserved even after powering down the system along with the RTC chip.

How To Replace The Cmos Battery?

A battery like this can last for many years, but it may need to be replaced at some point. The process of replacing the CMOS battery is relatively straightforward. 

Step 1: Unplugging the Computer

First, unplug the computer, and in the case of the laptop remove the battery. Then locate the battery on the motherboard. 

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It will look like a small, round coin. Gently pry the battery out of its socket and note the orientation of the battery. The positive side is usually marked with a + sign.

Step 2: Check the Battery’s Health

Once the battery is out to make to measure the voltage with a voltmeter. This is to check the health of the battery if the voltage is less than 3 volts then it is time to replace the battery.

When a good battery is used, it can last for many years, but if a cheaper battery is used, it might go bad sooner. If you need to replace it, buy a battery of good quality.

Step 3: Replace the Battery

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After getting the replacement battery, put it in the socket in the same orientation as the old battery. Once the new battery is in place, power on the computer and enter the BIOS. Check the time and date to make sure they are correct. If not, adjust them as needed. Save your changes and exit the BIOS. Your computer should now be keeping accurate time again.

When Is It Time To Replace Cmos Battery?

The average lifespan of a CMOS battery is about 3 to 5 years. However, this can vary depending on the quality of the battery and how often the computer is used. Here are a few symptoms that if occurred in your computer, then it might be the CMOS battery that is the culprit.

Date and time settings are incorrect

In the event that you turn your computer on and find that the time and date are both being reset to an older date and time. Then this means the CMOS chip is not getting power. During a battery malfunction, the BIOS will also be reset to its default settings.

Trouble booting along with a beeping sound

Another indicator of the weak battery is that the computer will have trouble booting up chances are the computer might not boot at all. You will also hear the beeping sound from the motherboard.

Driver not working

If the system does manage to boot up you will also see that the many drivers are not working properly. The disappearance of the divers is most probably the case due to the resetting of the BIOS.

If you experience any of these issues then it is recommended that you take a look at the CMOS battery on your computer or laptop.

Can A Motherboard Run Without A Battery?

So, the question arises does the motherboard can operate without a battery? Yes, it can. CMOS battery in the motherboard powers the component that saves the BIOS setting and the real-time clock. Other than that it does not cause any major inconvenience it’s just you will not be able to save the BIOS setting. 

The CMOS chip that keeps this setting in volatile memory, means the data will be lost if the power is turned off. That’s why a button cell is placed to power that chip. 

But the modern motherboard does not use a CMOS chip for BIOS settings. The reason for this is that up to 128 bytes of data can be stored on CMOS and modern BIOS settings require more. For that motherboard, a separate dedicated button for resetting the BIOS will be mentioned.

Can a CMOS battery cause a black screen?

Yes, the failure of the CMOS battery can cause a black screen. This is because one the BIOS is reset the computer might find it difficult to boot the setting so you might see a number of errors. 

It is possible that you will be asked to press F1 to start the computer since everything has been reset to default.

The removal of a battery may, however, be the best option in certain situations. For example, Is the BIOS locked by the password and you can remember what it was? Then removing the battery will reset the BIOS so does the password. Just don’t forget to place it back once it is done. 


Is CMOS battery necessary?

Yes, a CMOS battery is necessary. This battery powers the CMOS chip in a motherboard. This is responsible for saving the BIOS settings and the system’s internal clock. Which otherwise will be reset every time you unplug the computer or laptop. The system will start without the battery but you will face many issues.

How long does a CMOS battery last without power?

The CMOS battery usually lasts on average 3 to 5 years. The battery that is used in these motherboards is called the CR2032. These are the same battery that is used in most wristwatch and last longer than many other cell types. Remember CR2032 batteries are not rechargeable just replace them with a new one instead.

Is the RTC battery the same as the CMOS battery?

RTC batteries are also called CMOS batteries. These a small coin-like batteries that power your computer system even if it is turned off. These batteries help store the data in microchips like time and date settings.


The simple explanation for why a CMOS battery is used in the motherboard will be to save BIOS settings and to keep the internal clock running. Considering that these batteries can last for many years, they don’t need to be replaced very often. 

Also, we have explained how you can replace it in this article if it needs to be replaced at some point. If the time is getting reset to the default then it is a sign that battery replacement is needed. 

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