What Does A CMOS Battery Do? A Detailed Guide for You!

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What Does a CMOS Battery Do

CMOS battery acts as the core of a computer’s motherboard’s BIOS and is a central figure for a computer or laptop to keep its functionality. Many refer to the CMOS battery as the bridge that holds the connection between BIOS and motherboard.

So, what does a CMOS battery do? A CMOS battery works to provide RTC and constant power to the CMOS chip so that the data regarding BIOS settings and security can stay functional & secure even after a computer or a laptop is powered off.

A Little About CMOS Battery

CMOS battery powers the motherboard and BIOS of a computer. Whether from a computer or laptop, a BIOS needs to be powered even when the computer and laptop aren’t powered on or connected to a power supply. 

So, there comes a need for a different power source so that the BIOS can remain operational, and that is where CMOS enters the motherboard.

It also powers the CMOS chip that harbors the entire BIOS configuration and date & time information of the system. All of this information is vital for the computer to start up. 

But this information can’t function if there is no power, so there is a need for a volatile power source that can continuously sustain and provide power to the CMOS chip, and that power source is the CMOS battery.

CMOS battery contains four components:

  1. Digital Logic Circuits 
  2. Static RAM or SRAM
  3. Microprocessors 
  4. Microcontrollers

Together these components work to keep the data in the CMOS chip safe and secure. CMOS batteries have a lifespan of 10 years in an optimal environment.

So, in simple terms, we can say that CMOS battery offers non-stop power to the motherboard, specifically in the CMOS chip or BIOS chip where the data from BIOS settings are saved. 

Another thing that the CMOS battery does is that it acts as a watch for the components of the computer or laptop. 

Therefore, it maintains the RTC or real-time clock, which is regarded as the system clock. If RTC isn’t functioning correctly, a user will face problems using his computer because it will show startup issues.

What Happens When CMOS Battery Fails?

The first thing you will notice if the CMOS battery starts to fail is that your laptop or computer’s date and time settings will be off the mark. And no matter what you will do, the time & date will always be incorrect. And that’s the first stage.

Because of RTC or real time clock failure, your computer or laptop won’t be able to determine the exact time your device is booting up, which will then lead to startup issues. 

Your computer will face sudden shutdowns or require a long time before it can boot up even though power is already connected.

But the final blow comes when the CMOS battery of your computer or laptop completely fails, and if that happens, then your computer or laptop won’t boot no matter what. 

What’s more, you will lose every data in your CMOS chip, meaning you will have to say goodbye to every setting you have ever done to your BIOS.

So, you will lose all your data regarding boot settings, overclock settings for both processor and graphics card, RAM XMP settings, and many more. You will also lose any password that you incorporated with your BIOS.

Meaning you will have to reconfigure your entire BIOS settings from the ground up, and if you do not have complete mastery over the BIOS menu, this will be a huge burden when you switch to a new CMOS battery.

So, in short, if your CMOS battery fails, then your computer will be useless to you until you manage to add another CMOS battery to your motherboard.

Frequently Asked Questions

Here are the most common and frequently asked questions regarding the CMOS battery and its functionality:

1. My computer turns on without its display. Is it because of my CMOS battery?

It is highly unlikely that the CMOS battery causes the problem in display input. Because if a computer starts on perfectly, then that is the sign of CMOS battery working correctly.

2. I forgot my BIOS password. Can I change my CMOS battery to reset it?

Yes, if you change your CMOS battery, all BIOS-related data will be gone, and the BIOS settings will reset. So, it will by default reset your BIOS password

3. How can I find out if the CMOS battery is failing?

The battery failure starts when your system’s date and time show incorrect results; that’s the indicator of battery failure. 

Your computer or laptop will also show your notification at startup if your CMOS battery starts to show the sign of failure. Your motherboard will also begin to beeping when you try to start your system.

Final Thoughts

Without any doubt, CMOS battery plays a significant role in the performance and functionality of a computer or laptop. It protects the most crucial data without which a computer can’t even startup.

Hopefully, if you have come this far with this article, then it is safe to say that you now know what does a CMOS battery do. And if so, then you know how essential it is towards your system. So, take good care of it and best of luck!

About the author

David Huner

Hi, my name is David Huner, a Tech Lover. In my spare time I enjoy writing reviews and informative articles that I hope you find useful. Please enjoy as I have dedicated much time and effort into my work.

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