What Happens When A CMOS Battery Dies

What Happens When a CMOS Battery Dies?

The CMOS battery is an important part that is located on your motherboard. Its primary purpose is to hold date and time as well as BIOS settings, depending on the motherboard in question. But what happens when a CMOS battery dies?

In a nutshell, not much will happen and you might not even notice at first that your CMOS battery is failing or dead. Your computer will boot up normally and everything will be fine. The only thing that may happen is that Windows will ask you for the date and time. This may happen only once or twice a month, but as the battery gets weaker, it will keep happening.

So why does this all matter? How often should you replace your CMOS battery? You can learn more about what happens when a CMOS battery dies and how to fix it by reading the rest of the article. Let’s get started!

What Happens When a CMOS Battery Dies?

The CMOS battery holds the date and time settings. If you have ever moved out and your computer stayed unplugged for a few days and when you plugged it back in the date and time settings were still accurate, you have to thank the CMOS battery.

Another important role that the CMOS battery has is to store your BIOS settings. The battery achieves that by powering your computer’s firmware. Since the firmware requires very little power for this, the CMOS battery suffices. But, just like any other battery, the chemicals inside of it break down which eventually causes it to malfunction and fail.

So, what happens when a CMOS battery dies? How can you tell that it is dead? Here are some of the telltale signs of a failing CMOS battery:

  • Date and time settings in Windows are incorrect
  • Your computer turns off by itself
  • Drivers are not working correctly
  • While booting, you get an error message saying “CMOS checksum error” and “CMOS read error”

So, how often should you change your CMOS battery? How long do CMOS batteries last? They can last around 8 to 10 years, but they can fail much sooner or even be dead on arrival. Higher quality CMOS batteries will last longer and function better. If you have been using your computer for a long time and never changed the CMOS battery, then it is high time you changed it.

Since your CMOS battery only holds your BIOS settings as well as date and time, it is not essential for your computer to run as your CPU and RAM are. This means that you can use your computer even if your CMOS battery is dead or completely removed, but you should still replace it with a new one as soon as you can.

And when buying a new CMOS battery, get the best one that you can find. Japanese CMOS batteries are the best, but other manufacturers like Energizer and Maxell also make good CMOS batteries.

If you have a desktop computer, replacing the CMOS battery is very easy. If you are somewhat familiar with computers, you can do it by yourself. Otherwise, get someone else to do it for you.

You just have to open your computer, locate the CMOS battery on your motherboard (usually below the first PCIe slot), take it out by pressing on the hinge and putting the new one in. You will probably have to remove your graphics card first, so bear that in mind. Be careful not to touch the motherboard as you could short circuit and kill it.


Your CMOS battery’s primary function is to hold BIOS and date and time settings. If it is dead, your computer will let you know because it will send you a CMOS error when booting and, once you boot, your system will ask you to adjust the date and time.

If this is happening to you, don’t worry. CMOS batteries are very cheap and you should be able to replace it yourself. CMOS batteries last a long time, but they can die much sooner than expected or be dead from the box. Just make sure that you are grounded by using an antistatic wrist strap and be gentle. 

Leave a Comment

Your email address will not be published. Required fields are marked *