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Why Do Motherboards Have a Battery?

In case you are building a computer for the first time or have one for many years now, then you must have noticed that there is a small battery or a cell on your motherboard. And while desktops are certainly not battery powered, you may wonder about the need of such a battery on your motherboard.

Hence, we are here with a detailed explanation on why motherboards have a battery. You will learn everything about motherboard CMOS batteries, including how to remove them and check them for failure, by going through this guide until the end.

Motherboard BIOS & BIOS Settings

Before we go ahead and take a look at the importance of a motherboard battery, you should first know about motherboard functions in the first place. Apart from connecting all the various computer components together, your motherboard also stores a lot of system settings. And these system settings are independent of whatever operating system you are using.

In fact, you may even have heard about them before as they are named as the BIOS settings. And in layman terms, your motherboard’s BIOS or BIOS settings store information regarding boot settings, security settings, overclocking settings, and other system settings that need to be checked before even booting the operating system of your computer.

What is CMOS?

Apart from being independent of the operating system, the BIOS settings of your motherboard are also independent of all other hardware components. This means that even if you remove all other components of your computer, the motherboard will still check and consider the BIOS settings.

To make this possible, all motherboards have a CMOS which stands for Complementary Metal Oxide Semiconductor. And this is a short term storage module which stores all of your BIOS settings as long as its receiving power. Apart from the BIOS settings, the CMOS is also responsible for handling the Real Time Clock or RTC of your motherboard.

Why Do Motherboards Have a Battery?

Now that you know the basic functioning of a motherboard and how it stores your BIOS settings, you may have already figured out the need of a motherboard battery. If not, then let us explain. Since the CMOS is a short term memory module, it will lose all data in case of power loss. This means that if there is a power outage or you disconnect your computer from the mains power, the CMOS will lose power and reset the BIOS automatically.

To prevent this from happening, all motherboards have a CMOS battery. This battery ensures that the CMOS has power at all times whether you are using your computer or not. That way, you don’t have to set up your BIOS settings every time the power goes out. Similarly, it also ensures that the Real Time Clock of your computer does not change and you don’t have to set the time again in case of a power loss.

How to Remove CMOS Battery?

While having a CMOS battery is definitely important for the BIOS settings, there will be some cases where you may want to remove a CMOS battery. Apart from having a dead CMOS battery, you may even want to reset your BIOS intentionally. You may have to reset your BIOS if you want to change the settings to default for system stability. And in such a case, you will need to remove the CMOS battery from your motherboard.

Thankfully, removing a CMOS battery is quite easy. You simply need to take a sharp object like a screwdriver and push down on the latch of the CMOS battery. It will look like a small lever coming out on the side of the CMOS battery.  As soon as you push on this lever, the CMOS battery will pop out. You can then insert the same battery back in or get a new 2032 battery if yours has run out of juice. Just make sure to put the battery in the same orientation as it was before.

How to Check Your Motherboard’s Battery?

As mentioned earlier, you may have to remove your motherboard’s CMOS battery if it is not working anymore. Hence, you may also want to check your own motherboard’s battery and make sure that it is working properly. Thankfully, you can easily check a few indications for a failing motherboard CMOS battery. You will notice a few signs like the following ones if you have a dead CMOS battery:

  • Incorrect Date & Time: When your motherboard’s CMOS battery dies, your computer’s Real Time Clock will stop working. As a result, if you have a dead motherboard battery, you will see incorrect date & time every time you boot into the operating system.
  • Longer Boot Times: If your motherboard’s CMOS battery is not working anymore, your computer will have to set up the BIOS settings every time it turns on. And because of this, you will face longer boot times. Sometimes, you might not even be able to boot into your computer at all.
  • BIOS & CMOS Errors: In some cases, if you have a bad CMOS battery and you boot into the BIOS settings, then you will get an error right away. This can include BIOS battery error or a number of other errors. In this case, you can try switching your BIOS battery.

Motherboards Have a Battery – FAQs

1. Is the motherboard CMOS battery necessary?

Ans: If you just want to use a computer and turn it on, you don’t need a CMOS battery. This is due to the reason that once your computer is powered on, it will keep the BIOS settings intact. However, if you want a practical computer where you can turn it off without losing the BIOS settings, then you should definitely use a CMOS battery for faster boot times and keeping your BIOS settings intact.

2. What is the starting point of failure for CMOS?

Ans: When you are talking about the early signs that you will notice in case of a CMOS battery failure, you will see that your computer’s date and time will be incorrect every time you turn it on. Past that point, you may even face longer boot times as your computer won’t be able to store the BIOS settings and they will get reset on every boot.

3. Do laptops also come with a CMOS battery?

Ans: Even though laptops have their own battery, they still need a CMOS battery. This is due to the reason that if you accidentally exhaust the primary battery of your laptop under load, the CMOS battery will still preserve all of your BIOS settings and keep the Real Time Clock running at all times.

4. How long do CMOS batteries generally last?

Ans: While the lifespan of a CMOS battery depends on the battery brand that you are using, good ones can easily last for around 10 years without showing any issues. However, cheaper batteries may only last for a couple of years after which you will need to add a new battery.


Your computer’s motherboard is the key component of the whole system since all other computer components are connected to the motherboard. However, you will find more than just the components on your motherboard. A small battery or cell is one such thing on all motherboards. Since this battery cannot power your computer, you might be wondering about its use. Thus, we have already explained why motherboards have a battery. We have given all the details about this motherboard CMOS battery above. And if this has helped you learn more about computer motherboard batteries, consider dropping your suggestions and thoughts in the comments section below.

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