What a motherboard battery does and why you might need to replace it

Your motherboard contains a small coin-shaped battery called a CMOS battery (or sometimes a CR2032 battery by its size). This battery powers a chip that keeps your computer's date, time, and basic settings intact even when the machine is completely unplugged. When the battery dies, your computer will forget the time and date every time you shut it down, and you may see error messages on startup.

A motherboard battery typically lasts three to ten years depending on how often your computer runs. You'll know it's failing when your system clock resets to an earlier date after you power off, or when you see a CMOS checksum error message during boot. Replacing it is one of the simplest repairs you can do yourself — it takes about five minutes and costs between $5 and $15 for the battery itself.

Key Takeaways

  • The motherboard battery is a small coin-shaped CR2032 cell that you can buy at any pharmacy, grocery store, or electronics retailer for under $15.
  • You must power off your computer completely and unplug it from the wall before opening the case, then wait a few seconds to let any remaining power drain.
  • The battery sits in a spring-loaded socket on the motherboard and pops out with gentle upward pressure on the clip or the battery itself.
  • The new battery slides in the same way the old one came out, and you do not need to reset anything — the motherboard will keep working as it did before.

Preparing your computer for the battery swap

Start by shutting down your computer completely through the operating system — do not just put it to sleep. Once it is fully off, unplug the power cable from the back of the case or from the wall outlet. Wait at least 10 seconds. This step matters because even when a computer appears off, a small amount of power can remain in the system, and you want that to drain completely before you touch internal components.

If your case has a power supply switch (a small toggle on the back near where the power cable plugs in), flip that to the off position as well. Some people also recommend pressing the power button on the front of the case for a few seconds after unplugging — this can help discharge any remaining power. Once you've done this, you're safe to open the case.

Opening the case and locating the battery

Most desktop cases have two large thumbscrews or regular screws on the back panel. Remove whichever fasteners hold your side panel in place, then slide or lift the panel away. You may need to remove the front bezel or other panels depending on your case design — check your case manual if you're unsure which panel gives you access to the motherboard.

Once the case is open, look at the motherboard itself. The CMOS battery is a round, silver, coin-shaped cell about the size of a dime or slightly larger. It sits in a socket that looks like a small circular holder with a metal clip on one side. You'll usually find it somewhere in the middle or lower portion of the motherboard, though the exact location varies by manufacturer. If you can't spot it, check your motherboard manual — it will show you exactly where the battery socket is.

Removing the old battery

The battery sits in a spring-loaded socket with a small metal clip or tab on one side. To remove it, gently push the clip or the edge of the battery itself upward. The spring will push the battery up and out of the socket. You may need to use a plastic spoon, a plastic pry tool, or even your fingernail — just avoid metal tools that could cause a short circuit. The battery should pop out easily without force.

Once the battery is out, set it aside. You don't need to do anything with the old battery right away — you can recycle it later at a pharmacy, electronics store, or hazardous waste facility. Do not throw it in the trash, as it contains materials that should be recycled.

Installing the new battery

Before you buy a replacement, check what type your motherboard uses. The most common is a CR2032, but some older boards use CR2025 or other sizes. You can find this information in your motherboard manual or by searching your motherboard model number online. Buy the correct size — they cost the same and are available at any pharmacy, grocery store, or electronics retailer.

When you have the new battery, hold it with the positive side (marked with a + symbol) facing up. Slide it into the socket at a slight angle, then press down gently until the clip snaps over the edge and holds it in place. The battery should sit flush with the socket — if it's sticking up or seems loose, remove it and try again. Once it's seated properly, you're done with the hardware part.

Closing the case and powering on

Slide the side panel back onto the case and secure it with the screws or thumbscrews you removed earlier. Plug the power cable back in and flip the power supply switch to on if your case has one. Press the power button to start the computer.

When the system boots, it should start normally. You may see a brief message about the CMOS battery or the date and time being reset — this is normal and nothing to worry about. If you see a CMOS checksum error message, that's actually a good sign: it means the old battery was indeed dead and the new one is working. The error will disappear after the first successful boot. Check your system date and time in the operating system and set them if needed. From this point forward, your computer will keep the correct time even when powered off.

What to do if something goes wrong

If your computer won't start after you replace the battery, the most common cause is that the battery wasn't seated properly. Power off, unplug, wait 10 seconds, and open the case again. Remove the battery and check that the socket itself isn't damaged or dirty. If it looks fine, reinsert the battery and make sure you hear or feel the clip snap into place. Then close up and try again.

If the computer still won't start, the problem is likely not the battery — it may be something else that happened during the opening process, such as a loose cable or a component that got bumped. Check that all internal cables are plugged in firmly, especially the power connectors to the motherboard. If you're still stuck, you can take the computer to a repair shop or post photos of the inside to a tech forum for help identifying the issue.

Frequently Asked Questions

Can I replace the motherboard battery while the computer is on?

No. You must power off completely and unplug the computer. Even with the system off, power can remain in the circuits, and touching components while power is present can damage the motherboard or harm you. Always unplug and wait at least 10 seconds before opening the case.

What if I can't find the battery socket on my motherboard?

Check your motherboard manual — it will have a diagram showing the exact location. You can also search your motherboard model number plus "CMOS battery location" online. If you still can't find it, take a photo of your motherboard and post it to a tech forum; someone will point you to it quickly.

Do I need to reset my BIOS after replacing the battery?

No. The battery replacement itself does not require any BIOS changes. Your settings will remain as they were. If you had customized BIOS settings before the battery died, they may have been lost when the old battery failed — but replacing the battery won't change that.

Is a CR2032 battery the same as a watch battery?

Yes, they're identical. A CR2032 is a standard coin cell battery used in watches, calculators, and many other devices. You can buy one anywhere batteries are sold, and the price is usually the same whether you buy it as a "motherboard battery" or a "watch battery."

What happens if I install the battery backwards?

The battery won't sit properly in the socket if it's reversed, so it simply won't work — but it also won't damage anything. If your computer still shows the wrong date and time after replacement, remove the battery and check that the positive side (marked +) is facing up, then reinstall it.