The motherboard battery powers your BIOS settings when the computer is off

Your motherboard has a small coin-shaped battery — usually a CR2032 — that keeps your BIOS settings and system clock running even when you unplug the computer or the power goes out. When this battery dies, your computer forgets the date and time, resets BIOS settings to factory defaults, and may refuse to boot until you fix it. Replacing it takes about five minutes and costs $3 to $8 for the battery itself.

You do not need special tools or technical skill. The battery sits in a plastic holder on the motherboard, clips in and out by hand, and you can buy a replacement at any pharmacy, electronics store, or online. The hardest part is usually opening the case and finding the battery on the board.

Key Takeaways

  • A dead motherboard battery causes your computer to forget the date, time, and BIOS settings, but replacing it is a five-minute job with no special tools.
  • The battery is a CR2032 coin cell that clips into a plastic holder on the motherboard — you remove it by hand, not with a screwdriver.
  • Before you open the case, shut down the computer, unplug the power cable, and wait 30 seconds to discharge static electricity from your hands.
  • After you install the new battery, the computer will boot normally and you can reset the date and time in Windows or your BIOS if needed.

Signs your motherboard battery is failing

The most obvious sign is that your computer loses the date and time every time you shut it down. When you turn it back on, the clock shows a date from years ago — often 2000 or 2005 — and Windows or your operating system corrects it after a few seconds. This happens because the battery is too weak to hold the clock data.

You may also see BIOS error messages on startup, such as "CMOS checksum error" or "CMOS battery low". CMOS is the memory chip the battery powers. Some computers refuse to boot at all until you replace the battery, though this is less common. If you have not opened the case in five or more years, the battery is probably near the end of its life even if you have not seen these signs yet.

What you need before you start

Gather a CR2032 battery — this is the standard size for almost all desktop and laptop motherboards made in the last 20 years. You can buy one at a pharmacy in the watch battery section, at Best Buy, Micro Center, or Amazon. Have a small flashlight or headlamp ready so you can see inside the case. A Phillips head screwdriver is useful for opening the case, though some cases use thumbscrews or slide panels that need no tools.

You do not need an anti-static wrist strap for this job, but it is cheap insurance if you have one. If you do not, straightforward touch a metal part of the case before you touch the motherboard to discharge static electricity from your hands. Avoid working on carpet or fabric — a hard table or wood surface is better.

How to remove and replace the battery

Step 1: Shut down and unplug. Close all programs, shut down the operating system completely, and unplug the power cable from the back of the computer. Wait 30 seconds. This drains the power supply and reduces the risk of static discharge damaging the motherboard.

Step 2: Open the case. Most desktop cases have a side panel held by two or three screws on the back. Remove these screws and slide or lift the panel off. Laptop cases vary widely — look for a panel on the bottom held by screws, or search your laptop model number plus "remove CMOS battery" to find the exact steps. Take a photo of the inside before you remove anything, so you remember where cables go.

Step 3: Locate the battery. The motherboard battery is a round, silver coin about the size of a dime, sitting in a plastic clip or holder. It is usually near the edge of the motherboard or close to the RAM slots. If you cannot find it, look for a label on the motherboard that says "CMOS" or "BATT" — the battery will be nearby. Use your flashlight to see into dark corners.

Step 4: Remove the old battery. The battery sits in a plastic holder with a small metal clip on one side. Gently push the clip away from the battery — it will spring back and the battery will pop up slightly. Lift the battery out with your fingers. Do not force it; if it does not pop up easily, you are pushing the wrong direction.

Step 5: Install the new battery. Check that the new CR2032 has the positive side (marked with a +) facing up. Slide it into the holder with the positive side up, then press down gently until the metal clip snaps back over the edge. The battery should sit flush in the holder and not wobble.

Step 6: Close the case and power on. Replace the side panel and screw it back in. Plug the power cable back in and turn on the computer. It should boot normally. If you see a BIOS error message, enter the BIOS setup (usually by pressing Delete or F2 during startup) and let it auto-detect the settings, then save and exit.

Resetting the date and time after replacement

Once the computer boots, the date and time may be wrong. In Windows, right-click the clock in the bottom right corner and select "Adjust date and time". Click "Set time automatically" and Windows will correct it within a few seconds if you are connected to the internet. If you are not online, click "Change" and type in the correct date and time by hand.

If you see BIOS error messages, restart the computer and enter the BIOS setup menu during the boot screen (usually by pressing Delete, F2, or F10 — your motherboard manual will say which). Look for an option like "Load Defaults" or "Load Optimal Settings" and select it. This resets all BIOS settings to the factory standard. Save and exit, and the computer will restart normally.

When to replace the battery sooner

If your computer is a laptop and you rarely use it, the battery may die faster because the main power supply does not keep it charged. Laptops that sit unplugged for months at a time often need a new motherboard battery every three to five years. Desktop computers that stay plugged in typically last seven to ten years before the battery fails.

If you open the case for any other reason — to add RAM, replace a drive, or clean dust — it is worth checking the battery. If it looks swollen, leaking, or corroded, replace it even if the computer is not showing signs of failure yet. A leaking battery can damage the motherboard.

Frequently Asked Questions

Can I damage the motherboard by touching it while replacing the battery?

Static electricity can damage components, but the risk is low for this job. Touch a metal part of the case before you touch the motherboard to discharge static from your hands. Avoid working on carpet. If you have an anti-static wrist strap, wear it — they cost $5 and eliminate the risk entirely.

What if the battery does not pop up when I push the clip?

You may be pushing the clip the wrong direction. Try pushing it the other way. If it still does not move, the clip may be stuck. Gently wiggle the battery side to side while pushing the clip, or use a plastic spoon handle to explore gentle pressure. Do not use a metal tool — it can short the motherboard.

Do I need to replace the battery if the computer keeps the time correctly?

No. If the date and time stay correct and you see no BIOS errors, the battery is still working. You only need to replace it when the computer starts losing the time or shows error messages on startup.

Is a CR2032 battery the right size for my computer?

CR2032 is the standard for almost all computers made since 2000. If your motherboard uses a different size, it will be labeled on the holder or in your motherboard manual. Search your motherboard model number plus "CMOS battery" if you are unsure — the manual will list the exact part number.

What happens if I install the battery upside down?

The battery will not make contact with the holder and the computer will behave as if there is no battery at all — it will lose the date and time. The battery itself will not be damaged. straightforward remove it, flip it over so the positive side (+) faces up, and reinstall it.