The CMOS battery sits on your motherboard, usually near the center or edge

The CMOS battery is a small coin-shaped battery (typically CR2032 size) soldered or clipped to your computer's motherboard. It powers the BIOS settings and system clock when your computer is unplugged. To find it, you need to open your computer case and look at the motherboard itself — it's a silver disc about the size of a dime, often mounted in a plastic holder with a clip or sitting in a socket.

The exact location varies by motherboard model. On most desktop computers, it's positioned somewhere in the middle or lower-right area of the board. On laptops, it may be harder to reach because you'll need to remove the keyboard or bottom panel first. Check your motherboard's manual or search online for your specific model number to see a diagram showing the battery's exact location.

You can find your motherboard model by opening your computer case and reading the label printed directly on the board, or by using free software like CPU-Z (on Windows) or System Information (on Mac) to identify it. Once you know the model, a quick search like "motherboard model CMOS battery location" will show you exactly where to look.

Key Takeaways

  • The CMOS battery is a small silver coin-shaped disc on your motherboard, usually CR2032 size, and you can only reach it by opening your computer case.
  • Desktop CMOS batteries are typically located in the center or lower-right area of the motherboard; laptop batteries require removing the keyboard or bottom panel first.
  • Finding your motherboard model number (printed on the board itself or visible in system software) lets you search for a diagram showing the exact battery location.
  • Replacement batteries cost between $3 and $10 and are sold at electronics retailers, online marketplaces, and some hardware stores in the battery aisle.
  • If you are uncomfortable opening your computer case or removing components, a repair technician can replace the battery in 15 to 30 minutes for a service fee.

How to access the CMOS battery on a desktop computer

Shut down your computer completely and unplug the power cable from the back. Wait 30 seconds, then press the power button once to discharge any remaining electricity. Open your computer case by removing the side panel — most cases have two or three thumbscrews or clips on the back that hold the panel in place. Lay the case on its side on a clean, flat surface so you can see the motherboard clearly.

Look for the CMOS battery by scanning the motherboard for a silver disc about the size of a dime. It will either be sitting in a plastic clip holder (which you can pop open with your fingernail or a plastic spoon) or mounted in a socket that you can gently pry out. If the battery is clipped in, lift the clip arm away from the battery and the battery will pop out. If it's in a socket, use a plastic tool or your fingernail to gently rock it side to side until it lifts out.

Write down the battery model number (usually printed on the top) before you remove it, so you know exactly what to buy as a replacement. Most CMOS batteries are CR2032, but some older boards use CR2025 or other sizes. Once you have the old battery out, you can install the new one by reversing the process — clip it back in or press it into the socket until it clicks.

How to access the CMOS battery on a laptop

Shut down your laptop and unplug the power adapter. Remove the battery if it's user-removable (most modern laptops have sealed batteries, so this step may not explore). Open the bottom panel by removing the screws — you may need a small Phillips screwdriver. Take a photo of the screw locations before you remove them so you remember where each one goes, because laptop screws are often different sizes.

Once the bottom panel is off, look for the CMOS battery on the motherboard. On many laptops it's located near the center of the board or close to the RAM modules. Some laptops require you to remove the keyboard instead of the bottom panel — check your laptop's service manual online to confirm the correct approach for your model. If the battery is in a clip holder, lift the clip and the battery will pop out. If it's soldered directly to the board, you cannot replace it yourself and will need to contact a repair technician.

After you install the new battery, replace the bottom panel or keyboard and reinstall all screws. Power on your laptop and check that the date and time are correct in the system settings. If the date has reset to a default value (often 2000 or 2010), that confirms the old battery had died and the new one is working.

Where to buy a replacement CMOS battery

CMOS batteries are sold at most electronics retailers and online. Amazon, Newegg, and Best Buy all stock CR2032 batteries (the most common size) in packs of one or more. Local options include Best Buy, Micro Center (if you have one nearby), and some Walmart and Target locations in the battery aisle. Prices typically range from $3 to $10 per battery depending on the brand and whether you buy a single battery or a multi-pack.

When you order online, search for "CR2032 battery" or whatever size your motherboard uses. If you are unsure of the size, you can also search for "CMOS battery [your motherboard model]" and the results will tell you the correct size. Batteries ship quickly — most arrive within two to three days with standard shipping, and you can often pick one up the same day at a local store if you need it urgently.

Avoid buying the cheapest no-name brands if possible. Reputable brands like Energizer, Duracell, Panasonic, and Maxell are widely available and cost only slightly more. A quality battery will last longer and is less likely to leak inside your computer.

What happens if you cannot find or reach the CMOS battery

If your motherboard manual shows the battery is soldered directly to the board (not clipped or socketed), you cannot replace it yourself. This is common on some laptops and newer motherboards. In this case, contact a computer repair shop and ask for a CMOS battery replacement. Most shops can do this in 15 to 30 minutes and charge between $30 and $75 for the service, depending on how much disassembly is required.

If you open your case and cannot locate the battery after checking your motherboard manual, take a clear photo of your motherboard and post it in a computer repair forum or subreddit like r/techsupport. Include your motherboard model number in the post, and someone will point you to the exact location. Do not guess or poke around randomly — you could damage other components.

If you are uncomfortable opening your computer case at all, that is a reasonable choice. A repair technician can handle the entire job from start to finish. The cost is usually worth the peace of mind if you are worried about damaging your hardware.

Signs your CMOS battery is failing

A dying CMOS battery shows itself through a few clear signs. Your computer's date and time reset to a default value (often January 1, 2000 or 2010) every time you shut down and unplug it. You may also see error messages on startup like "CMOS battery low" or "CMOS checksum error." Some computers will beep repeatedly during startup or refuse to boot until you enter the BIOS settings and reset them manually.

Another sign is that your BIOS settings do not stick — you change something in the BIOS setup menu, save it, and the next time you start the computer, the settings have reverted to defaults. This happens because the CMOS battery is too weak to hold the settings in memory when power is cut.

If you see any of these symptoms, the battery is likely near the end of its life. A CMOS battery typically lasts five to ten years, so if your computer is older than that, replacement is a reasonable next step. Replacing it is straightforward and inexpensive, and it will stop the error messages and reset behavior when ready.

Frequently Asked Questions

Can I use a different battery size if I cannot find the exact CR2032?

No. Using the wrong size battery can damage your motherboard or cause the battery to not make proper contact. Always match the exact model number printed on your old battery or listed in your motherboard manual. If you cannot find the right size locally, order it online — it will arrive in a few days and costs only a few dollars.

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

Usually not. Once you install the new battery, your BIOS settings should restore automatically. However, if your date and time are wrong or settings have reverted to defaults, restart your computer and enter the BIOS setup menu (usually by pressing Delete, F2, or F12 during startup). Set the correct date and time, save, and exit. Your settings will stick once the new battery is working.

What if I install the new battery backwards?

A backwards battery will not make electrical contact and your computer will behave as if the battery is dead — the date and time will reset, and you may see error messages. straightforward remove the battery and flip it around so the positive side (marked with a + symbol) faces up. This is not dangerous; it just will not work until you orient it correctly.

Is it safe to touch the motherboard while replacing the battery?

Yes, as long as you have unplugged the computer and waited 30 seconds. Touching the motherboard itself is safe. To be extra cautious, touch a metal part of the case before you touch the motherboard to discharge any static electricity from your body, though this is rarely a problem in practice. Avoid touching the gold connectors on RAM modules or other components, and do not force anything — if a part does not come out easily, stop and check your manual.

How long does a new CMOS battery last?

A new CMOS battery typically lasts five to ten years, depending on how often your computer is powered on and off. Computers that run continuously use the battery less, so the battery may last longer. Once you replace it, you likely will not need to do so again for many years.