How to Find and Identify Your Computer's CMOS Battery

Where the CMOS battery sits in your computer

The CMOS battery is a small coin-shaped battery mounted directly on your computer's motherboard. It looks like a watch battery — usually silver, about the size of a dime or slightly larger — and sits in a plastic holder with a clip. To find it, you need to open your computer case and look at the motherboard itself.

The battery is almost always on the bottom half of the motherboard, away from the CPU and RAM. On most desktop computers, it sits somewhere in the middle-to-lower section. On laptops, it may be harder to reach because the motherboard is tightly packed, but it follows the same placement logic. If you have never opened your computer before, this is the moment to decide whether you are comfortable doing so — if not, a computer repair shop can locate it for you in minutes.

Key Takeaways

The CMOS battery is a small coin-shaped cell mounted directly on the motherboard, usually silver and about the size of a dime.
On desktop computers, it sits in the lower-middle area of the motherboard; on laptops, location varies but it is always soldered or clipped to the board.
You can identify it by its round shape, the plastic clip holding it in place, and the label on the motherboard nearby that says "CMOS" or "BATT".
If you cannot locate it visually, your motherboard manual or a search for your specific motherboard model will show you the exact spot.

How to safely open your computer to see the motherboard

Before you touch anything inside, shut down your computer completely and unplug the power cable. Wait a few seconds, then press the power button once to discharge any remaining electricity. This step matters — it protects both you and the components.

On a desktop, locate the two or four screws on the side panel (usually the left side when the computer faces you). Remove them and slide the panel off. You are now looking at the motherboard. On a laptop, the process is more involved: you will need to remove the bottom panel, which usually has many small screws. Take a photo of the screw locations before you remove them so you can put them back in the right spots. If your laptop is still under warranty, opening it may void that warranty — check before you proceed.

Identifying the CMOS battery by sight

Once you can see the motherboard, look for a round, flat, silver object about the size of a coin. It will be sitting in a plastic holder that has a small metal clip on one side. The clip holds the battery in place. Near the battery, you should see text printed on the motherboard that says "CMOS," "BATT," "RTC," or "BATTERY." This label confirms you are looking at the right part.

The battery itself is usually a CR2032, CR2025, or CR2016 — these are standard watch-battery sizes. The exact model is often printed on the top of the battery. If the label is worn away, the size of the battery relative to nearby components will help you identify it. It is always smaller than a postage stamp and much smaller than any other component on the board.

Using your motherboard manual to pinpoint the location

If you cannot find the battery by looking, your motherboard manual will show you exactly where it is. To get the manual, you need to know your motherboard model. Look for a label on the motherboard itself — it usually says something like "ASUS ROG STRIX B550-F" or "MSI MPG Z690-EDGE." Write down the exact model name.

Search online for "[your motherboard model] manual PDF." read the manual and search the document for "CMOS" or "battery." The manual will include a diagram of the motherboard with the battery location marked. This is the fastest way to find it if you are unsure. Most manufacturers also host manuals on their support websites — ASUS, MSI, Gigabyte, and ASRock all have searchable manual libraries.

What to do if you cannot locate it

Some older computers have the CMOS battery soldered directly to the motherboard instead of sitting in a removable clip. If you see a small round object that is permanently attached to the board with no clip, that is a soldered battery. You cannot remove it yourself — a technician with soldering equipment would need to do it.

If you have looked carefully and cannot find any battery at all, your computer may have a different power source for the CMOS. Some newer motherboards use a supercapacitor instead of a battery, or they draw power from the main power supply in a way that does not require a separate battery. In these cases, there is nothing to find. If you suspect this is the case, check your motherboard manual or contact the manufacturer.

Checking the battery type before you remove it

Before you take the battery out, note what type it is. Look at the top of the battery — it will have a code printed on it, usually "CR2032," "CR2025," or "CR2016." Write this down. You will need this number when you buy a replacement, because different motherboards use different sizes and you want to match the original exactly.

If the label is too worn to read, measure the battery with a ruler or compare it to a coin. A CR2032 is 20 millimeters across and 3.2 millimeters thick. A CR2025 is 20 millimeters across and 2.5 millimeters thick. A CR2016 is 20 millimeters across and 1.6 millimeters thick. The thickness is the main difference. Your motherboard manual will also list the battery type in the specifications section.

Removing the battery to inspect or replace it

To remove the battery, gently push the metal clip to the side. The clip will spring back, and the battery will pop up slightly. Lift it out with your fingers or a plastic tool — do not use metal tweezers, as they can cause a short circuit. Once it is out, you can read the label clearly and check whether it is dead or still working.

If you are replacing it, take the old battery with you to the store so you can match the type exactly. Do not guess at the size. Insert the new battery with the positive side (marked with a "+") facing up, then press it down gently until the clip snaps back into place. Close your computer case, plug in the power cable, and turn the computer on. The CMOS will reset to default settings, so you may need to adjust the date and time in your BIOS menu.

Frequently Asked Questions

What happens if I cannot find the CMOS battery?

If you have looked at the motherboard and cannot locate a removable battery, your computer may use a soldered battery or a supercapacitor instead. Check your motherboard manual to confirm. If you are still unsure, a computer repair technician can identify it for you in a few minutes.

Can I damage my computer by opening it to look for the battery?

No, as long as you unplug the power cable first and avoid touching components with wet hands or metal tools. The main risk is static electricity — if you are concerned, wear an anti-static wrist strap, which costs a few dollars and clips to your wrist and the computer case.

Is the CMOS battery the same as the main battery in a laptop?

No. The main battery powers your laptop when it is unplugged. The CMOS battery is separate and much smaller — it only powers the clock and settings when the laptop is off. You will find it on the motherboard, not in the battery compartment.

How do I know if my CMOS battery is dead?

Signs include the date and time resetting to a default value every time you turn the computer on, or the BIOS settings reverting to factory defaults. You can also test the battery with a multimeter if you have one — a dead CR2032 will read below 2.5 volts.

Do I need to replace the CMOS battery myself, or can a shop do it?

Either way works. If you are comfortable opening your computer and the battery is removable (not soldered), you can do it yourself for the cost of the battery. A repair shop will charge labor time on top of the battery cost, but they will handle it quickly and safely.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.