What is a CMOS Battery?

The CMOS battery is a small, round battery on the computer’s motherboard.
Its job is to keep basic system settings saved, even when the computer is turned off.

What Does It Do?

It keeps information like:

• Date and time

• Boot order

• Hardware settings (BIOS/UEFI)

Signs of a Weak or Dead CMOS Battery

You may notice:

• Computer forgets date and time

• Error like “CMOS checksum error”

• PC asks to press F1 or F2 on startup

• BIOS settings keep resetting

How to Fix It

• Turn off and unplug the computer

• Open the case

• Replace the old battery (usually CR2032)

• Power on and set date/time in BIOS

Why It Matters in Troubleshooting

If a PC won’t boot properly or keeps resetting settings,
checking the CMOS battery is a quick and cheap fix 🔧