How to replace the CMOS battery in your PC

The CMOS battery on the motherboard is responsible for preserving the date, time, and BIOS settings when your PC is powered off. Just like any other battery, it has a fixed lifespan and will get depleted even if you don’t use your system very often.

Fortunately, modern motherboards come with a CR2032 CMOS battery that’s pretty affordable and easy to replace. This guide contains everything you need to know to change the CMOS battery in your PC.

What you’ll need

You’ll require some tools to replace the CMOS battery. A Phillips screwdriver is necessary to remove the bottom panel of your laptop. It’s also useful if you need to remove the GPU and/or some expansion cards to access the CMOS battery slot. Since you’re dealing with the fragile components of your system, it’s a good idea to get an anti-static wristband to prevent static electricity from damaging the motherboard.

You’ll need a new CMOS battery that you can slot into your system. Most ATX and Micro-ATX motherboards are compatible with a CR2032 lithium coin cell regardless of whether they support Intel or AMD chipsets. CR2032 batteries are available on most online retailers and hardware stores, and you can get quite a few of them for $10.

Meanwhile, Mini-ITX motherboards and some laptops have a CMOS battery that’s wrapped in black plastic with a cable plugged into the motherboard. In fact, some laptop motherboards use the CR1220 variant instead of the usual CR2032 coin battery, so you should consult the laptop’s manual before ordering a new CMOS battery for your laptop.

When should you replace the CMOS battery

The most common symptom of a dead CMOS battery is your date and time settings resetting every time you reboot your system. However, it can also cause errors like the following:

  • CMOS Read Error
  • CMOS Checksum Error
  • CMOS Battery Failure
  • System battery voltage is low

If your PC frequently displays an error message about the BIOS settings being cleared, there’s a high chance your CMOS battery has been depleted. CMOS coin cells typically have a lifespan of three to five years, so even the best gaming motherboards will need their CMOS batteries replaced after a few years.

Replacing the CMOS battery is also one of the most preliminary troubleshooting tricks when your system fails to boot past the BIOS or the debug LED lights on your motherboard continue to flash after pressing the power button of your PC.

How to replace the CMOS battery in your PC

Once you’ve grabbed your tools and the new CMOS battery, it’s time to swap out the old one. To do so,

  1. Shut down your system and unplug its AC power adapter.
  2. Press and hold the power button for half a minute to drain any remaining charge from the motherboard’s capacitors.
  3. Unmount the front panel of your PC after loosening the thumb screws and securing it in place.
    • If you’re on a laptop, use the Phillips screwdriver to unfasten the screws on the underside of the laptop and gently detach the back cover with the help of a spudger tool. Be sure to disconnect the actual battery of the laptop before you change the CMOS battery.
  4. For most ATX and Micro-ATX motherboards, the old CMOS battery can be released by pressing down on the latch on the CMOS battery slot.
    An image of a CMOS battery inside an MSI B450-A Pro motherboard

  5. If you’re having trouble locating the CMOS battery, you’d want to unmount the GPU as most ATX and Micro ATX motherboards have the CMOS battery slot located around the PCI-e slots.
    Zoomed-in photo of a GPU

    • Most Mini-ITX motherboards have the CMOS coin cell located around the IO ports. You can remove the old battery by unplugging its connector from the motherboard.
  6. To install the new CMOS cell, place it on the CMOS battery slot with the positive side up (the side with the company name) and push it down until it settles into the slot.
    • Mini-ITX motherboard owners can simply insert the cable connector of their new CMOS battery into the motherboard.
  7. If you’ve unmounted the GPU, install it into the motherboard, and lock the front panel/back cover in place using the screws you removed earlier.

When you power on your PC, you’ll see a notification stating the BIOS settings have been cleared. You can ignore the message and restart your system normally, or restore any changes you had made to the default BIOS settings before replacing the CMOS battery. You’ll also need to set the proper data and time settings once you boot into the OS.