How Do I Replace the CMOS Battery on a PC?

Written by c. taylor
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How Do I Replace the CMOS Battery on a PC?
The coin-shaped CMOS battery is installed onto your computer's mother board. ( Images)

The typical CMOS battery is a small, coin-shaped battery that allows your computer's basic input/output system, or BIOS, to store its settings. When the battery dies or is removed, you risk the BIOS settings returning to their default values. It is a good idea to replace your CMOS battery ever few years to protect against unexpected loss of these settings. Although changing the battery resets the values, you at least have the opportunity to record them before changing the battery.

Skill level:

Things you need

  • Philips screwdriver
  • Pad
  • Pencil

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  1. 1

    Restart your computer and press "F2," "ESC" or "Delete" to enter your computer's BIOS set-up. The exact combination differs among computers, but it should be listed in the computer's instruction manual or displayed on the first screen during boot-up.

  2. 2

    Use your arrow keys to navigate through your BIOS and write down all the various settings, so you can reference them later.

  3. 3

    Shut down your computer and unplug it.

  4. 4

    Remove the computer cover, which usually entails unscrewing a couple of screws on the back of the case and sliding the side panel off. The procedure may differ on your computer, so consult your computer manual for instructions.

  5. 5

    Locate the coin-shaped CMOS battery and note which side is up.

  6. 6

    Pry the CMOS battery out of the socket. If there's a retaining tab, lift it up just enough to slide the battery out.

  7. 7

    Insert the new battery using the same orientation the previous battery used.

  8. 8

    Replace the computer cover and plug the computer back into a wall outlet.

  9. 9

    Boot your computer back into BIOS and change the settings to match the ones previously recorded.

  10. 10

    Press "F10" to save the BIOS and reboot your system.

Tips and warnings

  • CMOS batteries can be found in any electronic store. If you are unsure what type of battery you need, extract the old one and look at the alphanumeric code on the front. This will let you reference the exact battery you need. Bring the battery with you so a salesperson can help you.

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