How to Change Clock Batteries in a PC

By Jeff Grundy

Modern computers use the Internet to update their internal clocks on a regular basis so they can keep time reliably. However, even without an Internet connection, computers can keep time accurately as long as the CMOS battery on the motherboard has a charge and is working properly. The CMOS battery retains system settings, the current time and date when you power off the system and in most cases lasts for several years without issues. Nevertheless, if your system starts to lose time or resets its default settings often, you must replace the CMOS battery inside the system.

Things You'll Need

  • Phillips #2 screwdriver
  • Anti-static wrist strap

Replace CMOS Battery

Step 1

Shut down the PC, and then disconnect the power cord and all other accessories and cables from the system. Transfer the machine to a flat, sturdy work surface, such as a large desk or table.

Step 2

Remove the retaining screws that secure the cover or access panel on the computer case with the Phillips screwdriver. Remove the panel or cover from the case.

Step 3

Slide the looped end of the anti-static wrist strap on to your arm, and then clip the opposite end to a drive bay, case wall or other metal surface inside the computer case. Locate the coin-shaped CMOS battery on the computer motherboard. The CMOS battery resembles a thick coin and is silver in color.

Step 4

Disengage the clip that secures the CMOS battery by pushing down on it, and then use your fingers to lift the battery up and out of its slot carefully.

Step 5

Align the new CMOS battery with the slot. Insert the edge of the CMOS battery farthest away from the clip first. Push down on the other edge of the battery until it snaps into place in the slot.

Step 6

Replace the case cover or access panel, the secure it with the retaining screws. Move the computer back to the original location, then connect the power cord and other cables or accessories. Restart the computer and use normally.

Reset Time and Date

Step 1

Press "Windows-I," then click "Control Panel."

Step 2

Click "Clock, Language and Region" in the Control Panel window. Click "Set the time and date" under the Date and Time header in the Clock, Language and Region window.

Step 3

Click the "Change date and time" button. Click the current date on the calendar control, and then use the scroll arrows to set the current time. Click "OK" to save the changes to the date and time.

Step 4

Close the Date and Time window, and then close the Clock, Language and Region window.

Tips & Warnings

  • Depending on the model of your motherboard, the location of the CMOS battery may vary. Nevertheless, on most mainboards, the battery is located in the lower corner of the board on the edge closest to the front of the case.
  • You can keep the current time and date updated accurately by using the Internet Time feature in the Date and Time window. To do this, first open the Date and Time window from Clock, Language and Region section in Control Panel. Click the "Internet Time" tab in the Time and Date window, then click "Change Settings." Enable the "Synchronize with and Internet time server" option, then click "Update now." After Windows updates the current time and date, click "OK" and close all of the Windows.