A computer has a battery or special chip that retains computer (CMOS) settings and runs the computer clock even after the computer itself is turned off. If you have to reset the date and time on your computer every time you start it, you may need to replace your computer battery. This procedure applies to IBM-compatible computers that have a replaceable battery or a connector for a spare battery.
Record the current CMOS settings first. Turn on or restart your computer. As soon as the computer settings are displayed on the screen, press the Pause or Break key (upper-right corner of the keyboard) to freeze the computer display.
Press the Print Screen key to print the display, or write the settings on paper. Keep this information in case you lose your computer settings.
Turn off and unplug the computer. Remove the cover.
Record the type of battery that is currently installed, but do not remove it. Lithium or alkaline batteries are in holders attached to the motherboard. Built-in batteries are soldered onto the motherboard, but a connector should be available for a spare battery. Note the type of connector.
Purchase the replacement battery.
Remove the existing battery and replace it with the new battery in exactly the same configuration (same polarity, or + and – settings). Spare batteries with a connector generally fit one way only, but check the computer documentation.
Replace the computer cover, plug in the power cord, and start the computer.
Reset the computer date and time.