How to replace a CMOS battery

The system time is stored in your motherboard CMOS and is retained by battery power.

This is most commonly caused by a failing battery. First try replacing the battery, which is normally a type CR-2032 coin-cell style lithium battery that you can get from most any store that sells batteries for electronics.

Be sure to check your motherboard's manual for help with locating and removing the battery, and for confirming the type of battery you need.

First, disconnect the power and remove the side panel. Refer to this article for help.

To replace your CMOS battery, locate it on your motherboard. They are commonly located near the bottom of the board or in the bottom right quadrant, but this varies wildly from one motherboard to another.

The battery socket may also vary. Some have a retention clip that you can depress, and the battery pops right out. Others require you to use the tip of a small flat-head screwdriver to carefully pry the battery out. Some simply lift our with your fingers as seen below.

The installation process is as simple. Insert the new battery into the socket with the smooth top surface facing out. If you are unsure, the top side normally has a plus symbol (+) imprinted in the metal surface denoting the positively charged side of the battery. Once you reconnect and reboot, you will typically see a CMOS Checksum Error. This is expected, simply press the appropriate key as prompted to continue. You may need to reset certain settings in the BIOS depending on your hardware configuration.

Less commonly, certain software programs or hardware devices can interfere with the battery's normal operation. If you recently installed a piece of hardware or a software program, try uninstalling or removing it and see if that fixes the problem.