What Happens When a CMOS Battery Goes Dead?

When the complementary metal-oxide semiconductor (CMOS) battery in your computer goes dead, the machine will be unable to properly store its hardware settings. It is best to source the correct type of battery and replace it.

Your CMOS battery stores your PC settings.


The CMOS battery in your PC is used to maintain the hardware settings stored in the CMOS chip, located on your motherboard. As well as important settings related to your hardware, such as quantity of memory and type of drives connected, it also maintains the time and date.


If your CMOS battery is dead, you may see an error message before your computer boots into the operating system. You may be requested to go into the BIOS (basic input/output system) settings screens and confirm your hardware settings.


Check your documentation to ascertain which kind of battery you need. Batteries are usually simple to replace, but if you are not confident with replacing PC parts you may wish to get some technical assistance from a qualified person.