CMOS (complementary metal-oxide-semiconductor) is a type of memory that stores the computer’s BIOS settings. The CMOS battery is a small coin-cell battery that provides power to the CMOS memory when the computer is turned off. Over time, the CMOS battery can lose its charge and need to be replaced. If the CMOS battery is dead, the computer may lose its BIOS settings and may not be able to boot up properly.
There are a few different ways to check the CMOS battery life. One way is to use a multimeter to measure the voltage of the battery. The battery should have a voltage of around 3 volts. If the voltage is below 3 volts, the battery should be replaced.