The Complementary Metal-Oxide Semiconductor ,known as CMOS is an on-board battery semiconductor chip that stores information in the computer, it can also be referred to as (RTC) real time clock, CMOS RAM or (NVRAM) non-volatile RAM.

This small metallic object, helps to store information like, system hard ware settings and system time and date.

Cmos battery comes in different forms, some are soldered on the board, fix in a small round plastic case or comes with wire where it is fix into a small port in the board, whichever form you find them, they both perform the same functions.

How long does the cmos battery last.

The CMOS battery can last up to 10years which is it standard life, though this may vary depending on the environment the computer is and how it's been use.
When the CMOS battery fails, system hardware settings, date and time won't be saved if the system is turn off, it will automatically reset the system settings, date and time to factory settings.

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if the battery dies
can it be changed or better still charged?