Why Computers Have Batteries
When you use your computer, you certainly have noticed that every time you turn it on, it knows the correct date and time. Your PC stores date and time information each time you save a file. The reason your computer can do this is because there is a battery on the motherboard.
Every motherboard has a small quartz clock built into it to communicate to the computer and operating system the correct date and time (see Figure). Known as a Real Time Clock (RTC), this clock allows several features of your computer to run correctly.
The battery on your computer’s motherboard has a life of about 5 to 7 years depending on how you use your PC. This time period is longer than most computers last so many owners are unaware that a battery even exists in their PC and rarely have to change it before junking the computer for a new one.
However, the battery in your PC does more than just run the clock. The battery also helps to store your computer’s BIOS information. The Basic Input/Output System (BIOS) is a set of instructions that help your computer boot up. The BIOS stores information about your computer’s disk drives, memory, boot options, and more. Without this information, your computer might not start up correctly.
Since you turn off and sometimes unplug your computer, your PC needs a battery to store data in the volatile memory where the BIOS information is stored. When the battery goes dead, the BIOS can no longer store this information. This can lead to boot errors if the boot process is dependent on the information it gets from your PC’s BIOS.
Some modern computers store this BIOS information in non-volatile memory. This means that the PC does not need a battery for the BIOS memory to remain intact. Even if the battery goes dead, the PC would boot without any problems.
However, the RTC would cease to function and your operating system wouldn’t be able to tell the date and time. Consequently, even computers that take advantage of non-volatile memory still need a battery for the internal quartz clock.