System Battery

On 08/11/2011, in Questions, by Norman Dean

Darwin Thusius from Sula Technologies asks:

“What happens if the clock battery in my computer runs out of power can it be replaced and what happens when it does run out of power?”

Thanks Darwin, that is a great question.

The CMOS battery or system clock battery has 2 functions, 1 to power the computers internal clock when the computer is turned off and unplugged, and 2 to power the Complementary Metal-Oxide Semiconductor (CMOS) chip on your computers main-board. The CMOS chip is a chip that requires a low voltage to keep its memory stored. The CMOS chip stores the Basic Input Output System’s (BIOS) settings. These settings like hard drive and optical drive settings, boot drive options, internal component settings like Sound, USB, Network, Keyboard, & mouse. The chip is designed to revert back to the factory specified settings if power fails in case a setting that the user changes causes the system not to boot or becomes unstable during operation.

The symptoms:

Most computers will tell you if the battery is dead during startup. 

Apple Macs usually wont even boot if the battery is dead. 

Dell computers tell you that the configuration settings have changed or are not set and to press F1 to continue. 

Other systems just loose their time and date settings and windows requires you to continually update the time manually.


The battery depending on your system usually costs between $10 & $30 and is a 5 minute fix, requiring only a quick update of the BIOS settings to make sure your system is configured correctly.







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