What Happens If I Remove the Internal Battery in a Computer CMOS BIOS?

Written by daniel barrows
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What Happens If I Remove the Internal Battery in a Computer CMOS BIOS?
The CMOS battery is the silver disk located near the centre of this photograph. (Photos.com/Photos.com/Getty Images)

Desktop and laptop computers both feature a small internal battery installed on the device's motherboard. While this battery does not provide a significant source of power, it serves a useful purpose by retaining certain data that would otherwise be lost after a system shutdown. As such, removing the battery is not recommended, unless you intend to install a replacement.

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The CMOS chip on your computer's motherboard is a small component that stores information about your system's specific configuration, as well as other data, such as the current date and time. For the chip to function properly, it requires its own power source so that it can retain stored data even when the computer is powered down. Should the CMOS battery run down, your computer will likely still be able to function, but you may find it necessary to re-enter certain system information after every restart.


The CR2032 is one of the more commonly used CMOS batteries; this type of battery also powers a variety of other devices, including watches, calculators, clocks and toys. In many cases, you can use an ordinary CR2032, purchased from an electronics store, as a replacement CMOS battery, should your computer's original battery run down. Some manufacturers, however, have their own battery modules designed for use with specific models. Check your system's documentation before attempting a replacement.


On a desktop computer, the CMOS battery is reasonably easy to access. Disconnect the power cord and any other attached cables from the computer. Open the case and place the computer on its side. Look for a round, silver disc held in place by one or more metal clips; this is a CMOS battery. With laptop computers, the CMOS battery can prove more difficult to get to; you may find it necessary to remove the computer's palm rest, display and keyboard before you can gain access to the motherboard. If possible, locate a service manual for your model of laptop before attempting any disassembly.


In many cases, the removal process is fairly straightforward. Use your fingernails or a plastic pry tool to work the CMOS battery free of its socket. Be sure to push apart any clips before attempting removal, and, if you are using a pry tool, take care not to let it slip out of the battery's socket and strike another component on the motherboard. Once you've installed a replacement battery, reassemble the computer's case, start up your system and re-enter the current date, time and any custom boot settings that you require.

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