How Do I Replace a Dell 8400 BIOS Battery?

Written by lee nichols
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How Do I Replace a Dell 8400 BIOS Battery?
The BIOS battery is on the motherboard. (motherboard image by jovica antoski from

Your Dell 8400s motherboard has a watch-type battery in it that allows the system to retain settings, such as the date and time, when the computer is off. This battery has a lifespan of around five years, and it is better to replace the battery before it loses all power. It is not difficult to replace the battery, but keep in mind that a battery can explode if you install it the wrong way.

Skill level:

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Things you need

  • Plastic screwdriver (optional)

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  1. 1

    Reboot your computer and press "F2" when the blue Dell logo appears.

  2. 2

    Write down all of the system BIOS settings.

  3. 3

    Exit the system set-up by using your keyboard arrow keys to highlight "Exit" and pressing "Enter."

  4. 4

    Shut down the computer after it restarts completely.

  5. 5

    Disconnect all peripherals and the power cord from the computer.

  6. 6

    Open the computer case by pressing the release buttons on the top and bottom, then pulling on the side of the case gently. Release one side, and then release the other before you remove the entire side.

  7. 7

    Locate the battery on the motherboard, and gently pry it up with your fingers. You can use a plastic screwdriver to pry the battery up, but be careful not to damage the battery socket.

  8. 8

    Insert the new battery with the "+" sign pointing upward.

  9. 9

    Close the computer case by pivoting the cover down and pressing the sides until they close starting with the right side. Make sure that both sides are locked down before turning the computer right side up.

  10. 10

    Connect your power cord and reattach all of your peripherals.

  11. 11


  12. 12

    Restore all of the settings you recorded in Step 2.

  13. 13

    Exit the settings and allow the computer to finish booting.

Tips and warnings

  • Wearing an anti-static wrist band will ensure that your components are not damaged by static electricity.

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