Dell Optiplex 990 CMOS Battery Replacement

Replacing the CMOS battery is quite easy.  You simply need to locate the CMOS battery on the motherboard, depress the tab at the top to release the battery, remove it and insert the new battery until it locks into place.

If you have a Dell Optiplex 990 Desktop, however, it is a bit more involved as the CMOS battery is partially hidden by the DVD Optical drive.  The good news is that it is still quite easy.  Simply follow the steps below to replace the CMOS battery.

1. Lift the handle on the side of the case to remove the side panel.

2. Place the desktop flat on its back.

3. Locate the blue release handle on the side of the DVD Optical Drive mount (See below). 

DVD optical drive blue release handle

Lift release handle

4. Next, lift the DVD Optical Drive release handle while simultaneously pushing the back of the DVD drive forward just until the back edge of the DVD is flush with the mounting bracket.

You will now be able to see the CMOS battery on the motherboard. To access it, simply push the cables to the side (See below).

5. Using a small screwdriver or a pen tip, depress the gold release latch at the top of the CMOS battery mounting bracket. The battery will immediately pop up.

Push the cables to the side

6. Remove the old battery.

7. Starting at an angle from the bottom of the battery mounting bracket slide the new CMOS battery in and depress it at the top by the latch until it locks into place.

8. From the front of your DVD optical drive, push the drive back until it locks into place.

9. Replace the side panel.

Congratulations! You’ve replaced your CMOS Battery.

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