Dell OptiPlex Gxi - Manual (Page 85)

System Battery Removal (Midsize Chassis): OptiPlex GXi
1. If possible, enter the System Setup program, and make a printed copy of the System Setup screens.
2. Remove the expansion-card cage.
3. Remove the system battery.
Carefully pry the system battery out of its socket with your fingers or with a blunt, nonconducting object, such as a plastic screwdriver.
When you replace the system battery, orient the new battery with the "+" facing up. Insert the battery into its socket and snap it into place. Then restore the system
configuration information using the printed copy.
WARNING: There is a danger of the new battery exploding if it is incorrectly installed. Replace the battery only with the same or equivalent
type recommended by the manufacturer. Discard used batteries according to the manufacturer's instructions.