Remove the 7 screws on the base. These screws are captive and will not come out of the base after fully unscrewing.

Pull up from the top of the base and remove the base.

Pull up on the right edge of the battery connector and gently pull upwards to remove and disconnect the battery, then unscrew and remove the battery screws and remove the battery from the chassis.

Gently disconnect the CMOS (Real-Time-Clock/BIOS Coin battery) and remove the cell from the board.