Lay device flat on the table.

Firmly grip the device on the edges. Take the wedge portion of the spudger tool and push in between the battery and the screen with force. Begin pushing the spudger with the wedge underneath the battery all the way around in order to break the glue.

Repeat this step pushing further across and underneath until the battery is loose.

The battery is heavily glued to the screen and much force may be needed to break the glued bond.