HP ProOne 400 G1 All-in-One Hardware Reference Manual page 36

10. Rotate the shield to the right (2), and then lift it off the chassis (3).
Figure 3-22
The battery can now be seen on the left side of the memory modules.
Figure 3-23
11. To release the battery from its holder, insert a thin metal instrument into the slot on the side of
the holder below the battery (1) and pry the battery up and out of the holder (2).
30 Chapter 3 Hardware repair and upgrade
Removing the fire enclosure shield
Locating the battery