HP ProDesk 400 G4 SFF Hardware Reference Manual page 48

b. Insert the new battery and position the clip back into place.
NOTE:
9. Replace the computer access panel.
10. Reconnect the power cord and any external devices, then turn on the computer.
11. Reset the date and time, your passwords, and any special system setups using Computer Setup.
12. Lock any security devices that were disengaged when the computer access panel was removed.
40 Appendix A Battery replacement
After the battery has been replaced, use the following steps to complete this procedure.