!!
critical HP
Error Code 1Hz blinking battery LED
System board failure or power issues detected by embedded controller.
? What Causes This
Faulty system board, critical hardware malfunction or insufficient power supply.
✓ How to Fix It
Replace the system board and contact service provider for further assistance if symptoms persist.
Source: page 71 of the official manual
From the manual
This error code appears in:
HP Elitebook 840 G4 Notebook PC