Sony PCG-F540 Primary User Manual page 26

Connect the AC adapter to the computer.
Insert the battery pack.
The computer automatically charges the battery (the battery indicator
light flashes in a double-blink pattern as the battery charges). When the
battery is 85 percent full, the battery indicator light turns off. This
process takes approximately two hours. To charge the battery
completely, continue charging for an additional hour. See "Displaying
Detailed Battery Information" in the online manual Customizing Your
V AIO® Notebook for information on checking the battery life.
There are two battery indicator lights on the computer:
On
Single blink
Double blink
Off
Indicates the status of the battery pack in the battery bay
on the left side of the computer.
Indicates the status of the battery pack in the
multipurpose drive bay on the right side of the computer.
The computer is using battery power.
The battery is running out of power.
The battery is charging.
The computer is using AC power.