Sony PCG-R505TS - Manual (Page 29)

Connecting a Power Source
29
The battery indicator light on the front of the computer indicates the status
of the battery pack.
Battery Indicator Light
Battery Indicator
Light Status Meaning
On The computer is using battery power.
Single blink The battery is running out of power.
Double blink The battery is charging.
Off The computer is using AC power.
✍
Both the battery and power indicators blink when the battery is running out of power.
Battery Indicator
Battery Pack
(supplied)