Sony PCG-FX290K - Manual (Page 55)

Using a Second Battery Pack
55
To charge the second battery pack
Keep the battery pack in the computer while it is connected to AC power. The
battery indicator flashes while the battery is charging. See also “To charge the
battery pack” for more information.
Using weight saver for second battery cover
Charging the second battery
✍
To determine the amount of time the battery lasts, see “Displaying Battery
Information”
Battery pack
Weight saver
Battery indicators