Sony PCG-808 - Manual (Page 27)

Using Battery Power
You can use one or two battery packs as a source of power. The second
battery pack inserts into the drive bay on the right side of the computer.
(See “Using Power Saving Modes” on page 42.) Additional battery packs
are available as a separate option.
The battery pack that comes with your computer is not fully charged at
the time of purchase. Follow the steps below to insert and charge the
battery pack.
Using Your Notebook Computer
To insert the battery pack
1 Open the cover of the battery bay.
2 Insert the battery pack into the battery bay on the left side of the
computer.
Battery pack
(supplied)
3 Close the cover of the battery bay.