Sony PCG-TR5MP Hardware Manual page 18

Hardware Guide
Inserting the battery pack (PCG-TR series)
To insert the battery, proceed as follows:
1
Insert the tabs (1) on the battery into the notches (2) and push the
battery down into the compartment until it clicks into place.
2 Slide the lock lever into the Lock position to secure the battery on
the computer.
✍
When the computer is directly connected to AC power and has a battery pack inserted in
the battery bay, it uses power from the AC outlet.
Make sure the cover is closed before inserting the battery pack.
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Using your VAIO computer