Sony PCG-XG28 Primary User Manual page 29

Open the cover of the battery bay.
Pull out the battery pack.
Close the cover of the battery bay.
Never leave the battery pack in temperatures above 140 F (60 C),
such as under direct sunlight or in a car parked in the sun.
Battery life is shorter in a cold environment. This is due to decreased
battery efficiency at low temperatures.
Charge the batteries at temperatures between 50 F and 80 F (10 C
to 30 C). Lower temperatures require a longer charging time.
While the battery is in use or being discharged, the battery pack heats
up. This is normal and is not cause for concern.
Keep the battery pack away from all sources of heat.
Keep the battery pack dry.
Do not open or try to disassemble the battery pack.
Do not expose the battery pack to any mechanical shock.
If you are not using the computer for an extended period of time,
remove the battery pack from the computer to prevent damage to the
battery.