Motorola L3391 Owner's Manual page 63

If you often rely on battery power for a long period of time while
traveling, you may consider the purchase of an additional battery pack
from your dealer and keep it with you in a fully charged state as a
backup.
To replace the battery pack, follow these steps:
1. Make sure the computer is not turned on or connected to AC power.
2. Carefully place the computer upside down.
3. Slides the battery cover latch inward and remove the battery compartment
cover.
4. Pull the battery pack.
Battery Block
Managing Power
Battery Cover Latch
3-5