When The Power Supply Is Uncertain - HP Compaq NW8000 Software Manual

Power
Shutting down the notebook and removing the battery pack is
recommended to extend the life of the battery pack when the
notebook will be disconnected from external power for an
extended period. For details on battery pack storage, refer on the
Documentation Library CD to the Hardware Guide, "Battery
Packs" chapter.

When the Power Supply Is Uncertain

Make sure that Hibernation remains enabled, especially if you are
operating the notebook on battery power and do not have access
to an external power supply. If the battery pack fails, Hibernation
saves your work to a Hibernation file and shuts down the
notebook.
HP recommends that if you pause your work when the power
supply is uncertain, initiate Hibernation, shut down the notebook,
or save your work and then initiate Standby.
2–4 Software Guide