HP Compaq Presario,Presario V4000 Hardware And Software Manual page 46

Power
Resolving Low-Battery Conditions
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CAUTION: If the notebook has reached a critical low-battery condition
and has begun to initiate hibernation, do not restore power until the
power/standby light turns off.
To resolve a low-battery condition:
If external power is available, connect the notebook to the
external power source.
If a charged battery pack is available, turn off the notebook or
initiate hibernation, insert the charged battery pack, and then
turn on the notebook.
If no power source is available, save your work. Then initiate
hibernation or shut down the notebook.
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