HP Notebook Reference Manual page 8

Startup
Charging a New Battery Pack
The battery pack you inserted earlier begins to charge as soon as
the notebook is connected to external power. Charge status is
indicated by the battery light.
The battery light is on and orange while a battery pack
inserted into the notebook is charging.
The battery light is on and green when a battery pack
inserted into the notebook is fully charged.
HP recommends that you leave the notebook connected to
external power until the battery pack is fully charged and the
battery light turns green. (A partially charged new battery
pack can run the notebook after initial software setup is
complete, but battery charge displays will not be accurate
until the new battery pack has been fully charged.)
Identifying the battery light
1-6 Startup and Reference Guide—Part 1