Compaq Armada M300 Series Reference Manual page 38

When a battery pack is installed in the computer or an optional
Battery Charger or docking base, the battery pack is charged
whenever external power is available.
Charging may be delayed if a battery pack is new, has not
been used for 2 weeks or more, or is much warmer or cooler than
a comfortable room temperature.
If you are charging the battery pack in the computer—
External power can be supplied to the computer from an
external power source.
An optional Aircraft Power Adapter cannot be used to
charge a battery pack.
The battery light, shown below, turns on while the battery
pack is charging and turns off when the battery pack is
fully charged.