Compaq Armada 7400 Reference Manual page 40

The battery pack lets you check the remaining charge level before
you insert it into the battery bay.
To see how much power is left in the battery pack, press the
battery gauge . Five battery charge level lights indicate the
remaining charge level.
Each battery charge light represents approximately 20 percent of
remaining charge. If two lights are on, approximately 40 percent
charge remains. If all five are on, the battery is fully charged.