Compaq Armada 7400 Reference Manual page 51

Battery pack operating time varies depending on the system
components, options, and applications being used. You can
maximize battery operating time by controlling the energy
required by the computer and the energy stored in the battery
pack.
The display, processor, CD-ROM drive, DVD-ROM drive, and
hard drive components use the majority of battery power.
To notify you that the display is closed and the computer is still
on, the computer beeps three times every two seconds.
To turn off the beeps without turning off the computer:
1. Open the computer.
2. Initiate Suspend by pressing the suspend button.
The beeps stop and the computer begins conserving battery power.