Texas Instruments TravelMate 4000M User Reference Manual page 102

Optimizing Battery Operation
not display satisfactorily at lower values, so experiment
with your particular application. This has no effect on color
units.
I/O (Input/Output) Ports
You can individually disable the parallel or serial ports, if
not in use, to save battery power.
LCD Brightness Control
The is a major power user in the computer. Reducing
LCD
the brightness control level even a small amount
LCD
significantly reduces power usage. Always set the
brightness control to the lowest comfortable brightness
level, especially in low light conditions (for example, on an
airliner where longer battery charge life is important).
Power-Saving Utilities 5-9