Compaq 1610 Reference Manual page 36

To get the longest life from your batteries, follow these guidelines
when using your C-Series:
Use external power for PC Card operations
PC Card modems and other PC Cards use large amounts of
power to operate and can quickly drain the batteries in your
device. Use AC power or automobile power for PC Card
operations whenever possible.
Limit PC Card use when you must use battery power
When using battery power, limit the amount of time that you
use the PC Card, and remove it from the PC Card slot when it
is not in use.
Use external power for communications connections
Extended connections (communicating via the modem, serial
port, or IR port) can quickly drain batteries. Use the AC
Adapter to connect to an external power source when your
handheld PC is communicating through one of these channels.
Limit the use of backlight
Minimize backlight use when you are operating on battery
power.
When using the backlight and battery power, use the lowest
level of backlight needed to see the screen.
Use Display Properties in the Control Panel to turn off the
backlight automatically when running on battery power.
Shorten auto-suspend time
Your handheld PC automatically suspends operation to
conserve battery power if you have not used the keyboard or
the stylus after three minutes. To shorten auto-suspend time,
follow these steps:
Tap Start Settings Control Panel, then double-tap the
1.
Power icon.
Tap the Power Off tab, then select another auto-suspend
2.
setting.
Your handheld PC will not auto-suspend while it is
communicating through the modem, serial port, or IR port.