In addition, the PowerBook contai ns a rechargeable backup cell to keep
system information such as date and time. T h e backup cell is automatically
recharged whenever the external AC adapter is connected. The backup cell
also provides 4 mi nutes of power during system sleep while you change the
main battery. (See “Removing or Replacing the Battery” later in this chapter
for more information about changing batteries.)
Monitoring the battery charge
There are four ways you can determine the charge level of your battery:
mLook in the battery monitor portion of the ControlStrip.
For information on the battery monitor, see the “Batteries & Power” topic
area of Mac OS Guide, available in the Guide (h) menu.
mSee low-power messages on your display.
mLook at the battery level icon next to the clock in the menu bar.
mLook at the battery indicator level lights on the battery, visible when the
battery is out of the computer. (These lights are only on the lithium
ion battery.)

Responding to low-power messages

When the battery runs low, the computer displays a series of low-power
messages. The work time remaining after you see the first message
varies depending on how you are using the computer. It’s a good idea to
act promptly.
What you should do
When you see a low-power message, you should do the following:
1Plug in the power adapter, or
2Save your work and shut down the computer, then
3Quickly replace the empty battery with a charged one (within 30 seconds, if possible).
IMPORTANT
Always save your work when you see a low-power message.
84 Chapter 6