If you've registered your copy of MyBattery, you'll be able to display the History window. This window shows you a graph of recent battery information.
Reading the History window
 
The History window shows the history of the battery for the past several hours (some customization is available under the History menu).
On black and white PowerBooks, the following shades are used:
Black - PowerBook was asleep.
Gray - PowerBook battery is discharging.
Diagonal stripes - PowerBook battery is charging.
On grayscale (4-bit gray) PowerBooks, the following shades are used:
Black - PowerBook was asleep.
Lightest gray - PowerBook battery is discharging.
Darker gray - PowerBook battery is charging.
Darkest gray - PowerBook battery is fully charged/trickle charging.
On color PowerBooks, the following shades are used:
Black - PowerBook was asleep.
Yellow - PowerBook battery is discharging.
Green - PowerBook battery is fully charged/trickle charging.
Blue - PowerBook battery is being charged.
Battery temperature display
On PowerBooks that can support it, a separate graph showing battery temperature can be shown. The temperature scale (fahrenheit, centigrade or kelvin) can be selected from the File menu.
Battery power display
On PowerBooks that can support it, a separate graph showing power consumption in watts can be displayed.