Some PowerBook 1400 owners have noted that the first battery low warning message does occur earlier than expected. Apple is aware of this issue. The first battery warning message is not a good prediction of the total battery life. There are three warnings before the battery completely runs out. To truly test the battery life you should run the computer from the battery until the third (last) battery warning appears.
The computer should run from the battery for over an hour even if you have taken no steps to conserve power. A few of the things that affect battery life include: CD usage, PC card usage, screen brightness, hard disk access/usage, the amount of RAM installed, and whether or not processor cycling is enabled.
Note: Battery recharging takes longer if you use a power adapter designed for the PowerBook 200 or 2300 (Duo) series computers instead of the 45 Watt power adapter that shipped with the PowerBook 1400 series computer.