It may be worth re-setting the power manager. To quote this article, instructions are as follows:
"PowerBook 160, 165, or 180
1. Remove the AC adapter and the battery.
2. Let the PowerBook sit without power connected for 3 to 5 minutes.
3. Reinstall the battery and, if necessary, reconnect the AC adapter.
Note: Steps 1 and 2 will usually reset the Power Manager. However, if the computer still exhibits the same issue, repeat steps 1 and 2 and then follow the step listed below before reinstalling the battery.
1. Using two paper clips, simultaneously press and hold down the reset and interrupt buttons for 5 to 10 seconds. They are located next to the power button on the back panel of the PowerBook."
I've had seemingly dead 100-series PowerBooks that have been successfully resurrected with the two paperclip trick. Give it a shot!
"PowerBook 160, 165, or 180
1. Remove the AC adapter and the battery.
2. Let the PowerBook sit without power connected for 3 to 5 minutes.
3. Reinstall the battery and, if necessary, reconnect the AC adapter.
Note: Steps 1 and 2 will usually reset the Power Manager. However, if the computer still exhibits the same issue, repeat steps 1 and 2 and then follow the step listed below before reinstalling the battery.
1. Using two paper clips, simultaneously press and hold down the reset and interrupt buttons for 5 to 10 seconds. They are located next to the power button on the back panel of the PowerBook."
I've had seemingly dead 100-series PowerBooks that have been successfully resurrected with the two paperclip trick. Give it a shot!