My problem seems related to this issue. Specifically, my powerbook is unable to determine the charge level in the battery. Sometimes the charger plug light turns green when the charge percentage reads only 80-90%, and the battery charge time only reads "Calculating....".
If I recalibrate the battery, running my powerbook on the battery until it shuts down, then recharging without turning it on again, I can get it to register as 100%.....until the next time it suddenly turns off.
However, the big problem is my powerbook now suddenly shuts down when the charge still registers between 40% and 50%, and time remaining is almost one hour, with no warning message given. I worry about my data and I am forced to constantly save my work, as if I was back in time, using OS7.5 or (yikes) Windows.
This problem started with my upgrade to OS10.4.5. My battery is not old, having gone through only 158 charge cycles, and my system profiler tells me it has a capacity of 2426mAh. System profiler also says, under Battery Information, "First low level warning: No". I don't know if this is normal and, if not, how to change it. There is no option for turning on - or off - Low Level Warning in System Preferences.
I've tried most of the suggestions listed on the powerbook forum, including recalibrating the battery, resetting PRAM and PMU, and banging on it with a ball-peen hammer. Any other suggestions? Since my warranty has expired, I don't hold out much hope that Apple will address this in 10.4.6.
Here is my Battery Info, for reference:
Battery Installed: Yes
First low level warning: No
Full Charge Capacity (mAh): 2426
Remaining Capacity (mAh): 2426
Amperage (mA): 0
Voltage (mV): 12456
Cycle Count: 158