Battery life differs between the Microsoft Windows Battery Meter and the ThinkPad Battery Information Power Manager tool.
Any of ThinkPad systems that supports Power Manager.
Due to these two different methods for reporting remaining battery life, it is quite possible for the two applications to report slightly different values for the remaining battery life. This is normal behavior, and is no indicative of a problem with the ThinkPad or the battery.
The Microsoft Windows Battery Meter shows a value for the remaining battery life that might be different than the ThinkPad Battery Information tool. This difference is actually not a problem at all, but is due to differences in reporting remaining battery life between the two applications.
The Microsoft Windows Battery Meter reports a value for remaining battery life by dividing the remaining battery capacity by the current battery draining rate as described in the ACPI specification (chapter 3.9.3 'Battery Gas Gauge'). This method of reporting is a fair estimate for remaining battery life if the user continues to do what they are currently doing until the battery is drained.
The ThinkPad's Battery Information tool shows the remaining battery life by communicating more often with the Smart unit in the ThinkPad's battery pack. The ThinkPad's Smart battery has a custom processor inside that measures additional battery data values to calculate a more accurate remaining battery than the Microsoft Windows Battery Meter can.