On a MacBook with MacOS X, it is possible to "calibrate" the battery to optimise its performance and sync up the battery meter with the current battery charge.
I have a Lenovo IdeaPad S10e running Ubuntu 10.10 with the standard GNOME desktop. When my battery is fully charged according to the hardware (i.e. the amber charging LED on the front goes solid blue), the battery meter shows the battery as about 90% full. This is really only a minor annoyance, as the estimated time remaining is reasonably accurate, but I'd like to sync it up. Also, it's possible that my battery has built up a memory so that it is truly not fully charging.
The battery is the standard three-cell LiON battery that ships with the netbook.
Update: After a full charge, here is what the kernel reports about the battery:
: jmglov@alhana; cat /proc/acpi/battery/BAT0/info present: yes design capacity: 2808 mAh last full capacity: 0 mAh battery technology: rechargeable design voltage: 10800 mV design capacity warning: 280 mAh design capacity low: 84 mAh cycle count: 0 capacity granularity 1: 10 mAh capacity granularity 2: 25 mAh model number: LE30_S serial number: battery type: LION OEM info: Sanyo : jmglov@alhana; cat /proc/acpi/battery/BAT0/state present: yes capacity state: ok charging state: charged present rate: 0 mA remaining capacity: 2494 mAh present voltage: 12414 mV
The fact that last full capacity is reported as 0 mAh is very strange. I'm sure it used to report a number close to the design capacity.