GNOME Battery Monitor Applet 1.2.1 issues spurious low battery alerts even when AC is ON. Applet normally shows accurate battery level (e.g. 96%), but will occasionally dip down to 0% and issue an alert. This happens on a Compaq Armada M700 laptop.
I can't reproduce this on a Micron Transport. Wanna send me an Armada ;-)
While this is more likely a kernel problem, can you try with gnome-applets-1.4.0.1 and see if it is still there with the new battery applet?
I'll try this when I get a chance, but it's low priority...
The values come from the BIOS