Comment 9 for bug 933466

It's strange... indicator-power was listening for signals to be emitted from org.gnome.SettingsDaemon.Power, rather than listening for properties that changed. upower-monitor listens for properties, and dbus-monitor shows battery properties changing.

Patching indicator-power to listen for property changes (that is, listening for the "g-properties-changed" signal instead of the "g-signal" signal from its GDBusProxy) seems to fix the issue.