Battery

apm command : The apm utility controls the Intel / Microsoft APM (Advanced Power Management) BIOS and displays the current status of APM on laptop PCs. sysctl command : The sysctl utility retrieves kernel state. hwstat command : Another command line tool to display CPU temp and battery info. acpiconf command : The acpiconf command allows the user control of the ACPI power management functions and query laptop battery status.

http://www.cyberciti.biz/faq/freebsd-finding-out-battery-life-state-on-laptop/

gnome-power-statistics