Openbox does not load power management by default - you must load it, or configure it to load in autostart.sh.
There are various options you may have available, depending on your distribution.
pm-utils gives shell commands such as pm-hibernate and pm-suspend.
pm-utils on the Arch wiki has configuration details.
acpid is a flexible and extensible daemon for delivering ACPI events, including events triggered by:
- Pressing the power button
- Pressing a sleep/suspend button
- Closing a laptop/notebook lid
- Plugging or unplugging an AC power adapter from a laptop
See also acpid on the Arch Wiki.
If you have GNOME installed on the same installation of Linux that you are using with Openbox (or if you don't mind installing a few GNOME dependencies) you can run gnome-power-manager - simply type or paste at the command prompt:
Gnome power preferences provides a notify area icon, and lets you adjust the power managment settings used my gnome-power-manager. run:
xfce4-power-manager appears to require fewer dependencies than gnome-power-manager.
Notify area icons
Both the Gnome and the Xfce4 place icons in the notify area - this will hopefully work in most or all panels, including tint2 and LXPanel.