Battery indicator snippet from my AwesomeWM rc.lua.

bat.lua

...
 
-- Battery level widget
-- Create widget to show battery level
batterywidget = wibox.widget.textbox()
-- Create timer to update widget
batterytimer = timer({ timeout = 30 })
batterytimer:connect_signal("timeout", function()
   local battery_info = vicious.widgets.bat("This argument doesn't seem to be used for anything.", "BAT0")
   local battery_percentage = battery_info[2]
   batterywidget:set_text(" | " .. battery_percentage .. "% | ")
end)
batterytimer:start()
-- Trigger timeout immediately so that it shows the battery level as soon as awesome starts
batterytimer:emit_signal("timeout")
 
...
 
    -- Widgets that are aligned to the right
    local right_layout = wibox.layout.fixed.horizontal()
    if s == 1 then right_layout:add(wibox.widget.systray()) end
    right_layout:add(batterywidget)
    right_layout:add(mytextclock)
    right_layout:add(mylayoutbox[s])
 
...