Destroy existing notification prior creating a new one

batteryarc-widget/batteryarc.lua

@@ -112,6 +112,7 @@ local notification
 function show_battery_status()
     awful.spawn.easy_async([[bash -c 'acpi']],
         function(stdout, _, _, _)
+            naughty.destroy(notification)
             notification = naughty.notify {
                 text = stdout,
                 title = "Battery status",