I am using ubuntu 12.04 and whenever i disconnect it from power supply the panel battery icon shows me the remaining time at regular interval but it doesnot make an alert when the battery runs out of juice. I am in need of a solution if the battery turns critical it can show me an visual alert, notification or even a sound so that i do not have to monitor the remaining time regularly
Your NotifyOSD may be corrupted or set to do-not-disturb mode for some reason.
You can reinstall it by entering this command in the terminal:
Restart your system and from now on You'll get notifications when the battery is running out of power.