From exoSyphen Studios:
Laptop Battery Monitor, is an intelligent laptop battery monitoring software. It accurately displays an estimated time, until your battery will discharge, or fully charge. You no longer have to worry on how much battery power you have left, when you can have this information in hours, minutes and seconds. Features are display remaining time until the battery is fully discharged (when running on batteries), display remaining time until the battery is fully charged (when the battery is charging from the AC power supply), application runs in system tray, using minimum memory, and screen space, custom indicator colors, sound alerts when charging starts/stops, battery is full charged, or battery charge drops under a predefined percentage, automatically starts when you turn on your laptop. Works with any laptop and battery model, new or used.