The method for doing this consists of a program based on three charges that might be able to give your battery some extra life. The most important feature for improving your battery's life is the tool that deletes processes, which is included on Battery Doctor (Battery Saver).
This tool lets you kill processes, which is essential for improving your battery's life, since normally you would have many applications running in the background that, even if you don't use them, are consuming energy. Battery Doctor (Battery Saver) will delete them all.
By using Battery Doctor (Battery Saver), you can find out not only how much time you have left on your battery but also how long it would last performing any particular task. For instance, you can check how long it would last if you were playing Angry Birds or watching YouTube videos without stopping.
Battery Doctor (Battery Saver) is a good application for calculating your battery's life and also to improve its performance in some cases.
Requires Android 2.3 or higher