Battery Doctor from Cheetah Mobile, the creators of Clean Master, it a rounded battery app available for Apple and Android. This app diagnoses your battery: percentage of remaining, battery voltage, temperature... and they do a complete analysis and troubleshooting to extend its life. Also, when you change your phone, it calculates the time it will take, and charge it intelligently in three stages to ensure its completely and efficiently charged. The famous antivirus company, Avast, also has a popular battery saving application.