Measure the charging and discharging current of your battery. The app works on Android 4.0.3+ devices. Not every device is supported because there are devices which lacks an appropriate measurement chip (or the interface) and they can not be supported at all. Please read the list of not supported phones at the end of the description. The app is not meant to be mA accurate. It is only good for evaluate which Charger/USB cable combo is working the best for you on the same device. Start the app and wait ca. 10 seconds (“measuring” is on the display). After this time, the charging or discharging current will be shown.