BM2 is a free Android app developed by wanbaolu. It is a battery monitor application designed specifically for car batteries. The app can track and display real-time voltage, historical voltage, and battery startup voltage. It also supports idle and high-speed charging tests to ensure the battery's health.

One of the most significant features of the app is that it syncs all the data to the mobile app via Bluetooth. This allows users to track their battery's performance and health over time. The app is easy to use and provides accurate readings. Moreover, it is an excellent tool for those who are concerned about the health of their car battery and want to ensure its longevity.