The search for "Battery Monitor V2.1.9 Download" can lead you down several different paths, as the name is used for various distinct applications. Understanding the differences is the first and most critical step in getting the right tool for your needs.
Locate the downloaded file (typically named BatteryMonitor_Setup_v2.1.9.exe or .dmg ). Battery Monitor V2.1.9 Download
Go to Settings > Security > Install unknown apps (this step is necessary if not downloading from Google Play). The search for "Battery Monitor V2