If you are looking for a ready-to-use "Battery Monitor" app, you can find them on official and reputable third-party platforms:
Navigate to Settings > Apps > Special app access > Install unknown apps and grant permission to your browser or file manager. Download Battery Monitor build apk
You can often find native battery info by dialing *#*#4636#*#* in your phone's dialer to access the "Testing" menu. If you are looking for a ready-to-use "Battery