I have built a battery level indicator and have tested with a 12V battery Would it harm my arduino board if I connect a 48V battery? - Arduino Stack Exchange
Monitoring batteries voltages connected in series combination using arduino uno and utilizing relay technique
Powering Arduino With a Battery (with Pictures) - Instructables
Why do Arduino UNO boards heat up while connecting it to a 12V battery for supply? - Quora
Powering Arduino uno and servo from same battery? - Project Guidance - Arduino Forum