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 a LiPo battery while powering the Arduino UNO with it - Project Guidance - Arduino Forum
Battery Level Monitor Using an Arduino | Arduino | Maker Pro
How to calculate the battery percentage under load...? - Project Guidance - Arduino Forum
18650 Lithium Battery Capacity Tester using Arduino