QDrives , 02-13-2024, 10:04 PM
The DS1307 is for 5V operation (4.5...5.5V recommended).Then there is "Power-Fail Voltage (VBAT = 3.0V)" which is ~1.25*Vbat. When your battery is 3.0V, your supply needs to be 3.75V or more (typical). Hence, it does not work when you have the battery installed.