This DS3231 RTC module includes a charge path intended for a rechargeable LIR2032, implemented using a small series resistor and a glass diode feeding the VBAT node. Since I am using a standard CR2032 (non-rechargeable), I disabled the charging path.

To do this, I identified the resistor located directly next to the glass diode associated with the battery circuit (both resistors on this board are marked “102”). I lifted one leg of the resistor that feeds the diode, effectively opening the VCC → VBAT charging path while leaving the battery connected to the DS3231’s VBAT pin.

After lifting the resistor, I installed a CR2032 coin cell, set the time, unplugged the clock for several minutes, and then re-applied power. The RTC retained the correct time, confirming that VBAT backup is functioning normally and that the coin cell is no longer being charged from VCC.

This modification prevents unintended charging of a non-rechargeable coin cell while preserving full RTC backup operation.

-RR