The VCC_BATT input of the module (pin 40) powers the SNVS rail of the SoC. Beside the RTC and
power management function, the i.MX 6ULL SoC uses this rail also as IO rail for the pins in the
SNVS block (SNVS pins). Some of these interface pins are available on the SODIMM connector as
regular GPIOs (SODIMM pin 43, 45, 93, 95, 105, 107, 127, 131, 137, and 138). This means the pins remain powered in the “RTC Only” power mode by the VCC_BATT rail. Make sure there is no back feeding on this pin.
Be aware that RTC on the module is not designed for ultra-low power consumption. Typical power consumption is around 25 uA.