I am trying to use as little power as possible, I want my board to wake up every 30 seconds or so, check if battery has been sufficiently charged, if not, go back to sleep, if it has then turn off rtc and do a function. Is it possible to disable rtc ...

I have a stm32 mcu. I want to put it in a very low power mode until an event triggers it to wake up. What mode can give me the lowest power consumption? whilst still being able to accept an event to wake up? and what sort of power would that draw?