Please help me determine the circuit's power consumption from the battery and help me outline the steps to calculate?
It's not a simple matter of "calculating the power". Instead you need to:
- Calculate (or obtain) the current consumption of each individual sub-module or component
- Calculate (or obtain) the current consumption of the main MCU for each power state it operates in
- Calculate the current consumption of static items such as voltage dividers and power LED
For each unit examine the percentage of time it spends in different power states. From that create an hourly average current for the unit.
Sum up all the average hourly usages to get a final AH value for the whole circuit.
Most of the current values can be obtained either by calculation (e.g., Ohm's Law for resistive dividers and LEDs, etc), or from the datasheets for the devices you have attached.
Note that this will still only be an approximation, because (amongst other things) you have multiple power sources which will cause different drains on the system depending on which source is being actively used (different monitoring circuitry and components switched it), and that (I assume) is influenced by the weather.