I am creating a data logger that uses:

1. ATMega328p - microcontroller
2. SD card module to read and write data
3. SIM800l - modem to transmit data from SD card to API
4. OLED I2C display
5. DHT22 temperature sensor

I want to power all this using 4 or 6 AA batteries. I do not have much knowledge about power electronics.

* As the ATMega328p needs 5 V, I think the batteries should suffice, but the voltage output from AA batteries degrades over time and fluctuates, so do I need additional circuitry to control the input to the ATMega328p?
* The SIM800 needs 4.2 V input, but transmitting causes a voltage drop and current bursts up to 2 A. For that I am using the power circuit given in the datasheet.

[![enter image description here](https://i.stack.imgur.com/YHfcY.png)](https://i.stack.imgur.com/YHfcY.png)

So what I want to know is if a 4-6 AA battery bank would be sufficient for this project. The ease of replaceability of the batteries is very important. The batteries should be cheap and easily available at local stores, hence the choice for AA batteries.

Would I need additional circuitry to supply power to the ATMega328 and other components, or would a direct connection to the battery bank suffice?