Due to the current need for data collection, dataloggers are increasingly used, but before leaving the Arduino into a power supply plugged into the AC outlet, it is interesting to think about using a battery in shape of coin, a CR2032.
After 'Atmega' became a Microchip microcontroller, it no longer makes sense not to officially use a 'PIC' on an Arduino board. The PIC18F26K80 (or even the PIC18F46K80) could be a great example of a microcontroller that could be elected for an optimized version of the low power "Arduino UNO".
Because an Atmega328 may be able to reach 3.7uA in sleep mode, while such a PIC may be running on this amount of power (3.8uA)!
Another issue is the power supply, since an MCP1702 regulator consumes 2uA to operate (almost half of the 3.8uA PIC) makes no sense to use a regulator and a 3.7V LIR2032 battery seems interesting enough, but because reaching around 4.2V while charging, any version of 3.3V microcontroller (up to 3.6V maximum) cannot operate directly on the battery, leaving the 5V version as more suitable.
Summary
PIC18F26K80 is a high performance 8-bit MCU with Integrated ECAN™ featuring eXtreme Low Power consumption. New features in PIC18F66K80 include low sleep current for low power application, 1.8V to 5.5V operating voltage for automotive, building control, elevator control and industrial application, Timers/Enhanced Compare/Capture/PWMs for precision timing control, 12-bit ADC for advance analog interface and Charge Time Measurement Unit for easy capacitive touch user interface. The PIC18F26K80 family is ideal for applications requiring cost-effective, low-power CAN solutions with high performance and robust peripheral set in small package
Additional Features
Featuring nanoWatt XLP Technology ideal for battery applications
20 nA Sleep mode (Watch Webinar)
300nA Watch Dog Timer operation in Sleep modes
Integrated ECAN™ conforming to CAN 2.0B active specification
Extreme Low Power Sleep mode ideal for battery applications
Operating voltage 1.8V – 5.5V
Charge Time Measurement Unit (CTMU) supports Touch sensing and advanced sensing applications
11 ch, 12-bit ADC
4 Capture / Compare / PWM modules and 1 Enhanced Capture / Compare / PWM modules
1 MSSP serial ports for SPI or I2C™ communication
2 Enhanced USART modules
Two analog comparators
Digital Signal Modulator
Self programming Flash supports 10k erase/write cycles & 20 years retention
Source: https://www.microchip.com/wwwproducts/en/PIC18F26K80
Ref: (Atmega328) "gets this down to 3.7 µA …":
https://jeelabs.org/2009/05/16/power-consumption-more-savings/