I log the data from my 30-watt (nominal) solar system with a UNO, a datalogging shield from Adafruit (RTC & SdCard) & two INA219 breakout boards (also from Adafruit). One INA219 reports PV current into the batteries, the other current to the load (inverter). The breakouts are socketted on the proto area of the shield. Most of the complexity is handled by the various libraries.
I swap SdCards between 60-second samples and analyse the data (time, voltage, current in, out) with a perl script.