After puttering about with various incarnations of my Zanshin energy monitor with different Atmel processors and components, I finally decided that I'd played enough and started cobbling together a version that I could use non-stop for a couple of weeks to gather data.
This consists of:

Arduino ATMega I have one of these and decided to use it for this project, as it has several hardware serial ports and I'd had issues getting the Arduino “SoftwareSerial” library to work correctly
Bosch BME280 Sensor This little chip measures the ambient temperature, pressure and humidity. I don't know what I'm going to do with the humidity, but I'm storing the values in any case
GPS Module This chip outputs the latitude and longitude coordinates as well as the GPS altitude
EEPROM Memory The ATMega processor doesn't have a huge amount of memory to buffer the readings, so I've added a 8Kbit EEPROM
Micro SD-Card This is where all the bulk data goes, one CSV file per calendar day
Realtime Clock This part was necessary to keep the wall-clock time until I opted to add the GPS unit, which is also a very accurate clock
Power Regulator Takes 12V from the boat auxiliary bank and converts it to a regulated 5V power supply
Bluefruit Bluetooth Added so that I can query the logfiles directly from my PC without having to use wires. Optionally, I can also reprogram the logger using this interface
Reference 2.048V Ultra-accurate reference voltage used for the Analog-Digital conversion of the solar panel charging current

Soldering headers Using my nifty Hakko soldering iron, putting headers on components is simple and quick
(2016-04-14 15:41:56 NIKON D7100 [f/5.0, 1/20s] ISO 100)
Soldering headers
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