While the breadboard prototype helped prove out the electronic load design concept, there are numerous features that does not include. It cannot use the solar panel to recharge its battery. It is not in any way enclosed, so it cannot be placed outside in direct sunlight. It does not have any buttons or LEDs for user input. Finally, it does not have nonvolatile storage for data, which could be used to allow the system to wake up and sample much more often than it uploads data over WiFi, which would save power immensely while increasing sampling rate.

These issues were worked out for in a custom PCB design. It still uses the same electronic load circuit, ESP32, and solar panel, but adds charging ability, LED indication, touch sensor input, and 512 kbit of EEPROM storage. The board includes clips for a 18650 lithium battery, and is designed to be mounted in a COTS waterproof box, so it could be placed outside.

The design files have been uploaded. After review with fresh eyes I will get the parts on order!