The rover in the picture is an indoor prototype that I started in June 2015. It uses an Adafruit motor hat and has a LiPo 2S battery (7.4 to 8.4 Volts) because the motors require a supply voltage of 6-9 Volts. One question that this prototype answers is that is it possible to run the computer (over a buck converter to 5 Volts) and the motors at the same time. The Pi runs a LAMP web server, allowing the rover to be controlled with a web browser. Initially I wanted to find a solar charge controller, but ended up designing and building one myself <a href="https://hackaday.io/project/10671-arduino-mppt-solar-charge-controller" target="_blank">https://hackaday.io/project/10671-arduino-mppt-solar-charge-controller</a>