This is an implementation of a PWM charge controller for a Solar charger for my car. It's designed to be low power loss, and especially quiet during periods when the sun doesn't shine.
In Norther Europe in winter there are more hours dark than light and the strength of the sun is low. I found my cheap chinese charge controller used more power over the course of 24hrs than (nominally) 10W solar panel produced.
In this project is the code for the Arduino (tested on an R3, but soon to be tested on a mini) Also there is the circuit diagram for the controller. These was created on EasyEDA where the project is also public.
More updates as the project matures.
Have fun and let me know if you find this useful, or have suggestions for changes.
Gareth Davies, Brighton, England. April, 2018.