The purpose of the charge controller is to fill the battery with charge as quickly as possible without causing any damage.
Letting the battery voltage rise to 13.5 volts, then holding it there using PWM is fine, but the battery saturates (fills with charge) slowly. Allowing the voltage to rise initially to 14.4 volts, then dropping [...]
Continue reading about Saturation Charge and External Influences
At the moment, battery voltage measurements are not synchronised to the 122Hz PWM switching frequency. In fact, an analogue to digital conversion is carried out just as soon as the previous conversion is completed. This results in dozens of samples being taken throughout the PWM cycle.
In the current firmware version, these voltage samples are written [...]
This is the finished PWM5 Solar Charge Controller