How is PWM different from a shunt regulator?
The shunt controller will typically have two set points, a higher voltage that the battery charges up to where the controller turns off charging and a reconnect voltage where the charging starts up again. An example would be 14.3 for a high set point and 13.5 for the reconnect. This charge scheme allows the battery to charge up to a higher voltage than what can be maintained in a float or constant voltage scheme because it shuts down and lets the battery recover a little before it starts again. The benefit of this method, often called a single step charge mode, is that it pushes the battery voltage up higher, reaching a higher capacity sooner but without holding the battery there where it could overcharge.
