Here is a Behavioral simulation of a standard alternator charging system. You can quibble about the voltage set points, the battery model (which I had to monkey to get it to simulate in a reasonable time), etc., but this is a good approximation of how it works.
If you study the voltage regulator section, you will get insight into what is in a standard automotive regulator. The snubber diode is internal to most regulators, but has to be there to smooth the alternator field current.The model of both the alternator and Voltage Reg have realistic values.
Note that the field voltage/current starts out full-on. As the battery voltage comes up, it reaches a point at which the VR begins modulating the field excitation by turn the switch on/off. Both the rate as well as the PWM duty-cycle change to adjust the average field excitation to cause the alternator output to reduce as the battery reaches near full charge. In the limit, the field is turned on only for a very small fraction of the cycle. In your example, the system would stay in the mode where the field is on 100% for several hours before begin to taper.
Is your question "Given a particular alternator, how do I redesign the Voltage Regulator so that I can recharge large batteries in as short a time as possible?" If it is, then **broken link removed**. Then come back and let's talk about it.