I see Andrew gave you the link to his file, here's mine
The difference between my system and the Sterling system is that the Sterling system retains the original regulator. My system requires the alternator brush leads to be led outside the alternator for connection to nthe regulator.
I any event what both systems do is to control the field current to the alternator which in turn controls the output current of the alternator.
In both systems the alternator output leads are directly connected to the battery bank, there is no part of the system with high currents flowing through it except for the heavy cables that go directly from the alternator to the battery bank.
Trust this helps