Autobahnschleicher - you could do it either way.
Daox set up his Mirage to feed the alternator ~15 V via a DC-DC converter, which effectively turns the alternator off to reduce engine load & save fuel.
This also gives him the option of 12v regeneration via a switch tied to the brake lights. EG. Activate regen when going down hills [if trying to hold speed] or when actually decelerating.
Most of his regeneration happens by recharging the battery from the grid though. Regen just extends "range" a bit.
Thread:
A better alternator delete