When the vehicle voltage is uncontrollable then the DC to DC chargers can and do make more sense, but their prices are a bit on the ridiculous side.
My VR was a bipolar whack job choosing either 14.9 or 13.7 and rarely anything in between.
Now I twist a dial and choose 14.7 or 13.6v or any dang voltage I deicide will cause warm and fuzzies, and watch the Ammeter respond in kind. and it almost always reads 2/3 higher at 14.7v compared to 13.6v.
Hot Idle speed is my limiting factor, but at 1200+ rpm, I can almsot always feed my AGM battery as fast as safely possible, because I can adjust that target voltage and the alternator is capable of 120 amps when cold and spinning fast.
But before I could do so, thickening the circuit from alternatotr to battery was efffective in increasing amperage to some degree, especially when he Whackjob OEM VR was seeking 14.9v