Engineering speculation on my part but the efficiency of the Smart Alternator system could be affected by the condition of the car battery in terms of capacity and how well it can maintain that.I have checked the voltage of my Alternator, using a plug in Voltmeter, and it reads between 14.2 and 14.4 volts , the same as Gaffer bills, no dropping down to 12 volts, so I believe it is NOT a smart Alternator. I tested this over an hour's driving
Since the intent is to have the battery power the electrics whenever possible so that the Smart Alternator can reduce the load on the engine, a battery in poor condition could reduce the time that this can take place.