The dedicated alternator input provides current limiting and one-way traffic from the alternator into the battery, this so any size alternator (and start battery) can be safely connected to the Smart Lithium battery or batteries.
The BMS is also equipped with a remote on off connector, to turn the BMS (and the system) off via a remote switch, and a pre-alarm contact, to give a warning signal before the BMS will disconnect the batteries from the system.