Victron Energy ARG10020102, Argofet Battery Isolator. Argofet isolators allow simultaneous charging of two or more batteries from one alternator (or a single output battery charger), without connecting the batteries together. Has virtually no voltage loss. Voltage drop is less than 0.02 Volt at low current and averages 0.1 Volt at higher currents. 100 amps, 2 batteries.