Battery isolators are very common on powersports, trucks and recreational vehicles and typically paired with dual battery kits. They allow the primary battery to start and run the engine while allowing a secondary battery to power accessories such as LED Lights, Stereo, Winch. and other electronic devices.
Smart batter isolators have a voltage threshold established to start charging both batteries simultaneously. If the voltage drops below threshold level the isolator disengages charging of the second battery. Preventing the power of your start battery from being drained by use of the accessories powered from the second battery.