Fangrui Product Details The Upgraded Dual Power Supply Isolator Adopts Power Management Chips, And Has Relatively Novel Electronic Circuit Intelligent Automatic Management Functions. It Also Has The Characteristics Of Strong Waterproof, Low Loss, Good Heat Dissipation And High Efficiency. Instructions For Use: When The Voltage Of The Main Battery Is 13.3v, The Main Battery Charges The Auxiliary Battery; When The Voltage Of The Main Battery Is Lower Than 12.7v, The Main Battery And The Auxiliary Battery Are Disconnected. Prevents You From Draining The Battery. Automatically Combines Two Batteries When Charging And Isolates The Two Batteries When Not Charging. Suitable To Install Into Van, Car, Leisure Vehicles Marine Applications. Not 70 Amp Cable As Per Some Other Similar Priced Kits. No Voltage Drops Compared To Battery Isolator Diodes (0.6v). Robust Glass Fiber Reinforced Nylon Enclosure. Built-in Led Indication (on When Vsr Engages). Or Panel Mount Options Provide Flexibility When Installing. Optional Storage Mode Allows