Feature 1 Smart Charging: Automatically merge two batteries when charging, and automatically isolate two batteries when not charging. 2 Stable Working: Has a voltage sensitive chip to ensure your main battery will provide strong power for vehicle operation. 3 Extensive Uses: Allows for wide use on campers, for 4x4, recreational vehicle, marine application and so on, very practical. 4 Reliable Using: This dual battery isolator relay can also withstand extreme weather, shock, and it's waterproof as well. 5 Easy to Install: There are 4pcs screw and 1pc terminal in the set, bringing more convenience to the installation.Item Type: Dual Battery RelayProduct Material: ABSColour: BlackNominal Voltage: DC 12VCombine Harvester Voltage: DC 13.3VOpen Circuit Voltage: DC 12.8VContinue Rated Value: DC 125AIntermittent Rated Value: DC 140ABinding Post: M6 (1/4in)Waterproof Grade: IP67Application: Suitable for installation on campers, for 4x4, recreational vehicle and marine application. Package List1 x Dual Battery Relay4 x Screw1 x Terminal1 x English User Manual