We provide lifelong warranty service for the goods you buy in our store. We adhere to the principle of "customer is God" and wholeheartedly provide customers with the best quality service. We pay special attention to the satisfaction of the buyer. As long as you need to contact us at any time, we will answer all your questions at the first time! PRODUCT DESCRIPTION: Dual Battery Isolator Kit features a 12 volt 140 amp Voltage Sensitive Relay isolator, Voltage Sensitive Relay (VSR) turns on at 13.3V and turns off at 12.8V and lets your accessories use a separate one when the engine is not running on the vehicle battery operation to ensure your main battery is always charged and your vehicle is always ready to start. Features a rugged housing for extreme environments, an operating temperature range of -30°C to 105°C (-22 to 221°F), waterproof and shockproof. It also easily detects the voltage rise of the vehicle charging system when the engine is started to charge your second battery, suitable for most 12V 4WD marine, truck, caravan, and camping applications. SPECIFICATIONS: INCLUDES THE FOLLOWING PIECES: (1)VR (Voltage Sensitive Relay) with mounting screws (2)1/2" red shrink tube (1)1/2" black shrink tube (1)8.5mm*6000mm red cable with two 5/16" lug connectors (1)10mm*600mm black cable, with two 5/16" lug connectors (2)5/16" lug cable entds (1)3/8" lug cable end (2)Positive marine battery terminals (1)Negative marine battery terminal (1)Install Base (2)2cm Length screws (2)4cm Length screws (1)Ring-terminal Direct installation Built to strict quality control standards WORKING PRINCIPLE: When the voltage of start battery is higher than cut-in volts, the smart battery isolator (SBI) keeps engaging, two batteries (start and house) are charged simultaneously. The unit Indictor (LED) is on. When the batteries no longer have a charge from the alternator, and loads on the batteries begin to drain them. Unit Indicator (LED) is on. When the voltage drops below cut-off volts for 5 seconds, the SBI senses it and disengages, separating both batteries. Unit Indicator (LED) is off. When the vehicle is restartd, the start battery has reached the cut-in volts, the SBI engaged again. The device Indicator (LED) is on. POINTS TO NOTE 1. Before you buy, please check the model as much as possible to ensure that the product you buy is what you need! 2. Professional installation is highly recommended! 3.This Smart Battery Isolators Kit Assembly of ours has a lifetime warranty service, you can leave a message if you encounter any problems, we will be the first time to reply to you