Description: 1. Intelligent Dual-Battery Isolation Design Utilizing advanced VSR (Voltage Sensitive Relay) technology, it automatically monitors the main battery voltage. When the voltage reaches a set value (e.g., 13.3V), it automatically connects the secondary battery for charging. If the voltage falls below the threshold, it intelligently isolates the battery, preventing the main battery from running low and ensuring a worry-free vehicle start. 2. Stable High-Current Transmission Supports high-current loads up to 140A. Built-in high-quality relays with a low internal resistance design provide efficient conduction without overheating, meeting the power needs of high-power devices such as car refrigerators and inverters, ensuring safe power use during long trips or outdoor activities. 3. Convenient Installation Kit Includes a 3-meter red positive cable and a 1-meter black negative cable. The cables are made of thickened pure copper with high-temperature-resistant insulation and are designed to fit most vehicle layouts. A waterproof plug and mounting bracket are included as standard, making wiring simple and easy to do without special tools. 4. Multiple Safety Protections Equipped with overvoltage protection, short-circuit protection, and reverse polarity protection, the relay features a built-in arc extinguishing device to prevent sparks. Its ​very sealed, dust-proof, and splas h-proof design withstands harsh engine compartment environments like high temperatures and vibration, ensuring exceptional durability. 5. Wide Compatibility Compatible all types of batteries, including 12V lead-acid, lithium-ion, and AGM batteries, it can be used in trucks, RVs, off-road vehicles, and boats. Its compact design makes it an ideal power management solution for road trips, camping trips, or when adding onboard equipment. Package Included: 1 set Automotive Split Relay Kit.