--- product_id: 173975296 title: "Dual Battery Isolator Kit 12V 140Amp Voltage Sensitive Relay VSR Double Battery Automatic Charger & Wiring Cable Kit" brand: "mayspare" price: "$164.81" currency: USD in_stock: true reviews_count: 13 category: "May Spare" url: https://www.desertcart.us/products/173975296-dual-battery-isolator-kit-12v-140amp-voltage-sensitive-relay-vsr store_origin: US region: United States of America --- # Auto voltage-sensitive relay 140A heavy-duty current Complete wiring & install kit Dual Battery Isolator Kit 12V 140Amp Voltage Sensitive Relay VSR Double Battery Automatic Charger & Wiring Cable Kit **Brand:** mayspare **Price:** $164.81 **Availability:** ✅ In Stock ## Summary > 🔋 Stay charged, stay unstoppable — power your adventures without compromise! ## Quick Answers - **What is this?** Dual Battery Isolator Kit 12V 140Amp Voltage Sensitive Relay VSR Double Battery Automatic Charger & Wiring Cable Kit by mayspare - **How much does it cost?** $164.81 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.us](https://www.desertcart.us/products/173975296-dual-battery-isolator-kit-12v-140amp-voltage-sensitive-relay-vsr) ## Best For - mayspare enthusiasts ## Why This Product - Trusted mayspare brand quality - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - • **Dual Battery Freedom:** Run accessories independently without draining your starter battery—always ready to go. - • **Smart Voltage Sensing:** Automatically engages at 13.3V and disengages at 12.8V to keep your main battery primed. - • **Universal Compatibility:** Compact design fits ATVs, UTVs, boats, RVs, trucks, and caravans with ease. - • **Powerhouse 140A Capacity:** Handles high current loads effortlessly for all your vehicle’s power needs. - • **All-in-One Installation Kit:** Includes every wire and hardware piece for a seamless, professional setup. ## Overview The MaySpare Dual Battery Isolator Kit is a 12V, 140A voltage-sensitive relay system designed to automatically manage dual battery setups. It activates at 13.3V and cuts out at 12.8V, ensuring your main battery remains charged and ready while powering auxiliary accessories independently. The kit includes all necessary wiring and hardware for easy installation and fits a wide range of vehicles including ATVs, boats, RVs, and trucks. ## Description Buy MaySpare Dual Battery Isolator Kit 12V 140Amp Voltage Sensitive Relay VSR Double Battery Automatic Charger & Wiring Cable Kit: Battery Relocation Kits - desertcart.com ✓ FREE DELIVERY possible on eligible purchases Review: Great Product Quality, Easy to Install - This seller makes a great product. All the hardware and wire necessary to install the dual power isolator. Good instructions. I ran the dual power isolator to a AGM power box in the passenger floor area of my Dodge Caravan. Wanted to be able to monitor the isolator and connected a voltage meter to monitor the main battery and auxiliary battery. The gauge of wire is right and everything is working great. I glad I bought this product. Review: Failed after 2 weeks - Failed after two weeks. Had to buy another at an autozone on our road trip ## Features - 12V, 140A, 13.3V cut-in voltage, 12.8V cut-out voltage,; Package Include All the Bits and Pieces Needed for a Complete Installation - Working Voltage: Having Voltage Sensitive Chip,Rely Cuts in at 13.3 Volts and Cuts out at 12.8 Volts to Ensuring Primary Battery is Always Ready for Vehicle to Run. - Fuction:Like Having Two Separate Power Sources,The Dual Battery Isolator Kit Enables Your Accessories to Run From a Separate Battery While the engine is not running on your vehicle While keeping your Main Battery Charged and Your Vehicle Always Ready to Go and Start When You Want It. - Compatibility: This battery isolators are small and suitable for almost anywhere, for ATV, UTV, Boats, RV's，marine vehicle, truck, caravan - Premium service :Provide better service, please contact us if you have any questions! ## Technical Specifications | Specification | Value | |---------------|-------| | ASIN | B081JL6ZXP | | Best Sellers Rank | #684,423 in Automotive ( See Top 100 in Automotive ) #59 in Automotive Replacement Battery Relocation Kits | | Brand | MaySpare | | Brand Name | MaySpare | | Coil Voltage | 12 volts | | Connector Type | Screw | | Contact Current Rating | 140 A | | Contact Material | Silver | | Contact Type | Normally Open | | Current Rating | 140 A | | Customer Reviews | 4.4 out of 5 stars 371 Reviews | | Manufacturer | MaySpare | | Minimum Switching Voltage | 13.3 volts | | Mounting Type | Panel Mount, Surface Mount | | Number of Items | 1 | | Number of Terminals | 3 | | Operation Mode | Automatic | | Part Interchange Info | Voltage Sensitive Relay | | Part Number | US-Battery kit | | UPC | 742089521075 | | Unit Count | 1 Count | ## Product Details - **Connector Type:** Screw - **Contact Material:** Silver - **Contact Type:** Normally Open - **Current Rating:** 140 A - **Mounting Type:** Panel Mount, Surface Mount ## Images ![Dual Battery Isolator Kit 12V 140Amp Voltage Sensitive Relay VSR Double Battery Automatic Charger & Wiring Cable Kit - Image 1](https://m.media-amazon.com/images/I/71hE4P1kgzL.jpg) ## Questions & Answers **Q: what type of power runs continuously from the start battery to auxiliary to charge it through the cable???** A: When the isolator reads the need to charge the second battery it will be charged with the alternator of the vehicle **Q: Does this item have an internal fuse? Do I only need to fuse my auxiliary battery?** A: No it does not. I highly recommend installing a re-settable 150A fuse between your main battery and the isolator. **Q: are the cables copper clad aluminum or all copper?** A: Copper **Q: Can I use this to connect 2 RV batteries in parallel with differet amperage so that the leisure battery only kicks in when the primary battery low?** A: So they are connected in parallel when charging. The batteries can be of different amperages. However if the non stater battery drops below 12.8 volts it will disconnect from the system so your starter battery does not discharge. Starter and non-starter battery connections are labeled. The yellow wire coming out of the controller can be connected to a switch with the other side connected to ground. If you move the switch so yellow wire goes to ground it will bypass the disconnect and connect both batteries in parallel regardless of the voltage of either battery. Hope this helps. ## Customer Reviews ### ⭐⭐⭐⭐⭐ Great Product Quality, Easy to Install *by T***K on July 17, 2022* This seller makes a great product. All the hardware and wire necessary to install the dual power isolator. Good instructions. I ran the dual power isolator to a AGM power box in the passenger floor area of my Dodge Caravan. Wanted to be able to monitor the isolator and connected a voltage meter to monitor the main battery and auxiliary battery. The gauge of wire is right and everything is working great. I glad I bought this product. ### ⭐⭐⭐⭐⭐ Failed after 2 weeks *by A***N on July 19, 2024* Failed after two weeks. Had to buy another at an autozone on our road trip ### ⭐⭐⭐⭐ Exellent quality kit. *by K***R on May 4, 2023* Great kit I installed a second 100 amp Renogy AGM battery with an inverter and cigarette lighter and USB ports in the back of the canopy on my F150 4wd. Easy to wire, clear instructions. ## Frequently Bought Together - MaySpare Dual Battery Isolator Kit 12V 140Amp Voltage Sensitive Relay VSR Double Battery Automatic Charger & Wiring Cable Kit - MICTUNING LED Digital Double Voltmeter, Round Panel Voltage Monitor Blue for Car Pickup RV Truck Dual Battery Pack - TKDMR 10pcs 1/0 AWG-3/8 Battery Lugs,Heavy Duty Wire Lugs,Ring Terminals,Battery Cable Ends,0 Guage terminals,Battery Terminal Connectors with 10pcs 3:1 Heat Shrink Tubing --- ## Why Shop on Desertcart? - 🛒 **Trusted by 1.3+ Million Shoppers** — Serving international shoppers since 2016 - 🌍 **Shop Globally** — Access 737+ million products across 21 categories - 💰 **No Hidden Fees** — All customs, duties, and taxes included in the price - 🔄 **15-Day Free Returns** — Hassle-free returns (30 days for PRO members) - 🔒 **Secure Payments** — Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** — Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.us/products/173975296-dual-battery-isolator-kit-12v-140amp-voltage-sensitive-relay-vsr](https://www.desertcart.us/products/173975296-dual-battery-isolator-kit-12v-140amp-voltage-sensitive-relay-vsr) --- *Product available on Desertcart United States of America* *Store origin: US* *Last updated: 2026-10-19*