TRUE Dual Battery Kit (Large)

How the True® 12V Dual Battery Kit WorksThe 12v dual battery system kit utilizes the simplest and most advanced technology to keep all your batteries charged using the engine’s electrical system but isolating the starting battery so you never get stranded.The True® dual battery install kit for truck or car, uses the same voltage-sensitive relay we have installed in our boat and camper to keep the secondary batteries charged but isolating the starter battery system so it stays charged. The great thing about these is that you don’t have to reroute any alternator wires and they switch charging automatically.The best dual battery system kit allows a safe charging and separation of starting and auxiliary batteries in all types of boats, RVs, 4WD, camper, truck, caravan, and even solar applications. When the engine is started, starting and auxiliary batteries are separated allowing only the starting battery to be charged. When the charge voltage reaches 13.3 volts the voltage-sensitive relay engages allowing both the starting and auxiliary batteries to be charged.This is indicated by the light in the top LH corner being illuminated.When the engine is stopped and the battery voltage falls below 12.8 volts the (VSR) Voltage-sensitive relay disengages separating the start and auxiliary batteries, at this point, the indicator light will be out and the True® best dual battery cable kit for truck or car continues to power any accessories without risk of draining the starting battery.Trusted by Leading Brands A TRUE®  exclusive!Why Choose True® IsolatorFully Automatic Operation True® smart isolators use voltage-sensing technology to manage both batteries without manual switching.Heavy-Duty PerformanceTrue® isolators are built to handle high electrical loads, making them reliable for demanding applicationsEfficient Dual Battery ChargingWith a True® isolator, your alternator charges both batteries efficiently while driving. This ensures your auxiliary battery stays ready for use without affecting the starter battery. Testimonials from Our Amazon Store Ready to InstallEverything you need, right in the box. With detailed instructions and all hardware included, you’ll go from unboxing to fully mounted in no time. Simple, solid, and DIY-ready.Heavy-Duty Wiring & ComponentsIndustrial-grade cables, terminals, and connectors handle high current loads and are built for rugged use. eBay top-rated sellerOne of eBay’s most reputable sellers, consistently delivers outstanding customer service.Amazon Ratings: 4.8 out of 5 Reflecting consistently high satisfaction and positive reviews from Amazon buyers. Frequently Asked Questions Does installing this kit void my factory warranty? No. Because this is a non-intrusive “straight-to-battery” connection, you aren’t tapping into the fuse box or cutting factory wires. It functions as an independent add-on, keeping your factory electrical system intact. Why does the LED stay on after the engine is turned off? This is normal behavior. The LED indicates the isolator is still connected. To test disconnection, briefly turn on the headlights—the LED should turn off, confirming the isolator has opened the circuit. Do I need to run a ground wire from the auxiliary battery to the main battery? Yes, it is highly recommended. On modern GMC/Chevy trucks with a current sensor on the negative battery terminal (often on the starting battery), you must connect the negative terminal of the auxiliary battery directly to the negative terminal of the starting battery. Failing to do this can cause the truck’s voltage regulator to cut alternator output, leading to undercharging and premature battery failure for both batteries. Can I mount it without drilling holes? The kit works with most 12V battery types (AGM, gel, standard lead-acid). It is not recommended for lithium batteries unless specified. Is the isolator waterproof/durable? Yes, the isolator features an IP65 rating for water, dust, and vibration resistance, making it ideal for harsh automotive, marine, or off-road environments. Can I install a dual battery kit for truck myself? Yes, many dual battery kits for truck are DIY‑friendly with plug‑and‑play wiring. However, proper cable sizing and fuse protection are critical to avoid electrical issues. What is P.E.P.® (Proprietary Efficiency Programming)? P.E.P.® is TrueAm’s smart logic that optimizes battery protection and charging efficiency.It ensures the isolator only connects when safe and beneficial for both batteries Does it regulate charging amps? No, the SBI doesn’t regulate amperage. That’s handled by your alternator and voltage regulator.The SBI simply controls when the second battery is connected based on voltage thresholds. Can I manually override or shut it off?  The male connector underneath can be wired for remote shutoff.Inline switches are optional but not required—SBI handles disconnection automatically. How do I monitor battery status?  Optional Single Meter Dual Display (SMDD) shows real-time voltage for both batteries.Saves space and simplifies monitoring Is it compatible with all batteries? It’s designed specifically for Chevy Silverado and GMC Sierra trucks, but can also be adapted for other GM vehicles with similar 12V systems How does a dual battery kit for truck work? A dual battery kit for truck uses a smart isolator or voltage‑sensitive relay. It charges the starter battery first, then automatically connects the auxiliary battery once the system detects enough voltage.