Trusted by Leading Brands A TRUE® exclusive! The True® 12v second battery isolator for car audio uses the most simplistic and modern technology to keep all of your batteries charged, utilizing the engine’s electrical system and isolating the starting battery. Hence, you never get yourself trapped in a deserted area without charge.The True® automotive battery isolator kit employs the same voltage-sensitive relay that we put in our boat and camper to keep the secondary batteries charged while isolating the starter battery system to keep it charged. The beautiful thing about this is that you don’t have to rewire any alternator wires since they switch charging without you having to do anything!The auxiliary battery isolator kit for car audio and all other accessories offers the secure charging and isolation of starting and auxiliary batteries across all kinds of cars, RVs, four-wheel drives, campers, trucks, trailers, and even solar purposes. The starting and auxiliary batteries are split when you start the car, allowing you to charge only the starting battery. The voltage-sensitive relay activates when the charge voltage hits 13.3 volts, permitting both batteries to be charged. The light in the upper LH corner is activated to highlight this.When the engine is turned off, and the battery voltage falls below 12.8 volts, the VSR disengages, isolating the starting and auxiliary batteries. At this moment, the True® 12v auxiliary car battery installation kit will turn the indicator light off and will continue to power any accessories without depleting the starting battery.The voltage-sensitive relay (VSR) also includes dual sensing tech that monitors the charge of both batteries. As a result, if either battery receives a charge, for example, if a battery charger is attached to the secondary battery, the VSR will activate and charge both batteries. True® technology is renowned for its 12v car audio battery isolator with voltage-sensitive relay (VSR).The True® automotive battery isolators are simple to install and includes the manual and all necessary components. Plus, there’s no need to damage any factory wiring, which could invalidate the manufacturer’s warranty. Testimonials from Our Amazon Store Frequently Asked Questions 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. Do I need to add fuses to the system? Yes. It is a safety precaution to add an extra inline fuse or circuit breaker between the main battery, the isolator, and the auxiliary battery. A common recommendation is a 100-140 amp fuse or breaker on the line coming from the second battery. What is the purpose of the LED indicator? The indicator light (often blue or on a separate voltmeter) illuminates when the isolator is engaged, letting you know that the auxiliary battery is currently being charged from the alternator. What are the cut-in/cut-out voltages? The isolator engages (connects both batteries for charging) when the system voltage reaches 13.3V or higher (indicating the alternator is charging). It disengages (isolates the batteries) when the voltage drops to 12.8V or below (when the engine is off). Does it affect my vehicle's warranty? The technology is generally warranty-friendly and requires NO connection to the alternator or ignition system. It uses a voltage-sensitive relay (VSR) for automatic management. 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.
