Large 12V Dual Battery Isolator Kit True® Brand

(11 customer reviews)


Best 12v dual battery isolator kit for adding that 2nd or 3rd battery to your system in your car, truck, van, SUV, RVs, boat, or whatever you wish.

SKU: DBK12LARGE Categories: ,


Dual battery wiring kit contents

  •  1 (SBI) Smart Battery Isolator install kit with mounting screws
  •  20 feet #6 high flex red cable with tinned copper cable lugs
  •  3 feet #6 high flex black cable with tinned copper cable lugs
  •  2 positive brass alloy battery terminal ends
  •  1 negative brass alloy battery terminal end
  •  3 loose crimp-on tinned copper cable lugs
  •  2 sections of adhesive lined shrink tube
  •  5 zip ties
  •  1 installation instructions booklet
  • 12v dual battery wiring kit diagram included
  • Official True® retailer
  • Delivery: USPS first class or priority mail

A TRUE exclusive!

Product Features

  • Suitable for 12V automotive, boats, 4WD, trucks, Caravan, RVs, & Solar
  • 140 Amp Voltage Sensitive Relay
  • Priority charging for starting battery
  • Alternator outputs up to 150 amps
  • Fully automatic, proven technology
  • Easy to install DIY dual battery system kit with wiring diagram
  • Waterproof, shockproof, and heat resistant cables up to 130deg for safe and efficient use of the auxiliary battery system.

It 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 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 isolator 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® automotive dual battery kit continues to power any accessories without risk of draining the starting battery.

The VSR (voltage sensitive relay) also has dual sensing which senses the charge of both batteries. If either battery is receiving a charge, e.g. a battery charger is connected to the secondary battery; the VSR will engage and charge both batteries.

True® 12v dual battery kit is easy to install and comes with all components and instructions required to complete the install. There is no need to cut into any factory wiring that may void the manufacturer’s warranty.

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Additional information



11 reviews for Large 12V Dual Battery Isolator Kit True® Brand

  1. Jorge V. | Lakeworth, FL

    Just had my son install your dual battery kit and 2 additional isolators to connect all of my additional batteries to the main engine’s charging system. I now have 5 batteries all automatically connected to the charging source from the two engines. The single dual battery kit provided us with enough cable to make all connections we just had to purchase a couple more cable ends. He figured it would take the entire day but he was done by noon so of course we had to go fishing to try it out. We ran two hours offshore then ran all the electronics as well as the appliances including the TV.

    My son kept monitoring the dual battery isolators & checking the charge in each battery. When we finished fishing the charge in the accessory batteries had dropped to 12.1volts. The main batteries were at 12.8volts.

    We ran into shore and again checked all batteries and all five registered 12.9 volts with the engines off. While running the engines and all isolators showing indicator lights the voltage at each battery registered 13.4volts. Seems it was a big success and I no longer have to remember to turn the manual battery switches. Next week we will be staying offshore for two nights we’ll really have the opportunity to test them.

  2. Doug Z. | College Park, GA

    Just installed your boat dual battery cable kit in my pontoon boat to allow my second battery to charge when I’m running the main engine. Works great and had plenty of cables to reach the forward location of the second battery. Also discovered that my shore charger, which is connected to my second battery only, will now keep the main battery charged when I plug it in at home. Best dual battery install kit at a reasonable price.

  3. Ericofcourse

    Here is my review

    online customer

  4. Ray R. Kawal

    Here is the review of Ray R. Kawal

    Chevy Battery Isolator

  5. Robert

    This was easy to install and seems to be working great on my fishing boat. I added a second battery for everything besides the engine and I haven’t had a problem listening to music with the motor off since. Before adding this I had to use my jump box 3 times.

  6. Ulrich Urfer

    My Camper review

    Camper Review

  7. Jeff Ingalls

    This thing has been working like a champ. Not a single issue with this. Been about 5 months or so. I’m thinking of buying another one as a backup.

  8. Greg Garner

    Excellent customer service


  9. Bret

    This dual battery cable kit is perfect so far


    Works perfectly

    One thing to note: if you are going to charge your secondary battery with an ordinary charger or solar, understand that this device will turn on so that you will be charging your car battery as well. This is what it was designed to do. It connects/disconnects regardless of where the charge is coming from. You should install a manual override switch for safety and control charging.

  11. NormB

    I used this dual battery isolator, voltage sensing relay in my solar system install on my utility trailer.

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