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Best 12V DC Dual Battery Isolator 2020 Detailed Review

Best 12V DC Dual Battery Isolator 2020 Detailed Review.

Best 12V DC Dual Battery Isolator: Out of the factory, most vehicles only include one starter battery. Understandably, people often want to add a second battery. It could be for work lights, an audio system, a power winch, or even for the sake of having a backup.

If you’ve ever entered your car on a cold night and felt relieved when your engine actually turned over like it should, the component you need to thank is probably a battery isolator. 

Choosing the Right 12V DC Dual Battery Isolator 

Perhaps more importantly, ending up with the wrong detector could be more trouble than it’s worth. You don’t want your battery isolator to cause problems with your vehicle’s electrical systems, or with the devices connected to whatever local grid, you’re working on. Luckily, it’s not that tough to choose an effective battery isolator. 

Blue Sea Systems Add-A-Battery Kit (120 Amp)

Blue Sea Systems Add-A-Battery Kit (120 Amp) 

The Blue Sea Systems kit lets you share the charge between both of your batteries with great efficiently, far more efficiently than any single battery isolator.

The 12/24 Volt SC 120 Amp Automatic Charging Relay can be used to isolate batteries during an engine cranking up, or used to combine batteries during charging. 

Essentially, these devices are made to try and simplify the switching process. Consequently, they work just like you’d expect, by isolating an engine or house circuit.

Though the Add-A-Battery kit does have a minor automotive slant because these switches are supported by a start battery which can be used for emergency starting. 

Build & Design 

The components which come into contact with electrical current are tin-plated copper studs, used for optimal conductivity and their resistance to corrosion. The unit is further protected by a weatherproof chassis, specifically allowing the charger to be IP67 waterproof. 

WirthCo 20092 Battery Doctor (125/150 Amp) 

WirthCo 20092 Battery Doctor (125/150 Amp) 

The Battery Doctor is pretty close to a state of the art equipment. This dual battery controller is ideal for basically any vehicle that has an auxiliary battery.

The Doctor is somewhat smaller and lighter than similarly powered controllers, which probably reflects the automotive spirit of this device. 

Build & Design 

The Doctor is highly portable, measuring 5.1 x 5.7 x 2.3-inches, and weighing pretty close to one pound. It’s basically like a tremendously thick smartphone. The WirthCo 20092 Battery Doctor is also IP62 water-resistant, which makes it suitable for outdoor use. 

WirthCo claims you could use this device in a marine capacity, but you may be better off securing a greater waterproof rating for those kinds of jobs. 

Like you would expect, the Doctor offers priority charging for starting up a battery, and will automatically charge any auxiliary battery you connect. The Battery Doctor can also offer a manual override solution for starting a kit from scratch. 

KeyLine Chargers Isolator – VSR Pro Dual Battery Kit (140 Amp) 

KeyLine Chargers Isolator – VSR Pro Dual Battery Kit (140 Amp)

It’s tough to make an impressive battery isolator, but the KeyLine Chargers Isolator gets close. It allows you to keep your amperage output up, and in a way that solid-state devices generally cannot. 

The VSR in this unit will cut-in at 13.3 volts, and then gracefully cut-out when you approach 12.8 volts. In other words, it will help keep your battery perfectly charged, so the next time you throw on the power, your battery behaves exactly as you expect it to. 

Build & Design 

This highly compact isolator was constructed to be small enough to place essentially anywhere you’d want an isolator.

It measures 2.6 x 2.6 x 2-inches, which is certainly not a cramped fit under the hood. In any case, you can get the equipment close to your dual battery setup. 

KeyLine Chargers Isolator has been IP65 certified for off-road use. Whether it gets dusty or wet, you’re pretty well covered. But the IP65 certification isn’t rated for submersion.

It’s more like protection from rain and light spraying forces. Don’t consider this isolator to be totally immune from water and it shouldn’t become an issue. 


The Blue Sea Systems Add-A-Battery Kit is both basic and powerful. Whether or not you intend to use the isolator for automotive purposes, this system is intuitive to use and powerful enough for almost any dual battery setup.

This kit is somewhat on the expensive side, but when you want high-quality equipment, you typically have to be willing to pay for it. 

The WirthCo 20092 Battery Doctor is something that nearly any mechanic could use in their shop. But you don’t actually need any serious level of expertise to use the Doctor.

It’s highly portable and very approachable. Because of the battery inside of this unit, you’re well-equipped for jumpstarts as well. Though the Doctor can’t do everything, it’s an incredibly good value for people who are looking specifically for battery recovery features. 

Finally, the KeyLine Chargers Isolator VSR Kit is about as hands-on as isolators can be. If you want real control over your battery power, you’re going to have to be willing to go through the trouble of installing it.

For what it is, this kit is terrifically cost-effective. That makes the KeyLine Charger Isolator a good choice for anyone who’s looking for quality above all else.