Whether you have two batteries or more, a dual battery isolator is a must-have. These come with a host of features that improve convenience such as the ability to prevent the main battery from getting flat and failing to start up the motor vehicle. In this buying guide, we will have a look at six of the best dual battery isolators that are compact enough to be used in a car, RV or boat, weather proof which makes them ideal for use in dirt roads or in the open sea and come with a high quality construction so you do not have to worry about the isolator falling apart. Which dual battery isolator do we find to be the best? We will have a look at the features offered by each dual battery isolator and this will help you make a judgment as to which dual battery isolator is best for you. In addition, we will show you which dual battery isolator is best for those buying on a tight budget.

Alternatively, you can skip to the best dual battery isolator on Amazon.

Best Dual Battery Isolator Comparison Table

Product NameImageProduct Link
KeyLine Chargers 12V 140 Amp Dual Battery Smart IsolatorBest Dual Battery IsolatorCheck Price
Audew Battery 12V – 48V Waterproof SwitchGood Dual Battery IsolatorCheck Price
True UTV-SBI-CM UTV Dual Battery Connect & Monitor KitDual Battery IsolatorCheck Price
Blue Sea Systems Add-A-Battery KitBest Dual Battery IsolatorCheck Price
WirthCo 20092 Battery Doctor 125 Amp/150 Amp Battery IsolatorGood Dual Battery IsolatorCheck Price
AOPEC Dual Battery Isolator Kit 12V 140Amp Voltage Sensitive Relay for ATV UTVDual Battery IsolatorCheck Price

List of the 6 Best Dual Battery Isolators

1. KeyLine Chargers 12V 140 Amp Dual Battery Smart Isolator

Best Dual Battery Isolators

This is a battery isolator from the manufacturer, Keyline Chargers. This device is a high quality device that is made from durable materials. It will definitely last for a very long time. It is IP65 certified. This means that it can withstand humidity, water immersion as well as dust. This makes it ideal for dusty, wet and unexpected extreme weather environments. It is compact and is just 2.6 x 2.6 x 2 inches. This means that it will fit virtually anywhere. This makes it a perfect fit under the hood to get close to where your dual batteries are located. It has strong vibration protections. A tightly secured 4 screw mounting system along with a silicon coated cushion provides you with the ultimate vibration protection. This means that you can easily use this device on dirt roads and you will not have to worry about it failing due to the very many bumps that cause vibrations.

This unit is smart. It was designed and developed with cutting edge programming to deliver optimum performance. It has a voltage sensitive relay that cuts in at 13.3 volts and cuts out at 12.8 volts to ensure that your primary battery is always charged and ready to start your motor vehicle. This makes it feel like having two separate power sources for each battery while only having one alternator. Unlike other diode relay based and solid state devices, this dual battery isolator will not rob you of 2 amps. There is absolutely no sacrifice that you will encounter when you use this device. This device is backed by an industry leading 12 month warranty as well as a 30 day hassle free money back guarantee. This device has one main drawback. It can drain your starter battery if not connected correctly. Due to all these features, we have chosen this as the best dual battery isolator.

Pros
  • 12 month warranty + 30 day money hassle free money back guarantee
  • High quality device
  • Compact
  • Dustproof and Waterproof
  • Smart
Cons
  • Can drain your starter battery if not connected correctly

2. Audew Battery 12V – 48V Waterproof Switch

Best Dual Battery Isolators

This is an affordable, popular battery isolator from the manufacturer, Audew. This battery isolator is made from high quality ABS. It is durable and will definitely last for a very long period of time. It comes with a host of features. It comes with a dust proof side pad. This makes it suitable for use in dusty environments as the dust will not have the opportunity to cause havoc in the isolator device. It has a rear cover. This cover functions to insulate terminals against any short circuits. It can be used with both 12V and 48V DC systems. This means that you are able to use it in a wide variety of motor vehicles. It can be used independently, or it can be locked together with other switches. This allows for you to control several batteries at one time. This device is very simple to use. It has an On/Off switch that makes it very easy to check for the current position. When in the on position, a green portion will be exposed to indicate that the device is on. When it is off, there is no exposed green portion and this indicates that the switch is in the off position. It eliminates any power draw from the battery when the motor vehicle is not in use. It has a movable 4 side tab and rear cover that can be used to avoid connecting terminals. It is versatile and can be used in Caravans, RVs, Marine Boats, etc. It comes with a 12 month warranty and a 180 day money back guarantee. This product has a one main drawback. A few customers complained about the quality inspection process as they received defective products. Due to all these features, we have chosen this as the best budget dual battery isolator.

Pros
  • High quality ABS
  • Dust proof side pad
  • Affordable
  • 12 Month warranty and 180 day money back guarantee
  • Can be locked together with other switches.
Cons
  • Quality inspection process could be better

3. True UTV-SBI-CM UTV Dual Battery Connect & Monitor Kit

Good Dual Battery Isolators

This is a very popular dual battery isolator from the manufacturer, True Amalgamated. It is well built and a lot of customers praised it for its high quality. This device comes with a host of features. It comes with accessories needed to set it up. These are: a blue LED voltmeter, a true UTV-SBI-18 isolator with silicon insulators and a 3M dual lock fastener, true 12 inch sealed 6ga Red and Black cables with 6mm lugs, a sealed 6ga Red Cable with 6mm lugs, and an easy to follow instruction manual. This makes it very easy to install and setup the device.

This kit comes with a host of features. It comes with a shockproof and waterproof volt meter. This means that it can withstand harsh environmental conditions. It allows for you to perform real-time monitoring of the charge state of your batteries. All true kits feature the industry’s only fully adhesive sealed 100% waterproof cables. This means that you do not have to worry about any short circuits occurring due to moisture. The kits allow for three mounting options: traditional screws, a 3M dual lock fastener, or to leave it suspended in cables. The kit provides you with the best charge management of your accessory battery while protecting your primary battery for starting. This device has one main drawback. A few customers complained about poor customer service.

Pros
  • High quality device
  • Comes with a voltmeter
  • Fully adhesive sealed 100% waterproof cables
  • Allows for 3 mounting options
  • Kit comes with components needed
Cons
  • Poor customer service

4. Blue Sea Systems Add-A-Battery Kit

Good Dual Battery Isolators

This is a popular battery isolator from the manufacturer, Blue Sea Systems. The manufacturer is well known for producing high quality products, and this is one of them. This device comes with a host of features. It is compatible with 12V and 24V systems. This means that you do not have to worry about which battery you have, as long as it is either a 12 or 24V battery. It comes equipped with a charging relay. This device automatically combines batteries connected to it during charging. It then isolates batteries during engine cranking and when the batteries are not being charged. It shares the charge between two batteries in a highly efficient manner. It has an IP 67 rating. This means that it can be used in environments with a lot of moisture and in environments with dust.

This device is popular due to it being very easy to use. It has a dual circuit plus batter switch. This feature simplifies switching, isolates the engine and house circuits, combines batteries for emergency starting and has tin plated copper studs for maximum conductivity and corrosion resistance. It also makes it easy to manage the whole system. All you need to do is to turn the battery switch on when you are around, and turn it off when you are away. This allows anyone, even a novice to use the device with great ease. This device has a few drawbacks. A few customers complained about the customer service. In addition, a few customers complained that they had to find additional components to get the device working properly.

Pros
  • IP 67 rating – waterproof and dust proof
  • Works with 12 or 24V batteries
  • Very simple to use
  • Can use both batteries for emergency starting
  • Charging relay
Cons
  • Customer service not very responsive
  • Need to acquire additional components to get the device up and running

5. WirthCo 20092 Battery Doctor 125 Amp/150 Amp Battery Isolator

Dual Battery Isolators

This is a basic looking dual battery isolator from the manufacturer, WirthCo. This device is a state of the art device that is suitable for any motor vehicle with an auxiliary battery. It is very easy to install and setup. This means that you do not need to worry about being a technician in order for you to be able to setup the device. It is lightweight. It comes at a size that makes it smaller and lighter than other standard battery isolators. The battery isolator is automatic. This means that it automatically charges the auxiliary battery. This means that you do not need to worry about remembering to charge the auxiliary battery as the process is automatic. It has the manual override feature. In this feature all you have to do is to push an override button and change the batteries to parallel mode for jump starting.

This device comes with several additional features. It has an IP 62 rating. This means that it can withstand moisture and dust. This means that you can use this battery isolator in boats, RVs and in applications where there will be moisture and dust. It has an over current detection feature. This prevents the electronic systems present in the motor vehicles from being damaged. It also has the surge detection feature which also functions to protect the electronic systems present in the cars. This device comes with a mounting bracket that houses the 4 x 4 x 2 inch isolator. This device comes with a few drawbacks. A few customers complained that the battery isolator does not work properly when a solar panel is connected to the aux battery. It also struggles to work properly when the aux battery is full.

Pros
  • Suitable for any motor vehicle
  • Easy to install and setup
  • Lightweight
  • Over current detection feature
  • Manual override feature
Cons
  • Does not work properly when a solar panel is connected to the aux battery
  • Struggles to work properly when the aux battery is full

6. AOPEC Dual Battery Isolator Kit 12V 140Amp Voltage Sensitive Relay for ATV UTV

Dual Battery Isolators

This is a dual battery isolator from the manufacturer, Aopec. This device looks quite minimalistic and comes in a compact design. This makes it very easy to fit into restricted spaces. It comes with a host of features. It distributes the charger or alternator current effectively between the two batteries. It connects both batteries during the charging process and keeps them isolated when discharging. This is a great feature as you do not need to worry about the batteries running out of juice. It comes with the primary battery priority charging feature. In this feature, the device prevents the primary battery from being discharged and this lengthens the life of the primary battery when the engine is off. This reduces the scenario in which you will try to crank up your car and realize that your primary batteries’ voltage is too low for you to start the car.

The device is able to resist the elements. It is weather proof. It has an outer plastic housing and a silicone sealed internal layer. This protects your isolator from water, dust, dirt and sand damage. The battery isolator comes with a protective design. This protective design allows for the battery isolator to sustain surge protection, over voltage protection as well as over current protection. The manufacturer claims that each battery isolator is tested and inspected before being shipped. He shows great confidence and pride in his product and offers a 24 month warranty. This device has a few drawbacks. A few customers complained that the cables are rather short. In addition, a few customers complained that the quality of the device is not as good as they expected.

Pros
  • Comes in a compact design
  • Distributes current among the two batteries
  • Primary battery priority charging feature
  • Weather proof
  • Protective design
Cons
  • Cables rather short
  • Product caused a few problems for a few customers

Best Dual Battery Isolator Brands

The best dual battery isolator brands are KeyLine, Blue Sea Systems and Audew. The KeyLine product that we reviewed is a high quality device that is made from durable materials. It will definitely last for a very long time. The Blue Sea Systems device that we reviewed works with both 12 and 24 Volt systems and is very easy to use. The Audew device that we reviewed comes at an affordable price and comes with a host of features that you may find useful.

Best Dual Battery Isolator

KeyLine Chargers 12V 140 Amp Dual Battery Smart Isolator

Best Dual Battery Isolators

This is the best dual battery isolator. This device is a high quality device that will last for a very long time. It is IP65 certified. This makes it ideal for dusty, wet and extreme weather environments. It has a host of features that has made it popular among motorists and travelers.

Here are the key features that we liked about the dual battery isolator:

  • 12 month warranty + 30 day money hassle free money back guarantee
  • High quality device
  • Compact
  • Dustproof and Waterproof
  • Smart

Best Budget Dual Battery Isolator

Audew Battery 12V – 48V Waterproof Switch

Good Dual Battery Isolators

This is the best budget dual battery isolator from Audew. It can be used with both 12V and 48V DC systems, it can be used in a wide variety of applications and it is very simple to use – all you have to do is to turn it On when you want to use it and Off when you do not want to use it.

Here are the key features that we liked about the dual battery isolator:

  • High quality ABS
  • Dust proof side pad
  • Affordable
  • 12 Month warranty and 180 day money back guarantee
  • Can be locked together with other switches.

How Much Does a Dual Battery Isolator Cost?

The dual battery isolators can be found in the 15 – 150 USD range.

High End

Such devices approach the 150 USD mark. These are the devices that are made by reputable manufacturers. Such devices come with features such as integrated voltmeters, waterproof cables and a solid build quality. An example of such a device is the True UTV-SBI-CM UTV Dual Battery Connect & Monitor Kit.

Mid-range

These devices are in the 80 – 120 USD range. These are devices of decent quality that come with many features that a typical user will find useful. An example of such a device is the AOPEC Dual Battery Isolator Kit 12V 140Amp Voltage Sensitive Relay for ATV UTV.

Low End

These are the devices that are near the 20 USD mark. These devices lack advanced features such as being weatherproof and may have an inferior build quality as compared to the more expensive devices. An example of such a device is the Audew Battery 12V – 48V Waterproof Switch.

Why Do You Need a Dual Battery Isolator?

Reliability

There are cases in which you will want to buy electronic devices for your motor vehicle. Such devices range from LED lights to advanced navigation systems. These systems will need power for them to operate. Your main battery was designed to provide power to your motor vehicle and power just one or two systems. This means that you will need an additional battery to deal with this new load. This new battery is what is referred to as the auxiliary system. Adding an additional battery has the advantage that you can now power all your electronic circuits, but without putting any preventative measures in place, this will lead to your main battery getting drained as the batteries try to reach an equilibrium of some sort. Dual battery isolators completely avoid this problem by making sure that the power from the main battery does not get drained.

Extra Power

Have you ever had a scenario in which you have an emergency? Well everyone has those. I am talking about situations in which your main battery does not have enough power to start the engine but you need to start the engine as quickly as possible. And you will not have enough time to start charging your battery. In such scenarios, some dual battery isolators allow you to use both the main and the auxiliary battery to provide power.

Ease of Use

Dual battery isolators are usually easy to use. Some of them just need you to turn the switch to the on position and they will deal with everything. This includes charging both the main and the auxiliary battery as well as ensuring that the main battery does not get drained. When you do not need to use the batteries anymore e.g. if you want to park your RV for a while, then all you will need to do is to turn the switch to the off position. That is a very easy task that virtually anyone can do.

Types of Dual Battery Isolators

There are 4 main types of dual battery isolators:

Manual Switch

These are the isolators that are turned off and on from a switch that is near the ignition. As the name suggests, this is a manual process that relies on the human being to remember to turn the isolator on/off. You may have to open the hood to engage or disengage. If this task is forgotten, it can easily lead to a drained battery. This very basic dual battery switch approach has other limitations. It can place added demand on the alternator immediately after starting the engine as the alternator will have to charge both the main battery and the auxiliary battery.

Diode Isolator

These isolator systems can protect a starting battery and extend the power available for other purposes. These include powering auxiliary batteries to run electronic devices and more. The blocking diodes that serve to split the charges to each battery perform this function, but there is a voltage drop from the alternator to the batteries. There is always a half volt drop across the resistors that are present to protect the diodes. These resistors will dissipate up to 50 watts when power is flowing. This wastes power.

Solid State Relays

These are solid state relays that use control circuitry and power Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) to do the switching. This method eliminates the voltage drop that would have been present if diodes were used but there is still some resistance in the power transistor conduction channels and limited current is allowed to flow. These are susceptible to damage from voltage and current spikes and can be easily damaged if too much current is drawn through them. MOSFETs are expensive and this means the battery isolators that use this technology are pricey.

Programmable Isolators/Hybrid Isolators

These are dual battery isolators that employ semiconductor technology to monitor the charging and discharging process. They employ rugged, reliable solenoid contactors to allow a large amount of current to flow without damaging the electronics. This has the advantage of high precision, high reliability as well as a relatively low cost.

Factors to Consider When Purchasing a Dual Battery Isolator

Reliability

This is the most important factor to consider when selecting a dual battery isolator. You will need a device that will be able to perform flawlessly for as long a period as possible. You definitely do not want to get a device that will fail just a few months after operating. Make sure that you take your time to go through the reviews present in order to find the most reliable device present.

Type

As you know, there are different types of battery types that are available. These are solid state relays, programmable isolators, manual isolators and diode isolators. The manual isolators are the cheapest but will result in the worst performance because we human beings tend to be very forgetful. Diode isolators tend to work quite well but have the main disadvantage that they draw too much power. Solid state relays perform well but are more prone to failure and are more expensive than the others because of the MOSFET that is present. Programmable isolators are suitable for most applications and are usually the most reliable.

Battery Rating

You need to check the battery’s rating. As you know, most batteries use either 12 or 24V DC. Before you go shopping for a dual battery isolator you first need to check the battery rating present on your battery. If it uses 12V then make sure that your dual battery isolator is compatible. If it uses 24V, then also make sure that your dual battery isolator is compatible. If it supports both then that is great. If you change vehicles, then you may not have to replace your dual battery isolators.

Safety Features

Batteries are capable of storing large amounts of energy. The chemical reactions that occur in the battery allow it to produce large amounts of current. This means that it is capable of producing enough power to cause great harm. This means that your dual battery isolator must be capable of withstanding things such as over current, over voltage, and other problems that may occur. This will keep you safe from harm.

Weatherproof?

You need to think of the places where you want to use the motor vehicle. If you are going to use it in areas where there are dirt roads and rain, then you will probably need to go for a battery isolator that is dust proof and water proof. This will ensure that you will not have problems when you get into such environments. 

Warranty

When purchasing any electronic device it is best to consider the warranty offered by the manufacturer. The warranty gives a good indication of the manufacturer’s confidence in his or her product. As a general rule of the thumb, products with longer warranties are made from better materials and last much longer than similar products that have shorter warranties.

What is a Dual Battery Isolator?

A dual battery isolator is an electrical device that allows current to flow in one direction, and is frequently used in systems with a main and auxiliary battery system. This ensures that the main battery always has power to start the system even when the auxiliary battery system is flat.

How does a Dual Battery Isolator Work?

A dual battery isolator has three main components. The first component is the switching mechanism. This mechanism is used to switch the dual battery isolator on and off. This mechanism can be either mechanical or automatic. The mechanical mechanisms will need you, the human being to turn a switch on. Automatic mechanisms can work without you doing anything at all. The next component is the current restriction feature. This feature allows the current to flow in one direction only. This feature protects the main battery from being drained by the auxiliary battery. If this feature was absent, it means that when the auxiliary battery gets low, it will start to draw current from the main battery and will only stop when both batteries have roughly the same amount of power. This would then result in the main battery failing to provide enough power for the battery to start. The last component is the safety system. This safety system is what protects the dual battery isolators from catching fire, and causing damaging the motor vehicle. Components of this safety system include over current protection devices, and over voltage protection devices.

Dual Battery Isolator FAQs

I’m looking for a Kill Switch to Shut off My Travel Trailer Battery. Will This Work?

It must definitely work. A few customers used it for this purpose and it worked quite well for them.

If I Use System On My Truck, Do The Two Batteries Have To Be Identical In Amps And Size?

No the system doesn’t have to have identical batteries. By this we mean that they do not have to have the exact same dimensions. They need the same voltage 12/24.

Are Dual Battery Isolators Easy to Install?

Yes, in most cases. The instructions are usually easy to follow and in most cases all the hardware needed to setup the device is included.

Are Dual Battery Isolators Waterproof?

In some cases, yes. You need to make sure that you check with the manufacturer before purchasing the product.

Can I Use These On My Boat?

As long as the battery isolator is waterproof, you should not face any problems. Make sure you check with the manufacturer’s instruction sheet first!

Conclusion

In this article, we have explored the top 6 best dual battery isolators. We have given a thorough analysis of each dual battery isolator. We also included a comprehensive guide aimed at equipping you with the skills of identifying the best dual battery isolator to suit your unique needs. In addition, we included a list of comprehensive FAQs for your convenience.

Check out the best dual battery isolator on Amazon.