UniEnergy Technologies Battery » How To Install A Battery Isolator Switch? (Step-by-Step Guide)

How To Install A Battery Isolator Switch? (Step-by-Step Guide)

Do you want to prioritize safety above all when working on various equipment like big vehicles or other electronic devices? Well, one of the best tools to help you out is a battery isolator switch. And if you’re planning to buy one, it’s also important to know not just its main functions but also its technicalities.

Here, we will discuss everything about battery isolator switches, including their basic features and installation process. So, after reading the article, you are now adept at the ins and outs of how to install a battery isolator switch on your own.

How To Install A Battery Isolator Switch

Why battery isolators are important?

Also considered a giant mechanical switch, a battery isolator is widely utilized in the agricultural line. It’s also beneficial in many marine works, where big machines are used. To better picture what a battery isolator is, take a look at the main features of the device:

  • It is made of a sturdy metal casing for seamless panel mounting.
  • It is generally corrosion-resistant with a chrome finish for long-lasting performance. 
  • It makes use of a key that you can easily remove according to your preferred position. 

All these characteristics are combined to create a variety of functions. Generally, the isolator serves as a circuit breaker to disconnect the battery from the equipment easier. Accordingly, it ensures that any electrical work that needs to be connected to the main electrical supply is done safely and securely. 

Aside from this, the device helps in eliminating issues related to battery drain. One of the isolator’s tasks is to permit the alternator in charging the main battery. In doing so, it does not allow other heavy loads in the charging systems to avoid draining the battery. 

Therefore, if there is a weak or dead battery, it does not impact the other batteries even if these are connected together. Instead, it adds power to the vehicle or the equipment because of the separation of the battery system from the auxiliary battery. 

So, regardless of the number of batteries, the isolator manages the current flow in the electrical system. And until all batteries reach the same level of charge, the engine does not turn on. Following this kind of arrangement, each battery is an independent power source.

With these remarkable functions, a battery isolator is highly recommended by professional electricians. It may be an added expense but it’s surely worth it in terms of safety features and excellent servicing. 

Furthermore, there are four primary methods to create a wire connection to the auxiliary batteries, and these are―Manual Switch, Diode Based Isolator, Basic Relay, and Voltage Sensitive Relay (VSR). In this section, we will focus more on the first option, which is the manual switch. 

Why battery isolators are important?
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What is a battery isolator switch? 

Manual switches are the simplest way to charge batteries at a very limited cost. These are cheap options that can easily be matched with other systems, encompassing a hard disconnect for additional safety features. These devices are largely used in cars, camper vans, and even race cars. 

Although battery isolator manual switches are quite popular, you need to be careful at all times. It’s because you are required to switch them off once you stop the vehicle. If you, unfortunately, forget to switch it off, then expect the battery to drain from the starter. 

How to install a battery isolator switch?

Wiring the battery isolator switch all by yourself may appear like a stressful task. Well, in reality, it’s quite challenging, especially if you don’t know the basics. But fret not because we will list down all steps that you ought to know beforehand.

Step1. Read the instructions thoroughly. 

A key aspect of every installation process is to read the manual. Often than not, battery isolator switches come with detailed information about the parts as well as the core steps that you need to follow through. So, go over the instructions and make sure you understand the terminologies for better comprehension.

Step2. Disconnect the negative terminal first, and then the positive cable.

The procedure begins with the disconnection of the negative terminal of the battery (black cable). This is a crucial one because if you remove the positive terminal (red cable), it can lead to accidents. It may cause direct short to the system or the ground, and worst, sparks and battery explosion. 

Step3. All connections should be secured. 

The next one is to carefully check the battery section for damage or other elements. Make sure that all connections are well-secured to prevent unfortunate situations like a battery voltage spike or drop, electrocution, fire, and the like.

All connections should be secured. 
Image Credit: rampromasterdiycamper

Step4. Capitalize on heat shrink tubing.

As you continue with the process, you shouldn’t forget about the exposed cables and terminals. To ensure your safety, make use of heat shrink tubing to insulate key electrical parts from external forces such as dust, cuts, and moisture.

Step5. Gather other relevant parts for the installation of the battery isolator.

There are lots of components that encompass the entire battery isolator installation. For one, you need at least 4 to 6 ring terminals to efficiently link two or more wires to a single connection end. For all wiring installations, it’s important to have a fuse holder and stranded battery wire.

Other tools that may be required are a crimping tool, screwdriver, drill, wrench, voltmeter, and such. Keep the alternator output, ring eye, and cable lugs within your reach as well. And to complete the circuit for the alternator charging, don’t forget the secondary battery cable.

Step6. Locate the starting battery and mount the isolator.

Ideally, the best location to position the battery isolator is within the scope of the starting battery. This way, there will be a seamless transfer of energy. Just be sure that the location is away from possible heat elements. Then, screw down the device to the metal chassis. 

Step7. Link the wires to the isolator.

Shred a section of the red cable’s end, then curb the end using a ring terminal. Subsequently, place a blue insulated ring terminal on the black cable’s end, connecting to the isolator. Don’t forget to crimp the connections.

Afterward, you’ll find bolts along the isolator’s underside. Before you attach the long red cable to the red bolt of the isolator, create holes in the wires that are stationed underneath the battery isolator. Then, connect the short red cable to the other side of the bolt and secure the wire along the chassis ground.

Link the wires to the isolator.
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Step8. Connect the battery isolator to the main system.

Considering you’ve chosen the manual switch to connect the second battery, it’s pivotal that you know the general arrangement first. Check the installation diagram or the infographic provided by the retailer. Make sure you understand the ins and outs, from the layout to the entire electrical system. 

Use the diagrams to serve as your manual. To give you an idea, you should tie the short red wire to the auxiliary battery’s positive terminal. Attach both red cables of the starting battery and isolator to the positive terminal of the main system. After connecting the red cables, continue with the black ones.

Follow the same procedure by connecting the black cable of the secondary battery to the negative ground of the car. Then, link both to the negative battery terminal.

Step9. Ensure that all connections are tight and protected.

Before you test the isolator, all connections should be well-secured to avoid electrical damage to the parts and the main system in general. If you are uncertain, don’t hesitate to contact a professional electrician to verify your concerns.

Step10. Test the battery isolator switch.

After ensuring all connections are safe, it’s time to test the performance of the isolator. The completed circuit should ensure equal charging for both batteries. To check if the voltages are the same, you need to use a voltmeter. This measuring device is downright helpful to identify differences between two points. 

Compared to analog ones, digital voltmeters are the most recommended as these provide faster and more accurate readings. These also come with an automatic range selection for added convenience.

What are the things to consider when buying a battery isolator switch?

Before you kick off your purchase, there are factors that you need to take into account. One of the most important things is the compatibility of the isolator with your alternator. Typically, alternators encompass a maximum amperage, depending on the unit.

And when choosing an isolator, you need to pick something that is at least equivalent to or higher than the common measurement. Make sure that you don’t overload the alternator to avoid problems in the long run. 

It’s also pivotal to know that not all isolators are designed to keep the system performing a certain circuit line. There are smart isolators that have override switches to alter the functionality of the system. Thus, you should verify this with an expert and pick the appropriate battery isolator switch for your needs.


Truly, electrical systems have evolved, and lots of advancements were created to elevate the workings of your vehicle and devices. Battery isolator switches, for one, are remarkable tools that help extend the lifespan of your battery and equipment in general. So, grab one and install them like a pro! 

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