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Dual Battery Guide | What do you need to know?

Dual Battery Guide


While going on a trip or touring someplace via road, we usually take along a lot of stuff with us. This includes gadgets like fridges (to keep stuff cool) and other electronics like smartphones, laptops, cameras, etcetera (to capture memories and keep connections). Obviously, all electronic items need battery power. The chances to start your engine as well as charging these items with a single battery (starting battery) is near to impossible. This means that it is important to have two batteries, and this is where the dual battery system comes. There are some ways in which a second battery can be wired into the car. The installation solely depends upon the intended use and flexibility of the system. In this article, there is everything that you need to know about the dual battery systems, so keep on reading!


What is a Dual Battery System?

Let us first begin by explaining what actually is the dual battery system. 

So basically, when a vehicle battery system uses a secondary battery, in addition to a vehicle’s starter battery is known as a dual battery system. This secondary battery is used to power auxiliary gear and other such accessories. There are a few types of secondary batteries that will be further discussed in the article.  


How Does Dual Battery System Work?

The batteries in the dual battery system work as two isolated systems. When your car’s engine is running, your alternator and starter battery work together in order to provide power to your vehicle as well as its accessories. 


When your vehicle’s engine is turned off, now it’s the turn of your secondary battery to provide power to all the equipment and accessories that are attached to the car. This implies that all your electronics, including your phones, portable fridge, laptops, lights, cameras, and inverters, can run without having to run your engine. 


This working of the two batteries separately is achieved by an isolator. This isolator is used to disconnect your starter battery from your secondary battery. This implies that due to isolators, you can only draw power from one battery at a time.


Without a doubt, both the batteries must keep working independently to ensure that your starter battery does not get drained, and then there might be a problem while starting up the car. Another function that is done by a dual battery kit is ensuring that both batteries charge properly. 


Types Of Auxiliary (Secondary) Batteries:

Here are a few types of secondary batteries that are used by dual battery systems


Lead Deep Cycle:

This type of secondary battery is suitable under the bonnet or in an open tub. These batteries are cheap. If these batteries are not fully discharged and recharged after each use, they will suffer from a reduced lifespan.



The most popular batteries among any rig are AGM batteries. These batteries are suitable anywhere. This is because no hazardous gases are set out while charging. If you are looking for a battery that is suited to partial use and recharges, this type of battery is the one for you. 


Gel Cell:

After the AGM batteries, the next big step is Gel cell batteries. The usual liquid acid of common batteries is replaced with gel acid. This makes these batteries spillproof and maintenance-free. 



In a partial use cycle, lithium batteries are the most durable batteries. These batteries are known to boast reduced weight and increased capacity. The only issue is that this type of battery can not be fitted into the bonnet of the vehicle because of heat restrictions.


How to install a dual battery setup?

If you want to install a dual battery system yourself, have a look at our step-by-step guide to see if you’re capable of performing the task. 


1. To ensure that there is enough wire to make connections to the secondary battery, one should mount it on the rig. 


2. While setting up a dual battery system, firstly, make sure to disconnect your starter battery.


3. The next step is to set up the Voltage Sensitive Relay (VSR). Ensure that VSR is placed close to the main battery. It should be kept away from hot or moving parts.


4. After that, according to the needed length, cut the cables.


5. Strip away 15mm of insulation, crimp them in place, and fit lugs on the bare ends of the cable. Over the lug, slide the heat shrink and in order to provide a waterproof seal, apply heat.


6. In order to earth the relay, utilises the black wire that is attached to the VSR. After that, you should connect the main battery to the VSR and earth the second battery.


7. Connect the VSR and mounting plate. It should be noted that positive cables might not get attached to both batteries.


8. Firstly connect the negative leads to the starter battery and then to the second battery.


9. Test if your dual battery system kit is working with a multimeter.


The Advantages and Disadvantages of Installing a Dual Battery System:

If you are still not sure whether a dual battery system is a suitable option for you, consider the following advantages and disadvantages.



✓ With a dual battery system, you can power your electronic appliances like laptops, fridges, cameras, lights, inverters

✓ You can charge everything even when your engine is off

✓ Having a dual battery system implies that you do not need to worry about draining your starter battery

✓ If you need to use your winch, the dual battery system will increase the available power

✓ With a dual battery systems setup, you can charge your secondary battery with solar panels

✓ You will always have an extra battery even if the primary battery fails



✓ An extra battery box will add weight to your rig

✓ If you are tight on budget, having dual battery system kits are a little pricey


Final verdict:

If you are a traveller who takes a lot of gear while touring, then you will need a dual battery system to power your equipment like a portable fridge, camera, smartphones, etcetera, when your vehicle’s engine is off. Therefore, we would recommend you eradicate the risk of losing power to your gear and make sure that your engine is always ready to start up with a 4WD dual battery system. Besides that, a smooth journey also requires a smooth car. In order to get all the hidden history of your vehicle, write down your car’s details at Quick Revs’ online platform and get every detail of your car right in front of your eyes. For more information, feel free to contact us!


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