What is it, how does it work, and why would I need one? 


Basically it’s a set up where you have a secondary battery in addition to your vehicle’s starter battery. The secondary battery being used to power your accessories.   It’s a great system for anyone who has extra gear they need to power such as safety lights, portable fridge/chilly bin.  You could of course connect your accessories to your main vehicle starter battery, but you do run the risk of your accessories drawing too much power and leaving you caught out with a flat battery and vehicle that won’t start. 

So, if you’re someone that likes to go off road a fair bit, this is a particularly great system.  It gives you peace of mind knowing you’ll be able to power your additional gear without running the risk of flattening your starter battery. 

So how does it work? 

A standard dual battery system is comprised of two batteries: a starter battery (this is your vehicle’s main battery), a secondary battery (the auxiliary battery), cabling to connect the two batteries, a battery isolator (operated manually)and or a VSR (which operates automatically) -this ensures each battery functions as an isolated system and protects both batteries from being drained. While your vehicle’s engine is running, your main vehicle battery (the starter battery) works with your alternator to power your vehicle and its electronics, and when you your turn your vehicle engine off, your secondary (auxiliary) battery will kick in and power all the accessories attached to your vehicle, such as your portable fridge and emergency lights. 

In a nutshell the dual battery system works thanks to the battery isolator which will disconnect your main vehicle (starter) battery from your secondary (auxiliary) battery, this ensures you only draw power from one battery at a time, it also ensures both batteries charge properly.  Finally, most importantly of all, it is going to give you peace of mind, as it ensures your starter battery isn’t drained flat from your accessories. 

What types of batteries are used in a dual battery system? 

You could expect to see any one of these 3 batteries in a dual battery system, being; Lithium, AGM or Lead Deep Cycle.  In most cases though, you’d expect to see an AGM battery used as the secondary (auxiliary) battery in a dual battery system, primary because its designed to be repeatedly discharged and recharged without being damaged or shortening its’ lifespan.  

Is a Dual Battery System right for me? 

Depending on the number of accessories you have, how often you use them, and how often you go off grid can all be factors to take into consideration when deciding if a dual battery system is right for you.  Below we’ve also popped down some pros and cons to help you weight up your decision.   


  • It allows your vehicle to power your portable fridge, lights, radio, and anything else you need when your vehicle engine is switched off. 
  • Peace of mind that you won’t be left stranded because you’ve drained your starter battery flat 
  • You’re able to charge your secondary battery with solar panels (if you have them fitted). 
  • Additional power if you have a winch 


  • The cost 
  • Additional weight in your vehicle 


You can rely on our experience 

If you’re considering a dual battery system, then you can always rely on the guys at the Battery Warehouse to have the expertise to help you in making the right decision to best meet your needs.  They stock a wide range of quality batteries at great prices.  Drop in and see them today and they’ll fit you with the right battery for your needs.