How to Install a Dual Battery System

Whether you’re heading out for serious off-roading or taking the family on a weekend camping trip, having auxiliary power is critical. The best way to get your hands on the power you need is with a dual battery system. A quality dual battery system works to make sure you always have the power you need to start your car and run those accessories that make your campsite more comfortable. Getting more from your batteries means designing a system that’s right for your vehicle and the accessories you want to run. In this article, we’re going to go over the basics of designing and installing a dual battery system for your car or 4×4.

1. Choose Your Battery Chemistry

The dual battery system you design will be based on the type of car battery you choose to use. The best choice for your secondary battery is a Deep Cycle Battery. Deep cycle batteries are designed to handle deep discharge while powering auxiliary devices. 

The most common types of deep cycle battery are:

  • Flooded Lead Acid. Similar to starter batteries, deep cycle lead acid batteries are affordable and easy to find, but they’re heavy and have a shorter total lifespan than other types.
  • AGM. Absorbent Glass Mat batteries don’t leak and don’t emit any gases, making them a good, affordable choice for most dual battery systems.
  • Gel Cell. Gel batteries are another leak-proof and low-maintenance type of deep cycle battery.
  • Lithium. Lithium batteries are available with a few different chemistries, but they’re the smallest, lightest and most powerful option on the market.

2. Choose Your Charging System

The charging system you need depends on a lot of different factors, including how you’ll use the battery and the type of vehicle. Older cars with simpler alternators offer a lot more flexibility in charging, while modern cars with newer types of alternators may require more complex systems.

Generally speaking, most dual battery setups use one of three charging systems:

  • Alternator charging. In the simplest systems, the vehicle’s alternator is used to charge both batteries. Whether this is right for your setup depends on the vehicle and the alternator.
  • DC to DC charging. Different types of batteries need to be charged differently. Your alternator is designed to charge your starter battery, but it doesn’t provide the right type of charging for some batteries (like Lithium). A DC to DC charger solves this by taking power from your alternator and converting it to the correct output for your auxiliary battery.
  • Solar charging. Dual battery systems are ideal for use on vehicles that have solar setups. A steady trickle of power from the sun ensures both batteries are always charged. If you have solar panels you’ll need to include solar chargers as part of your system.

3. Mount Your Secondary battery

Deep cycle batteries are big and heavy, so it’s important to mount them securely. You absolutely don’t want your battery to be able to move or tip over when you’re tackling an off-road trail. It’s common for the second battery to be mounted in your engine bay. But, you can also securely install batteries in the boot, under your seats, behind your seats or in the tray of the vehicle.

4. Connect Your Wiring & Components

It might sound obvious, but the way your system is wired is critical to its performance. If you use low-quality wiring and components, the system will perform badly and you could find yourself replacing expensive batteries often. Ensure your wiring, fuses, solenoids, Voltage Sensitive Relay (VSR) and charging systems are rated for your use, and carefully install them as per manufacturer specifications. If you’re doing a DIY installation then you might need to invest in some new tools, like a battery cable lug crimper. Doing a poor job here could cost you big down the line, so take the extra time to get it right.

5. Test the System

Double check your connections and earth points before testing the system. The most important thing to check is the VSR. It controls the flow of charging from your alternator to the secondary battery and prevents your auxiliary systems from draining your starter. It should turn on when the engine is running and the alternator is charging, then turn off when the engine is off and the battery is in use.

Looking to Install a Dual Battery System? Contact Access Auto Electrics Today!

The right dual battery system for your setup depends on dozens of factors. How you use the vehicle, where you take it and the accessories you run all play a role in choosing a system that suits your needs. Getting it right is important, and choosing all your components can get complex. If you need help, get in touch with Access Auto Electrics and Air Conditioning today! We’re expert auto electricians, and we can design and install the perfect dual battery system for your vehicle, ensuring it’s compatible with your lifestyle and equipment. Get in touch with us today to find out more or to get a quote on a dual battery system from Access Auto!

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