A dual battery system is one of the best upgrades you can make to your 4WD, caravan, or camper – giving you the ability to run fridges, lights, fans and other 12V gear without draining your starter battery. But get the setup wrong, and you could find yourself stranded, or with a battery system that just doesn’t perform as it should.
Here are five of the most common mistakes people make when installing a dual battery system – and how to steer clear of them.
1. Using the Wrong Cable Size
The mistake: Running undersized cables between your batteries or to your loads.
Why it matters: Undersized cable leads to voltage drop – meaning your gear may not get the power it needs, and your secondary battery may never fully charge.
How to avoid it: Use appropriately thick cable for the current you're drawing and the distance you're running. As a general rule, the longer the cable and the higher the current, the thicker it needs to be. Our KickAss Wiring Kits take the guesswork out of this – they’re designed for real-world use with heavy-duty cable throughout.
2. Poor or Incomplete Earth Connections
The mistake: Only earthing one battery – or not earthing properly to the chassis.
Why it matters: A bad earth can lead to unreliable performance, battery drain, or your system not working at all.
How to avoid it: Always ensure both batteries have solid earths to the vehicle chassis, with clean, rust-free metal contact points. Use short, thick cables and avoid relying solely on small bolts or dirty connection points.
3. Not Using a DCDC Charger
The mistake: Relying on an isolator or direct alternator connection in modern vehicles.
Why it matters: Many new vehicles use smart alternators that reduce output voltage to save fuel – meaning your second battery might never charge properly.
How to avoid it: Always use a quality DCDC charger. KickAss DCDC Chargers not only boost and regulate voltage for proper charging, but also handle solar input, battery type selection, and automatic dual input switching.
4. Mounting Batteries in Unsafe or Unsuitable Locations
The mistake: Installing your battery in a hot engine bay or somewhere without ventilation.
Why it matters: Heat shortens battery life, especially for lithium, and poor ventilation can pose a safety risk if using non-sealed lead acid batteries.
How to avoid it: Use lithium batteries in cooler locations like the rear of the vehicle or in a battery box. Always ensure good ventilation, secure mounting, and keep clear of water ingress or direct heat sources.
5. Mismatching Battery Types
The mistake: Mixing different chemistries, ages or capacities in the same system.
Why it matters: Mismatched batteries charge and discharge at different rates, which can cause imbalance, reduced capacity, or premature battery failure.
How to avoid it: Use batteries of the same type (e.g. lithium to lithium), size, and ideally from the same brand and batch. If you're adding to an existing system, consider replacing both batteries or keeping them on separate circuits.
Final Thoughts
Setting up a dual battery system isn’t rocket science – but it does require attention to detail. Avoiding these common pitfalls will help ensure your setup runs reliably, safely, and gives you the off-grid power performance you’re counting on.
Need help designing the perfect dual battery setup for your vehicle or camper? The KickAss team is here to help with expert advice and top-quality gear that’s built for serious adventures. Give us a ring on (07) 3123 4715, or drop into one of our retail stores – we love a chat.
