If you’re trying to set up a working 12v system in your car, van or 4×4 but you’re getting a little overwhelmed with all the technical jargon, don’t stress! We’re exactly the same – facts, figures and phrases fly over our heads sometimes, so we’ve created this simple-to-understand guide to selecting the right gear to charge your auxiliary deep cycle or AGM battery. Follow this guide and you’ll make sure you choose the right gear the first time, and avoid wasting your money on the wrong dual battery charger!

Firstly, why would you want a dual battery system? If you’re going camping and want to run 12v accessories like a portable car fridge, LED lighting or an inverter to charge the phones, tablets and laptop, you’re going to drain a lot of power from your battery. If you only have one battery, you’ll probably find that in the morning it won’t have enough power to start the engine! Definitely not ideal, especially if you’re out at a remote bush or beach campsite somewhere. A dual battery system lets you charge a second battery while you’re driving, and power all your electrical accessories off the second battery at camp, leaving the first battery safely alone so there’s always power to start your 4WD or car.

Now you know why you want a dual battery system, let’s talk about how to make it happen. You need a way for your car to charge the second battery when you’re driving, but isolate it from the first battery when you’re parked up at camp. The first option is to us an Adventure Kings Dual Battery System. This is what’s known as a ‘smart isolator’, because it uses a tried-and-true Voltage Sensing Relay to connect or disconnect the second battery from the first one. When it senses an input voltage above 13.5v (when the car is running), it connects the two batteries together and both charge up at the same time. When you turn the car off and it sees the voltage drop below 13.2v, it splits (or ‘isolates’) the second battery. Clever hey?

You may have heard of a different type of charger, known as a ‘DC-DC’ charger like the CTEK D250SA. The best way to understand this type of charger is to think of it like the battery charger you have at home in your garage. The only difference is, instead of plugging into the wall socket for its power, it uses 12v power from your alternator to run. The CTEK D250SA has some very clever functions, like the ability to vary the rate of charge depending on how full or empty your second battery is, as well as varying the rate of charge depending on what type of battery is being charged. It’s a true battery ‘charger’, whereas the Adventure Kings Dual Battery System is a ‘smart isolator’ – it doesn’t develop any power to charge batteries itself, rather it directs charge from the alternator.

So which one is best for you? For any vehicle prior to about 2010 running a single second battery as well as the starting battery, the Adventure Kings Dual Battery System is perfect. That’s because you’ll have an old-school alternator that just pumps full charge out at all times (assuming the alternator is healthy). However, if you drive a modern vehicle from about 2010 onwards, you’ll likely have what is known as a ‘smart alternator’. In an effort to reduce emissions, vehicle manufacturers realised they could electronically control the alternator to reduce its output depending on how full the battery was. If the alternator didn’t need to charge as much, load on the engine could be reduced and hence emissions would be lower. The problem is these alternators sometimes only put out as little as 13.0v-13.2v when you’re driving – nowhere near enough to charge a second battery.

The CTEK D250SA comes to the rescue here by being able to accept varying input voltages and still output a nice healthy 14.0V+ to the auxiliary battery. It essentially ‘smooths out’ the changing voltage rates from the smart isolator and allows your deep cycle AGM battery to be properly charged as you drive.

The other benefit to the D250SA is its ability to handle large banks of auxiliary batteries. These days it’s completely normal to run two, three or more auxiliary deep-cycle batteries in a 4WD so you can stay at camp for extended periods of time. The CTEK D250SA can charge up to 400Ah of batteries – enough to power your campsite for days at a time!

And remember, 4WD Supacentre has a price-match guarantee on the entire range of the incredible CTEK battery chargers. That means if you can find a better genuine price anywhere in Australia, we’ll match it! Terms and conditions apply, see https://www.4wdsupacentre.com.au/terms#ctek.