When you’re on a camping trip for a few days, you want your appliances to run smoothly without any interruptions. You could connect them to your vehicle battery, but what if your gear draws too much power and leaves you stranded with a flat battery? You could always leave your engine running to prevent this, but that’s both a noisy and costly exercise. One solution is to charge your battery with portable solar panels or a generator. However, maybe you do not have any solar panels or a generator, or maybe the weather conditions do not permit you to generate enough solar power. A dual battery system offers the perfect solution to overcome this problem.
A dual battery system offers a quick and safe way to recharge your batteries, ensuring your starter battery isn’t drained flat from running your gear.
A standard dual battery system consists of two batteries: a primary battery (your vehicle’s battery), a secondary battery, cabling to connect the batteries, and a battery isolator (this protects both batteries from being drained). In this system, the vehicle’s alternator will charge the primary battery; the charge will flow through the cabling and the battery isolator to the auxiliary battery.
It is recommended to use a deep cycle battery as your secondary battery because it is designed to be charged and discharged on a regular basis, and provides sustained power over longer periods of time. A starting battery is not designed to be frequently discharged and charged, and as such will reveal a shorter battery life than a deep cycle battery.
Although standard dual battery systems will do the trick, they have one big disadvantage: they typically cannot charge your secondary battery back up to full. For this reason, we recommend to use a DC charger rather than a battery isolator. A DC charger draws power from your primary battery, increases the voltage, and automatically manages the current flowing to your auxiliary battery.
A DC charger is a charger that supplies a constant DC or pulsed DC power to the battery that is being charged. DC chargers are particularly popular within the camping environment as they can boost the voltage going to the auxiliary battery, which means there is no voltage loss (unlike with the battery isolator).
Unlike a standard battery isolator, the DC charger can achieve a maximum run time and a maximum life expectancy from your auxiliary battery. A basic battery isolator can charge your secondary battery for approximately 60 – 70 percent whereas a DC charger can charge it to 100%. A fully charged secondary battery is essential because it maximizes the battery life, guarantees full value for your money, and offers a maximum running time of your appliances in between charges.
Additionally, in the last few years new Australian vehicles have to meet the Euro 5 exhaust emissions standards, and as such car manufacturers had to introduce a new technology: ECU. This technology was designed to connect with the alternator and to monitor the electrical load, and can shut off the alternator in certain circumstances or adjust its output voltage. This makes it harder for campers to charge their auxiliary battery solely through the primary battery, because it can be interrupted at any given time by the ECU.
Depending on the battery you’re using and the appliances you are trying to run from your dual battery system, you will need a different type of DC charger. It also depends on your vehicle and the kind of alternator it has.
These alternators are found in most vehicles manufactured before the year 2000. They are able to charge your secondary battery to approximately 70 to 80 percent. With these alternators you can get by without using a DC charger, but if you’re using a long cable to connect the main battery with the auxiliary battery, you are advised to use a DC charger as it will overcome voltage drops and will in fact boost the voltage.
Most vehicles manufactured after the year 2000 that use a Common Rail Diesel engine will have a Temperature Compensating Alternator. With this alternator, your dual battery system will charge a little less than the Fixed Voltage one and will charge to a maximum percentage of approximately 60 to 70. When the engine is running, it will charge the auxiliary battery at about 13.4V and when the engine is cold, it will charge at roughly 14V. Because deep cycle batteries need more than 14V to charge completely, it is recommended to use a DC charger for this type of alternator if you want to charge your battery up to full.
As mentioned above regarding the ECU, these alternators are installed in vehicles that use Common Rail Diesel and Petrol engines which were typically manufactured in the last 3-4 years. These alternators will charge the auxiliary battery at less than 13V which is far too low to charge a deep cycle battery, and won’t activate a standard isolator. As such, a DC charger is a must for a dual battery system in these types of vehicle. Furthermore, because the ECU recognises the current in your vehicle’s electrical system, additional appliances have to be grounded to the vehicle chassis (not the primary battery’s terminal) to be correctly recognised.
As a final note, keep an eye out for DC chargers that feature built in solar regulators, making it easy to add an additional charging option to your auxiliary battery. If you’re going to be camped out for an extended period, having solar allows you charge less from your vehicle’s alternator. One thing to keep in mind though is that you can’t connect two regulators together; portable solar panels with an existing regulator will need to either be wired with a bypass to skip the built on regulator (going straight to the DC charger regulator), or have the regulator removed altogether.
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