DC chargers, What are they? Do I need one?

What is a DC charger and do I need one?

This is one of the most popular questions we are asked today and we are happy to say that here at Home of 12 Volt, we attempt to educate you on whether you do in fact need a DC charger and where best to spend your money for the best 'bang for buck'. 

So lets get in to it; what is a DC charger?

Put simply, a DC charger is an 'in vehicle battery charger'. The charger will have the ability to convert a low voltage input from the vehicle (as little as 9 Volts) and increase it to produce an output voltage to your auxiliary battery to approx 14.4 Volts. In addition to boosting the voltage, a DC charger will operate through a number of charging cycles, meaning it will perform an analysis of the battery it is charging, perform a soft charge, bulk charge, etc, depending on the chemistry of the secondary battery.

So all of this is great, but again .. I hear you asking, why do I need one?

Again, put simply, it basically comes down to the changing emission laws on the market. It has been found that when vehicles are not running at full capacity, then their emissions are less. If the emission are less, then the vehicle manufacturers are given a big green tick of approval for the release of their new model vehicles and they hit the market with what we all know as a 'variable alternator / or smart alternator'. 

 But what is a smart alternator and how do you know if you have one? 

It's pretty safe to say that the majority of vehicles manufactured 2017 or later would have a smart alternator of some sort. This means that the vehicle was manufactured within a time in which it was made to comply with certain emission requirements.

The easiest way to explain how a smart alternator works is as follows:

When the vehicle is initially turn on, the alternator will run at full output, providing a good, high voltage through to charge your starter battery and provide power to all accessory connections throughout the car. After a few minutes, the starter battery will reach a full rate of charge and this will indicate to the vehicle that this 'bulk power' is no longer needed. The alternator will then reduce it's output provided, which results in a lower voltage output and lower ability to harness power throughout the vehicle's system. This reduction in output from the vehicle means the vehicle is not working as hard, and as a result, it will emit less pollution's across the board. But this doesn't help those of us that are wanting to charge secondary battery systems as now we have a low voltage output!

Introduce the DC charger.

The DC charger is designed to be installed in these vehicles will low voltage outputs, or variable (smart) alternators as it will act to boost the low voltage output back to a higher output of approx 14.4 Volts to your secondary battery. The DC charger is designed to installed in between the vehicle starter battery and the secondary battery you are charging (whether the secondary battery is located in the rear of the vehicle, the caravan, or even under the bonnet).

DC chargers have become more common on today's market for the above reasons and there exists many brands available for purchase, which can make things confusing to the average consumer looking to purchase one. So what do you need?

Consider this, the size of the DC charger will depend on what vehicle you are charging through (what size is your alternator), and also what size secondary battery bank you are charging.

If you are only charging one battery, say a 120 AH AGM, then a standard size 25 Amp DC charger is the perfect option. A 25 Amp DC charger will produce 25 Amps per EVERY HOUR you are driving. The DC charger needs a FULL 60minutes of driving in order to produce the nominated 25 Amps that the charger is rated to. This is the same when you choose a 40 Amp DC charger, you will need a full hour of drive time in order to produce the nominated 40 Amps from the DC charger back into your battery system. Once the vehicle has been switched off, then the DC charger is no longer operational.

Usually a 25 Amp charger is common for a secondary battery system of 1-2 batteries, around 120 AH each in size. When you increase your battery system from here, then it is usually recommended to increase the size of a DC charger to approx 40 Amps. Consider this, if you had 3 x 120 AH batteries = 360 AH of total capacity, and you were only using a DC charger that was 25 Amps, then you would be looking at a charge time of approx 14.5 hours (360 / 25) if the batteries were completely discharged. If you instead opted for a 40 Amp DC charger, this charge time would reduce to 9 hours instead* variables apply.

Home of 12 Volt recommend Projecta, Redarc, Victron and Powerhouse as good, reliable and cost effective options for DC chargers.

DC chargers will also act to 'isolate' the main battery from the secondary battery when the vehicle's ignition has been switched off. This isolation is designed to protect the starter battery and reserve it for the sole purpose of starting the vehicle.

Many DC chargers have a solar regulator connection offered as an additional component to the vehicle charge. The solar connection will act to regulate a 'non-regulated' solar panel to ensure it does not overcharge the battery it is connected to. Regulating a solar panel basically means that it will reduce the initial voltage produced by the panel (usually 17-24 volts) down a voltage suitable to the battery (usually approx. 14.4 Volts).

If you have any questions about DC chargers, we would recommend to contact our staff direct on 08 8391 3121 to discuss further

Battery box with dc chargerBattery isolatorDc dc