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).
What is a 12-volt battery charger used for?
A 12 V - 12 V battery charger (or DC Battery Charger) is designed to charge and maintain 12V batteries commonly used in vehicles, caravans and camping setups. It can be used with various battery types, such as AGM, gel, lead-acid and lithium. It regulates the charging process to ensure optimal battery performance, extending the life of your battery and keeping it ready for use.
What types of batteries can be charged with a DC charger?
A DC to DC charger is compatible with a range of battery types, including AGM, gel, calcium and lithium. These chargers are designed to manage the specific charging needs of each battery type, optimizing performance and longevity. Most DC Chargers will require you to set the battery type on connection, this will act to adjust the charging profile accordingly, ensuring a safe and efficient charge.
Do I need a DC to DC charger for solar?
Yes, and no. Many DC Chargers will act as a solar regulator, allowing you to connect an unregulated solar panel to charge your auxiliary battery. It regulates the energy from your solar panels, providing the correct charging current to your battery. This ensures your battery charges safely and efficiently, maximising the power you receive from the sun.
If you do not choose a DC Charger with a solar regulator, then you must ensure the solar panel is regulated either internally, or via the use of another solar charge controller.
Do I need a DC to DC charger for a lithium battery?
Yes, lithium batteries require the use of a DC to DC charger to ensure adequate charging. Unlike AGM or lead-acid batteries, lithium batteries have different charging needs. A dedicated Lithium DC battery charger is ideal to regulate voltage and protect the battery from overcharging or damage, maximising its lifespan and performance.
If I do fit a DC Charger, do I need to run the ignition / low voltage wire?
In order to understand if you need the ignition wire, it is important to first understand how a DC charger operates. When no ignition wire / over-ride is used, the DC charger will act as 'voltage sensitive.' This method requires the vehicle starter battery to reach a voltage of approx. 13.2 volts to engage the DC charger and allow for charge to flow through to the secondary battery. When the vehicle's starter battery falls below 12.7 volts (indicating the ignition is off), the DC charger will disconnect and will act to isolate the start battery from the secondary battery. This method is the perfect option for vehicles that maintain a higher voltage output (13.2 volts or more). In this case, the ignition wire (Blue wire) will not be required and is optional to fit.
For vehicles that produce less than 13.2 volts, or, for vehicles that have a voltage output below 13.2 volts when running, they will require the ignition / over-ride wire to be installed. The ignition wire will act to 'over-ride' the voltage required to engage the DC charger. With the ignition wire installed, the DC charger will activate immediately when the vehicle's ignition is ON and will disconnect immediately when the vehicle's ignition is OFF. This will occur regardless of the voltage of the vehicle's starter battery. The ignition wire acts to overcome the potential problem of the DC Charger disconnecting when used in low voltage vehicles. It will allow the DC charger to remain active in the vehicle until the ignition has been switched OFF.
What can I do to make the DC Charger low voltage without running an ignition wire?
If you do not have the ability to run an ignition wire, then the easiest alternative to still have the DC Charger run as 'low voltage' would be to tap the ignition wire into the positive feed to the battery of the DC Charger. This will basically 'trick' the DC Charger into operating immediately, regardless of voltage. HOWEVER, it is important to note that doing this will require you to INSTALL AN UNDER BONNET isolator in order to separate the DC Charger from drawing down the main starter when the ignition is off.
If you do choose to tap in the ignition wire to the positive feed of the battery, this will remove the ability for the DC Charger to act as an isolator. An under bonnet isolator will be required in order to protect the main battery from discharge when the vehicle has been switched off. We would recommend to use the RELAY MOUNT for easy installation.
If you have any questions about DC chargers, we would recommend to contact our staff direct on 08 8391 3121 to discuss further