Dual Battery Systems
A lot can (and needs!) to be said about dual battery systems, there are a lot of products out there that are good for making setups that suit almost any budget or level of functionality.
When determining the right gear for powering your trip away, the most expensive option isn't always the best, and getting you the right products to suit your vehicle, power usage, and wallet will always be our priority.
But first, a second battery is not always essential for everyone who runs 12V devices in their vehicle, if your power usage is low enough you might simply want to replace your vehicles main battery with one that is designed to both start your engine and run other devices. This is an inexpensive option that will likely result in the single battery lasting longer than a cranking only battery would. If you need a new battery anyway because the old one failed, a dual rated battery makes perfect sense.
If your power usage dictates a battery whose primary job is running devices and not starting your engine, this is where things get more complicated.
Once you have a second battery you need a place to put it and a way to charge it. Regardless of where the battery is located, keeping it charged is the most important part of maintaining your system.
If your secondary battery spends its life somewhere in your vehicle it will likely get most of its charge from the alternator, just like your starting battery does, this means connecting the two batteries so that charge from the alternator flows through to both of the batteries.
The most important component of your dual battery setup is the part that allows current through your cable connecting the two batteries when the engine is running, but breaks the line when the engine is switched off for the purpose of protecting your starting battery by only letting your devices draw current from the secondary battery. What follows is a basic overview of some possible options.
The most simple method, somewhere along your positive cable connecting the two batteries you put a hand switch to cut the line as soon as you turn off your engine. This method is cheap and works magnificently as long as you always remember to switch it on and off as needed.
Voltage Sensitive Relay
A voltage sensitive relay is almost just like the manual hand switch method, the difference being that it automatically cuts or connects the line for you depending on if your engine is running or not. It does this by only allowing current through when it detects a charging voltage applied to the input side of the switch. This method is relatively inexpensive and is reliable as long as your alternator is putting out an appropriate charging voltage.
Although this is the most expensive method of charging your secondary battery while it is situated in vehicle, it is also the most effective way of keeping your battery charged and in the best possible condition. The DC-DC charger acts as a switch cutting the line between your batteries just like the previous options do, but it has the added benefit of taking the raw current from your alternator and transforming it into the optimum voltage and amps required by the secondary battery.
DC-DC chargers are particularly beneficial in newer vehicles with variable voltage alternators, and in cases where there is a long cable seperating the two batteries. DC-DC chargers are capable of taking unsuitables voltages, whether too high or too low, and transforming them into appropriate charging current. The best way to think of a DC-DC charger is that it is exactly like the smart battery charger you keep in your garage, it just sits under your car bonnet and is powered by your alternator.
Many brands also include solar inputs into their units, allowing you to plug solar panels into the charger without the need to have an additional solar regulator between the panel and the charger.
This has been written only as a very general overview of some of the methods used to charge secondary batteries and isolate them from starting batteries.
Everything you need to know would require a great deal more information, but this article gives you some information about the most commonly asked question when it comes to dual battery setups. For more information we are happy to talk to you about your needs via email, telephone, or by dropping by to see us in-store.