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FAQ - Dual Battery Systems/Setups

In here you will find answers to commonly asked questions about verious modifications. You will also find some great DIY's for doing mods to your Isuzu. If you have a mod to add here, please contact a member of the FAQ Team.

FAQ - Dual Battery Systems/Setups

Postby Pissy » Thu May 21, 2009 2:23 pm

Dual Batteries Sytems, this is a huge topic and is always open to debate, so I tried to keep any opinions and or brands to a minimum . Any products mentioned or shown, are purely there as an example. I am in no way recommending any brands or types of setup over another. Plus any figures stated here are only approximates as every product has a slightly different set of numbers.

Before you even think about a Dual Battery System, you should consider if you really need one in the first place, how often you will use it, how much it will cost and finally, whether you have room to fit it all in. This FAQ does not get into the battery side of it as it has already been discuss here, viewtopic.php?f=26&t=104
One other thing to remember with Dual Batteries systems and setups is that some systems recommend using identical batteries for starting and auxiliary applications, while others don't, plus some battery types can be mixed with others, while other batteries should not be mixed.
Best to discuss these points with a battery and dual battery System specialist.


BACKGROUND
Firstly, a dual battery system usually means “More than one battery” and can have more than 2 batteries. Just because a car has 2 batteries doesn’t mean it’s a dual setup. Confused,..let me explain, some vehicles, especially larger cars or and cars in cold climates can have a "PARALLEL" system which increases the capacity of the batteries making it more powerful to start large or cold engines. The Other system, again usually found in larger vehicles, is called a "SERIES" system and its used to increase the voltage to 24 volts. Both systems can incorporate 2 or more batteries to act as ONE battery and therefore is not a true Dual Battery system.

Batteries in Parallel
battpara.jpg


Batteries in Series
battseries.jpg


A true Dual Battery System (DBS) is one that uses a starting battery(cranking battery) and then has second/Auxiliary battery (usually a deep cycle batteries but not always the case) for uses other than starting your car. So the basic Definition of all DBS is a system where the auxiliary battery is isolated from the main battery and charging system by means of a Switch, solenoid or Electronic Isolator.

As you can now tell, there are 3 ways to setup a DBS, each will have its own positives and negative, which I only touch on. Before buying a setup make sure what you are buying is compatible with your alternators ampage, or you might overload, damage and/or destroy your new setup.


1. The Switch
This is the simplest and cheapest of all setups BUT it can lead to flatting batteries by accident too easily. The switch is basically a manual operation that you physically turn a switch at the batteries on and off. Batteries go flat too easy if you forget to turn the switch on (no charge goes into the aux battery) or turn off at the right time (and then the starting battery gets drained as well).

Battery switch.jpg


2. Solenoids
Solenoids can be divided in to 2 types, Simple and Smart Solenoids.

Simple or Plain Solenoid
These Solenoids have an electromagnet which pulls a steel cylinder in when you connect your battery to the electromagnet coil wire. So the mechanical motion of the cylinder can be used to close switch contacts or valves of various sorts. The Solenoid receives a large electric current from the car battery and a small electric current from the ignition switch. When the ignition switch is turned on, (when the key is turned to start the car), the small electric current forces the solenoid to close a pair of heavy contacts, thus relaying the electric current to the auxiliary battery. These are cheap and easy to install and do OK.

solrnoid.jpg


Relay/Smart Solenoid (Voltage sensing)
These Solenoids works as mentioned but its primary role is ensuring the vehicle’s main battery is fully charged before the second battery receives charge. It does this by monitoring the voltage of the starting battery and will only energies the solenoid and links the auxiliary battery when the starting battery reaches approx 13.2 volts. Conversely, the control unit disconnects the auxiliary battery when the starting battery voltage drops below approx 12.6 volts. This process is continuous and automatic. This setup is affordable and easy to install, deemed to be hassle free, reliable and many people have gone for this.

red arc.JPG


3. Electronic Isolator
These devices do the same as smart Solenoids instead of using an electromagnet, it uses electrical circuits and diodes. This allows the unit to have more features such as solar top up charging applications, spike and surge protections. These are by far the most expensive but offer more features and options than anything else on the market therefore many people opt for this setup.

piranha.jpg


Before you even think about a Dual Battery System, you should consider if you really need one in the first place, how often you will use it, how much it will cost to complete and finally, whether you have room to fit it all in. Fitting a second battery tray usually requires some modifications in your engine bay. In my case I had the move the fuel filter and power steering reservoir about 20cm plus I removed the EGRs (were not working anyway) to allow for a larger battery, mine is a 130amp hours and is bigger and heavier than a normal N70 battery.

engine.JPG


This system does not get into the battery side of it as it has already been discuss here,
One other thing to remember with Dual Batteries systems and setups is that some systems recommend using identical batteries for starting and auxiliary applications, while others don't, plus some battery types can be mixed with others, while other batteries should not be mixed.
Best to discuss these points with a battery and dual battery System specialist.


Simple wiring diagram of the average setup using any of the system setups discussed.

smart solenoid.jpg





Cheers
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94 3.1L MU,2.5"suspension lift,2"body Lift,33"Bighorns,F&R Autolockers,Rock Sliders,winch bar,240 lightforces,UHF,120amp alternator,dual batteries,snorkel,turbo timer etc
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Pissy
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