A BRIEF EXPLANATION OF DUAL BATTERY
SYSTEMS
On every 4x4
forum I come across, someone is always asking ‘Which dual battery system do I
choose?’ No doubt they have read through several online articles only to become
even more confused about the options available for their 4x4 set-up. So with
this article I will briefly explain the different systems that I believe to be the
most beneficial to the everyday 4x4 owner.
The first
question I ask people when they ask how much a dual battery system will cost
is:
How much is
your budget?
Some people
see this as a marketing ploy but honestly there is no point in me trying to
sell you a dual battery system built around the Redarc BCDC1240 charger when
your budget is $800, as the charge unit alone is over $450 not including
battery, cables, battery tray etc.
The second
question is:
What are you
using the system for?
There is no
point in having a $1700 system in your vehicle when you only plan on using it
twice a year or to simply run a fridge overnight, unless you feel that is really what you
need. You will also need to know what you will be running off it and the
wattage of each of these items.
If a
customer can answer these two questions then they are already well on their way
to designing the system they require.
I will break
down the three most popular systems as follows:
System 1 -
Manual dual battery switch
This is
perhaps the most basic dual battery system available and is built around a
manual battery switch (such as Narva 61090) where the user selects the battery
required to be used and/or charged or both. A very simple system that works
well however the switch and wiring required is quite cumbersome. This system is
what I call a ‘direct parallel system’ (DPS). There is also the downside of the
user having to remember to switch the master switch to the desired setting,
which if forgotten could inadvertently drain both batteries by accident.
·
Good
for high current situations, winch etc.
·
Easy
to use.
·
Relatively
cheap although larger cable size can become expensive over larger runs.
·
Not
recommended if different battery types are being used together.
·
Can
jump start vehicle if auxiliary battery is charged.
System 2 –
Voltage sensitive relay/solenoid
This is a favourite
amongst most 4X4 owners, utilising a solenoid (such as the Redarc SBI12) due to
the relatively low cost of the solenoid and the ease of installation. This
simple solenoid (also a DPS) detects when your main (start) battery has reached
a high state of charge and then closes the contacts to join the two batteries
together to start charging the auxiliary battery. These solenoids have served
the industry well for a number of years but with advances in battery technology
they have since been less desirable when using different battery types together.
·
Simple.
·
Cheap.
·
May
not work with newer vehicles that utilise variable voltage alternator output.
·
Can
also cater for jump starting.
·
Can
also be used where higher current demand is required.
·
Can
also be used for winch applications.
System 3 –
The DC to DC Charger
The DC to DC
Charger has really changed dual battery systems in the last few years, allowed
us to do so much more with our dual battery systems and take care of our
auxiliary batteries so much better. Put simply, the DC-DC charger has allowed
us to charge batteries efficiently, and electrically isolate the main battery
and the main charge system (the alternator). The main benefit of the DC-DC
charger is the ability to be able to charge different battery types using pre-set
charge algorithms selected for the battery type being used. This ensures that
the battery being charged is charged at the optimum rate which means it is
charged as high as possible (some batteries require different charge rates to
reach full capacity). The other benefit is that electrically both batteries are
separated and if either battery fails or starts to degrade then it won’t
compromise the other battery, as the DPS type may.
·
Maximises
battery life by charging to optimum level.
·
Expensive.
·
Set
and forget – no user input required.
·
Current
output is limited to capability of unit.
·
Can’t
be used for jump starting alone.
·
Capable
of supporting small amounts of volt drop.
In both of
the DP systems, if one battery starts to fail or degrade then it will start to
drag the other battery down with it. If different battery types are used in the
DP systems then this will also cause premature battery failure (over time) and
it’s always recommended that if one battery fails in this instance, then both
batteries should be replaced at the same time. In saying that, if matching
battery types (preferably make and model) are used in the DP system then this will
maximise battery life. Yes of course everyone will know someone that has used
the DPS type, never had to change a battery and will never want to part with
the money to buy a DC-DC charger. Each system has its strengths, weaknesses and
its place in the dual battery world but I will never recommend using different
battery types together in a DPS type set-up.
This article
was never intended to explain dual battery systems at length but rather, give
the reader an idea of what is out there and how it might benefit them. Time
again we have had customers come in saying they got a dual battery system
installed but they have no idea what they paid for or how it works. If you
don’t know what you paid for then how do you know what the system will do or if
it’s right for you? Some customers have come in thinking they want a super
dooper dual battery system that could cost upwards of $800 only to be sent away
with a Arkpak type battery box because that is all that they require to run
their fridge for a few hours or overnight while fishing every now and again.
If I have
missed something or you feel something else might be more relevant then don’t
hesitate to contact me.
Regards,
Gavin.
Current Tech Automotive
No comments:
Post a Comment