so if you want to install a secondary fuse block this is what you'll basically
need I've got some six b&s cable I've chosen 6b&s for a specific reason
which I'll talk about later and most importantly I also have a circuit
breaker which is put between the battery and this cable so in the event of
electrical fault somewhere along this cable length this shuts off and stops a
fire after that I've got a STfuse block holder then of course various
connectors grommets and shrink wrap and then the lighter duty cable for running
to my accessories such as this 12 volt socket so let's get into the
installation for your fuse block i'd recommend something like this st fuse
block holder this one comes with the negative bus which i'd recommend as it
allows you to trace all your earths back to the one single source which is your
12-volt battery so your main cable lead will come here connect to this the positive
connects to this it reduces any chance of reliability issues being introduced
from poor earths if you try earthing to the chassis in various points something
like a defender for instance with corrosion in different areas dissimilar
metals cause aluminium corrosion old rust dirt in between panels it reduces
the effectiveness of the earthing system but by running all the earth back to one
place then you reduce or minimize completely that reliability issue from
poor Earth's plus all the fuses are in one place and can be labeled and easily
found these are made in six and twelve block fuse holders so this time I
opted just for a six fuse holder as I don't need much more but should ever
want to upgrade I can pull this out swap it over to the 12 fuse variety and I'm
good to go again I found a spot in the back end in my
rear storage box where I'm going to install the fuse block it's a fairly
protected spot so I know it's safe and it's easy to get to if I have a blown
fuse
another thing to consider for your wiring to ensure reliability is to make
sure you don't have any places where you've drilled a hole and run a wire
through that is bare steel it's using this scrap steel as an example if a wire
went through a hole it would sit on the bare steel and over millions of
corrugations it would sit there rubbing and rubbing and rubbing until eventually
the insulation rubs through and it earths to your bodywork which could
cause a fire or at least many blown fuses so to stop this from happening you
should always use rubber grommets these basically run the cable through it so
you're protecting any holes in your firewall or any bodywork panels you've
ran wires through and this now protects the wire so it's bouncing around and
protected by insulation another possibility is to use split tubing if
you're running a wire on the outside of the vehicle this is a simple way of
running it into the split tubing through in the inside
as you see there it's nicely protected so that could also be used if running
through a wall a hole in the in the bodywork just again making sure you have
a reliable electrical system which isn't gotta start a fire when you're in the
middle of nowhere. The following section is a general guide for entertainment
purposes only. Consult an auto electrician for your particular needs.
So let's look now at the two cables I've chosen this is six b&s cable it has a
thirteen point five millimeter square cross-section of copper and has a maximum
carrying capacity of eighty two point four amps at thirty degrees Celsius this
one is six millimeter auto cable and it's 11 b&s approximately it is a
four point five millimeter square cross-section of copper and has a
maximum of thirty eight amps so to work out which cable is good for what we need
to take into consideration the voltage drop so there are three ways of
calculating voltage drop for your system there are formulas you can use which I
have two here to show you as an example there are tables online plenty
available online Just do a quick search for 12 volt voltage drop calculator
or table and there are apps available as well such as on your smartphone or as
free calculators online so there's plenty of ways to do it if you don't
want to work out the maths itself let's look here at a couple of these formulas
which you can work out so voltage drop equals amps by the total length of a
positive and minus so if it takes three meters to run to the battery to the fuse
block then it's three meters of positive and three meters of negative
totaling six meters You times that by the resistance the ohms per meter which you
can get from the manufacturers website so in this case six b&s I made a
theoretical 50 amp carrying capacity just in case I want to add a anderson
plug in the back end in the future and run maybe a small inverter for 240
electricity or if I buy a secondary fridge which might take another six amps
or so to run or any future additions I want to make sure that I never have to
upgrade this again so 50 amps by 6 meters at the two lengths times the
resistance equals point four two volt voltage drop which works out three point
five percent loss so three point five percent is between three and four
percent which is about the maximum you want in the 12 volt system so 6 b&s
for my particular cable run here of 3 meters from the battery to the fuse
block is excellent this will be plenty for all future additions in reality I'm
only drawing twelve point five maximum now with all my current accessories so
assuming I do get a second fridge or a little camp oven or something crazy like
that then we'll say 20 amps of a maximum current draw by the six meters by the
resistance equals 0.16 volt or 1.4 percent loss so this is more than
capable of running a highly efficient electrical system to my
fuse block without any real power loss let's look at the six millimeter auto
eleven b&s. this is running from the fuse block out to the accessories the most
I'd ever draw through a 12 volt cigarette lighter adapter it'd be about
10 amps a laptop is currently the greatest draw I have which is at a 8
amps so assuming a 10 amps for a bit of leeway 10 amps by the 8 meters by
resistance equals 0.33 volts or 2.7 percent loss so again this is below the
three percent recommended maximum so this is also quite sufficient of
carrying 10 amps the 4 meters with less than 3% voltage drop which makes
quite an effective reliable system another calculation you can get if you
do not have the ohms per meter or ohms per kilometer manufacturer's numbers is
to use this formula down here voltage drop equals a total length of the
positive and minus times the amps you want the cable to carry times point zero
one seven which is a standard rating for resistance of copper divide that by the
copper cross-section in millimeters squared which you get up here such as
six millimeter Auto is four point five millimeter square you can get that from
tables online if you don't know the exact number that works out down here
to 0.30 volt voltage drop which works out very similar to the 0.33 volts of 2.7%
again using either formula I'm well within a safe range for voltage drop for
this particular sized cable for the length that I wanted to carry and the
current it must transport so hopefully that's a bit of a rundown of why I've
chosen these particular cables another thing to note too is I also chose to get
fully sheathed dual core positive and negative in a single wire that
just adds an extra layer of protection on the outside to protect the wire from
chafing I also chose marine tinned copper cable which is a
higher spec for marine environments good for when it's getting near water such as
a Defender going through water crossings as this cable will be running on the
outside of the vehicle down below along the bottom chassis rail so it's just one
extra level of protection to ensure a long-term reliable system not necessary
but I was happy to spend the extra few dollars to get tinned copper wire I
found a spot I'm going to run my cables unfortunately there's a lot of wiring
there already so rather than trying to force the cable through the grommets
already in place I'll drill a new hole put a new grommet in and that way it
keeps everything separate and there's less chance of wires chafing and rubbing
together or contacting bare steel and rubbing through the insulation
and there's two of my finished cables one end has Spade terminals for the
12-volt sockets and the other end ring terminals for the fuse block
everything's crimped heat-shrinked so there's very little chance of any
moisture getting into the cable and causing corrosion down the track this
cable should give me many years of reliable service in the outback when
running cables on the outside of the vehicle I like to add split tubing just
as an extra layer of protection although this cable does come in its own
protective sheath it's just one extra layer which protects against heat for
example if it comes close to the exhaust or from any other stones or chips or
potentially even rats or mice out in the bush climbing in and having a nibble
which I've had happen before all the connections were completed with the
battery and the fuse block wired up I added a cover over the socket
connections for protection on the passenger side I have a 12 volt socket
and a dual USB charger and the driver side to 12 volt sockets the fuse box
also powers all the lights in the backend I also did something crazy and
bought myself a 12 volt oven.
Did you enjoy this video? Then please click subscribe and share it on Facebook
and Twitter. If you'd like to help support me create new videos then please
consider becoming a Patreon. Click on the Patreon button on the screen now. Thanks