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The MEGA Guide to Wires for Campervans

Updated: Sep 23

Wiring is EVERYWHERE. 🔌 Inside the phone or laptop you're using; in the lights above your head; even in your grandmother's pacemaker! Yet, so few of us know anything about them... In this guide you will learn everything you could ever want to know about wiring as it relates to campervans. What are the different types of wires? How do you size wires? How do you connect wires together? How do you crimp, solder, and heat shrink? This information-packed guide will give you everything you need to know about how to wire up your campervan electrics. I'm Shane, I've been teaching people to convert campervans for many years, I'm the author of The Van Conversion Newsletter, the van conversion instructor at Udemy, and the proud owner of a beautiful self-build campervan called Beans. So let's jump in and have a look at wires for campervans!


The ultimate guide to wires for a campervan (cutting, crimping, connecting)

Items linked in this guide are affiliate links. By using these links, you are helping me to continue writing free educational van conversion content!

You can find the full list of van conversion supplies here.


Index

 

Note: Before we hop in, you will definitely want to grab yourself a wiring diagram which you can get for free by signing up to The Van Conversion Newsletter (the wiring for an entire van conversion is included in the diagram 🙂 - wiring diagram gets sent out to you straight away).

 

This is the complete list of supplies mentioned in this guide

Tools:

Wire Connectors:

Wires: Sizing, Material, and Types

Electricity is the flow of electrons. When electrons are "lost" from an atom, the free movement of these electrons constitutes an electric current. Electricity travels through wires - a metal conductor that is sheather by an insulator (usually rubber or plastic). A conductor is a material that allows electricity to flow through it. The insulator blocks electrical force from passing through it.


What types of metal are wires made from?

Wires are typically made using the following metals:

  • Copper

  • Aluminium

  • Gold

  • Silver

  • Tungsten

Copper is by far the most common metal used. It is highly conductive, bendy, thermal resistant (safer), and a lot less expensive than most of the other metals.


Aluminium is the second most common metal used in wiring. It is very light weight, long-lived, an extremely good conductor, and corrosion-resistant.

Copper wire (left) vs. Aluminium wire (right)
Copper wire (left) vs. Aluminium wire (right)

Aluminum has 61 percent of the conductivity of copper, but is only 30 percent of the weight of it. Consequently, aluminum offers a lower cost per amp and provides up to 48 percent mass reduction over copper. Aluminium is becoming increasingly popular and I would recommend it. However, if you use the campervan a lot by the sea, you should go for copper as aluminium corrodes easily.


What is tinned cable?

Sometimes copper wire will be tinned, whereby the wire is coated with a thin film of tin to protect against corrosion. This gives the wire a silvery appearance as opposed to the usual brass/copper color. Tinned cable is useful if you are using the campervan by the sea. Solar cable should be tinned as being on top of the campervan, it is constantly exposed to the elements.


What is the difference between solid wire vs stranded wire?

Solid wires consist of a solid core, whereas stranded wire consists of several thinner wires twisted into a bundle.

Solid vs stranded wiring

Stranded (concentric) wire has many layers of wires, gently twisted into a helix shape. Each layer has six more wires than the previous layer (6^n).


Stranded wire is more flexible and more resilient to damage and being bounced about.

Solid wire is a better conductor, but a lot less flexible.


For campervans (and in all vehicles), we should use stranded wire.


What are the different types of wire insulators?

Three types of wire insulators are available: plastic, rubber, and Fluoropolymer.


Plastic:

Plastic insulators have a number of useful characteristics ideal for wire insulation; including ductility, electrical resistance, UV resistance, and fire resistance. PVC is the most commonly used and is quite cheap.


Rubber:

Rubber insulators are more flexible than plastic, especially at lower temperatures. They are resistant to a broad range of temperatures, UV radiation, and wear.


Fluoropolymer:

Fluoropolymers are polymers that are especially resistant to bases, acids, and solvents. These are specialized wire insulators


For campervans, people will usually use plastic (PVC) insulated wires.


Note: All wire insulation has a temperature rating printed on the outside; the maximum safe operating temperature (eg. 200°C).



How to calculate wire size for your campervan

To calculate the size (diameter) of wire needed in a system we need two variables:

  1. The length of the wire (distance to the appliance AND back)

  2. The amps the wire will be carrying (ie. the amp rating of the appliance)

  3. Is the circuit critical or non-critical? (voltage drop discussed below)

When we have these two pieces of information we can plug the variables into the wire size calculator over at http://circuitwizard.bluesea.com/ or consult the BlueSea diagram below (the formula for wire sizing is quite complex, so use these tools instead!)


van conversion wire sizing diagram

Note: AWG (American Wire Gauge) and mm² (cross sectional area) are the units of measurement used to describe wire size. AWG is used in North America, mm² is used everywhere else. There is a third unit of measurement called CMA (Circular Mil Area) which is very precise, and technically better when dealing with stranded wire. However for most people, this level of precision will not be needed.


What is voltage drop and why is it important?

Voltage drop occurs when the voltage at the end of a section of cable is lower than at the beginning. Voltage drop normally occurs when there is resistance in current flow usually due to cables, contacts or connectors.


We can only allow a 3% voltage drop on sensitive/critical circuits, whereas we can allow up to a 10% voltage drop on non-critical appliances (eg. LED lights).


Here is the wire sizing I used in my conversion (you can get a free wiring diagram of my system by signing up to The Van Conversion Newsletter):

  • 12V appliances: 14AWG

  • Solar panels to solar charge controller to batteries: 8AWG

  • Batteries to inverter: 2AWG

  • Batteries: 0AWG

For a more detailed guide on wire sizing, fuses, and electrical concepts in general, you can check out this guide.


Bonus content: If you're interested, here's a cheesy video showing you how wires are made!


How to cut and strip wires

Knowing how to cut and strip wires is as important to an electrician (and van converter) as knowing how to use a knife is to a chef. It's the basics, upon which all else is built.


How to cut wire

Here are the three types of wire cutting tools that are typically used to cut wire:


1. Small wires (22-10AWG) can be cut using a wire stripping multi tool, or simple pliers. A multi tool cuts, strips, and crimps smaller wires. I would definitely recommend getting one!

Wire stripping multi tool van conversion

2. Medium-sized wires are commonly cut using a cutting pliers (Knipex).

Knipex for van conversion

3. Large wires are cut using large wire cutters, which give extra leverage.

Large wire cutters van conversion

How to strip a wire

Stripping a wire, simply means cutting back the rubber insulator around the wire


It is important that we strip the wire correctly, meaning not nicking, cutting, or breaking wire strands!


If we nick or cut strands, it results in decreased electrical and mechanical strength. If we have an uneven or tapered strip, it will result in a poor crimp connection (for connecting to another wire), it will also give less effective insulation support

Examples of bad wire stripping

To strip a wire, we use a wire stripping tool.


Small wires (22-10AWG) can stripped using a wire stripping multi tool.


Wire stripping multi tool van conversion

Large wires are typically stripped manually using a Stanley blade.


To strip a wire using a Stanley blade, hold the wire with your thumb and trace around the rubber with the knife.

stripping a wire with a stanley blade

It's very important that you don't press too hard with the Stanley blade when you are cutting as there is a high likelihood that you could cut some of the strands off the wire. Bare in mind that with stranded wire, 63% of the wire strands are on the outside!

cross section of stranded wire

How do I connect wires together?

There are four ways we can connect wires together:

  • Twisting

  • Screw / Lever connectors

  • Crimp connecting (cold welding)

  • Soldering

Note: We should always try and cover our electrical connection with a heat shrink (or at least electrical tape) after we have made the connection. We will discuss heat shrinking after we learn about the four methods above. Jump to: Heat Shrinking.


Twisting

Twisting is the most primitive technique for connecting two wires together.


Twisting wires together by hand

If you're feeling really quick and dirty, you can twist the exposed ends of the two wires together and pop some electrical tape over the connection to insulate it. This is not recommended as the connection may not be very good and it can very easily break apart.

How to twist wires together

Wire nuts

A slightly better way of connecting wires together by twisting is to use wire nuts. Wire nuts are the oldest wire connectors around, they have been around since 1929.

connecting wires with wire nuts

Wire nuts definitely have their downsides though;


You need to make sure that when you are removing the wire nut, you should snip off the top of the wire too, as the wire nut leaves bite marks (indentation) in the wire after it is removed which can affect conductivity and cause overheating (smaller wire = more heat).

Twisting wire in wire nut

You should also make sure to use the same size wires when twisting them together. If you use different size wires you will likely have a poor connection that can easily come apart. Wire nuts are not recommended for campervans.

Another way to twist wires for wire nuts


Screw / Lever Connectors

Screw and lever connectors are a really quick and easy way to connect two wires together and certainly better than the twisting technique.


Lever connectors (Wago)

If you want to connect wires together and you are not cold-welding or soldering, lever connectors are definitely the way to go! They are easy to use, cheap, reusable, and more secure.


The functionality is pretty self-explanatory... just pop the wires inside and close the lever down to secure them in place. Wago makes lever connectors with 2, 3, or 5 inlets.


One important difference between lever connectors and wire nuts is that lever connectors have a current rating while wire nuts do not have a current rating. Wire nuts are not rated, they are not intended to conduct electricity. They are simply intended hold the wires in intimate contact.

WAGO wire conector

And for the nerds out there who want to delve deeper, here is a fantastic video comparing wire nuts to lever connectors. If you're into that kind of thing...


Strip terminals and Chocboxes

A strip terminal and chocbox are types of screw terminals; a type of electrical connection where a wire is held by the tightening of a screw. Quite simply you put a wire into each end of the screw terminal and tighten the screw to connect the wires together.

Wire strip terminal

Sometimes screw terminals are housed in plastic casings to make the wiring look neat and increase safety. This device is known as a chocbox; short for 'chocolate box', and rather aptly named.

Wire chocbox

NOTE: When using strip connectors, it is important that we attach ferrules onto the ends (terminals) of each wire. We insert the wire with the ferrule on the end into the strip connector. You should not insert bare wire into strip connectors as the wires typically break and have a poor electrical connection. Use ferrules instead. Jump to: Ferrules


Crimp Connecting

Cold welding or contact welding is a welding process in which joining takes place without fusion or heating at the connection of the two parts to be welded.


In cold-welded connections, wires are connected using wire/crimp connectors. A crimp connector is a device used to create an electrical connection between parts of an electrical circuit.


Quick Disconnects for van conversions
A set of crimp connectors

A crimp connector typically has a male (plug) and female (socket) side, to connect two wires together.


In a nutshell, crimp connectors work like this: We have two wires we want to connect. We put a female connector on one wire and a male connector on the other. We apply mechanical pressure (crimp) on the wire connector to cold weld it to the wire. We can then insert the male wire into the female wire.


Crimp connecting is the most popular and arguably the best way to connect wires. Because no alloy is used (as in solder), the joint is mechanically stronger and more reliable.


Crimped connections are permanent (i.e. the connectors and wire ends cannot be reused).


Crimp connectors are colored and sized according to the current rating they support. Here's a table of the generally accepted colors and supported wire gauge of crimp connectors:

Color of crimp connectors to AWG


How to crimp correctly

A crimp is the applying of mechanical pressure (squeeze) to the crimp connector in order to cold weld it to the wire.


To crimp a connector, we use a crimping tool. For small wires we can use a cutting/stripping/crimping multi tool, the tool discussed previously. For large crimp connectors (eg. attaching a lug to a 0AWG battery cable), you will need a large crimping tool.

Large crimping tool

First strip back the rubber from the end of the wire to expose the metal threads; the precise amount you strip back will vary depending on the size of the connector, but it is generally about half an inch. Then, insert the wire into the appropriate crimp connector. The wire is inserted into the crimp connector with the end of the wire flush with the exit of the connector to maximize cross-sectional contact.

How much wire should be exposed when crimping

Next, place the crimp connector into the crimping tool (Make sure you are using the appropriately sized crimp barrel). Squeeze the handles of the crimp tool to compress and reshape the crimp connector until it is cold welded to the wire.


It is very important that we crimp correctly, lest we put the strength, safety and efficiency or the wire at risk. Here is a diagram of what a crimp should look like.

correct pressure when crimping

If the crimp is too loose there will be no mechanical support or strain relief for wire. Conversely, if the crimp is too tight, the barrel digs into the wire strands and can break wire strands. Additional force applied beyond what the crimp connector is designed to handle can result in a rapid reduction in performance both electrically and mechanically.

Effect of overcrimping a wire connector

Optimal crimp: Wire insulation held firmly. Slight indentation of insulation. Good mechanical support and strain relief.


What are the different types of crimp connectors?

There are many different types of crimp connectors, so let's look at some of the most important types and understand what they are used for.


Quick disconnects

Quick disconnects, also known as blades or snap-ons are the most common type of wire connector. They connect two wires together. Sometimes the female side can be used to connecting to other devices (eg. the back of a cigarette lighter socket or a 12v switch).

quick disconnect for campervan

Bullet connectors

Bullet connectors function in the exact same way as quick disconnects, but are cylindrical rather than flat.

Bullet connector

Ring connectors

Ring connectors are typically used for connecting wires to bus bars. For example, on a 12v fuse box, there are many bolts to which we can connect a wire.

Ring connector

On the ring connector, you will find two numbers beside each other. The number of the left is typically the cross-sectional area (eg. 8mm^2), ie. the size of wire that the lug will take. The number on the right is the size of the hole in the lug (thus dictating what size bolt can fit through it); this number will typically be M2, M4, or M6 (ie. 2mm, 4mm, or 6mm diameter).


Wiring a fuse box with ring connectors

Lugs

A lug is the same as a ring connector, only bigger (and consequently able to handle more current).


Lugs are also used for connecting wires to bus bars. In a campervan, we would use a lug to connect the leisure batteries to the bus bars.

Heavy duty lugs

On the lug, you will find two numbers beside each other. The number of the left is typically the cross-sectional area (eg. 35mm^2), ie. the size of wire that the lug will take. The number on the right is the size of the hole in the lug (thus dictating what size bolt can fit through it); this number will typically be M6, M8, or M10 (ie. 6mm, 8mm, or 10mm diameter).


Fork connectors

A fork connector (spade) is used for connecting a wire to a bus bar. These connectors are very commonly used for connecting a wire to a fuse box as they can slide onto the side of a bolt, rather than having to put it through the top of the bolt.

Connecting wire to bus bar with spade connector

Butt splice connectors

Butt splice connectors are very simple crimp connectors for connecting two wires together. Simply put a wire into each side and crimp down on the middle.

But splice connector

Ferrules

Ferrules are an important crimp connector that a lot of people overlook. They are used when we want to insert a wire into a socket with a screw down mechanism (also known as a screw terminal). For example, wiring our solar charge controller (eg. the Epever 40a MPPT), wiring into a connector strip (which we use to wire up our sink tap switch), or for wiring up the plug sockets in our van.


For example, if we simply placed a bare wire into the back of the plug socket and screwed it down to secure it, it will very likely result in the wire breaking inside (without you realising). The majority of the time you will also have a poor connection between the wire and the socket as not all the wire is in contact with the screw.

Using a ferrule to wire a plug socket

For this reason, we should instead crimp a Ferrule (looks very similar to a bullet connector) onto the end of the wire and insert that terminal into the socket. We can then safely screw down onto the wire and know that we will not break any strands and create a good connection.

Effect of not using a ferrule

The one caveat with ferrules is that unfortunately we need a special ferrule crimper to get a solid, square-shaped crimp on the wire. Though to save money, some people may choose to use a normal crimper.


Solar MC4 connectors

This one is more of an honorable mention. When we are connecting solar cables together we use MC4 connectors. They make wiring your solar array much simpler and faster. You can learn all about solar power for campervans here.

MC4 solar connectors

T-tap connectors

T-tap connectors are used when we want to splice one wire into the middle of another wire.

How to use t-tap splice wire connectors

We commonly use t-tap connectors when we are wiring up devices in parallel. For van conversions, most people will use these connectors when wiring up the 12v LED puck lights in the roof.

Using t-tap wire connectors to wire LED lights in parallel

In the diagram above, the two LED puck lights in the top left and top center are wired in parallel, we would tap into the main wire here using t-tap connectors.


Piggy back connectors

For all intents and purposes, piggy back connectors are the exact same as t-tap connectors. They are like three way quick disconnects.

Piggyback connectors

Soldering

Soldering is the process of joining electrical components together by melting solder to make an electrical connection.


Soldering is very commonly used by electrical engineers, but is not as commonly used in campervans; however it is important that we cover this concept.


The reason soldered connections are not commonly used in campervans is because soldering may not provide a robust mechanical connection. Why? If the joint gets hot (through excessive resistance or a high current), the solder may melt and the joint will fall apart. Rattling of the vehicle may also weaken the soldered connection

Soldering a wire

How does soldering work?

Two metal surfaces (eg. two wires) are placed beside one another. By adding heat (using a soldering iron), we can melt the surface coatings of the wires together to form a new conductive path for the electrical circuit. However, the metal coating of the wires aren't very thick, so we also need to add more metal (called solder) to help form a stronger connection. The connection created is called a 'solder joint', it is the mixture of the metals from the two surfaces and the solder all melted together.


Solder is a metal alloy. There are three types of solder:

  1. Leaded (most common)