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 campervan wiring. 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 years; I'm the author of Roaming Home; The Comprehensive Guide for Converting Your Van Into a Campervan, writer of The Van Conversion Newsletter, instructor of The Van Conversion Course over at Udemy. And full-time vanlifer for 4 years!
Now let's jump in and have a look at wires for campervans!
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
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Supplies list 🛒
What are wires made of?
Electricity travels through wires - a metal conductor that is sheathed 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.
Wires are typically made using the following metals:
Copper is by far the most common metal used. It is highly conductive, bendy, thermally 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 lightweight, and long-lived.
Aluminium has 61 percent of the conductivity of copper, but is only 30 percent of the weight of it. Consequently, aluminium offers a lower cost per Amp and provides up to 48 percent mass reduction over copper. Unfortunately aluminium is a metal that corrodes very easily. As a result, it should not be used in a vehicle as it is very common to have high humidity inside - especially if you use the campervan a lot by the sea. Use copper instead.
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 colour. 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.
Solid vs stranded wire
Solid wires consist of a single, solid core, whereas stranded wire consists of several thinner wires twisted into a bundle.
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.
In campervans (like all vehicles) we should use stranded wire.
Note: Flexible vehicle cable starts at about 42 strands and goes all the way up to several hundred strands on thick cable.
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 specialised wire insulators
In campervans, we 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 diameter for your wiring
To calculate the size (diameter) of wire needed in a system we need three variables:
The length of the wire (distance to the appliance AND back)
The amps the wire will be carrying (ie. the amp rating of the appliance)
Acceptable voltage drop
Note: 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 or connectors. For critical circuits we should use the value ‘3%’, for non-critical circuits (eg. LED lights), we can use the value ‘10%’.
12V DC wire size chart (mm²)
Here is the campervan wire sizing I used in my conversion (please size your own wires):
12V appliances: 1.5mm² (16 AWG)
Solar panels to solar charge controller to batteries: 10mm² (8 AWG)
Batteries to inverter: 35mm² (2 AWG)
Batteries: 55mm² (0 AWG)
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.
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
Small wires: Small wires (22-10 AWG) 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!
Medium wires: Medium-sized wires are commonly cut using cutting pliers(Knipex).
Large wires: Large wires are cut using large wire cutters, which give extra leverage.
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
To strip a wire, we use a wire stripping tool.
Small wires (22-10AWG) can stripped using a wire stripping multi tool or a wire strippers.
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.
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!
How do I connect wires together?
There are four ways we can connect wires together:
Screw / Lever connectors
Crimp connecting (cold welding)
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.
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.
A slightly better way of connecting wires together by twisting is to use wire nuts. Wire nuts are the oldest wire connectors available, they have been around since 1929.
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).
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.
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. They are a great solution to campervan wiring.
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 secure.
The functionality is pretty self-explanatory... just pop the wires inside the connector 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 intended to conduct electricity. They are simply intended to hold the wires in intimate contact.
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 choc boxes
A strip terminal and choc box 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.
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. We will learn more about ferrules later in this chapter.
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 Crimp Connectors
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.
A crimp connector typically has a male (plug) and female (socket) side, to connect two wires together.
How do crimp connectors work?
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 connector into the female connector.
Crimp connecting is the most popular and arguably the best way to connect wires. Because no alloy is used (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 coloured and sized according to the current rating they support. Here's a table of the generally accepted colours and supported wire gauge of crimp connectors:
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.
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 maximise cross-sectional contact.
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.
If the crimp is too loose there will be no mechanical support or strain relief for the wire. Conversely, if the crimp is too tight, the barrel digs into the wire strands and can damage them. Additional force applied beyond what the crimp connector is designed to handle can result in a rapid reduction in performance both electrically and mechanically.
Optimal crimp: Wire insulation held firmly. Slight indentation of insulation. Good mechanical support and strain relief.
Wire crimp connector types
There are many wire crimp connector types. Let's look at some of the most important types and understand what they are used for;
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 alone is used to connect to other devices (eg. the back of a cigarette lighter socket or a 12V switch).
Bullet connectors function in the exact same way as quick disconnects, but are cylindrical rather than flat.
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.
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).
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.
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).
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.
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.
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 (screw terminal). We use ferrules when wiring our solar charge controller or for wiring up the plug sockets in our van.
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.
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.
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.
T-tap connectors are used when we want to splice one wire into the middle of another wire.
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.
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.
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.
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:
Leaded (most common)
Silver (not used for connecting wires, but has other purposes)
Using solder with a flux core is recommended. Flux helps prevents oxidation of the metal when you are soldering. Oxidation occurs when metal comes in contact with oxygen (particularly moisture laden air). As example of oxidation is rust. Rosin, a resin from the pine tree is the most common flux that is used when soldering. Most people use a 60/40 Rosin solder.
What do equipment do you need to solder?
You can easily buy soldering kits online, they should include the following:
Silicone paste (dielectric grease)
Rosin paste flux
The soldering iron heats top a high temperature in order to melt the metals together. A temperature of 320°C is recommended for 60/40 leaded solder.
Rosin paste flux helps the solder flow into the wires during soldering.
Silicone paste helps prevent oxidation of the metal after soldering.
The helping hand is used to hold the wire up while you solder; it is optional but very useful.
How to solder
When you are soldering, there are some key safety precautions you must beware of:
Always wear goggles (if hot lead solder splashes into your eye, you are going to have a VERY BAD TIME)
Don't solder near flammable material
Don't breath in the lead fumes (do this outdoors or use a fan)
Always wash your hands after using lead solder
Step #1: Splice (twist) the wires together
Step #2: Rub rosin paste flux on the connection
As well as the 'built-in' rosin in the solder, you will also want some rosin paste flux. This helps the solder flow into the wires.
Step #3: Heat up your soldering iron
Press down the trigger of your soldering iron. As it heats up, rub the tip on a damp sponge; doing this removes any oxidation.
Step #4. Tin the tip of your soldering iron if it is not already tinned
Add a little but of solder to the heated tip of your soldering iron.
Then wipe the tip on the wet sponge again to get rid of any excess solder.
Step #5: Solder!
Place the tip of the soldering iron UNDER the wire connection.
Feed a little bit of solder in between the tip and the wire to speed up the heat transfer
Once the wire is heated, press the solder into the top of the wire to slowly have it flow through the connection.
After a successful solder, no copper should be visible
Step #6: Wipe the soldering gun on the wet sponge
Do this after every time you solder
Step #7: Heat shrink the exposed connection
Heat shrinking is the placing of a rubber tube over an exposed electrical connection and heating the tube up to shrink it. We are going to be talking more about heat shrinking in the next section.
Before placing the heat shrink over the connection, rub some Silicone paste over the exposed connection to help prevent oxidation. Then go ahead and heat the heat shrink to seal up the connection!
A heat shrink, is a shrinkable plastic tube that shrinks radically when exposed to heat. It is a great way to cover up electrical connections and important in campervan wiring. We should always use a heat shrink after making an electrical connection, be it by twisting, screw/lever connectors, crimp connecting, or soldering.
There are three types of heat shrinks:
Thin wall (most basic insulation)
Dual wall (weather proof)
Heavy wall (weather proof & abrasion resistant)
Simply place the heat shrink over the exposed connection, and blow hot air on the heat shrink with a heat gun.
Note: If you really don't want to use heat shrinks (which I really think you should), you can use electrical tape instead to cover up the connections. However, these do not form as strong a seal.
These days you can find crimp connectors with built in heat shrinks. They're super cool and super useful. Crimp them, then heat them, and you're good to go!
And there we have it! What an electrical adventure that was... I truly hope you found this article on how to cut, crimp, and connect wires in your campervan useful! That's all there is to campervan wiring!
Don't forget to subscribe to The Van Conversion Newsletter for everything you need to get started with your own van conversion (I'll send you a free wiring diagram when you join).
If you're looking for some guidance with your van conversion, you might be interested in Roaming Home; The Comprehensive Guide for Converting Your Van Into a Campervan. In the 380-page book (or ebook), you'll learn directly from me how to convert a van into your dream home - no prior experience needed!
Until next time,