Campervan Electrical System Diagram: How to Read and Draw One

A wiring diagram (or schematic) is the single most useful planning and build tool for a campervan electrical system. It shows how every component connects, makes it easy to spot problems before wiring starts, and gives future-you (or a mechanic) a map of the system.

Why you need a wiring diagram

Without a diagram:

• You will forget to fuse something
• Cable routing decisions get made on the fly and produce chaos
• Fault-finding later becomes guesswork

With a diagram:

• Every connection is planned before you buy cable
• Fusing is explicit — every positive cable shows its fuse rating
• The diagram becomes documentation for insurance, resale, and repair

What goes on a campervan wiring diagram

A complete diagram shows:

12V DC system:

• Leisure battery (with polarity)
• Main ANL fuse (on positive, near battery)
• Battery shunt (on negative main cable, between battery and bus bar)
• Positive bus bar
• Negative bus bar / chassis earth
• Each charge source: MPPT, DC-DC charger, mains charger — with connections to bus bars
• Each load: inverter (with its own ANL fuse), fuse box, individual circuits

230V AC system:

• Shore power inlet
• RCD (residual current device)
• Consumer unit / MCBs
• 230V sockets
• Inverter output connection

Control wiring:

• Ignition sense wire to DC-DC charger
• Remote on/off to inverter
• Battery monitor shunt connections

Standard symbols used in 12V schematics

Many builders use simplified box diagrams rather than strict electrical symbols — clarity matters more than convention.

A typical UK campervan wiring diagram (text description)

[Leisure Battery]
    |
    +--- (+) terminal --- [ANL fuse 150A] --- [+ve Bus Bar]
    |
    +--- (-) terminal --- [SmartShunt 500A] --- [-ve Bus Bar] --- [Chassis Earth]

[+ve Bus Bar] connections:
    → [ANL fuse 100A] → [Inverter 1000W] → AC output → [RCD] → [Consumer Unit]
    → [Fuse 40A] → [MPPT output (+)] (MPPT input from solar panels)
    → [Fuse 40A] → [DC-DC charger output (+)] (DC-DC input from starter battery via fuse)
    → [Fuse 30A] → [Mains charger output (+)] (mains charger input from hook-up via RCD)
    → [Fuse 70A] → [Blade fuse box] → individual circuits (10A fridge, 10A lights, etc.)

[-ve Bus Bar] connections:
    ← [Inverter (-)]
    ← [MPPT output (-)]
    ← [DC-DC charger output (-)]
    ← [Mains charger output (-)]
    ← [Blade fuse box (-) returns]

How to draw your own diagram

Tools:

• Paper and pencil is fine for planning
• Google Slides / LibreOffice Draw (free, good for digital diagrams)
• Lucidchart (online, free tier available)
• Dedicated tools: Schematics.io, Fritzing

Process:

1. Start with the battery in the centre
2. Draw the main positive cable with ANL fuse to the positive bus bar
3. Draw the main negative cable with shunt to the negative bus bar
4. Add each charge source: draw from bus bar to the charger label, then a separate label for the input source
5. Add each load: draw from bus bar to the component, noting fuse ratings
6. Add the 230V system: shore inlet → RCD → consumer unit → sockets
7. Add note lines for control wiring (ignition sense, remote switch)

Including cable sizes and fuse ratings

Make the diagram useful by annotating key values:

• On each cable: cable size (e.g., "25mm²")
• On each fuse symbol: fuse rating (e.g., "ANL 150A")
• On each load: power rating (e.g., "Inverter 1,000W")

This turns the diagram into a complete specification that can be used for cable purchasing.

Keeping the diagram updated

Update your diagram when you make changes — adding a circuit, changing a component, or rerouting cable. A diagram that does not match the real build is worse than no diagram, because it misleads future fault-finders.

Store a copy outside the van (cloud storage, email to yourself) so it is available if the van is broken down away from home.

FAQ

Do I need professional-grade software for my wiring diagram?

No. A clear hand-drawn diagram on paper, photographed and stored digitally, is perfectly adequate. The most important quality is accuracy, not appearance.

Should my diagram show physical locations or just electrical connections?

Both are useful: a schematic shows connections; a layout diagram shows where components are physically mounted. Many builders do a schematic first (planning), then a layout diagram once they know where everything goes.

Does my insurance need to see a wiring diagram?

Some campervan insurers ask for evidence of electrical system quality for specialist van life insurance policies. A diagram showing correct fusing and earthing demonstrates a competent installation. Check your specific insurer's requirements.