Building a safe and reliable campervan electrical system means more than just connecting a battery and a few lights. Your battery bank, fuses, isolators, solar controller, DC-DC charger, inverter, busbars, grounding points and cable sizes all need to work together in the correct order.
To make this easier, MKGT® has created a practical campervan wiring diagram together with free technical PDFs and electrical calculators to help you plan battery wiring, solar charging, fuse protection and cable sizing for 12V and 24V systems.
📄 Download Campervan Wiring Diagram PDF
Who this guide is for
This guide is useful if you are planning or upgrading:
- campervan electrical systems
- motorhome and van conversion electrics
- 12V or 24V battery systems
- solar charging and DC-DC charging setups
- off-grid leisure battery installations
Campervan Electrical System – Wiring Diagram
The MKGT® campervan wiring diagram below shows a typical layout for a modern 12V / 24V DC system. It includes the house battery bank, main fuse and isolator, DC-DC charger for alternator charging, solar MPPT controller, inverter, positive and negative busbars and the 12V fuse box supplying interior loads.
This is a simplified, high-level wiring reference designed to show safe component order and good electrical structure. It is not a substitute for a complete installation design or professional verification.
Download the high-resolution PDF version here:
📄 Download Campervan Wiring Diagram (PDF)
What the diagram includes
- House battery bank (AGM, GEL or LiFePO4)
- Main fuse on the positive battery cable
- Battery isolator switch for safe shutdown and maintenance
- DC-DC charger for alternator charging from the starter battery
- Solar panels connected to an MPPT charge controller
- MPPT to battery wiring with low voltage drop
- Positive and negative busbars for clean distribution
- 12V / 24V fuse box feeding interior loads
- Typical campervan loads: lights, fridge, water pump, heater, roof fans, USB sockets
- Inverter DC wiring for 230V AC output
- Chassis and ground connections
Choosing the Correct Cable Size
Correct cable sizing is one of the most important parts of campervan wiring. Undersized cables can cause excessive voltage drop, hot cables, poor charging performance and unreliable appliances. Oversized cables are safer electrically, but they increase cost and can be harder to route neatly.
MKGT provides free cable sizing tools to help you choose suitable cable cross-sections for both low-current and high-current circuits:
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Cable Size Calculator
Use this for general low-voltage circuit sizing based on system voltage, current or power, cable length and allowed voltage drop.
Open Cable Size Calculator -
Voltage Drop Calculator
Check actual voltage loss for a selected cable size, current and cable run length.
Open Voltage Drop Calculator -
Fuse Size Calculator
Estimate a practical fuse size for your cable and circuit load.
Open Fuse Size Calculator -
All MKGT Calculators
Browse all technical calculators in one place.
Open All MKGT Calculators
These tools help calculate recommended cable size, estimated voltage drop in volts and percent, and practical fuse suggestions for 12V and 24V campervan systems.
Fusing and Protection
Every positive cable leaving the battery should be protected with a correctly rated fuse mounted as close to the battery as possible, typically within 15–20 cm. The fuse is there to protect the cable in the event of a short circuit.
A fuse that is too small may blow during normal use or startup surge. A fuse that is too large may not protect the cable correctly. Fuse choice should always be checked against cable size, load current and circuit type.
Typical fuse types used in campervans
- Blade fuses (ATO/ATC) – lighting, USB sockets, small pumps, low-current accessory circuits.
- MIDI / MEGA fuses – DC-DC chargers, battery feeds, medium to high current circuits.
- ANL fuses – larger inverters and very high-current DC applications.
You can also use the MKGT fuse sizing tool here: Fuse Size Calculator.
Grounding and Negative Busbar
A clean campervan electrical install should usually bring negative returns back to a dedicated negative busbar, which is then bonded to the vehicle chassis at a solid single grounding point. This helps keep the system organised and reduces the chance of poor or inconsistent grounds.
High-current devices such as inverters, DC-DC chargers and main battery feeds should normally return directly to the battery negative or to a correctly sized negative busbar using appropriately sized cable.
Common Campervan Circuits to Plan Correctly
| Circuit | Typical use | Main design concern |
|---|---|---|
| LED lighting | Interior lights, ambient strips, reading lamps | Voltage drop on long runs |
| 12V fridge | Compressor fridge supply | Stable voltage and correct fuse |
| Water pump | Sink or shower pump circuits | Motor startup current |
| DC-DC charger | Alternator charging to leisure battery | Cable size and fuse protection |
| Solar MPPT to battery | Solar charging cable run | Low voltage drop for charging efficiency |
| Inverter feed | 230V AC output from battery | Very high current battery cable sizing |
Download Additional MKGT Technical Guides (PDF)
If you want more detail, you can also download our free technical guides with diagrams, example calculations and cable tables:
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MKGT 2-Core Cable Technical Guide (PDF)
Explains voltage drop, cable sizing for 12V / 24V / 60V and typical current ratings.
Download 2-Core Cable Technical Guide (PDF) -
MKGT Battery Cable Technical Guide (PDF)
Covers 10–95 mm² battery cables, current capacity, application examples and best practices.
Download Battery Cable Technical Guide (PDF) -
MKGT Campervan Wiring Diagram (PDF)
High-resolution version of the diagram shown above, ideal for printing or using as a planning reference.
Download Campervan Wiring Diagram (PDF)
Plan the Full Campervan System
Combine the wiring diagram with MKGT cable size, voltage drop and fuse calculators to plan the full electrical system from battery bank to inverter, DC-DC charger, lighting, pumps and solar charging.
Recommended MKGT Products for Campervan Wiring
To build a safe and reliable campervan electrical system, use correctly sized copper cable and properly rated accessories. Below are some popular MKGT products suitable for 12V / 24V campervan installations.
Low-Voltage 2-Core Automotive Cable (Interior Circuits)
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0.75 mm² 2-Core Flat Twin Red/Black – up to approx. 14 A
Ideal for short runs to LED lighting, USB sockets and small loads. -
1.5 mm² 2-Core Flat Twin Red/Black – up to approx. 21 A
Suitable for medium loads such as fridges, fans and pumps. -
2.5 mm² 2-Core Flat Twin Red/Black – up to approx. 29 A
Recommended for heavier interior circuits and slightly longer cable runs.
View the full range here:
MKGT 2-Core 12V Flat Automotive Cable Collection
Battery & Inverter Cable (High-Current Circuits)
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25 mm² High-Flex Battery / Welding Cable – approx. 170 A
Suitable for small inverters, DC-DC chargers and short high-current runs. -
50 mm² High-Flex Battery Cable – approx. 345 A
Common choice for 1500–2000 W inverters and heavy-duty starter cables. -
70 mm² High-Flex Battery Cable – approx. 485 A
Recommended for large inverters, powerful winches and long high-current runs.
Browse the full range here:
MKGT Battery & Welding Cable Collection (10–95 mm²)
FAQ
What cable size do I need for a campervan?
The correct cable size depends on current, cable length, system voltage and acceptable voltage drop. Interior lighting circuits often use smaller 2-core cable, while battery feeds, DC-DC chargers and inverter supplies usually require much larger cable sizes.
Should every positive cable be fused?
In practice, every positive cable leaving the battery should be protected by an appropriately rated fuse. The purpose of the fuse is to protect the cable in the event of a fault or short circuit.
Where should the main battery fuse be installed?
The main fuse should usually be mounted as close to the battery positive terminal as possible, typically within 15–20 cm, so that the cable is protected for almost its full length.
Can I ground everything to the chassis?
Many campervan systems use a chassis bond, but it is usually best practice to collect negative returns on a dedicated negative busbar and then bond that busbar to the chassis at a single reliable point.
What size cable is needed for an inverter?
Inverter circuits are often among the highest-current cables in the entire system. Cable size depends on inverter wattage, system voltage and cable length. Inverters often need large battery cable and correctly rated MEGA or ANL fuse protection.
Is 12V or 24V better for a campervan?
For many campervans, 12V is the most common setup. Larger systems with heavier inverter loads may benefit from 24V because current is lower for the same power, which can reduce voltage drop and cable size requirements.
For more tools and technical resources, visit the MKGT Knowledge Hub.