Campervan fuse size chart

This quick reference table covers the most common 12V circuits found in campervans. Final fuse size should always match both the expected current and the cable size used on that circuit.

The golden rule: the fuse protects the cable

The most common mistake in campervan wiring is choosing a fuse only based on the appliance. In reality, the fuse is there primarily to protect the cable from overheating if a fault or short circuit occurs.

• The device determines expected current draw
• The cable determines the maximum safe fuse size
• The final fuse should be high enough for normal operation but low enough to protect the cable

How to calculate fuse size

A simple method is to take the normal operating current and add a safety margin. In many 12V campervan circuits, a fuse around 125% of the continuous current is a sensible starting point.

• Fuse size ≈ operating current × 1.25
• Then round up to the nearest standard fuse size
• Finally check that the chosen fuse does not exceed the cable rating

For example, if a circuit draws 8A continuously:

• 8A × 1.25 = 10A
• Choose a 10A fuse if the cable supports it safely

Estimate fuse size faster with the Fuse Size Calculator.

Where to place fuses in a campervan

Every positive cable connected to a battery should be fused as close to the power source as possible. This reduces the risk of an unfused cable shorting to chassis and overheating.

• Main fuse near the leisure battery positive terminal
• Separate fuse for inverter cable near the battery
• Fuse on each side of a DC-DC charger where required
• Fuse between starter battery and split charge relay cable
• Fuse block feed protected near the leisure battery

Main fuse layout diagram

Common blade fuse ratings

Most low-current campervan circuits use standard automotive blade fuses. These are common in fuse boxes for lighting, pumps, fans and small 12V accessories.

For high-current battery cables, inverters and charging systems, larger fuse formats such as MIDI, MEGA or ANL fuses are often used instead.

Fuse size by cable size

This table gives a practical guide for common automotive cable sizes used in campervans. Actual safe current can vary depending on installation method, insulation, ambient temperature and cable run, so this should be treated as a sensible reference rather than a hard universal rule.

Check your wiring with the Cable Size Calculator and confirm voltage loss using the Voltage Drop Calculator.

Inverter fuse size chart

Inverters can draw very high current from a 12V battery, especially at full load. This means both cable size and fuse rating need careful selection.

See full install guidance here: How to Wire an Inverter in a Campervan

DC-DC charger fuse sizes

DC-DC chargers usually need protection on both the starter battery side and the leisure battery side. Fuse size is normally chosen above the charger rating, while still matching the cable safely.

Compare cable sizing using the DC-DC Charger Cable Size Calculator.

Solar fuse sizes

Solar systems can require protection between the solar panel and controller, and between the controller and battery. Exact layout depends on panel configuration and controller type.

Solar cable losses can be checked with the Voltage Drop Calculator.

Common campervan fuse mistakes

• Using a fuse that is too large for the cable
• Placing the fuse too far from the battery
• Copying a fuse size from another van without checking cable size
• Forgetting to fuse inverter or charging cables
• Assuming appliance current and cable protection are the same thing

Recommended cable and fuse products

• Battery cable
• Single core automotive cable
• Fuse Size Calculator
• Cable Size Calculator

Useful calculators for campervan fuse planning

Related campervan electrical guides