Fuse Selection Guide

Fuses protect your wiring — not your appliances.
Choosing the correct fuse size is essential for keeping your van safe.

If a circuit becomes overloaded or develops a fault, the fuse blows before the cable overheats.
That means the fuse must always protect the cable, not the device.

Let’s walk through how to choose the right one.

1. Why Every 12V Circuit Needs a Fuse

A fuse prevents:

• Melted cables

• Electrical fires

• Damaged batteries

• Short-circuit explosions

• Faulty appliances causing wiring failure

The goal is simple:
👉 If something goes wrong, the fuse sacrifices itself instead of your wiring.

2. The Golden Rule of Fuse Selection

Fuse size MUST be chosen based on the cable size — not the appliance.

For example:

• If your fridge draws 5A

• And you’re using 6 mm² cable

• You do not use a 5A fuse

• You use the correct fuse for 6 mm² cable (usually 25–30A)

Why?
Because the fuse protects the cable, not the fridge.
If the fridge faults and tries to pull 30A, the fuse blows before the cable melts.

3. Recommended Fuse Sizes for Cable Gauge

Here are the standard automotive fuse ratings for thin-wall cable:

To be safe:
👉 Choose the next fuse rating BELOW the cable’s maximum capacity.

Example:
2.5 mm² cable = rated 29A → choose a 25A fuse.

4. Where to Place Fuses

Every circuit should have one fuse, installed:

As close to the battery as possible.

Ideally within 15–20 cm.

This protects the full length of the cable.

Never run an unfused cable through walls, insulation, or the van body.

Special Cases

• Fridge circuits → fuse at the battery or main distribution block

• Diesel heater → fuse at battery feed

• Solar → fused between battery and charge controller, NOT between panels and controller

• Inverters → use a correctly sized MEGA fuse on the positive battery feed

5. Types of Fuses Used in Campervans

1. Blade (ATC/ATO/Mini) Fuses

Most common for everyday circuits.
Use in:

• Lighting

• Pumps

• Fans

• USB sockets

• Fridges

• Diesel heaters

2. MEGA / MIDI Fuses

Used for higher loads:

• Inverters

• DC-DC chargers

• Split-charge systems

• Battery-to-battery circuits

3. Glass Fuses

Old-style. Avoid them for new installations — less reliable.

6. Step-by-Step: How to Choose a Fuse

1. Choose your cable size

Use our tool:
👉 <a href=”/cable-sizing-tool-test-page/”>Cable Sizing Tool</a>

2. Look up the cable’s safe current rating

Use the table above.

3. Choose a fuse rated BELOW the cable’s maximum

example: 29A max → 25A fuse.

4. Pick a fuse type

Blade / MIDI / MEGA depending on load.

5. Install the fuse at the battery end

Protect the whole cable run.

7. Example Circuits (Real Van Builds)

A) LED Lighting Circuit

• Estimated load: 2A

• Cable size: 1.0 mm²

• Max current: 16A

• Use a 10A fuse

B) Compressor Fridge

• Load: 4–6A

• Cable: always 6 mm² minimum

• Fuse size: 25A or 30A

C) Diesel Heater

• 10A startup

• Cable: 6 mm²

• Fuse: 25A

D) Water Pump

• Load: 6–8A

• Cable: 2.5 mm²

• Fuse: 15A–20A

E) Inverter (600W)

• Load: 50A

• Cable: 16 mm²

• Fuse: 60–80A MEGA fuse

8. Common Fuse Mistakes to Avoid

❌ Using a fuse the same size as the appliance amps
❌ Putting fuses halfway down the cable
❌ Running unfused cables behind insulation
❌ Using too small a cable then trying to “protect it” with a tiny fuse
❌ No fuse on inverter/DC-DC chargers

9. Safety First: Always Overspec the Cable, Not the Fuse

If unsure, always:

✔ Use a larger cable
✔ Use the correct fuse for that cable
✔ Keep the fuse near the battery

This keeps the system safe even if an appliance develops a fault.