Collection: Heavy Caliber / Japanese & Maxi

Maxi fuses: main circuit protection

Maxi fuses (29 mm format) protect the main power cables of the central fuse box—usually located directly at the battery or alternator output. They activate in the event of a severe short circuit, before the main cable heats up to the point of catching fire.

Common amperages: 40 A, 50 A, 60 A, 80 A, 100 A. The golden rule: choose an amperage less than or equal to the maximum capacity of the protected cable—never above, otherwise the protection will be eliminated.

JCase fuses: the format for modern Japanese vehicles

Japanese vehicles manufactured since the 2000s (Toyota, Honda, Nissan, Mazda, Subaru) frequently use flat rectangular profile fuses called JCase (or J-Case). Their shape is different from European Maxi and Midi fuses—they are not interchangeable. Identify the required format on your wiring diagram or by looking at the fuse box before ordering: a JCase fuse will not fit in a Maxi holder, and vice-versa.

Midi and high-power fuses for 12V installations

Motorhomes, boats, and high-power 12V installations (4×4 winches, inverters, auxiliary batteries, absorption refrigerators) require high-power fuses placed as close as possible to the power source (the battery). This rule is fundamental: a fuse must always be positioned less than 30 cm from the battery to cut off the circuit at the source in the event of a short circuit.

Midi fuses (38 mm format, amperages 60 A to 120 A) are perfectly suited for these applications. Bolt-on versions (ANL, MEGA) go even higher, up to 200 A and beyond.

Choosing your amperage: the cable dictates the value

Common mistake: choosing the fuse amperage based on the connected equipment. Incorrect—it is the cable cross-section that determines the fuse's amperage:

• 2.5 mm² cable → 15-20 A fuse
• 4 mm² cable → 25-30 A fuse
• 6 mm² cable → 40-50 A fuse
• 10 mm² cable → 60-70 A fuse
• 16 mm² cable → 80-100 A fuse
• 25 mm² cable → 120-150 A fuse

An undersized fuse will blow too often in normal use. An oversized fuse no longer protects the cable—the cable becomes the "fuse" in the event of a short circuit, with a high risk of fire.