MEGA Blade Fuses — 40A to 300A

Q: What does MEGA actually mean?
MEGA (sometimes written AMG) is a bolt-down cartridge fuse format built for high-current DC circuits, first standardised by Cooper Bussmann in the 1990s. Two M8 studs hold the fuse to a holder or bus bar, and the fusible element inside is sized for currents that plug-in blade fuses simply cannot carry. Anything above the Maxi blade ceiling of 100A that is not big enough to need ANL usually goes on MEGA.

Q: How do I pick the right amperage?
Size the fuse to the cable, not to the load. Every cable has a rated current-carrying capacity, and the fuse must blow before the cable overheats. A 100A load on 4 AWG cable takes a 100A fuse. A 150A load on 2 AWG cable takes a 150A fuse. The size guide above pairs each MEGA rating with the cable it protects and the loads it typically handles at 12V.

Q: MEGA vs MIDI vs ANL, which do I need?
MIDI covers 30A to 200A on a smaller bolt-down footprint. MEGA covers 40A to 500A on a larger footprint (this range goes to 300A). ANL covers 35A to 750A and is the format you move to when the current is above what MEGA can handle. All three are time-delay bolt-down fuses. Match the format to the current draw and the physical holder you already have.

Q: Are these time-delay fuses?
Yes. MEGA cartridges are time-delay by design. The element mass takes long enough to reach melting temperature that a short inrush current (an inverter switching on, a fridge compressor starting, an alternator field ramping) does not blow the fuse, but a sustained overload or short circuit still trips it well before the cable is damaged.

Q: Do I need a specific holder?
Yes, MEGA fuses need a MEGA holder. Any single, twin or four-way bolt-down holder built to the standard AMG footprint accepts these. See the Related section for the holder we pair with these fuses in our workshop builds.

Q: Can I upsize the fuse if it keeps blowing?
No. A fuse that keeps blowing is telling you the circuit is drawing more current than the cable is rated for. Upsizing the fuse defeats the point of having one and lets the cable become the fuse instead. Find the cause (a bad connection, a stalled motor, a fault to chassis) or upsize the cable and the fuse together.

Q: Do these work with lithium battery banks?
Not as a primary battery-side fuse. LiFePO4 banks can deliver a short-circuit current of tens of thousands of amps for an instant, and standard MEGA carries a lower interrupting rating than that fault can push. Use a Class T fuse on the battery-side of a LiFePO4 bank. MEGA is fine on the load side, after the Class T.

Q: What voltage systems do these cover?
Standard MEGA is rated to 32V DC, which covers 12V and 24V vehicle systems with margin. Some manufacturers make a 58V-rated MEGA for 48V systems (electric vehicles, tools, industrial applications). If you are on 48V, ask before ordering so the right rating goes in.

Q: Can I use these on 240V AC mains?
No. MEGA is a DC-only fuse. 240V AC circuits need HRC fuses or RCBOs installed by a licensed electrician under AS/NZS 3000. Elevate is EC17073 (Building & Energy WA) if you need that side of the work done properly.