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HomeTips & GuidesWhat is a Mega Fuse: Key Features and Applications

What is a Mega Fuse: Key Features and Applications

What is a Mega Fuse? Electricity can have damaging/fatal effects, especially when it exceeds certain thresholds. 

For instance, connecting an electrical appliance to more power than it needs may blow it up. 

Fuses are handy in curtailing such occurrences by ensuring they disconnect the current pathway in the event of a surge. 

In today’s guide, we’re exploring a type called a mega fuse and its qualities. Let’s dive right into it.  

Table of Contents

What is a Mega Fuse?

It is a fuse designated for the control of high currents of up to 500 amps. The capacity for a Mega fuse is so high that it can handle a current higher than the MIDI fuse. A typical use of a mega fuse is in the following: 

  • Alternator/battery protection
  • Solar charge system
  • Power distribution panels.

Also noteworthy is that it is a bolt-down fuse that perfectly fits with M8 mm bolts. 

The choice of the Mega fuse you use will depend on the voltage of the system in question. 

For instance, if you’re dealing with a 12-volt or 24-volt system, the ideal is the Fuse – Mega 32v. 

But for systems with a higher voltage, such as 48 volts, you should go for a 58V DC fuse. 

Mega Fuse vs. ANL Fuse: What is the Difference Between a Mega Fuse and an ANL Fuse?

Fixing a Car Fuse. 

Fixing a Car Fuse. 

An ANL fuse is a viable alternative to the Mega fuse, as both are primarily bolt-down fuses with Ultra-High Current Protection capabilities. 

But while the mega fuse is slow, the ANL fuse is remarkably fast-acting. Both are useful in controlling high loads. So, how else do they differ? 

Ignition Protection

With an ANL fuse, you can tell when it blows, as primarily, it features a window from which to check.

Moreover, it has an ignition protection feature. Therefore, it is safe for use in engine compartments of gasoline engines with the risk of blowing up. 

However, you cannot safely use a Mega-Fuse in a gasoline-powered engine compartment. 

Unlike the ANL fuse, the mega fuse will form a spark when it blows, so it’ll likely start a fire in the engine. 

Interrupt Rating

It’s a measure of the maximum current a fuse can safely interrupt. An ANL fuse has a relatively high interrupt rating of 5000 Amps.  Hence, it fits large power banks’ primary circuit protection perfectly.

Conversely, the Mega fuse features a lower interrupt rating of 2000 Amps and is thus unfit for larger power bank circuit protection. 

Other differences are as per the table below: 

ANL FuseMega Fuse
It is cost-effective and ideal for cabling protection.It is useful in applications such as the following Hydraulic hatch motors: DC Motors, Bow Thrusters, Engine trim pumps, and Davits Anchor Winches.
They are available in high amperages, and quite a lot are made of ceramic. It has a lower protection rating than an ANL fuse.

Symptoms of a Bad Mega Fuse

The Mega Brand Fuse is probably the issue if a car doesn’t crank.

Does a car have a Fuse Failure Indication System? Most cars, especially the old ones, don’t have such a mechanism. But you can still tell when the fuse is the problem. 

A fuse is at the center of a perfectly working car’s electrical system. Hence, when it blows up or is faulty, there won’t be any connection, and the system will fail. So, how can you tell when your mega fuse is blown?

Most of the time, when you find there’s no current flow, there’s every chance that the fuse is blown. 

If your car’s ignition system fails, the most probable cause is a blown fuse. Therefore, a mechanic should diagnose what caused the fuse to blow. After fixing the issue, you can then install a new fuse. 

Replacing the Mega Fuses

Replacing a Victron fuse. 

Replacing a Victron fuse. 

Sometimes, the fuses making up the mega fuse can break due to vehicle vibrations, leading to a loss of the car’s electrical power. 

The solution in such an occurrence is to replace the mega fuse with a staked one for improved performance with dielectric enamel. It will strengthen the ends, making them less prone to breakage and increasing their lifetime. 

Parts Required

A Hex Nut. 

  • A Mega-Fuse (the number will depend on how many you want to replace)
  • Hex Nuts
  • Flat washers

Here are the steps to replace the car’s mega fuse(s): 

  • First, switch off the engine and ensure you disconnect the battery from the negative terminals for safe use. 
  • Next, locate the mega joint junction and replace one at a time (assuming all the mega fuses are faulty). 
  • Unlock all the terminals of a mega fuse and scrub the area with a soft brush to remove rust. 
  • Replace the mega fuse you remove with a new one and restore the power cable onto the fuse to continue the previous connection. 
  • Reinforce and lock the fuse using a flat washer and a hex nut. Remember to apply a layer of dielectric grease between the washer and the hex nut. Tighten the hex nut and finally wipe off the excess grease. 
  • Next, apply a dielectric red enamel cover on the mega fuses junction and reconnect the disconnected negative battery cable
  • Finally, coat the battery terminals with dielectric grease and test whether the new fuse works well. 

How to Size Fuses

Different fuse sizes. 

Different fuse sizes. 

Picking the right fuse size is key in choosing one that protects the system from an overcurrent. 

It should also ensure the system functions normally and that the right current reaches all the components. 

Here are the primary tips: 

Manufacturer’s recommendations

Usually, manufacturers will provide the details of the ideal fuse for a particular device/component. 

Their recommended fuse size is the best, as it has been tested, proven effective, and compatible with the device. 

The only time you should defer from following the manufacturer’s recommendations is when there are certain reasons to do so, such as follows: 

  • If the local regulations do not allow you to use the recommended fuse size
  • When there’s a code conflict
  • If there is a poor/wrong translation of the user manual. 

Calculating Fuse Sizes

How about when there are no manufacturer recommendations on the right Amp Load Fuse to use? 

In such scenarios, you can still pick an appropriate fuse by primarily performing some calculations. 

Recommended Fuse Size = 1.2 x Continuous Amperage of device 

We multiply the continuous amperage by 1.2 because the aim is to achieve 120% of the continuous amperage. 

With such a factor, you pick a fuse that enables the device to function effectively without much overhead. 

The alternative is to use a fuse sizing calculator. There are many kinds you can find online.


A Mega-Fuse ensures a car’s electrical system runs smoothly and has current circuit protection. They are also useful in alternator protection applications. 

In cases where you cannot access mega fuses, you can go for ANL fuses that are equally effective and arguably easier to use. 

Above everything, always choose the right fuse for your application. Contact us, and we can help you get reasonable electrical components and wiring harnesses for your DIY projects.

I am Lillian Yang, having been a sales manager for over 10 years.

I have received many positive reviews from customers. They have praised our excellent service, on-time delivery, and high-quality cable assemblies.

For your projects, please provide cable assembly files/images/smples, etc., so that I can send you a quotation within 24 hours.

Contact me now and let’s get started on building your wire harnesses!

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