Which Fuse is the Right One?

Fuses come in many shapes and versions. Choosing the right fuse is often underestimated. Often, only the current rating is considered, but many other specifications are important as well. For example, the Interrupt Rating (IR) indicates the short-circuit current that the fuse can safely disconnect. If this is not adhered to, it may happen that the arc formed during a short circuit cannot be extinguished, or it takes longer to extinguish it. Surrounding components may be damaged by the explosion of the fuse. Therefore, it is important to adhere to the IR.

In lithium battery systems, the possible short-circuit current is significantly higher than in lead-acid batteries. Therefore, a fuse that works perfectly in a lead-acid battery system may be problematic in lithium battery systems.



In the image, you can see a commonly used Mega fuse on the left, which has an Interrupt Rating of only 2 kA. This is insufficient for most lithium battery systems. Therefore, always calculate the necessary interrupting capacity for your application. Our automotive fuses (on the right) can safely interrupt between 10kA and 50kA. They were specifically developed by a German company for the electric vehicle market. Please also note that the Interrupt Rating for DC is much smaller than for AC. Therefore, always inquire about the DC IR when comparing fuses from suppliers. Our NH fuses also have an interrupting capacity of at least 25 kA DC. Both our NH fuses and our automotive fuses can also be used in boats and motorhomes. However, NH fuses are less compact, but they can be used as main switches directly in fuse disconnectors.

The differences in the mechanical design can also be clearly seen in the image. For example, the 500A Mega fuse has copper tabs with a thickness of only 2mm. On the right, our 500A electric vehicle fuse, on the other hand, is equipped with a 6mm copper tab and M10 screw terminals. The NH fuse in the image also has 6mm thick terminal tabs. Both the NH fuses and the electric vehicle fuses are equipped with extinguishing agents, whereas the Mega fuses are not.

 
A Note on Fuse Rating:
Fuses should not be continuously loaded to their rated current. They will become very hot and age quickly. Additionally, the rated values are given for an ambient temperature of 20°C. However, the ambient temperature is often higher. Therefore, it may be necessary to reduce the continuous load or use larger fuses. For example, Victron recommends a 400A fuse for the 3kW 12V inverter, even though the current flow is much lower. If you're unsure, please call us before placing an order. We are happy to advise you! If you can't find the fuse you're looking for, let us know. We will check whether we can source it.