In this video, we’re going to talk about protecting against catastrophic shorts, why some fuses explode, and why that’s bad. We’ll use Electric Vehicle battery arrays as an example, but this can apply to any situation where high voltage, high current shorts are possible. What do we mean by “catastrophic”? Just watch.
That is not how a fuse is supposed to work.
With EV battery arrays, you have the potential for high-voltage, high-current short circuits to occur, especially after an accident. Inadequate protection puts passengers and those assisting at risk of fires or explosions from these shorts. It’s a typical application for the seemingly simple wire-in-air fuse, but the video you just saw shows that maybe they aren’t so simple. And the point of the fuse is to prevent fires and explosions, not be the source of them.
Inside the battery enclosure, you will typically find a circuit board connecting battery cells with the battery management system with an array of wire-in-air fuses intended to protect against overcurrent events. In rare, but very real circumstances—like after a collision—the sensing cables could be shorted and these fuses that typically handle half an amp or less could be exposed to very high voltages and currents.
Test boards, like the one pictured below, are used to characterize how circuit protection devices on the connecting circuit board react to these extreme events.
Examples of blown test board
So, let’s look at a conventional wire-in-air fuse.
Again, this is a problem. You saw the fuse blow but then it continued conducting, likely due to prolonged arcing caused by the solder used in the cavity, and then it finally opened. These fuses go inside battery packs, which are sealed to keep out fluids and other contaminants. A fuse exploding like this would likely break that seal or break the seals on the batteries, themselves. In either case, this leads to more potential shorting or ignition of the battery pack, which would be a much larger fire.
AEM Components has taken a different approach with the construction of their AirMatrix wire-in-air fuse.
We can see this in the scope shots, as well.
We’ve highlighted some potential risks and issues with fuse selection for high-voltage, high-current applications—like PCBs in EVs or power storage—and shown how the construction of AirMatrix fuses yield consistent, reliable performance, even beyond their datasheet rating.
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