Car Fuses and Solar - Not a Good Mix

Car Fuses and Solar – Not a Good Mix

When it comes to protecting your solar investment, it couldn’t be easier than adding a fuse.  In the event that the current in your solar array goes too high, the fuse opens up.  This removes the current draw on the system and protects it from further damage.  The problem comes from the fact that not all fuses are right for this application.  In this article, we are going to discuss why using just any car fuse isn’t a good idea.

I’ve seen a lot of talk about using car fuses in solar applications.  Why wouldn’t you use them?  They’re rated for up to 32V of DC electricity.  Most small off-grid solar arrays are running at 12V to 24V of DC electricity.  All of our requirements are met so far, aren’t they?

Truth be told, our requirements are not met.  A key component to fuse sizing is the AIC or Amperage Interrupt Capacity.  During a short circuit event, a solar array may produce amperage in the thousands.  This is especially true when talking about the batteries.  It is not uncommon for batteries to have short circuits in the 5000 amp range.  To keep it simple, the AIC rating tells you how much current the fuse can withstand.  If the short circuit of the solar array exceeds the AIC rating of the fuse, the fuse will fail to operate properly, causing damage to the array.

A standard car fuse typically has an AIC rating around 1000 amps.  During a short circuit event, this fuse will fail.  This is why there are specific fuses created for solar arrays.  An example of this is the KLKD Series from Littlefuse.  The KLKD series fuse can handle up to 600V DC with an AIC rating of 100,000 amps.  If you still choose to use a car fuse, be sure to use an ANL type fuse.  An ANL fuse will generally have an AIC rating of at least 2,700 amps.

Protect your investment, use the right fuse.