Port Washington Electric Vehicle Association
Safety Notes

In the course of working on our electric vehicles, we come across various safety issues.
As we do, we'll report them here.

Fuse Holder Problems

While working on our NiCd battery upgrade for our Solectria Force EV, I ran into a problem with a fuse holder.  I had installed a 10-amp fuse on the 12-volt supply line running to the new battery cooling pump/fan assembly in order to be nice and safe.  A few days after completing the project, I was inspecting things to make sure all was well when I noticed something strange with the fuse holder -- It was melted!  See the photo below...

The pump and fan were still operational but as you can see, the two halves of the plastic in-line fuse holder were melted and had actually come apart, the plastic threads of the screw-together housing being completely distorted.

Logic tells you that it couldn't have been over 10 amps because that's what the fuse was rated for, but I thought I'd better check just in case the fuse had been mislabeled.  I cut the fuse out of the circuit and hooked my ammeter to the circuit, and verified that no more than 8.5 amps were flowing through the circuit.

I've had problems with this kind of fuse holder in the past, because it's spring-loaded, with the spring maintaining pressure on the contacts on each end of the fuse.  This theoretically maintains electrical continuity, but I know from one incident that you have to be careful to keep the wires loose -- Any tension applied to them will compress the spring and pull them away from the fuse contacts.

My theory in this case is that the electrical contact wasn't perfect at the ends of the fuse, and there was some unwelcome heating going on, which caused the melting.  I have now replaced the fuse holder with a blade-type automotive fuse holder from Radio Shack, part number 270-1213.  These holders provide a much better, positive contact for the fuse.  I strongly recommend using them!

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This page last updated 06/07/02