Why you should avoid cheap fuses

[FridgeFreezer]

I saw this post today and thought it was useful enough info to share given a lot of folks aversion to electrickery :

https://hackaday.com/2023/07/05/a-fuse-is-just-a-fuse-right/

Quote

What about fuses? We would assume they are all essentially the same, but [Ham Radio A2Z] says he’s throwing away his generic fuses after he found they didn’t work as he would expect.

Of course, name-brand fuses are tested to very specific tests, and you get to see the plots of how the fuses are supposed to melt for Bussmann fuses. Then he takes out a generic assortment of fuses he bought at a hamfest. No Bussmann fuses in that batch!

Comparing the generic fuses with some from Bussmann and Littlefuse, they all work fine to carry current. That isn’t the problem. The problem is when you feed the fuses 20 A and expect them to clear. A 5 A generic fuse carried over 20 A for a very long time, and, as you might expect, it got very hot. We kept waiting for the fuse to blow, but after three minutes, he gave up.

For comparison, a 10 A Bussmann fuse in the same conditions blew almost immediately — about 350 milliseconds. None of the generic fuses blew, and, in fact, the fuse in the video had been subjected to 20 A of over-stress several times already. It seems like it is nearly impossible to blow them at that current level despite it being four times the marked current. Not much of a bargain.

As the video points out, fuses aren’t as much to protect your equipment as much as they are to prevent fires, so don’t forget to include them even on simple projects

 

Here's the slightly long video demonstrating the problem:

 

Bonus reading: Littelfuse's "Fuseology" technical document: https://www.littelfuse.com/~/media/automotive/catalogs/littelfuse_fuseology.pdf

[Ed Poore]

I've had exactly this issue in the 110. A partial short in the Argo trailer caused the sidelight fuse to get warm to the point it melted the housing and the fuse holder behind it. This resulted in the two bits of the fuse touching and therefore shorting out eliminating the fuse.

Smoke started coming from the dash (headlight switch) and I was quick enough to realise what was happening and stop it progressing further.

[Snagger]

It’s a Chinese plot to destroy all our vehicles!  Seriously, though, most stuff from there needs very careful assessment if it’s the only option, and avoidance on principle where there are alternatives.  One Life, too valuable for Chinese carp…

[FridgeFreezer]

8 hours ago, Snagger said:

Seriously, though, most stuff from there needs very careful assessment

TBH I think they'll just make whatever people ask for - someone comes along with a fuse and says "Like this but 1/10th the price please" and they will do it because no-one specified (or checked) that it should still actually work the same. The folks in their bedrooms in the UK running a drop-shipping gig on the side don't care or check what they are buying and there's no comeback to them either.

My rule these days is that if it's safety critical, mission critical, contains a battery, or is mains powered (which are the same thing 4 times really) I won't buy the random unbranded stuff or from random sellers.

[Ed Poore]

It's not quite that straightforward @FridgeFreezer, we've had some dealings with them after we were after some quite specific LEDs and getting them built to spec in China was one of a very limited set of options. They put a lot of effort into the first small batch to make them as requested and very high quality and then once they've nabbed you and secured the order for a bigger batch then the quality control gets thrown out the window. I'm guessing not everyone can be tarred with the same brush but we've not been alone in our experiences. We were lucky enough that we were able to work with Plessey and they designed and built the LEDs we wanted at a reasonable price.

[elbekko]

53 minutes ago, Ed Poore said:

It's not quite that straightforward @FridgeFreezer, we've had some dealings with them after we were after some quite specific LEDs and getting them built to spec in China was one of a very limited set of options. They put a lot of effort into the first small batch to make them as requested and very high quality and then once they've nabbed you and secured the order for a bigger batch then the quality control gets thrown out the window. I'm guessing not everyone can be tarred with the same brush but we've not been alone in our experiences. We were lucky enough that we were able to work with Plessey and they designed and built the LEDs we wanted at a reasonable price.

That's exactly what I read and hear everywhere.

[FridgeFreezer]

1 hour ago, Ed Poore said:

They put a lot of effort into the first small batch to make them as requested and very high quality and then once they've nabbed you and secured the order for a bigger batch then the quality control gets thrown out the window.

Oh yeah we've seen that too.

Luckily my current place they own the factory over there & have a director who speaks the lingo so he can phone them up and b*ll*ck them when they get lazy. It's a constant struggle though because they are just so used to doing thing that way.

[Snagger]

Even their viruses quickly become defective and unreliable…😉

[ped]

another couple of things to avoid are cheap crimps and hose clips
i bought a large box of assorted crimps of the bay of evil and even using good quality ratchet crimpers it was 50/50 if the wire would pull out
what i've been doing is removing the plastic then opening up where the wire goes then crimping with a flag terminal crimper and then soldering the joint and heat shrinking
on the hose clips i got a bag from screwfix and a good half tightened then clicked as the worm drive slipped these have been replaced with terry clips and jubilee clips problem solved

[FridgeFreezer]

Very true - I try to buy Tyco/Amp crimps from the likes of RS although it does mean buying 100 at a time, I have pretty much decided it's worth the expense (which is not massive, really, in the scheme of things) compared to having random wiring faults forever more.

And I found you can buy the display stand full of 100 genuine Jubilee clips for about £100 on eBay with flexi drivers thrown in, so now all my clips are genuine too and that's just so much nicer.