Inline Fuses

[Sci]

Why can't a regular car fuse, the flat plastic ones, be used in a mod? If the current gets over X amps, the fuse does it's job & breaks the connection. Current flow stopped...
Wouldn't that cure these battery explosions that I have been reading about in here? Could it be that simple? I dug through my car spare fuse box & found some 2,3,4, & 5 amp fuses. What is the max allowable current in a mod before it starts getting dangerous?
Or - could the a section of the wiring be of such a diameter that when the current reaches X it simply melts & stops current flow? Basically a homemade inline fuse?
I'm just getting into HV mods & would really appreciate some feedback on this. I use a master switch, trigger switch, regulator(for HV), & protected batteries from a trusted source in everything I do.
Thanks.

[petercro]

Why can't a regular car fuse, the flat plastic ones, be used in a mod? If the current gets over X amps, the fuse does it's job & breaks the connection. Current flow stopped...
Wouldn't that cure these battery explosions that I have been reading about in here? Could it be that simple? I dug through my car spare fuse box & found some 2,3,4, & 5 amp fuses. What is the max allowable current in a mod before it starts getting dangerous?
Or - could the a section of the wiring be of such a diameter that when the current reaches X it simply melts & stops current flow? Basically a homemade inline fuse?
I'm just getting into HV mods & would really appreciate some feedback on this. I use a master switch, trigger switch, regulator(for HV), & protected batteries from a trusted source in everything I do.
Thanks.

I was thinking about this same solution this morning.
It's a very good Idea (A little research is required)
Or if Scottbee could jump in and help.

I would guess that the fuses in the car are rated for 12v use.
I don't know.
Maybe a 12v 1 amp fuse would allow 3 amps at 3.7v, again I don't know.
You do find small fuses in household electronics, (rated between .5 - 2 amps at 5v). Would these be better.
Lots and lots of questions, and I'm sure and electronics wizz will jump in and help find the answers.

Great Idea.

[Scottbee]

There is absolutely nothing wrong with this idea.. as a matter of fact, in some ways it is quite good.

An automotive style fuse will add a small amount of series resistance to the circuit, but really not enough to impact PV performance. And in this case, current is current, regardless of the max or nominal voltage rating of the fuse. As long as the voltage rating of the fuse is higher than the voltage you are using, you're good to go. In other words, a 12V fuse is fine for this application. And a 12V 3A fuse will give you 3A of circuit protection when used at 3.7V.

Personally, if I was going this route, I would use a Polyfuse since they are quite small and auto-reset. But a traditional fuse is fine too.

[Lightgeoduck]

and the idea seed has been planted looking forward to this in the near future

[Sci]

I think that I read in here a normal atty is about 3.2 ohms? At 5 volts, that should produce 1.56 A. What is the danger zone when it comes to current with these batteries?

[petercro]

Scott
Thanks for the answer

Peter..............

[JollyRogers]

Doesn't the spring in the screwdriver act sort of like a fusible link? Could the same sort of principle be used, a fusible link inline with the atty from the hotside of the battery? I have not sat down and calculated the required fusible link wire size you would need, but it could work. Only draw back would be IMO, is if the atty shorted and the fusible link separated, it is not easy to replace unless specifically designed that way. Where as an inline fuse is easy to replace, but possibly clunky to design with. Also, won't the fuse/fusible link only protect against shorting to the switch or atty, depending on design?

[Scottbee]

A unit like this would be quite easy to incorporate into most of the mods that we are talking about.

Digi-Key - F3181-ND (Manufacturer - 16R300GU)

They also come in "surface mounted" (chip) form factors, for smaller mods such as the tubulars. Very easy to integrate of you are using FETs for switching (although most FETs make dandy fuses all by themselves!).

[Sci]

If you put that on the positive side before the switch, wouldn't that save everything else in the circuit in case of battery problems?
Depending on size, it might be possible to create a "protection" circuit & attach it to the top of the battery? If necessary, you could always trim the spring on the negative side. That way, you could use your current mods by, basically, creating a fused link between the battery & the mod.

[Scottbee]

Depending on size, it might be possible to create a "protection" circuit & attach it to the top of the battery? If necessary, you could always trim the spring on the negative side. That way, you could use your current mods by, basically, creating a fused link between the battery & the mod.

????

Why not just use a "protected battery" and be done with it?