# Fuse in cigarette lighter plug



## ahbdesign (Apr 20, 2012)

Hi,

I'm hoping someone can answer my unusual question.

I've been testing some cigarette lighter plugs and sockets (the ones people use for their car fridges).

I've noticed that some plugs have in-built fuses whilst others have fuses in the wiring (that goes to the battery). 

What I want to know is that, does it matter where the fuse is located? Is it better to have it in the plug? Or is it better to have it in the wiring instead? Or it doesnt matter?

For reference, I've been running the system at about 12.6V and a load current of 4.5A.


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## octaneman (May 13, 2009)

Hi ahbdesign


It doesn't really matter where its located as long as the voltage and current are respected.


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## WereBo (Apr 5, 2008)

Also, just as long as it's easily accessible too :laugh:


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## ahbdesign (Apr 20, 2012)

octaneman said:


> Hi ahbdesign
> 
> 
> It doesn't really matter where its located as long as the voltage and current are respected.


Oh ok! that's cool! 

Although is there a way I can test for this? As in how can i prove it?


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## octaneman (May 13, 2009)

ahbdesign said:


> Oh ok! that's cool!
> 
> Although is there a way I can test for this? As in how can i prove it?



Yes, the fuse has its maximum rating written on it, but for the socket in order to determine its voltage rating the inside and outside diameters must be measured with a vernier and then compared to a parts catalog.


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## ahbdesign (Apr 20, 2012)

octaneman said:


> Yes, the fuse has its maximum rating written on it, but for the socket in order to determine its voltage rating the inside and outside diameters must be measured with a vernier and then compared to a parts catalog.


diameters of?

Also, I was actually asking how to prove that a fuse in the wiring is the same as a fuse in the plug! I am not concerned about how well the fuse works, I am more keen on knowing where it should be placed in the system. Would I have to dig up my old electronic circuits books to find this out?


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## octaneman (May 13, 2009)

ahbdesign said:


> diameters of?


The actual socket.




ahbdesign said:


> Also, I was actually asking how to prove that a fuse in the wiring is the same as a fuse in the plug! I am not concerned about how well the fuse works, I am more keen on knowing where it should be placed in the system. Would I have to dig up my old electronic circuits books to find this out?




Its proven through a car's schematic either its at the fuse box or on the pigtail it doesn't really matter where its placed.


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## gcavan (Aug 13, 2009)

In any electrical circuit, the preferred place for a fuse or circuit breaker is as near as possible to the source. This protects the wiring itself. 

If you are wiring your socket direct from the battery, you will require a fuse in line with the wiring at the battery. Preferred would be to take power from a vacant, fused, position on the automobile's fuse panel. A second fuse, at the device, rated for the device, never hurts.


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