Fuse rating for installing a cigar lighter / twin usb socket, (a single unit).

[FairweatherDave]

Got my non-electrician's brain in a spin. So I am installing this socket, see here
Force 4 Dual 12V & 2 x USB Charger Socket - Surface Mount | Force 4 Chandlery
On occasions this socket will be powering a 12v camping fridge, rated at 60watts. So the cable size I choose will match that of the fridge lead, which is reasonably chunky cable. From what I have read the fuse rating is determined by the cable size, but also it does no harm to oversize the cable. Now I should be able to work out the fuse rating for the cable supplying the socket. But my question is if I am running a computer fan off the USB side of this socket should this also have a small inline fuse, as the wires for the fan are tiny by comparison? Help / suggestions welcome.

PS Perhaps I should add the fan is cannabilised from an old computer so does not have a plug on it, but I was going to put a USB plug on .

 

[LadyInBed]

The combind unit that I bought off eBay came with in-line fuse unit. I can't remember the value but probably 5A.

 

[PaulRainbow]

Use 2.5mm cable to the cig socket to allow for some voltage drop and a 20a fuse, which will protect the cable. Anything you plug into the cig socket should be fused, usually in the plug.

Link the negative to the USB socket from the cig socket. You can use 1.5mm cable to the USB socket. You can then run a 1.5mm positive cable, with a 3a fuse, to the USB positive. You could take the 1.5mm positive cable from the back of the cig socket and fit an inline fuse inside the housing, but i don't like hidden fuses.

 

[FairweatherDave]

Thanks LIB and Paul. Subsequent reading an old thread got me to almost a similar conclusion, but great to have it spelt out - and I like the idea of a small 3a fuse between the Cigar and the USB parts . Point taken about not hidden.