Hard-wiring a USB extention cable?

[Domokun]

Ahoy,

I'm a total 12v/electronics novice, but I'd like to fit a female USB port into my car in order to charge a GPS, PSP or any of my other USB devices. It'd be so helpful if I could run my idea by someone who knows what they're doing... :D

I appreciate any time you can give to post in reply, so I'll try and keep this succinct.

I have a 04 Model Skoda Fabia. I'd like to run a wire from the fusebox, which looks like this, (minus the red wires), using an add-a-circuit device like this, so I don't have to solder anything or deal with any wire ends at that stage.

At the other end of the wire running from this add-a-circuit I'm going to attach an in-line cigarette lighter socket like this, making the circuit more modular. From this I will connect a common 12v -> USB adapter, and from that a USB extension cable.

The USB extension cable and the 12v -> USB device is something I already have, so this isn't a problem. My question is, does my circuit make sense other than this.

I'll be plugging the add-a-circuit into the fuse for the existing cigarette lighter and using the same rating of fuse for the new circuit.

Secondly, the add-a-circuit device seems to only have one wire coming out, does the cigarette lighter adapter not require a ground or neutral? It certainly has solder tabs for one.

Somewhat useful diagram...

Mini blade fuse gap in fusebox -> Add a circuit device -> wire behind the dashboard -> cigarette lighter adapter -> 12v/usb converter

I'd be very grateful of any insight or help anyone can give to me and others considering the same with the Fabia, Polo or Ibiza cars, or any other models which use the mini-blade fuses.

Thankyou.

Domokun