12v socket switched live conversion

[Dundrummin]

I know there are quite a few threads on this already (which I have read) but I have a quick question.

I want to convert the top of the dash 12v socket to switched live for a MagSafe charger. Just want to know, if I cut and extend the +I've cable to the fuse box using a fuse tap, do I also need to reconnect the -I've to ground or can I just leave it as is?

 

[Bramley Moore]

Probably be easier and look neater to tap in to the ignition live row and wire it straight in like a dash cam