Wiring up a USB charging port in +ve earth

[bergxu]

Hi gents,

Quick question for the group; I purchased a USB charging port with a plastic body as well as a plastic bracket to completely isolate it from any metal on the car. Being that the car is +ve earth and the fact that the socket will be totally isolated from any metal, should I run the hot wire to the + terminal on the USB and the earth to the - terminal on it or do I need to keep the hot feed to the - terminal on the back of the port and the earth on the + terminal? My only concern is charging my iPhone with the reverse polarity hence am wondering if I can wire the socket as normal (hot to + and earth to -) or if I need to hook it up the opposite way. I am aware that the end of the USB cord that plugs into the phone (it’s a USB-C actually) will need to be protected from touching any metal part of the car if the socket is wired as if positive earth so will take due caution there. I just don’t want to fry my iPhone or its battery. Thanks all in advance.

[Rob Reilly]

If this port is really totally isolated, then the words hot and earth do not apply.
Connect positive to positive and negative to negative.
You might put an inline fuse holder in the negative line just for extra security.