What gauge wire should I use for adding USB ports to my car?

Question

I want to add powered USB ports to my car to charge various devices with. My plan is to order these USB soldering connectors fuse holders, 3amp fuses, and some wire.

Now I would find a hot wire somewhere before the dash panel, probably a connection from the 12v cigarette lighter, splice wire from there and run wire to fuse holder, which would hold the 3amp fuse, then wire from the fuse holder to the positive lead on the usb soldering connector, and then a ground from the positive lead to a ground mount somewhere in the car. Then simply put the soldering connector in the dash panel somehow.

I would use one 3amp fuse for a pair of ports, and would have 2 pairs, one in the front and one in the back.

Now my questions are, what size wire should I use for this? Do I need any diodes or anything? Do I have the right fuse size? Should I have a resistor or anything of that nature? Does everything else sound like it should work fine? I'd also imagine that the current would already be DC since it's using the car battery, but I could be wrong.

I don't have a ton of knowledge on electronics but I feel like I have enough to get this simple task done. That's why I want make sure every thing sounds right and don't end up messing something up.

Thanks!

Answer 1

Wiring a usb port directly to a cars 12V wire will fry a usb device. Never do this. If you want to do this, you should go with a 12v to 5V regulator. Preferably, a dedicated car usb charger. Then you have a few options.

• You can remove from its case, and attach it directly where you want the usb port to go.
• You can use a usb extension cable, either normal or one meant for mounting in a car mod.
• You can desolder and extend the usb port as needed.

The second option is simplest. They tend to have mounting clips, and no soldering needed. Various styles too.

For any modern phone, you want to extend all four usb pins from a dedicated charger, or they will refuse to charge at high speed or at all. Here is a simplified explanation on why using just a 12v to 5v charger wouldn't work well.

For wiring from your chosen 12V wore to the usb charger, 18 AWG wire would be best. The extra fuse is not necessary, as the cigarette lighter circuit should already be fused at a reasonable 10 Amps.

_{Frankly I found that slim usb chargers that flush mount to a cigarette outlet to be the easiest. Unless you need the outlet for something or its in a weird place...}