I needed 5 volt power from 12 volt car stereo unit to connect wireless charging for an iPhone 6. Needed it the dash, and wanted it to look clean. This is my rendition on this how to.

Step 1: My Unit

It was the most available, cheapest, smallest, and had the fast charging option. "Lifetime Warranty"... But I'm sure I voided it.

Step 2: Disassemble

Take apart, screws and top that screws off. Some units I would imagine you would have to carefully split open, especially if you want to reuse the casing.

Step 3: Snip Spring and Connect Wires

Cut spring as close to start to have as much room for the wires coming out. Thinner wires than I used would be better. I'm working with what I got, which is 18 gauge. Loop red to power (snipped spring loop). Then cut metal piece off ground and strip, carefully. Not much wire to work with fro ground. Then you must solder, and tape off ground.

Step 4: Guide Wires

Guide the wires through the hole as best you can. Second time around I found the ground fits best through the bottom. Snug fit because of my thick wires, but got it done.
Put everything back together and put electrical tape in the side holes were the pressure tabs used to be and done.
Function and form for $6.
I hate aux, and power cables.