Usb standard has 4 wires iirc, this way u have data in and out of the device..... And power to the device. Usb is supposed to provide 5v i thought.My phone technically says charging but it has no power. It should just he a USB slot for the radio interface?
What this mofo said. My phone will show charging but the port is really meant to connect to the radio for data like updates. There isnt enough power to charge it up like a cigarette portI believe after some digging that most of the USB ports are only 500mA, that is enough to trickle charge something like a current iPhone but you might notice it not keeping up if you have the screen on and gps running. iPhone and most other modern smartphones need 1amp for full function, and 2amps for fast charging.
That being said, even with the screen off and not running gps, the media connection on mine is hit or miss with with my iPhone 7plus. Never had an issue with an old fashioned iPod though. With my limited sample size, I’d assume the data connection works but just doesn’t have enough juice for most modern devices.
This is with my 2015 non-premium entire system.