I know this is an old post, but it’s what came up when I was trying to solve this issue on my wife’s new-to-us 2013 Leaf, so I thought I’d share what I’ve figured out in case it helps anyone. Best I can figure out is that there’s some sort of safety circuit that disables the USB port if anything tries to draw more than the 500mA that’s the USB 2 max allowed draw, and that circuit resets when the car is powered off and back on. I tested with a USB flash drive, and an iPhone 6 with and without a Mophie battery case. The USB drive lighting up let me know there was power to the port, then I’d swap in the phone/case. Connecting the phone by itself was fine, but as soon as I connect the case (which has a higher power draw), the port powers down until I turn the car off and on without the case connected. I repeated this a few times and just decided that we’ll have to skip the battery cases connecting to the car.