iPhone (not) Charging Surprise

So iPhone 15 was meant to solve all charging compatibility problems for good. With the long awaited switch to USB-C the promise of a universal charging standard and a single cable to rule them all finally arrived.

Except when it just does not work.

I've been a huge fan of USB-C (the connector) and all the related standards - from the legacy 480Mbps data transfer to 5/10Gbps USB 3/3.1 to 20Gpbps (and sometimes even 40Gbps) Thunderbolt. And of course USB Power Delivery (USB-PD), which is independent from the data transfer schemes.

Of course, as any new standard, USB-C suffered from bad implementations, the most common mistake has been vendors failing to include 5.1kΩ resistors to properly trigger compliant chargers.

But then on my recent vacations trip I was surprised a simple A-to-C cable would not charge the iPhone. The cable seemed to be just fine. Actually it was the cable which came with one of my Logitech accessories (the Bluetooth keyboard) and I picked it to take with me because it was nice and slim. And the Logitech brand was somehow a guarantee of quality and performance.

But it just would not charge the iPhone.

It was charging perfectly other low power accessories (the Bose earbuds) as well as regular power devices like my son's OnePlus phone. So with this we ruled out the potentially faulty USB-A chargers (including the i-seat aircraft sockets) and the cable itself. But the puzzle remained unsolved. And I was scratching my head wondering what might be the issue.

At one point I thought I found the answer. By plugging the cable to my power bank (which has a nice display showing the details and progress of charging) I noticed it was reporting 4.7V charging voltage (instead of the expected 5V). So I thought the thin cable was simply introducing a voltage drop which the iPhone rejected as non-compliant (even though it is perfectly sufficient to charge a 3.7V battery).

But that theory was dismissed as back at home I tried another A-to-C cable which had even bigger voltage drop (down to 4.6V) and it was charging the iPhone just fine.

So the puzzle remains unsolved. And the lesson learned is - despite all looking just perfectly fine - cross check your gear before the trip. As you may find your gear inoperative and impossible to fix when on a remote hiking trip far from the civilization.