Samsung’s sudden recall of its Galaxy Note 7 devices must have come as a shock to the millions who have bought those flagship products. The manufacturer has blamed a very small proportion of defective batteries, putting to bed early rumours that the fault could be related to USB-C: this being one of the increasing numbers of mobile devices which now rely on USB-C for their charging and connectivity.
The prospect of devices catching fire or even exploding haunts many users. It should serve as a timely reminder of some of the potential problems with USB-C.
Until USB-C, devices including laptops which needed mains power supplies normally incorporated separate power ports and cables designed for that purpose and, most importantly, designed to cope with the power demands. There are exceptions which have integrated charge-and-connect ports, such as Apple’s iPads and iPhones, which is one of the reasons that Apple has insisted that cables and hardware which connect to its devices are properly certified.
USB-C can be different in this respect. Not only can you get cables which take USB-C to plain old Type-A USB sockets, but the market for USB and USB-C cables and related hardware is only lightly regulated. Yet USB-C allows a device to draw up to 3 amps over a cable. Fully USB-C compliant cables and ports should find that no problem, but old Type-A cables and devices may be limited to 0.9 or even 0.5 amps.
A correctly-designed USB-C to USB Type-A (or Micro-B) cable or adaptor should not find this a problem. It should inform the USB controller of its limited capacity to handle power, and that is all that it should be given. But some cables do not do this properly, and the USB-C end could try to draw up to 3 amps from an old port, leading to damage.
The moral is that, if you have a computer or device which has USB-C support, such as a MacBook, you must be assiduous in ensuring that the cables you buy to connect to that are up to the job. Shortcomings are most likely in cables which have USB-C at one end, and old USB Type-A or Micro-B at the other: ensure that they are of good quality, and that they are fully compliant. You can check that on the list of A to C Cables, as they are known, on the USB-C Compliant website. If you are in any doubt, segregate the cable and don’t use it for any purpose in which it could be excessively loaded.
We always hope that these issues and risks will settle as new standards become more widely used. In this case, I suspect that USB-C and power will be a longer-running saga.