Testing USB Cables and Chargers: Not All Are Created Equal

While similar in form and function, various USB cable types can behave differently. Learn how USB cables have improved over the years, and what it might mean for the future.

If you’re old enough to remember Amiga computers or the Pentium chip’s impact on processing power, you probably also remember that era’s plugs and ports. These connectors looked and functioned in completely different ways, each designed for a specific purpose. A serial port could drive various accessories, but you also needed a parallel port for your printer, PS/2 ports for your keyboard and mouse, and of course a game port to plug in a joystick to play Mech Warrior and various fuzzy flight simulators.

In 1996, that all changed when the Universal Serial Bus, or USB, hit the market. No longer would you need specific ports for different devices; just plug your accessory into a USB-A socket on your computer. This change took some time to become the industry standard—and you may still run across older ports in the wild— but the upside to this technology is that you can plug in any accessory and expect it to work. It can be a keyboard, mouse, flash drive, or even a smartphone. Your device is then free to interact with your computer or just draw power for charging.

USB Cable Improvements Seen and Unseen

A standard form-factor is interesting, but developing the USB port into its current form took a great deal of work. While 1996 marked the release of the first USB standard, USB 2.0 was released in 2000. These cables look no different, but USB2.0 included the following capabilities:

- Dedicated battery charging

- On-The-Go specification that allows two USB devices to talk to each other directly

- Higher data transfer speeds at 35MB/s

USB 3.0 debuted in 2008, 3.1 in 2013, and 3.2 in 2017, allowing transfer speeds up to a staggering 2500 MB/s.

Most smartphones use USB, which means you can swap cables and devices for charging and data, and not worry about finding the specific connector for your phone. On the other hand, while cables may look similar, some may not function as well as others, leading to possible bottlenecks in data speed and charging.

Along with these physically unseen improvements, developers introduced new smaller connectors, like the mini and micro USB-B connector, as well as the USB-C. Unlike older cables, USB-C cables are reversible in orientation, featuring two identical plugs on either end of the same cable.

USB Cable and Charge Testing

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Fig 2: USB Cable Transmission test setup

To see how cables in the wild—our office—stacked up, we took a variety of available USB cables and tested them to determine the following:

- Correct power and data transmission.

- Resistance between each power and ground connector.

- Voltage and current transmission with a variety of chargers.

Consult the table below for our findings.

USB Signal Continuity and Resistance Tests:

0818_usb-chart

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 USB splitter and power cutoff tested with Micro USB1 cable. Cables 1, 3, 5 were in good shape and from respected brands. Cables 2, 4, 6 were of unknown origin. Cable 2 was well-used and had a frayed cover; cable 4 had been partially melted in a previous experiment.

Charge Tests: USB-C on Partially-Charged GoPro 5 camera, Micro USB on Smartphone

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Varied intermittently from 0 amps and charging.

It’s evident that the USB cables I tested do indeed work in nominally the same manner. There were three exceptions:

1. The Micro-USB (2) cable only charged intermittently. The cable connected in the original test, though it was noticeably loose in my phone’s port. Perhaps both connectors were made to one end of their respective tolerances, but this junction seems to be the Achilles’ heel when charging over USB.

2. The USB splitter cable only provided data lines on one of the two output wires.

The USB power switch didn’t provide a data connection at all. This isn’t too surprising given its function, but in some specialized applications, independent control of the data lines would be essential.

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Fig 3: USB Charging test setup

This limited test makes it difficult to identify a pattern of charger/cables/charged devices. With a properly-rated charger, your chief charging concern is whether your connector is robust enough to handle the rigors of repeated attachment/detachment.

Initial tests indicated that none of the cables could communicate via the USB 3.1 standard, so data transfer rates may bottleneck with lesser cables. Testing also showed that both USB-C cables feature a pull-up resistor, and picked up on plug reversal as a digital input. Plugging in the cable is certainly convenient, and this feature could be employed to switch between different functionalities depending on how it’s inserted.

The Future of USB Cables?

Curious tech users, test your own cable inventory. If you don’t have the time for scientific evaluation, at least consider throwing away those that perform noticeably worse than others. Spend that money on high-quality cables instead of buying test equipment to ensure 100% optimized results.

Poor-performing cables aside, it’s amazing how far we’ve come from the specialized ports of old. Perhaps in the future, USB-C will become so standardized that you can order a device with or without a cable, saving you money and preventing e-waste from the buildup of cables. Or maybe a universal wireless charging and data transfer standard will emerge, freeing up desk and drawer space worldwide. Either way, the future holds exciting communication and charging developments, and we’ve come a long way from the Amiga computer days.

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