Like all digital packrats, I have accumulated a wide variety of USB-C to USB-A cables over the years, but only recently did I realize how many of them were dangerous to my electronics and should have been destroyed. Yours probably should too.
Why destroy a fully functional USB-C to USB-A cable? Well, it all goes back to the introduction of USB-C in 2014. The reversible connector was a big departure from previous USB designs and was so complicated that many cable manufacturers didn’t know how to build a secure USB-C cable. Simply put, each lead should have a 56k ohm resistor. This lets your phone, tablet or laptop know if the USB-C port is plugged into an old square USB-A port or not.
If the device detects the 56K resistor, it limits the amount of energy it draws from the port. If, however, there is no 56K resistor, the phone or tablet assumes it is connected to a higher powered USB-C port. In that state, the cable can potentially draw too much power from the port it is connected to, burn the port, and sometimes cause damage to connected devices.
Gordon Mah Ung
The good news? This problem was fixed years ago and even the cheapest USB-C to USB-A cables I recently purchased were built to specification.
The bad news happens if you come across an older cable that was built incorrectly. It might seem unlikely since this problem stopped being a problem four years ago or more, but nobody throw away useful cables. We either dump them all in a shoebox or wrap them up and put them in a bag. Sure, sometimes I’ll do away with old serial cables and printer cables, as well as MicroUSB and MiniUSB stragglers, but USB-C rules the world. I also don’t need the cable, someone else might. In the box it goes.
So in the interest of seeing how many actually damaged cables there are in my collection, I took almost every USB-C to USB-A cable I could to find out how good they are. Turns out I’m a digital pack rat and have amassed no less than 43 cables.
Only one cable was fast
You can see the result of my tests below, but one of the surprises was just how many of my cables are absolutely terrible for data transfer. USB-C to USB-A cables can support up to USB 3.2 10Gbps if they have additional cables. Without the extra cables, you typically get the 40 Mbps base transfer speed of USB 2.0. This means that using a USB-C to USB-A cable for your NVMe SSD would make transferring large files minutes instead of seconds.
Of the 43 cables I tested, only one cable supported USB 3.2 speeds at 10Gbps. Only one.
In addition to classifying the cables based on the speed of data transfer, I also placed them in the containers based on the resistance of each. For cables primarily used to charge devices, a cable with a lower resistance generally means thicker or higher quality wires were used in the construction and more power comes to the device you are charging.
The good news is that most of them were decent, but I found six cables that I threw in the “bad for charging” bin because the resistance was so high. In practice, it might not be a big difference in the total time charged, but if a cable needed to be eliminated, I wanted a good reason for that.
Charging only cables
You know a cable connector standard came when companies start to really slaughter it by making cables that are literally charge-only cables. So it goes from USB-C to USB-A. Among my cables I discovered four charge-only cables that only had charging wires. Why build cables like this? The main reason is to save money by doing them. But the problem with charging-only cables is that they look identical to charging and data cables.
Perhaps worse, though, is that these charge-only cables actually experienced very high resistance. This, ironically, makes them terrible charging cables.
But on the plus side, all the cables I’ve mentioned so far were all wired correctly with 56k ohm resistors. Even the most terrible charge-only cable would keep your phone or tablet from blowing up your laptop’s USB-A port.
That luck did not last. The remaining 10 cables were improperly constructed. Five were built incorrectly with a 22k ohm resistor or wrong wires with 56k ohm resistors. The remaining five did not have 56k ohm resistors and should be classified as dangerous to use and likely destined for destruction. These were the cables on which red flags were raised in 2015 and are probably still floating in similar boxes around the world.
These compromised USB-C to USB-A cables could probably be used safely when plugged into dedicated wall chargers that can’t exceed the power required by your phone. Problem is two years from now, that dangerous cable could be used in a pinch and again mixed with good cables, potentially causing a laptop door to explode.
And don’t make the mistake of thinking that dangerous cables only came from poor manufacturers. Having a brand name cable won’t necessarily save you. Of the five dangerous cables without whatever 56k resistors, two were from a well-known phone manufacturer and another was from a very popular aftermarket cable manufacturer that I still buy cables from today. Of the cables that were wired incorrectly, two were from another phone manufacturer. Another USB-C cable that didn’t make the cut came with an expensive high-performance SSD. So tightening the branding to the chest may not always work.
Gordon Mah Ung
How to avoid a bad cable in your collection?
The easiest way to fix this is to select the damaged cables from your collection. Unfortunately there is no easy way that I know of without spending money. The easiest way I’ve found is ADUSBCIM’s Cable Checker 2. It allows you to easily evaluate the capability of a USB-C-to-C and USB-C-to-A, as well as Micro and Mini USB cables. The small display offers a quick and dirty view of the cable resistance and the presence of the 56K resistor. It can also tell you if it’s wired oddly (56K on two lines instead of one) or if it’s using the wrong resistors.
At $ 65 on Ebay (otherwise I haven’t found it at retail in the US), it’s probably the easiest way to test your cables, although other methods that are a bit cheaper are available.
The obvious problem? Spending $ 65 to test your free USB-C cable collection doesn’t make any financial sense. The cheapest option for most people is one thing no one wants to do – shred your current battery and simply buy new USB-C cables that are known to be safe and good, for a lot less than $ 65.
Should you destroy your cables?
Whether you should carry scissors to your old USB-C to USB-A cables depends on your comfort level with the risk. If you’ve been using the same cable for years, that’s probably fine. Bad USB-C cables mostly run the risk of damage when you connect a computer to your USB-C device, so if you only use them with chargers, the risk is greatly reduced. If a relative comes around, however, and you unplug that cable to transfer some quick files from a phone to the laptop, you run the risk of it getting damaged.
The last thing you might want to change is your behavior on abandoned cables. If Bob throws the bird at the company and leaves, leaving a pair of USB-C to USB-A in his cubicle on his last day, leave them alone. Rather than seeing this as a “free” pair of cables, you should probably just buy a new set of cables that you know will be safe.
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