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Semi-related to Identifying data transfer micro USB cables vs charge only micro USB cables, is a USB cable that only works when plugged into a computer a suspicious sign? I bought a set of cheap USB-A to USB-C cables due to my wife having misplaced most of ours when borrowing them for charging. At first, I thought I had one bad cable, when I tried to use it with the car's AC adapter, but the others worked when I got home, at least when I plugged a phone into my computer. Then, I tested the first one, and it worked as well! So, I tried again, using a portable battery, and a wall-plug, and the cables don't work in that case.

I actually do not need these cables for data transfer — I usually use specific ones for that that I keep with the computer — but it feels a bit suspicious that the cables would only work in a case where they're connecting to a computer. That feels like it would require additional steps versus making one that works for power and data.

u1686_grawity
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Sean Duggan
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    What are the specifications for the computer's port? Are you sure that the device isn't charging in the car, or is it just very slow? – harrymc Jul 16 '23 at 15:39
  • @harrymc: I'm honestly not certain what the specifications are on the port other than I tried it on both the USB 2.0 and USB 3.0 (blue) ports on the front of my machine and they both showed charging on the phone, while three different ports I tried in the car that normally put out power (admittedly not much for the Aux ports) didn't show the phone charging at all, even after waiting for a few seconds for it to notice. – Sean Duggan Jul 16 '23 at 17:45
  • Did another cable ever give better results in the car (is it only this batch of cables)? – harrymc Jul 16 '23 at 18:01
  • @harrymc: Other cables work just fine. It's this batch that doesn't seem to work with the car or the power bank. – Sean Duggan Jul 16 '23 at 19:11
  • I'm not an electrical engineer, so can't explain it scientifically. My two-cents idea is that these cables don't transmit power too well, so a stronger (voltage?) power-source is required, and your car is not strong enough. – harrymc Jul 16 '23 at 20:40

1 Answers1

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There are 3 variables

  • Source
  • Cable
  • Device

Source

The source has evolved from USB 1 to 2 to 3 to 3.1.

USB 2.0 and 3.0 both operate at 5V, 1.8A, but USB 3.1 rose it to 20V, 5A.

From What’s the Difference Between USB 1.0, 2.0 and 3.0?

At the same time the pin used for power has changed.

Cable

To get the full fast-charge, requires a decent cable with a chip in the connector. Without that, the manufacturer may connect one or other or all pins at supply-side.

While USB-C is reversible, not all cables connect power to both pins. Some cheap ones (without a chip) connect one voltage to one pin and another to the other pin (based on my experience). Which is why, sometimes flipping the connector makes the device charge or makes it charge faster.

Device

Not all devices can handle all power levels.

So, its not surprising at all. If you are plugging into USB3.0 or higher than you need to get a decent cable.

P.S. On my mobile, so its a bit difficult. I will find a few more references later.

Rohit Gupta
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