Re: Is a USB cable for data, or only power; how to tell without testing it?

On 12/2/2021 5:46 PM, micky wrote:
> Short of testing a cable, is there a way to tell by looking if a USB
> cable is data/power or power only?

No. Well you could peel off the outer insulation and see how many wires 
are inside. 4 to 8 wires and it's not power-only. 1 red and 1 black and 
it's power-only. I also think I remember a data-only cable, intended to 
be used between two powered devices, where they didn't want to connect 
the power rails of the two devices together 
<https://www.amazon.com/dp/B00WFF5FZS>.

> If not, why not?  Do they want to drive us crazy?

Power-only cables aren't that common. You can buy them, but with 
Quick-Charge chargers they won't be able to negotiated for higher charge 
current so they're normally used with a dumb charger that puts out 
500-2000mA. Power-only cables often come with devices that are powered 
via a USB connector but don't use the data pins. I have some 
rechargeable bicycle lights and flashlights like that.

Amusingly, some vendors try to charge extra for power-only USB cables, 
marketing them as "Data Block" cables 
<https://www.amazon.com/dp/B00RQ5AZ6Q/>.