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> Cables aren't the ones limiting current draw Incorrect. All USB-PD cables, whether their connectors are USB-A, -B, and/or USB-C, are responsible for honestly

> Cables aren't the ones limiting current draw Incorrect. All USB-PD cables, whether their connectors are USB-A, -B, and/or USB-C, are responsible for honestly declaring their charging power limit to the charger and to the device, and in the USB-PD specifications are specifically responsible for limiting current draw to the rated capacity of the cable. Per USB PD spec: > Sources Shall detect the type of Attached cable and limit the Capabilities they offer based on the current carrying capability of the cable determined by the Cable capabilities determined using the Discover Identity Command (see Section 6.4.4.2) sent using SOP’ Communication (see Section 2.4) to the Cable Plug. > The Cable VDO returned as part of the Discover Identity Command details the maximum current and voltage values that Shall be negotiated for a given cable as part of an Explicit Contract. Cheap, lying, uncertified USB cables that declare their ability to support higher charging rates — for example, 100W which is 5A at 20V in USB — have been known to short out and destroy chargers and devices in the process of doing so. This was discussed in a couple hundred comments across multiple posts when a Google engineer had to pressure Amazon through product reviews to enforce USB-IF certification on all USB-C cables several years ago: 2015: https://news.ycombinator.com/item?id=10508494 https://news.ycombinator.com/item?id=10508494 2016: https://news.ycombinator.com/item?id=11387212 https://news.ycombinator.com/item?id=11387212

izacus 4y ago
The cables are declaring their capability, but they're not LIMITING anything. That's on the charger and chargee side. >Cheap, lying, uncertified USB cables that declare their ability to support higher charging rates — for example, 100W which is 5A at 20V in USB — have been known to short out and destroy chargers and devices in the process of doing so. Yes, HN loves to discuss and gripe about it over and over again (quoting the same kind of unconfirmed posts that are out of date by years)... it just fails to prove that this is still any kind of widespread issue worse than any other cable connector issue.
- altairprime 4y ago
  Narrow roads aren’t limiting driver speed, and yet they’re used specifically by traffic planners to limit driver speed — with full knowledge that some drivers will disregard all limits. Compliant USB-PD devices honor those cable limits. Non-compliant devices do not, but ignoring them does not negate their definition as limits.

izacus 4y ago

The cables are declaring their capability, but they're not LIMITING anything. That's on the charger and chargee side. >Cheap, lying, uncertified USB cables that declare their ability to support higher charging rates — for example, 100W which is 5A at 20V in USB — have been known to short out and destroy chargers and devices in the process of doing so. Yes, HN loves to discuss and gripe about it over and over again (quoting the same kind of unconfirmed posts that are out of date by years)... it just fails to prove that this is still any kind of widespread issue worse than any other cable connector issue.

altairprime 4y ago
Narrow roads aren’t limiting driver speed, and yet they’re used specifically by traffic planners to limit driver speed — with full knowledge that some drivers will disregard all limits. Compliant USB-PD devices honor those cable limits. Non-compliant devices do not, but ignoring them does not negate their definition as limits.