[illumin8]

This is my wife. She purchased a bunch of USB-A to USB-c cables off Amazon and wonders why her laptop runs out of power while plugged in - it's because the laptop needs 25-30 watts and those cables can only put out 5 watts because they're limited by the USB-A port.

USB-c PD is such a dumpster fire of a standard. Even with supposedly high end cables like Anker you often can't charge a Macbook Pro faster than it can drain it's own battery under load. We can't expect normal people to understand why there are a dozen different cable types that all have the same tip but charge at vastly different rates...

[literalAardvark]

That's true of all things that don't respect standards, not a PD issue. If you buy a wheel and it's not up to spec it'll crack. If you buy a power cable and it has a type-c on one end and a 110/220v plug on the other, that's not going to work well either.

Buy stuff that's up to spec, and it'll be fine.

[Dylan16807]

The charging speed of USB-C cables (C on both ends) is pretty much just the slow ones and the fast ones, and "slow" is 60 watts.

[j16sdiz]

No. PD is optional in standard.

[Reason077]

No, all compliant USB-C cables support 60W minimum (3A @ 20V). That is the minimum baseline for all USB-C cables.

Higher power levels beyond 60W are optional. The newest PD spec goes up to 240W (5A @ 48V).

[OkGoDoIt]

Compliant being the keyword there. Are you saying all of the crappy cheap low-end USB-C cables you find on Amazon are fully compliant? You have to put an effort to find brands that are actually legitimate, and pay more for that. Hence the vast majority of people probably won’t successfully do so. Standards compliance is theoretical in the real world that involves cheap crap from Amazon.

Anyway the GP post is referring to a USB A to C cable and an old-fashioned USB A wall charger, many of which barely output a single watt. My family members have had similar problems due to similar confusion.

[seba_dos1]

As long as the cable isn't completely broken and has wires that actually conduct the current, you're getting 60W over USB-C PD. It's 100% passive. Compliance means "it connects one end with another without causing fire", it only gets more complex at more than 60W.

If it doesn't have the wires inside, you've been scammed into buying a piece of junk that merely looks like a USB cable.

When using a USB-A charger, you're guaranteed* at least 2.5W, and the charging standard (BC 1.2) goes up to 7.5W (though usually you can go higher with proprietary protocols, such as QC, or even PD 1.0, although it's very rare for something to support PD 1.0 and pretty common to support QC or Apple signaling). Sure, you won't be able to charge a laptop from a USB-A port, but it's not a hard thing to grasp.

I don't think you know what you're talking about.

* You could probably find some chargers that do less than 500mA, but you'd have to search among 20 years old ones at this point and they wouldn't really work with anything modern anyway, PD or not. The hard requirement is that a port has to provide at least 100mA, but that's only relevant to data ports that can do USB enumeration - for charging-only ports, everything assumes at least 500mA, and it would be really hard to find something with less than 1A or even 1.5A (7.5W) these days. Of course, if you try hard you can find any kind of weird stuff out there - I've got a water fountain for cats with power adapter that has a USB-A port providing 9V, so connecting anything else to it may make it release its magic smoke - but that's hardly a problem with USB itself.

[Dylan16807]

Optional in what way?

Having power wires isn't optional. The ohm limits aren't optional. And they can handle 20 volts by virtue of using normal insulation.

The 60 watt limit is for completely passive cables that don't implement anything PD-specific.

[throwaway2990]

No.

[Dylan16807]

Yes.

Every conforming cable supports 3 amps and 20 volts.

If you think something's incorrect with that, be specific. But the spec is pretty clear.

The exact details of the faster cables are murky because there's old and new versions of that section of the spec, but very few devices use enough power to care about that.

[throwaway2990]

USB-C spec is not very clear. And even in cases where it is clear. It’s not followed. There’s so many bad cables around. Cables that work on 1 device but not another, cables which do data and not PD, cables that do PD and not data, USB-C has the nicest plug with the worst experience.

[Dylan16807]

The power handling of a basic cable is very clear.

If something breaks that, it doesn't make sense to blame USB. Whatever the manufacturer was doing, it was such a mess that it would fail with any other standard.

Supporting data and PD is just three tiny wires, it's not hard.

[oarsinsync]

> Every conforming cable

The problem is all the non-conforming cables that people have, that look exactly the same as conforming cables.

[seba_dos1]

In this particular context, a "non-conforming" cable would cause troubles by starting fire or dropping voltage below usable range, not by limiting charging current. The only sane thing to do with such cables is to throw them away.

Really, we're talking about physically broken cables here. As long as there's electrical connection, there's no other way for a cable to not work at 3A/60W with USB PD. Its cable requirements only start when you want to go higher than that - and 60W is plenty of power already.

[geoelectric]

Except they were responding to a comment criticizing USB-C PD as a standard. Non-standard cables are irrelevant to that discussion.

[oarsinsync]

> We can't expect normal people to understand why there are a dozen different cable types that all have the same tip but charge at vastly different rates

Is the part of the GP comment I was responding to. The connectors form part of the standard. There’s no way to identify a standards-conforming cable from a non-standards-conforming cable by looking at it. They all look the same.

[seba_dos1]

There are no USB cables that are limited to 5W, and standard non-PD USB-A ports can give you up to 15W.

The only case where you may need a different (non-passive, "e-marked") cable is when going above 60W (3A).

[dhosek]

I recently discovered that I can use my iPad and MacBook charging brick to test PD of a usb cable. If it’s low wattage, the charging brick will not provide any power to the iPad. High wattage and it will.

[diffeomorphism]

It is a bit curious that you immediately jump to PD being a dumpster fire instead of the much more immediate "apple is a dumpster fire and incompatible just to be obnoxious".