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Comment by ytch | Hacker News Reader

Out of curiosity, does 5V/5A USB-C changer common?

All of my USB-C Chargers has 5V/3A only.

It does not appear to be common, or at least, it's not in the spec. Per USB-C spec, chargers only have to supply 3A at various voltages, with 5A used only for the 100W 20V profile.

If you buy a charger advertised to support "PPS" at 65W or so or more, you are more likely to get one that does this, though not all will actually do it.

Thanks for all reply, I guess it's my misunderstanding on the 5V/5A requirement:

https://www.raspberrypi.com/news/introducing-raspberry-pi-5/

> When using a standard 5V, 3A (15W) USB-C power adapter with Raspberry Pi 5, by default we must limit downstream USB current to 600mA to ensure that we have sufficient margin to support these workloads.

Therefore 5V/3A can still boot RPi5, but it cannot provide enough power to its USB-A port. Therefore it cannot use something like 12V/2A, since RPi5 doesn't have transformer circuit on its board.

They're not, and it's a very annoying requirement. Even 5V/3A was hard to provide reliably. On the other hand, rock pi supports 12V/2A, which modern chargers will provide without any issue.

Anything that can't supply 5V/3A is not a modern charger, that combination is mandated by USB-PD for anything that can provide 15W.

Oof, this sucks. I wish they supported the wide variety of Anker/Apple/etc. USB-PD chargers out there that can deliver 100W so I can use my existing power bricks. None of them do 5V5A though, they just created yet another nonstandard piece of "USB-C" equipment and it's going to suck.

5V/5A means at least 25W. Plenty of chargers at that level and above on Amazon.

25W is easy, but most of them will not do it at 5V. I checked one of my 100W chargers, it'll only do 5A @ 20V. 3A at every other voltage. Looking at many other chargers on Amazon do the same.

I just did a quick review on Amazon of adapters ranging from 30 to 120W. Not a single one claimed to support 5V/5A DC. Only a couple claimed 5V/4.5A and they were expensive. 5V/3A is common in the $15+ category.

Most 65W chargers are 20V/3A. Standard USB cables are built to carry at most 2-3A, and e-marker cable authentication chips are required for 5A, I believe, because people running 100W on a random USB cable is scary.

Chargers that would do 5V/5A probably do PD 20V/5A as well, = 100W. Or it'll be a non-conforming special Pi PSU of sorts.

Unfortunately that's not how USB PD works. In PD Land, 25W means 9V/2.8A. A charger is allowed to offer 5V/5A but at no power level is it mandatory, so even a fully USB PD compliant 100W charger which can do 20V/5A is not guaranteed to power the Pi 5.

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