Silly question, but is it fine to use PI4 PSU to charge phone?

[piglet]

I'm fairly sure it should be ok...but can I use my spare Pi 4 PSU to charge a USB-C phone?

We've had little luck getting quality USB-C cables that charge well, and am confident that the Pi4 PSU is quality...

[jamesh]

I believe that will be fine. I've used Pi3 PS to charge uUSB phones

[drgeoff]

I'm fairly sure it should be ok...but can I use my spare Pi 4 PSU to charge a USB-C phone?

We've had little luck getting quality USB-C cables that charge well, and am confident that the Pi4 PSU is quality...

Yes should be OK but might not charge the phone as quickly as the original PSU does if it and the phone are "smart".

[plugwash]

It's almost certainly safe, how functional it is is another matter. I know my phone charges very slowly when I use one of the raspberry pi micro USB bricks to charge it.

Is there any documentation on how the USB C connector on the official PSU is connected up?

[Imperf3kt]

My phone uses USB-C at 5v only and with the official Pi3 power supply attached via a micro usb to usb c adaptor, it appears to charge slower than a 2A usb cable alone.

Using the Pi4 power supply appears even slower, but it does charge it just fine.

I'm guessing it's the phone itself doing some kind of "smart" charging, where it confuses itself about what is connected to it and actively reduces the charging current to avoid harming the power supply / charger.
Gotta love "smart" tech, it's so much dumber than regular tech.

[ehem]

Gotta love "smart" tech, it's so much dumber than regular tech.

Dunno about you, but being smart enough not to set buildings on fire seems like a Good Idea. Problem is the USB-C specification has gotten extremely complicated and implementing it correctly is a major challenge, even if you have the right experience.

[piglet]

I've been using it and it's fine. Nice fast charge. Had to get another one as family using it to charge...

[Imperf3kt]

Gotta love "smart" tech, it's so much dumber than regular tech.

Dunno about you, but being smart enough not to set buildings on fire seems like a Good Idea. Problem is the USB-C specification has gotten extremely complicated and implementing it correctly is a major challenge, even if you have the right experience.

What was wrong with using a 9v charger for a 9v device or a 20v charger for a 20v device? Why must the charger be 'smart' and supply multiple voltages at all?

[ehem]

What was wrong with using a 9v charger for a 9v device or a 20v charger for a 20v device? Why must the charger be 'smart' and supply multiple voltages at all?

What happens when some complete nincompoop plugs the 20V charger into the device which requires 3V? Devices are supposed to include some level of protection against that, but it is rarely 100%. Does the device start overheating, then catch on fire? Once on fire does it short out the power supply and cause it to catch on fire? Does it take an hour to do this, thus giving the person time to go to another room and start ignoring the item and not realize the situation until it is a full on structure fire?

What about when you've got some $random_device and you don't know its power requirement? Do you throw it out due to being unable to figure out an appropriate power supply?

Years back there was at least one attempt to standardize power supplies such that each voltage used had a distinct connector. One of the problems was that there are only so many variants of barrel connector you can make. They were distinct sizes, but the loose tolerances required meant incompatible devices had a distinct chance of being able to be plugged in.

Keeping a device paired with an appropriate power supply is good, but the real world has shown that this never works. What of cellphones? If you're isolated at an airport in the middle of nowhere would you rather be able to borrow someone else's charger or have no way to charge your phone which you forgot the power supply for?

[Imperf3kt]

If you're in an airport your phone should be turned off or in flight mode by law...
Charging it is the least of your worries.

[W. H. Heydt]

Keeping a device paired with an appropriate power supply is good, but the real world has shown that this never works. What of cellphones? If you're isolated at an airport in the middle of nowhere would you rather be able to borrow someone else's charger or have no way to charge your phone which you forgot the power supply for?

My usual solution is to make labels for both devices and their associated PSUs so I know what PSU goes with which device. Second line of defense is to put the PSU in the same container (for smallish electronics, this is often a 1 gal. ziplock bag, which has the advantage of being transparent so you can see what's in there).

The major effort make common chargers for phones was to require the companies to agree on a connector then everyone use it. That worked moderately well--with the glaring exception of Apple refusing to do so--with micro-USB-B (which is why the RPF adopted it in the first place). USB-C appears to taking over that space...with the partial exception of Apple. In deference to moderation policy I will refrain from expressing a personal opinion about the situation.