[Linux-aus] USB-C chargers
russell at coker.com.au
Mon Nov 28 22:20:49 AEDT 2022
On Monday, 28 November 2022 18:53:32 AEDT Adam Nielsen via linux-aus wrote:
> > I have a Thinkpad Carbon X1 Gen5 which shipped with a 65W USB-C PSU
> > and which runs well with a 45W USB-C PSU. The above advert and
> > others like it imply that 30W is adequate to power that laptop.
> > https://www.kogan.com/au/c/black-friday-sale-22-tech/shop/category/phones-> > accessories-smartphones-accessories-44025/?facet-features-furniture-filter
> > able=GaN+Technology
> > Kogan offered some deals on GaN chargers, the above is the one that's
> > still on sale, they also had a 30W one for $10 which I bought
> > expecting it to work with my Thinkpad, but it didn't.
> > How do I work out why the charger didn't work? If I buy the 68W
> > version of that charger is it likely to work? Could it be the USB-C
> > - USB-C cables that I used (I tested 3 cables of different brands
> > from my collection)?
> "Didn't work" is too generic of a term to really offer any suggestions.
> This could mean:
> - The charger didn't switch on when connected to the laptop.
> - The laptop did not react when the charger was connected.
> - The laptop did react but rejected the charger.
> - The laptop took its operating power from the charger but did not
> charge its battery.
> Without knowing what happened when connecting the charger it's
> impossible to say.
I've attached a message I get from KDE when I hover the mouse over the battery
icon, it says "The power supply is not powerful enough to charge the battery".
My problem is that I don't know enough about this topic to know what to look
> As far as cables, it could be the USB-C cable. You can get cheap ones
> that are only wired for USB 2.0 internally (but with USB-C plugs), and
> these won't work for USB 3.0 or USB PD (power delivery) as they
> physically need more wires in the cable. The only way to confirm this
> is to test a cable with a known good charger and device, and where the
> device is one that you know will refuse to use USB 2.0's 5 volts. You
> might think a thicker cable means there must be more wires in it, but
> not when companies produce USB 2.0 cables with extra thick insulation
> to mislead unsuspecting customers.
I don't know if I have any such devices. I have a bit of a chicken and egg
> As for the charger itself, if you look at the specs they list the
> voltages and currents supported for USB PD. I think the Thinkpad wants
> 20 volts (although it may accept less, I don't know), and both chargers
> you have linked to claim to output 20 volts in their specs, so in theory
> they would work.
The one I have specifies 20V 1.5A.
> However without knowing the specs on the 30 W charger you have, it's
> hard to say whether this is the problem. If the 30 W charger can't
> output above 17 V then I'd suspect that could be why it doesn't work,
> given a known good USB-C cable.
I know the USB-C cables work for "fast charge" of phones. I don't know if
that means much, probably not.
> As more devices start to use USB PD, you may want to consider getting a
> USB power monitor that supports PD, so you can plug it in between the
> device and charger and actually see what's going on. These devices
> will show the actual voltage and current on a small screen, so you can
> see exactly what's going on and more easily compare different devices
> and chargers. Here is an example I picked randomly from Aliexpress:
> There are heaps, just make sure you get one with USB-C plugs and
> support for USB PD.
Thanks for the suggestion! I sent the URL to a friend who's really good at
buying stuff from China.
> If you have a known working set up (say the official Thinkpad charger
> and laptop) you can plug the charger into the power monitor, then
> connect the power monitor to the laptop with a suspect USB cable. You
> will then see on the power monitor screen whether it jumps up to 20
> volts (meaning the suspect cable is good) or whether it stays at the
> standard 5 volts (meaning the suspect cable is not PD-compatible so
> it can only be used for basic USB 2.0-compatible charging).
The power monitor has a male USB-C connector to go to the PSU and a female one
to go to the device being charged. So to put it between a laptop and a laptop
PSU I'll need 2 adaptors.
On Monday, 28 November 2022 19:38:15 AEDT Paul Wayper via linux-aus wrote:
> If the new 30W charger does actually deliver 20V, then it's under-spec - the
> minimum should be 45W.
The documentation says it does 15V-2A and 20V-1.5A.
> So why were we trying to get a low power charger? I don't find the Thinkpad
> one very bulky... is it?
It's not that big, but when you already have an inverter for powering things
in a car it adds up. Also I can fit my Thinkpad in my jacket pocket and a
small charger takes less space in one of my other pockets.
On Monday, 28 November 2022 21:10:31 AEDT James Henstridge via linux-aus
> You can sometimes find some information in /sys/class/typec as described
> However, it really depends on what information the hardware exposes to
> the OS. I've got an X1 Gen5, and only a small amount of that info is
> exposed (at least on kernel 5.19: there's no ). I think most of the
> USB-PD stuff is being handled in the firmware without the OS's
Maybe it's all in firmware, those sysfs entries gave me nothing about the
connector. KDE got the data somehow so I'd like to know where that came from.
> The spec sheet for the laptop seems to indicate that it won't fast
> charge with the official 45W charger, so I suspect a 30W charger won't
> cut it.
That's a possibility, I'll buy the 68W version of the same thing and hope it
gives a better result.
Thanks for all the advice!
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
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