What I've got:

  • A car with a USB port that only supplies 500 mA.
  • An android phone with USB-C that supports QC3.0 and PD2.0

...So the phone discharges while driving with Android Auto.

What I want:

  • I want to improve this so the phone actually charges while driving.

What I've tried:

Adding a USB-A Y cable

Adding a USB-A Y cable

[CAR USB A]─── USB 2.0 ──────┬───────>
[2A CHARGER]── USB Power ────┘

(of course this didn't work, as in this question)

Adding a 150 Ω resistor between D+ and D-

Still with the Y cable, I tried this to trigger USB BC and unlock 1 A.

  • Charging works at 1 A as expected !
  • Data transfer does not work, so neither does Carplay / AA.

Modding a USB-C charger

I modified a USB-C PD charger so the D+ and D- lines from the car are wired to the receptacle.

  • Powering the charger from the bench (with D+ and D- unplugged from the car): the phone charges at 14 W.
  • Powering the charger with D+ and D- plugged in the car: phone charges at 4 W (not enough) and no communication with the car.


Is it possible to charge the device at higher power while maintaining USB 2.0 data transfer?

Especially through PD2.0 since it's supposed to negotiate power over a separate wire that's not D+ or D-?

And as much as possible using ready-made modules or parts?

Sorry for the question being so long. I want t share everything I've tried!

  • 2
    \$\begingroup\$ I'd try a USB hub in between that works from a 12 V supply. \$\endgroup\$
    – Finbarr
    Aug 3, 2023 at 8:15
  • \$\begingroup\$ I just tried that with a powered hub plugged on the 2A charger. It only charges at 4.5W. \$\endgroup\$
    – uiguig
    Aug 3, 2023 at 14:27
  • \$\begingroup\$ From your section "Modding a USB-C charger", it looks like your phone is not designed for fast charging AND communicating at the same time. When the phone charges at 14W, what voltage was on VBUS wires? Did you try to measure the charge wattage when plugging your phone into a good laptop? \$\endgroup\$ Oct 5, 2023 at 4:12

1 Answer 1


You can use so-called "USB-C charging hub" to accomplish your task. Something like this, from Amazon:

enter image description here

The captive upstream cable can use a Type-C-to-TypeA small adapter and it will fit into the car's port. And you will need a separate Type-C source to feed the hub from the bottom port (encircled) with a separate Type-C charger with proper power rating. Still a question can arise if the power delivery profiles from hub's side ports will match the power request from your phone.

It might be possible to modify the hub to accept the 12V car voltage directly, but it will be challenging to fool the hub's firmware to accept it.

And most likely you might need to upgrade your phone with PD3 and no proprietary extras as QC.

CORRECTION: The pictured hub does not show if it provides PD charging capabilities to downstream ports. At most it should provide the default CC advertising, but it is unclear, what they are (as always). So it might not work. Also, as Justme noted, the car audio system may fail to provide USB hub support, so the hub idea needs additional research.

It is also unclear if the particular phone supports fast charging and data connection at the same time.

Overall, the solution is to upgrade the entire car to have full-functional Type-C port on its entertainment system. :-)

  • \$\begingroup\$ I doubt it. Will the car allow a hub between phone? Also, this will require an adapter with Type-A plug to Type-C receptale. Such adapters are explicitly "not defined or allowed" by USB specification. As they should not exist and yet you appear to be able to buy those, I would definitely not suggest plugging dangerous and specifically forbidden adapters to an expensive-to-replace port of car multimedia system. \$\endgroup\$
    – Justme
    Oct 5, 2023 at 4:42
  • \$\begingroup\$ @Justme, yes, support for hubs in the car might be lacking, this is a very valid concern. But it should be easy to check with any old USB2 hub and a flash drive with MP3 music. And if you don't like the tiny c-2-A converter dongles, cut the upstream cable C connector and attach an ordinary Type-A plug with D+/D- wires only. \$\endgroup\$ Oct 5, 2023 at 4:53
  • \$\begingroup\$ The question isn't if anyone likes them or not. They should not exist as per the standard, because they are dangerous, they allows you to accidentally connect two USB hosts or power supplies tohether, and that will do damage. That's why we don't have cords with mains plugs on both ends either. And what you propose by cutting off the upstream Type-C connector and replace it with Type-A, it does not work like that - you will be missing the negotiation pins of Type-C so it will render the hub useless. It will definitely not work with D+ and D- wires only. \$\endgroup\$
    – Justme
    Oct 5, 2023 at 5:40
  • \$\begingroup\$ @Justme, "because they are dangerous, they allows you to accidentally connect two USB hosts or power supplies tohether, and that will do damage. That's why we don't have cords with mains plugs on both ends either. " - please don't use the slippery slope argument. If the adapters are so dangerous, all these producers would be sued to hell and go out of business. And why do you think that these adapters cannot be USB compliant? Many of them do have a CC controller with superspeed MUX inside. HP supplies one of these with nearly every USB4 dock. \$\endgroup\$ Oct 6, 2023 at 5:34
  • \$\begingroup\$ @Justme , "replace it with Type-A, it does not work like that" - oh yes it does work. Most USB3 hubs with type-c captive cable don't have enough intelligence to handle CC advertising and work just fine - just tested a SSK SC-109 hub (mobile, based on latest VL822 controller) - it works just fine. And if a more intelligent "charging" hub is smarter, a simple 56k resitor(s) from CC to VBUS will likely satisfy its need. \$\endgroup\$ Oct 6, 2023 at 5:45

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