Basically I’m trying to de-clutter the cables to my charging station, and was hoping to use a 3-way cable for my phone, watch, and headphones.
My main concern is if one device is able to successfully negotiate QuickCharge or PD, would that send 9-20 volts to the other devices?
e.g. if I grabbed the wrong cord and hooked it into my laptop, the laptop requests 20v, would that PD negotiation succeed and also send 20v to my 5v devices on the other two leads?
I’ve only used these kinds of cables with USB-A and chargers that can only output 5V. Most of my chargers now are QC/PD so I’m curious if I should avoid those or take any particular precautions.
No. In QC it is the main voltage that is changed. No extra signal lines.
USB-PD changes thr main voltage in response to a handshake protocol on the C1 and C2 data lines, which this cable likely doesn’t connect for precisely this reason. Qualcomm QC still uses D+ and D- to negotiate the higher voltage, which this cable likely wouldn’t connect either.