Car head unit - Slow USB charging

[Naz]

OK so I just bought a new car with Android Auto and Apple CarPlay. I like the features that are included and wish to use it all the time. However, the problem is that the USB port that I have to plug the phone into only puts out 500mA or less, just enough to maintain the charge of the phone while it is in use. Would it have killed them to put out 2A?!

Aaaanyway... I was wondering if I could make a frankencable that connects the data wires to the car, and the power wires to my cigarette lighter charger.

For anyone familiar with wiring USB cables, the standard cable does something like this:

What I am proposing is to make a cable that does this:

I do not know if this is possible, if it will work, if it will damage my phone, or if it will cause my car to explode dramatically while on the freeway bringing joy to other drivers.

Are there any people in this forum familiar with USB wiring who can provide me with some feedback as to the possibility of doing something like this, and how hard it would be?

Thanks in advance!
- Naz,

 

[Qualcomm_inside!]

as long as your phone isn't a Samsung note 7.. hurhurhur.

In the days before USB 3.0, when you bought a device like a pocket HDD that needed more than 450-500mA that is typical current draw,
The device came with like a bridge cable that had dual USB A connectors on a single Mini or Micro B cable.

One A plug had both the power and serial lines inside while an other A plug branched off to another USB port on your PC for a second power line. This was essentially adding 500mA + 500mA in parallel to get 1A ( enough to spin a 3.5" hard drive ).

Alternately you could just use a car cig charger and go Bluetooth to your Android auto unit

 

[Naz]

In the days before USB 3.0, when you bought a device like a pocket HDD that needed more than 450-500mA that is typical current draw,
The device came with like a bridge cable that had dual USB A connectors on a single Mini or Micro B cable.

One A plug had both the power and serial lines inside while an other A plug branched off to another USB port on your PC for a second power line. This was essentially adding 500mA + 500mA in parallel to get 1A ( enough to spin a 3.5" hard drive ).

Alternately you could just use a car cig charger and go Bluetooth to your Android auto unit

Bluetooth does not provide all the functionality that plugging it in does, which is why I haven't already done that.

So if I can find one of those bridge cables, it'd be fine to have one into the head unit, and the other in the charger? I don't think Vbus in USB is so simple that it can just be paralleled across disparate USB hosts.

 

[Qualcomm_inside!]

Should be fine, as long as you're providing no more than 500mA at each point.
That is how most high current USB devices worked in 2.0. when you bridge current sources in parallel the voltage will remain the same but the current will double.

 

[mzlinadl]

Found these on ebay

 

[Kiwi]

Those cables are to power a device, usually an external hard drive, from two USB ports on a computer to get sufficient power output.
Not sure I would recommend using one to solve your problem by taking power from two different sources.

 

[elleevan]

very good

 

[Naz]

Yes I am NOT sure that a parallel arrangement of power from both USB ports is safe. Furthermore, the USB charger is QuickCharge capable, meaning that it provides variable voltages up to 9v, so if the Vbus of both USB sockets were in parallel, then I'd be feeding power from the USB charger into the car head unit, which would be a Bad Thing.

This is why my original diagram does not show a parallel hookup from the two sources, but shows using each socket exclusively either for data or power.

 

[garublador]

I'm not sure any of that will work. Your phone is what decides how much current to draw and it decides that based on what it sees on the data lines. So even if you hook up the power lines to a different charger your phone will still think it's attached to the head unit and only draw the 500mA. The hard drives probably had some other power scheme baked into them to allow the parallel power supplies.

I'm not sure there's anything in the USB 2.0 spec that allows for higher current charging and data transfer from the same host.