[MTCB Hardware Development] doctorman:
got my stuff and I was going to open up the car and noticed a problem, the USB Hub I got limits the current to 460ma which does not help, I am trying to get the phone charged at 1.8A while has data communication with the head unit.

tried the following :

USB 2 hub powered: 460ma max no matter what

USB 3 hub powered: 460ma max no matter what

USB 3 hub Charging port: 1.8A

Laptop UPS port : 460ma max no matter what

Laptop Charging USB port : 1A

Tired many USB cables and saw very little difference based on the USB cable.

Galaxy S4 and Galaxy S5 was used for testing.

Battery Charging Specification, Rev 1.1, 4/15/2009 (BC1.1) goes beyond the power distribution described in USB 2.0 by defining additional power sources for charging. It defines three different source types:

[B]Standard downstream port (SDP)[/B] This is the same port defined by the USB 2.0 spec and is the typical form found in desktop and laptop computers. The maximum load current is 2.5mA when suspended, 100mA when connected and not suspended, and 500mA (max) when configured for that current. A device can recognize a SDP with hardware by detecting that the USB data lines, D+ and D-, are separately grounded through 15kΩ, but it still needs to enumerate to be USB compliant. In USB 2.0, it is not strictly legal to draw power without enumerating, although much of present-day hardware does just that, and in violation of the spec.

[B]Charging downstream port (CDP)[/B] BC1.1 defines this new, higher current USB port for PCs, laptops, and other hardware. Now the [B]CDP can supply up to 1.5A[/B], which is a departure from USB 2.0 because this current can be supplied before enumeration. A device plugged into a CDP can recognize it as such by means of a hardware handshake implemented by manipulating and monitoring the D+ and D- lines. (See USB Battery Charging Specification, section 3.2.3.) The hardware test takes place before turning the data lines over to the USB transceiver, thus allowing a CDP to be detected (and charging to begin) before enumeration.

[B]Dedicated charging port (DCP)[/B] BC1.1 describes power sources like wall warts and auto adapters that do not enumerate so that charging can occur with no digital communication at all. DCPs can supply up to 1.5A and are identified by a short between D+ to D-. This allows the creation of DCP "wall warts" that feature a USB mini or micro receptacle instead of a permanently attached wire with a barrel or customized connector. Such adapters allow any USB cable (with the correct plugs) to be used for charging. Additional details on these port types are described in the USB Battery Charging Specification, Rev 1.1, 4/15/2009.
Some devices do not use the standard. Apple for one, created a different standard (before BC 1.1 was released) for their own devices, allowing them to distinguish between non-supported chargers, 500mA standard chargers (enumerated usb), 1A high current chargers, and 2.1A highest current chargers. This is done with varying voltage dividers on the DP and DM pins. Some other manufacturers have adopted that, and the regular standard, at the same time. Some IC manufacturers have created USB host/battery charger detection ICs which figure out what kind of charger is being used and adapt accordingly.

so based on that I can do 2 things:

1) give up the data and just charge the phones from a nice 2.1A car charger - no data

2) make the Head units USB port in to a "Charging downstream port (CDP)" with 1.5A power.

I prefer the CDP

any idea how to do that?

Found a great article on Fast charging USB

http://apcmag.com/android-usb-charging-secrets.htm/

Found an App that lets you enable the "Fast charge" in the Kernel of the Rooted phones that support it

https://play.google.com/store/apps/details?id=com.grarak.kerneladiutor

my S5 supported it the Fast charge in Kernel , S4 did not, maybe I install a custom Kernel.

with Fast charge enabled I get 1A charge on regular USB Data port instead of 460ma

UPDATE:

It seems like I need a USB charging Hub so the USB ports are not SDP but CDP so they can provide 1.5A

and there is no easy way to change SDP to CDP

you can trick a device to think it is connected to DCP by shorting the D+ and D- but it wont work on apple products as they need specific Voltage in D+ and D- wire. 2v vs 2.7v.

I will see if I find a cheap 4 port charging USB hub to use in this project.