Is there a way to bump up the output of a USB port on a car stereo?

Discussion in 'Automotive Electronics' started by briandye, Jun 7, 2016.

  1. briandye

    Thread Starter New Member

    May 29, 2016
    5
    0
    So I installed an iPad Mini (2) in my dash. I was doing some research and the headunit I bought I was under the assumption it charged at 1 amp which would be sufficient for the iPad Mini. Wouldn't be a fast charge but it wouldn't die as I was using it.

    Is there anything I can do like opening the headunit and modifying the power output to the USB or anything to bump it up?
     
  2. briandye

    Thread Starter New Member

    May 29, 2016
    5
    0
    Sorry, meant to add more info before posting and I don't see an edit option.

    I was looking at a website for the specs and it falsely stated a 1a output so I was happy because it was a very cheap model that did everything I needed. (Basically using it as a DAC and volume control that's all)

    But I can't change out the lightning USB cable because it's epoxied in place and the kit was installed over that.

    Would an option possibly be to get a USB extension (I don't want to cut into the Apple cable as if I mess it up, I'm SOL on having a connection) and splice into the power and ground wires, and run them to something like a 12v 2.1a USB charger?
     
  3. Papabravo

    Expert

    Feb 24, 2006
    10,143
    1,790
    I'm not clear what you want to do. When you say "bump it up", what exactly are you talking about? Do you:
    1. Want to increase the current available from a USB plug? Normally you have to negotiate this with the host device, which simple charges usually can't do.
    2. Want to increas the voltage on the power pair from +5V to some higher value. This is extraordinarily dangerous since any normal device you plug in will likely get fried.
    You sound a bit spacey about what you want, so could you clarify things for us? A schematic would be most helpful.
     
  4. briandye

    Thread Starter New Member

    May 29, 2016
    5
    0
    Sorry, I'm looking to have the headunit charge at a higher amp rate. (I'm assuming it charges at .5a maybe a bit more, I would love to be able to charge the iPad with more than 1a, 2.1a would be great)

    I was wondering if there's any way possible to get more amperage from the USB port, no matter what the way is.

    What I mean is I'm open to try anything such as internal modification of the radio, or just bypassing the power from the radio USB all together and wiring the power to a 2.1a charger, but still allowing the radio to get the audio through USB, or I wondered if a powered USB hub would work? The USB hub should allow the device to communicate with the radio but bypass the weak radio charging output and charge at the rate the hub was designed for.
     
  5. Papabravo

    Expert

    Feb 24, 2006
    10,143
    1,790
    Normally a device that provides power to a USB port will provide 100 mA by default. Some devices will supply up to 500 mA if you use the USB protocol and exchange the required messages to "negotiate" the higher current level. There is no facility that I know of to run 2 Amperes through a USB cable or connector.
     
  6. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,805
    833
    Not would you want to. I'm sure that a USB cable is not rated for 2A. You may have such a custom cable, but someone else may unintentionally use the port.
     
  7. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,034
    1,659
    Yes, it would be possible to rewire the dash units front USB port to be powered by an external power supply of higher amp capacity.

    If it were me I would run the two signal wires with any lighter gauge and run the + and - wires with something like a 16 gauge or larger and if possible bump the voltage up to around 5.5 volts by tweaking its feedback loop with a resistance change or by putting a small diode in the voltage sensing loop of it's internal regulator system.

    Pretty much all devices that can charge off of a USB port have tiny SMPS's built into them being their batteries are only 3 - 4 volts which makes them fairly tolerant to moderate overvoltages on their nominal 5 volt input rating.

    Being able to cheat the supply end up an extra half a volt or so compensates for the line losses thus allowing the tiny USB cables to handle 2 amps without affecting the devices actual 5 volt supply voltage it wants.
     
Loading...