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What's the best way to achieve this without damaging my car's audio?
I want to connect my iPhone to my car's audio and charge it at up to 4.2A iPhone will draw up to 2A instead of 500mA.
Or would it be easier to use a USB hub with external power source, such as 2A?
Unless it's possible to "bump up" the car's audio current to more than 500mA.