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Old Jan 06, 2011, 02:48 PM
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I don't have an HD, but in the past have had problems getting some devices to charge when a "dumb" USB charger is connected. It turns out that if the device believes it is connected to a live, intelligent USB port, it will not draw charging current until it has negotiated permission to do so with the USB hub controller. But if it believes it is connected to a dumb port, which is just a source of +5VDC, it will go ahead and charge because there's nobody there to negotiate with.

The modern standard is that dumb chargers identify themselves as such by having the two Data lines shorted together, but not otherwise connected to the other pins or the shell. This standard isn't universally followed, but I have built such a dumb charger, and I haven't found anything yet that wouldn't charge when connected to it.

If the car charger can be disassembled, it would be interesting to see if it's anything more than a power source, and if not, how the Data pins are connected.
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