1. There may be a problem with the data cable. In addition, the original usb port is used to read data, the current is too small, charging too slow.
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2, this USB interface is not used for charging, but extended out of the back of the machine, for MP3\/MP4 playback, the power part of which is probably a few hundred MA, charging is not enough.
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3, buy a cigarette lighter interface converter, product win on more than 20, more easy to use.
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4, this USB is inserted U disk or other for data communication, not charging. To charge it, buy another car charger.
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6, the power is too small. The USB power supply is basically 1A, if the 2A charging effect will be much better. Intermittent inspection of jacks or wiring...