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These chargers do not short the D+/D- signal lines to tell the device being powered that they are chargers rather than data connections, so a modern device like an iPhone or Android phone will not take the full available current from the device. So they are limited to 500mA rather than 900mA so they power but will not simultaneously charge a modern smart phone. From the Wikipedia page for USB: "The Dedicated Charging Port shorts the D+ and D- pins with a resistance of at most 200 '. The short disables data transfer, but allows devices to detect the Dedicated Charging Port and allows very simple, high current chargers to be manufactured." When I power a Samsung Galaxy S phone with this it sees it as a data port and offers to connect as a mass storage or media device, as expected for an incorrectly wired charger.