Dual Port 20W / 4.2A (2.1A+2.1A) USB Car Charger charges your iPad, iPhone, iPod, HTC, Blackberry, MP3 Players, Digital Cameras, PDAs, Mobile Phones at the same time. Provides maximum charge speed to mobile devices for uninterrupted performance of navigation and media streaming utilities when driving. Use your existing USB charging cables to charge most USB charged devices / Easy-to-see LED confirms whether USB charger is properly connected. Input: DC 12-24V; Output:DC 5V 4.2A or 20W (Shared by two ports). Sophisticated circuit design with over-heated, over-current, over-charging protection. Charging will automatically stop when battery is full.