Don't be stranded with a dead cell phone while you're out and about! The AT&T Nokia AC3U Car Charger with USB Port conveniently plugs into your car's 12-24 Volt DC auxillary port for a rapid battery charge, keeping your cell phone battery in top operating condition. Built-in smart chip recognizes a full charge and automatically switches to a save mode, protecting your battery and preserving battery life. There is even an additional USB port that allows you to charge any USB compatible device simultaneously!