IOGear"s GMP2000P rechargeable battery pack adds up to 3.5 hours of additional talk time. Simply charge the battery via an available USB port using the cable provided. Bring the Power Pack with you and connect to the bottom of your iPhone/iPod via the Apple 30-pin connector when you need extra power for your device. The battery is Lithium-Polymer 1500 mAh. This is a "must have" item that addresses the power hungry iPhone & iPod family. In addition to 3.5* hours of talk time, the battery pack adds up to 24 hours of audio playback and 8 hours of video playback. Great for emergencies or when you just need more chat time. Keep the power flowing and stay in touch with IOGEAR. *Your talk times may vary according to useage and settings.