The EnerPlex charger for iPhone 4/4S weighs only 72 grams, and can dramatically increase the usage time of your device. With a full charge, the EnerPlex charger adds:

Standby Time: up to 170 hours
Internet Surfing: up to 3.5 hours
Wi-Fi: up to 5.6 hours
Audio Play: up to 19 hours
Video Play: up to 5.6 hours