Dark Energy® Reservoir High Capacity External Portable Backup Battery Charger w Dual USB & Built-In Protection for Smartphone, Tablet,  Google Glass, iPhone, iPad - BLACK
Built-In Protection: Short circuit Protection, Overcharge Protection, Over discharge Protection Very light weight, 5.9oz (168g); very thin, .47in (12mm) Recharges two USB devices simultaneously; (1) 2.1A USB port for tablets, etc and (1) 1.0A port for smartphones Retains capacity up to 1 year if unused (at least 80% charge remaining); 500+ cycle life High-speed recharge for USB devices