Lenmar Portable Power Pack for Laptops and Notebooks is a 16500mAh Lithium-Polymer battery externally powers your laptop while charging the internal battery, providing several hours of extra productivity; Includes a USB output port for charging cell phones, mp3 players and other USB powered devices; Compact, lightweight and ultra-thin - fits easily into your laptop case, backpack or briefcase for travel; Fully recharges in 3-4 hours using your laptop's AC power adapter and included adapter tips.