Technical Specifications Compatible with most smart phones & MP3 players with external speakers Built-in rechargeable battery: charge via micro USB (Universal Serial Bus) cable (included) Play Time per recharge: 10 hours Optional 3.5mm jack input (cable not included) Speaker: 4 Ω/3W Rating output: 100 Hz-20 K Hz Charging voltage: DC 5V Battery: 3.7V 850m Ah lithium ion battery