Best Quality Guranteed. Wirelessly connect up to 2 smartphones or tablets to the speaker and take turns enjoying powerful sound. Built in rechargeable li ion 7800mAh battery supports up to 20 hours of playtime and charges your device via USB port. Take charge 4 to the beach or the pool without worrying about spills or even submersion in water. Amplify your listening experience to epic levels and rock the party perfectly by wirelessly connecting more than 100 connect+ enabled speakers. Please note* the charge 4 does not include a USB wall adapter.