QCell AT&T Samsung Galaxy S2 / SII SGH-i777 3600mAh Extended Battery + FREE Battery Cover! (NOT Compatible with i9100/T989/D710) AT&T Galaxy S2 Extended Battery by QCell! Highest Capacity Battery in the Market! Designed in Canada! Double Your Battery Life with this High Capacity Battery! Comes with Free Battery Cover! DYNAStop overcharge IC stopper built in! Voltage: 3.7V / Premium Quality and Best Material used!