QCell T-Mobile Samsung Galaxy S2 / SII T989 3650mAh Extended Battery + FREE Battery Cover! (NOT Compatible with i9100/i727/D710/i777) T-Mobile Galaxy S2 Extended Battery by QCell! Highest Capacity Battery in the Market! Designed in Canada! Double Your Battery Life! Optimized for Galaxy Series! Comes with Free Battery Cover! DYNAStop overcharge IC stopper built in! Voltage: 3.7V / Premium Quality and Best Material used!