X0306 4 2012-09-04 0 0001167178 A123 SYSTEMS, INC. AONE 0001472308 Riley Jr. Gilbert N C/O A123 SYSTEMS, INC. 200 WEST STREET WALTHAM MA 02451 1 1 0 0 CTO and VP of Res. and Dev. Common Stock, $0.001 par value 2012-09-04 4 S 0 20000 0.2566 D 393705 I By The Yusun Kim Riley Revocable Trust Common Stock, $0.001 par value 603671 D The sale reported in this Form 4 was effected pursuant to a Rule 10b5-1 trading plan. Includes 211,614 restricted stock units ("RSUs"). Upon vesting thereof, the Reporting Person is entitled to receive one (1) share of common stock for each one (1) RSU. /s/ Eric J. Pyenson as Attorney-in-Fact for Gilbert N. Riley, Jr. 2012-09-06