X0202 4/A 2005-07-26 2005-07-28 0 0001103345 BEACON POWER CORP BCON 0000927752 PEARL FRANK H C/O PERSEUS CAPITAL, L.L.C. 2099 PENNSYLVANIA AVENUE, NW, SUITE 900 WASHINGTON DC 20006 1 0 1 0 Common Stock 2005-07-26 4 M 0 1785714 0.84 A 12145208 I Through Perseus 2000 Expansion, L.L.C. and Perseus Capital, L.L.C. Obligation to Purchase 0.84 2005-07-26 4 M 0 1 0.00 D 2005-04-22 2005-09-30 Common Stock 1785714 0 I Through Perseus 2000 Expansion, L.L.C. Acquired pursuant to an Investment Agreement, dated as of April 22, 2005, by and among the Issuer, Perseus 2000 Expansion, L.L.C. and Perseus Capital, L.L.C., pursuant to which the Issuer had the right to require Perseus 2000 Expansion, L.L.C. to acquire shares of the Issuer's common stock on one or more dates to be specified in the future, at the Issuer's sole option. The Reporting Person controls entities that have director representation on the Issuer's board of directors and which entities are deemed to be directors of the Issuer by deputization. The Reporting Person disclaims beneficial ownership of the reported securities, except to the extent of his pecuniary interest therein. By: Rodd Macklin, Attorney-in-Fact 2005-09-02