X0202 4 2005-08-19 0001103345 BEACON POWER CORP BCON 0001247580 SPIEZIO JAMES M C/O BEACON POWER CORPORATION 234 BALLARDVALE STREET WILMINGTON MA 01887 0 1 0 0 VP of Finance, CFO Common Stock 2005-08-19 4 F 0 11730 3.46 D 187921 D The restricted stock units described in the Form 4 that was filed on February 17, 2005 are issued in lieu of cash compensation. The transaction reported by this additional Form 4 is driven by the Company's policies restricting open market trading by senior personnel who have access to material nonpublic information. As those policies prevent management from selling shares to the market to generate cash to fund the withholding tax obligations that arise from the compensation income which is generated by the restricted stock units, the Company has withheld shares in sufficient quantity to pay tax liability in connection with this second installment of restricted stock as reported on the above February Form 4. James M. Spiezio 2005-08-22