UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 8-K
                                 CURRENT REPORT
                     Pursuant to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934

         Date of report (Date of earliest event reported): May 24, 2005

                            BEACON POWER CORPORATION
               (Exact Name of Registrant as Specified in Charter)

           DELAWARE                      001-16171              04-3372365
(State or Other Jurisdiction of   (Commission File Number)    (IRS Employer
        Incorporation)                                      Identification No.)

               234 BALLARDVALE STREET
                  WILMINGTON, MA                          01887
      (Address of Principal Executive Offices)         (Zip Code)

        Registrant's telephone number, including area code: 978-694-9121

Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions:

[  ] Written communications  pursuant to Rule 425 under the Securities Act (17
     CFR 230.425)

[  ]  Soliciting  material  pursuant to Rule 14a-12 under the Exchange Act (17
     CFR 240.14a-12)

[  ]  Pre-commencement  communications  pursuant  to Rule  14d-2(b)  under the
     Exchange Act (17 CFR 240.14d-2(b))

[  ]  Pre-commencement  communications  pursuant  to Rule  13e-4(c)  under the
     Exchange Act (17 CFR 240.13e-4(c))



                Section 1 - Registrant's Business and Operations


Item 1.01  Entry into a Material Definitive Agreement.

         As permitted by General Instruction B to the Form 8-K, this Current
Report incorporates by reference the information contained in a previously filed
report relating to an Investment Agreement dated as of April 22, 2005 (the
"Investment Agreement") by and among Beacon Power Corporation (the "Company"),
Perseus Capital, L.L.C. ("Perseus Capital") and Perseus 2000 Expansion Fund,
L.L.C. ("Perseus 2000 Expansion"): Form 8-K filed on April 25, 2005 (File No.
001-16171) (the "Previously Filed Report").

         On May 24, 2005, the Company completed certain transactions
contemplated by the Investment Agreement pursuant to which (a) the Company
issued 1,666,667 shares of its common stock to Perseus 2000 Expansion (the
"Shares"), (b) the Company issued to Perseus 2000 Expansion a warrant (the
"Warrant") to purchase up to 800,000 shares of its common stock (the "Warrant
Shares"), (c) the Company, Perseus Capital and Perseus 2000 Expansion entered
into a Registration Rights Agreement (the "Registration Rights Agreement") and
(d) the Company extended, by two years, the term of a preexisting warrant issued
to Perseus Capital (the "Extended Warrant") to purchase up to 1,333,333 shares
of its common stock (the "Extended Warrant Shares"). The aggregate purchase
price received by the Company for these transactions was $1,500,000. As stated
in the Previously Filed Report, the Company has an additional investment option
whereby it may require Perseus 2000 Expansion to purchase additional shares of
its common stock. In addition, Perseus 2000 Expansion has an option whereby it
may make a further investment in Beacon. If these options are exercised by the
Company and/or Perseus 2000 Expansion, Perseus 2000 Expansion would be required
to pay additional funds to the Company.

         The Warrant is exercisable by Perseus 2000 Expansion for five years
from the date of issuance at an exercise price of $1.008 per share. The exercise
price is subject to adjustment upon the occurrence of certain specified events,
including certain issuances by the Company of any shares of its common stock at
a price that is less than the Warrant's initial exercise price of $1.008 per
share, stock dividends, stock splits and mergers or reorganizations. The Warrant
also includes a "cashless exercise" feature, which permits the holder to
exercise the Warrant by surrender of a portion of the Warrant.

         The Extended Warrant may be exercised by Perseus Capital on or prior to
May 23, 2007 at an exercise price of $2.25 per share. The exercise price is
subject to adjustment upon the occurrence of certain specified events, including
stock dividends, stock splits and mergers or reorganizations.

         Pursuant to the Registration Rights Agreement, the Company has agreed
to file a registration statement with the U.S. Securities and Exchange
Commission registering the Shares, the Warrant Shares, the Extended Warrant
Shares and the shares related to the additional investment options of the
Company and Perseus 2000 Expansion, if exercised.

         The full terms and conditions of the financing are set forth in the
Investment Agreement, which was filed as an exhibit with the Previously Filed
Report, the Warrant, the Extended Warrant and the Registration Rights Agreement,
each of which is filed as an exhibit to this Current Report, and are
incorporated herein by reference.

         The Company also issued a press release dated April 25, 2005, which was
filed as an exhibit with the Previously Filed Report and is incorporated herein
by reference.

Item 3.02  Unregistered Sales of Equity Securities.

         The disclosure provided in Item 1.01 of this Form 8-K is hereby
incorporated by reference into this Item 3.02 with respect to the sale and
issuance of 1,666,667 shares of the Company's common stock and warrants to
purchase 800,000 shares and 1,333,333 shares, respectively, of the Company's
common stock. The closing of the sale and issuance of the shares and the
warrants occurred on May 24, 2005.

         The shares and warrants were issued without registration with the
Commission, pursuant to Section 4(2) of the Securities Act of 1933, as amended,
and Rule 506 promulgated thereunder. The Company determined that this exemption
was available because of the nature and limited number of purchasers. In making
this determination, the Company relied in part upon representations made by
Perseus 2000 Expansion and Perseus Capital.

                  Section 9 - Financial Statements and Exhibits

Item 9.01 Financial Statements and Exhibits.

(c) Exhibits

10.1 Warrant issued by Beacon Power  Corporation to Perseus 2000 Expansion Fund,
     L.L.C. on May 24, 2005

10.2 Amended and Restated Warrant issued by Beacon Power  Corporation to Perseus
     Capital, L.L.C. on May 24, 2005

10.3 Registration  Rights  Agreement  among  Beacon Power  Corporation,  Perseus
     Capital, L.L.C. and Perseus 2000 Expansion Fund, L.L.C. on May 24, 2005




                                    Signature

         Pursuant to the requirements of the Securities Exchange Act of 1934,
the registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                       BEACON POWER CORPORATION

Date:  May 26, 2005

                                      By:/s/ James M. Spiezio
                                         -----------------------
                                         Name:  James M. Spiezio
                                         Title: Chief Financial Officer







                                  Exhibit Index

Exhibit No.        Description
- ---------------    -------------------------

         10.1      Warrant issued by Beacon Power Corporation to Perseus 2000
                   Expansion Fund, L.L.C. on May 24, 2005

         10.2      Amended and Restated Warrant issued by Beacon Power
                   Corporation to Perseus Capital, L.L.C. on May 24, 2005

         10.3      Registration Rights Agreement among Beacon Power Corporation,
                   Perseus Capital, L.L.C. and Perseus 2000 Expansion Fund,
                   L.L.C. on May 24, 2005