SEC FORM 4/A

SEC Form 4

FORM 4

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

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

PEARL FRANK H

(Last)

(First)

(Middle)

C/O PERSEUS CAPITAL, L.L.C.

2099 PENNSYLVANIA AVENUE, NW, SUITE 900

(Street)

WASHINGTON

20006

(City)

(State)

(Zip)

2. Issuer Name and Ticker or Trading Symbol
BEACON POWER CORP [ BCON ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
07/26/2005

4. If Amendment, Date of Original Filed (Month/Day/Year)
07/28/2005

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock⁽¹⁾	07/26/2005		M		1,785,714	A	$0.84	12,145,208	I⁽²⁾⁽³⁾	Through Perseus 2000 Expansion, L.L.C. and Perseus Capital, L.L.C.

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Obligation to Purchase⁽¹⁾	$0.84	07/26/2005		M			1	04/22/2005	09/30/2005	Common Stock	1,785,714	$0.00	0	I⁽²⁾⁽³⁾	Through Perseus 2000 Expansion, L.L.C.

Explanation of Responses:

1. 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.

2. 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.

3. The Reporting Person disclaims beneficial ownership of the reported securities, except to the extent of his pecuniary interest therein.

Remarks:

	By: Rodd Macklin, Attorney-in-Fact	09/02/2005
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.