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

                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934*

                                Active Power, Inc.
                                 (Name of Issuer)

                                  COMMON STOCK
                         (Title of Class of Securities)

                                    00504W100
                                 (CUSIP Number)

                                  August 13, 2007
(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

     / /  Rule 13d-1(b)
     /X/  Rule 13d-1(c)
     / /  Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities,
and for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 ("Act") or otherwise subject to the liabilities of that section of
the Act but shall be subject to all other provisions of the Act (however, see
the Notes).




CUSIP No. 00504W100

1.  Name of Reporting Persons.

HBK Investments L.P.

2.  Check the Appropriate Box if a Member of a Group

    (a) /X/

    (b) /  /

3.  SEC Use Only

4.  Citizenship or Place of Organization: Delaware

              5.  Sole Voting Power: 0
Number of
Shares
Beneficially  6.  Shared Voting Power:  4,800,000
Owned By
Each
Reporting     7.  Sole Dispositive Power: 0
Person
With:
              8.  Shared Dispositive Power:  4,800,000

9.    Aggregate Amount Beneficially Owned by Each Reporting Person:

4,800,000

10.  Check if the Aggregate Amount in Row (9) Excludes Certain Shares   / /

11.  Percent of Class Represented by Amount in Row (9): 8.0%

12.  Type of Reporting Person: IA





CUSIP No. 00504W100

1.  Name of Reporting Persons.

HBK Services LLC (1)

2.  Check the Appropriate Box if a Member of a Group

    (a) /X/

    (b) /  /

3.  SEC Use Only

4.  Citizenship or Place of Organization: Delaware

              5.  Sole Voting Power: 0
Number of
Shares
Beneficially  6.  Shared Voting Power:  4,800,000
Owned By
Each
Reporting     7.  Sole Dispositive Power: 0
Person
With:
              8.  Shared Dispositive Power:  4,800,000

9.    Aggregate Amount Beneficially Owned by Each Reporting Person:

4,800,000

10.  Check if the Aggregate Amount in Row (9) Excludes Certain Shares   / /

11.  Percent of Class Represented by Amount in Row (9): 8.0%

12.  Type of Reporting Person: IA

- --------------
(1)  HBK Investments L.P. has delegated discretion to vote and dispose of the
     Securities to HBK Services LLC ("Services").  Services may, from time to
     time, delegate discretion to vote and dispose of certain of the Securities
     to HBK New York LLC, a Delaware limited liability company, HBK Virginia
     LLC, a Delaware limited liability company, HBK Europe Management LLP, a
     limited liability partnership organized under the laws of the United
     Kingdom, and/or HBK Hong Kong Ltd., a corporation organized under the laws
     of Hong Kong (collectively, the "Subadvisors").  Each of Services
     and the Subadvisors is under common control with HBK Investments L.P.  The
     Subadvisors expressly declare that the filing of this statement on
     Schedule 13G shall not be construed as an admission that they are, for the
     purpose of Section 13(d) or 13(g) of the Securities Exchange Act of 1934,
     beneficial owners of the Securities.





CUSIP No. 00504W100

1.  Name of Reporting Persons.

HBK Partners II L.P.

2.  Check the Appropriate Box if a Member of a Group

    (a) /X/

    (b) /  /

3.  SEC Use Only

4.  Citizenship or Place of Organization: Delaware

              5.  Sole Voting Power: 0
Number of
Shares
Beneficially  6.  Shared Voting Power:  4,800,000
Owned By
Each
Reporting     7.  Sole Dispositive Power: 0
Person
With:
              8.  Shared Dispositive Power:  4,800,000

9.    Aggregate Amount Beneficially Owned by Each Reporting Person:

4,800,000

10.  Check if the Aggregate Amount in Row (9) Excludes Certain Shares   / /

11.  Percent of Class Represented by Amount in Row (9): 8.0%

12.  Type of Reporting Person: HC





CUSIP No. 00504W100

1.  Name of Reporting Persons.

HBK Management LLC

2.  Check the Appropriate Box if a Member of a Group

    (a) /X/

    (b) /  /

3.  SEC Use Only

4.  Citizenship or Place of Organization: Delaware

              5.  Sole Voting Power: 0
Number of
Shares
Beneficially  6.  Shared Voting Power:  4,800,000
Owned By
Each
Reporting     7.  Sole Dispositive Power: 0
Person
With:
              8.  Shared Dispositive Power:  4,800,000

9.    Aggregate Amount Beneficially Owned by Each Reporting Person:

4,800,000

10.  Check if the Aggregate Amount in Row (9) Excludes Certain Shares   / /

11.  Percent of Class Represented by Amount in Row (9): 8.0%

12.  Type of Reporting Person: HC





CUSIP No. 00504W100

1.  Name of Reporting Persons.

HBK Master Fund L.P.

2.  Check the Appropriate Box if a Member of a Group

    (a) /X/

    (b) /  /

3.  SEC Use Only

4.  Citizenship or Place of Organization: Delaware

              5.  Sole Voting Power: 0
Number of
Shares
Beneficially  6.  Shared Voting Power:  4,800,000
Owned By
Each
Reporting     7.  Sole Dispositive Power: 0
Person
With:
              8.  Shared Dispositive Power:  4,800,000

9.    Aggregate Amount Beneficially Owned by Each Reporting Person:

4,800,000

10.  Check if the Aggregate Amount in Row (9) Excludes Certain Shares   / /

11.  Percent of Class Represented by Amount in Row (9): 8.0%

12.  Type of Reporting Person: PN




Item 1(a).     Name of Issuer:

The name of the issuer is Active Power, Inc. (the "Issuer").

Item 1(b).    Address of Issuer's Principal Executive Offices:

The principal executive offices of the Issuer are located at 2128 W. Braker
Lane, BK12, Austin, Texas 78758

Item 2(a).    Names of Persons Filing:

This Schedule 13G statement is hereby filed by the persons set forth below.

HBK Investments L.P.
HBK Services LLC
HBK Partners II L.P.
HBK Management LLC
HBK Master Fund L.P.

Item 2(b).    Address of Principal Business Office, or if None, Residence:

The address of the principal business office for each Reporting Person is set
forth below.

HBK Investments L.P.: 300 Crescent Court, Suite 700, Dallas, Texas 75201.
HBK Services LLC: 300 Crescent Court, Suite 700, Dallas, Texas 75201.
HBK Partners II L.P.: 300 Crescent Court, Suite 700, Dallas, Texas 75201.
HBK Management LLC: 300 Crescent Court, Suite 700, Dallas, Texas 75201.
HBK Master Fund L.P.: c/o HBK Services LLC, 300 Crescent Court, Suite 700,
Dallas, Texas 75201.

Item 2(c).    Citizenship:

HBK Investments L.P. is a Delaware limited partnership.
HBK Services LLC is a Delaware limited liability company.
HBK Partners II L.P. is a Delaware limited partnership.
HBK Management LLC is a Delaware limited liability company.
HBK Master Fund L.P. is a Cayman Islands limited partnership.

Item 2(d).    Title of Class of Securities:

This statement relates to the Common Stock of the Issuer (the "Securities").

Item 2(e).    CUSIP Number:

The CUSIP number of the Securities is 00504W100.

Item 3.  If this statement is filed pursuant to Sections 240.13d-1(b) or
240.13d-2(b) or (c), check whether the person filing is a:

(a) / /  Broker or dealer registered under section 15 of the Act (15 U.S.C.
78o).

(b) / /  Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c) / /  Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C.
78c).

(d) / / Investment company registered under section 8 of the Investment Company
Act of 1940 (15 U.S.C. 80a-8).

(e) / /  An investment adviser in accordance with section 240.13d-
1(b)(1)(ii)(E).

(f) / /  An employee benefit plan or endowment fund in accordance with section
240.13d-1(b)(1)(ii)(F).

(g) / /  A parent holding company or control person in accordance with section
240.13d-1(b)(1)(ii)(G).

(h) / /  A savings associations as defined in Section 3(b) of the Federal
Deposit Insurance Act (12 U.S.C. 1813).

(i) / /  A church plan that is excluded from the definition of an investment
company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C.
80a-3).

(j) / /  Group, in accordance with section 240.13d-1(b)(1)(ii)(J).

Item 4.  Ownership.

Ownership is incorporated by reference to items 5-9 and 11 of the cover page of
each Reporting Person.

The percentage disclosed in item 11 of the cover page of each Reporting Person
is calculated based upon 60,353,376 shares of common stock issued and
outstanding, 50,353,376 shares of which are reported in the Issuer's Form 10-Q
filed with the Securities and Exchange Commission on July 27, 2007 and
10,000,000 shares of which were issued in connection with a private placement
by the Issuer as reported in the Issuer's current report on Form 8-K filed
with the Securities and Exchange Commission on August 14, 2007.

Item 5.  Ownership of Five Percent or Less of a Class.

If this statement is being filed to report the fact that as of the date hereof
the reporting person has ceased to be the beneficial owner of more than five
percent of the class of securities, check the following / /

Item 6.  Ownership of More than Five Percent on Behalf of Another Person.

Jamiel A. Akhtar, Richard L. Booth, David C. Haley, Lawrence H. Lebowitz, and
William E. Rose are each managing members (collectively, the "Members") of HBK
Management LLC.  The Members expressly declare that the filing of this
statement on Schedule 13G shall not be construed as an admission that they are,
for the purpose of Section 13(d) or 13(g) of the Securities Exchange Act of
1934, beneficial owners of the Securities.

Item 7.  Identification and Classification of the Subsidiary Which Acquired the
Security Being Reported on By the Parent Holding Company.

Not applicable.

Item 8.  Identification and Classification of Members of the Group.

See Item 2.

Item 9.  Notice of Dissolution of Group.

Not applicable.

Item 10.  Certification.

By signing below I certify that, to the best of my knowledge and belief, the
securities referred to above were not acquired and are not held for the purpose
of or with the effect of changing or influencing the control of the issuer of
the securities and were not acquired and are not held in connection with or as
a participant in any transaction having that purpose or effect.





                                  SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.

                                            DATED: August 17, 2007

                                            HBK INVESTMENTS L.P.

                                            By:  /s/ Jon L. Mosle
                                                 Jon L. Mosle
                                                 Authorized Signatory (1)


                                            HBK SERVICES LLC

                                            By:  /s/ Jon L. Mosle
                                                 Jon L. Mosle
                                                 Authorized Signatory (1)


                                            HBK PARTNERS II L.P.
                                            By: HBK Management LLC
                                                General Partner

                                            By:  /s/ Jon L. Mosle
                                                 Jon L. Mosle
                                                 Authorized Signatory (1)


                                            HBK MANAGEMENT LLC

                                            By:  /s/ Jon L. Mosle
                                                 Jon L. Mosle
                                                 Authorized Signatory (1)

                                            HBK Master Fund L.P.
                                            By:  HBK Services LLC
                                                 Investment Advisor

                                            By:  /s/ Jon L. Mosle
                                                 Jon L. Mosle
                                                 Authorized Signatory (1)



(1)  An Authorization Certificate authorizing Jon L. Mosle to act on behalf of
each Reporting Person was previously filed.





                                    EXHIBIT 1

                              JOINT FILING STATEMENT
                             PURSUANT TO RULE 13d-1(k)

The undersigned acknowledge and agree that the foregoing statement on Schedule
13G is, and all subsequent amendments thereto shall be, filed on behalf of each
of the undersigned pursuant to and in accordance with the provisions of Rule
13d-1(k) of Regulation 13D of the General Rules and Regulations under the
Securities Exchange Act of 1934, as amended.

                                            DATED: August 17, 2007

                                            HBK INVESTMENTS L.P.

                                            By:  /s/ Jon L. Mosle
                                                 Jon L. Mosle
                                                 Authorized Signatory


                                            HBK SERVICES LLC

                                            By:  /s/ Jon L. Mosle
                                                 Jon L. Mosle
                                                 Authorized Signatory


                                            HBK PARTNERS II L.P.
                                            By: HBK Management LLC
                                                General Partner

                                            By:  /s/ Jon L. Mosle
                                                 Jon L. Mosle
                                                 Authorized Signatory


                                            HBK MANAGEMENT LLC

                                            By:  /s/ Jon L. Mosle
                                                 Jon L. Mosle
                                                 Authorized Signatory

                                            HBK MASTER FUND L.P.
                                            By:  HBK Services LLC
                                                 Investment Advisor

                                            By:  /s/ Jon L. Mosle
                                                 Jon L. Mosle
                                                 Authorized Signatory