Document:

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                                                              Exhibit 10.1.11

THE SECURITIES EVIDENCED BY THIS WARRANT CERTIFICATE HAVE NOT BEEN REGISTERED
UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), AND MAY NOT
BE SOLD, TRANSFERRED, OR ASSIGNED OR OFFERED FOR SALE OR OTHERWISE DISTRIBUTED
UNLESS THERE IS AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT
COVERING SUCH SECURITIES, THE SALE IS MADE IN COMPLIANCE WITH RULE 144 UNDER THE
SECURITIES ACT, OR THE COMPANY RECEIVES AN OPINION OF COUNSEL FOR THE HOLDER OF
SUCH SECURITIES REASONABLY SATISFACTORY TO THE COMPANY STATING THAT SUCH SALE,
TRANSFER OR ASSIGNMENT IS EXEMPT FROM THE REGISTRATION AND PROSPECTUS DELIVERY
REQUIREMENTS OF THE SECURITIES ACT.

No.: CC-2

                                     WARRANT
                            TO PURCHASE COMMON STOCK
                                       OF
                            BEACON POWER CORPORATION

                          (void after January 31, 2002)

     1. ISSUANCE OF WARRANT. FOR VALUE RECEIVED, commencing at the Commencement
Time, and subject to the terms and conditions herein set forth, the Holder (as
defined below) is entitled to purchase from Beacon Power Corporation, a Delaware
corporation (the "Company"), before 5:00 p.m. New York City time on January 31,
2002 (the "Termination Date"), 50,000 shares of the Warrant Stock (as defined
below) at a price per share equal to the Warrant Price (as defined below) upon
exercise of this Warrant pursuant to Section 6 hereof.

     2. DEFINITIONS. As used in this Warrant, the following terms have the
definitions ascribed to them below:

          (a) "Business Day" means any day other than a Saturday, Sunday or
     other day on which the national or state banks located in the Commonwealth
     of Massachusetts are authorized to be closed.

          (b) "Commencement Time" means immediately prior to the consummation of
     a Liquidity Event.

          (c) "Common Stock" means the Company's Common Stock, $.01 par value
     per share.

          (d) "Holder" means Cox Communications, Inc., or its assigns.

          (e) "Liquidity Event" means the consummation of an underwritten public
     offering of Common Stock pursuant to an effective registration statement
     under the Securities Act of 1933, as amended (a "Public Offering").

          (f) "Person" means any individual, corporation, partnership, limited
     liability company, or other entity.

          (g) "Warrant Price" means the initial offering price per share of the
     Common Stock in the first Public Offering, in each case subject to
     adjustment under Section 3.

          (h) "Warrant Stock" means the Common Stock.

          (i) "Warrant Stock Class" means the class of capital stock or other
     securities that includes the Warrant Stock.

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     3. ADJUSTMENTS AND NOTICES. The Warrant Price and/or the Warrant Stock
shall be subject to adjustment from time to time in accordance with this Section
3. The Warrant Price and/or the Warrant Stock shall be adjusted to reflect all
of the following events that occur on or after the Commencement Time.

          (a) REORGANIZATION, MERGER ETC. In case of any (i) merger or
     consolidation of the Company into or with another corporation where the
     Company is not the surviving corporation, (ii) sale, transfer or lease (but
     not including a transfer or lease by pledge or mortgage to a bona fide
     lender) of all or substantially all of the assets of the Company or (iii)
     sale by the Company's shareholders of 50% or more of the Company's
     outstanding securities in one or more related transactions, the Company, or
     such successor or purchasing corporation, as the case may be, shall, as a
     condition to closing any such reorganization, merger or sale, duly execute
     and deliver to the Holder hereof a new warrant so that the Holder shall
     have the right to receive, at a total purchase price not to exceed that
     payable upon the exercise or conversion of the unexercised or unconverted
     portion of this Warrant, and in lieu of the shares of Warrant Stock
     theretofore issuable upon exercise or conversion of this Warrant, the kind
     and amount of shares of stock, other securities, money and property
     receivable upon such reorganization, merger or sale by the Holder of the
     number of shares of Warrant Stock then purchasable under this Warrant. Such
     new warrant shall provide for adjustments that shall be as nearly
     equivalent as may be practicable to the adjustments provided for in this
     Section 3. The provisions of this subparagraph (a) shall similarly apply to
     successive transactions of the type described in this subparagraph (a).

          (b) CERTIFICATE OF ADJUSTMENT. In each case of an adjustment or
     readjustment of the Warrant Price, the Corporation, at its own expense,
     shall cause its Chief Financial Officer to compute such adjustment or
     readjustment in accordance with the provisions hereof and prepare a
     certificate showing such adjustment or readjustment, and shall mail such
     certificate, by first class mail, postage prepaid, to the Holder. The
     certificate shall set forth such adjustment or readjustment, showing in
     detail the facts upon which such adjustment or readjustment is based. No
     adjustment of the Warrant Price shall be required to be made unless it
     would result in an increase or decrease of at least one cent, but any
     adjustments not made because of this sentence shall be carried forward and
     taken into account in any subsequent adjustment otherwise required
     hereunder.

          (c) NO IMPAIRMENT. The Company shall not, by amendment of its
     Certificate of Incorporation or through a reorganization, transfer of
     assets, consolidation, merger, dissolution, issue, or sale of securities or
     any other voluntary action, avoid or seek to avoid the observance or
     performance of any of the terms to be observed or performed under this
     Warrant by the Company, but shall at all times in good faith assist in
     carrying out all of the provisions of this Section 3 and in taking all such
     action as may be necessary or appropriate to protect the Holder's rights
     under this Section 3 against impairment. If the Company takes any action
     affecting the Warrant Stock Class other than as described above that
     adversely affects the Holder's rights under this Warrant, the Warrant Price
     shall be adjusted downward.

          (d) FRACTIONAL SHARES. No fractional shares shall be issuable upon
     exercise or conversion of the Warrant and the number of shares to be issued
     shall be rounded down to the nearest whole share. If a fractional share
     interest arises upon any exercise or conversion of the Warrant, the Company
     shall eliminate such fractional share interest by paying the Holder an
     amount computed by multiplying the fractional interest by the fair market
     value of a full share.

     4. NO SHAREHOLDER RIGHTS. This Warrant, by itself, as distinguished from
any shares purchased hereunder, shall not entitle its Holder to any of the
rights of a shareholder of the Company.

     5. RESERVATION OF STOCK. The Company will reserve from its authorized and
unissued stock a sufficient number of shares to provide for the issuance of
Warrant Stock upon the exercise or conversion of this Warrant. Issuance of this
Warrant shall constitute full authority to the Company's officers who are
charged with the duty of executing stock certificates to execute and issue the
necessary certificates for shares of Warrant Stock issuable upon the exercise or
conversion of this Warrant.

     6. EXERCISE OF WARRANT. This Warrant may be exercised as a whole or in part
by the Holder, at the Commencement Time and prior to the termination of this
Warrant, by the surrender of this Warrant, together with

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the Notice of Exercise and Investment Representation Statement in the forms
attached hereto as ATTACHMENTS 1 AND 2, respectively, duly completed and
executed at the principal office of the Company, specifying the portion of the
Warrant to be exercised and accompanied by payment in full of the Warrant Price
in cash or by check with respect to the shares of Warrant Stock being purchased.
This Warrant shall be deemed to have been exercised immediately prior to the
close of business on the date of its surrender for exercise as provided above,
and the person entitled to receive the shares of Warrant Stock issuable upon
such exercise shall be treated for all purposes as the holder of such shares of
record as of the close of business on such date. As promptly as practicable
after such date, the Company shall issue and deliver to the person or persons
entitled to receive the same a certificate or certificates for the number of
full shares of Warrant Stock issuable upon such exercise. If this Warrant shall
be exercised for less than the total number of shares of Warrant Stock then
issuable upon exercise, promptly after surrender of this Warrant upon such
exercise, the Company will execute and deliver a new warrant, dated the date
hereof, evidencing the right of the Holder to the balance of the Warrant Stock
purchasable hereunder upon the same terms and conditions set forth herein.

     7. CONVERSION. In lieu of exercising this Warrant or any portion hereof, at
any time after the filing of a registration statement for an initial
underwritten public offering of securities by the Company, the Holder hereof
shall have the right to convert this Warrant or any portion hereof into Warrant
Stock by executing and delivering to the Company at its principal office the
written Notice of Conversion and Investment Representation Statement in the
forms attached hereto as ATTACHMENTS 2 AND 3, specifying the portion of the
Warrant to be converted, and accompanied by this Warrant. The number of shares
of Warrant Stock to be issued to Holder upon such conversion shall be computed
using the following formula:

                                 X=(P)(Y)(A-B)/A

     where             X = the number of shares of Warrant Stock to be
                           issued to the Holder for the portion of the Warrant
                           being converted.

                       P = the portion of the Warrant being converted expressed
                           as a decimal fraction.

                       Y = the total number of shares of Warrant Stock issuable
                           upon exercise of the Warrant in full.

                       A = the fair market value of one share of Warrant Stock
                           which means (i) the fair market value of the Warrant
                           Stock as of the last Business Day immediately prior
                           to the date the notice of conversion is received by
                           the Company, as reported in the principal market for
                           such securities or, if no such market exists, as
                           determined in good faith by the Company's Board of
                           Directors, or (ii) if this Warrant is being converted
                           in conjunction with a public offering of stock the
                           price to the public per share pursuant to the
                           offering.

                       B = the Warrant Price on the date of conversion.

Any portion of this Warrant that is converted shall be immediately canceled.
This Warrant or any portion hereof shall be deemed to have been converted
immediately prior to the close of business on the date of its surrender for
conversion as provided above, and the person entitled to receive the shares of
Warrant Stock issuable upon such conversion shall be treated for all purposes as
the holder of such shares of record as of the close of business on such date. As
promptly as practicable after such date, the Company shall issue and deliver to
the person or persons entitled to receive the same a certificate or certificates
for the number of full shares of Warrant Stock issuable upon such conversion. If
the Warrant shall be converted for less than the total number of shares of
Warrant Stock then issuable upon conversion, promptly after surrender of the
Warrant upon such conversion, the Company will execute and deliver a new
warrant, dated the date hereof, evidencing the right of the Holder to the
balance of the Warrant Stock purchasable hereunder upon the same terms and
conditions set forth herein.

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     8. NOTICE OF LIQUIDITY EVENT.The Company shall provide the Holder with at
least 10 Business Days advance written notice prior to the consummation of any
Liquidity Event describing in reasonable detail the terms and conditions of such
Liquidity Event and an estimate of the Warrant Price derivable from such
Liquidity Event.

     9. TRANSFER OF WARRANT. This Warrant may be transferred or assigned by the
Holder hereof as a whole or in part, provided that the transferor provides, at
the Company's request, an opinion of counsel satisfactory to the Company that
such transfer does not require registration under the Securities Act and the
securities law applicable with respect to any other applicable jurisdiction.

     10. TERMINATION. This Warrant shall terminate at 5:00 p.m. New York City
time on the Termination Date.

     11. LOCK-UP. The Holder will not, without the prior written consent of
Salomon Smith Barney Inc., offer, sell, contract to sell, pledge or otherwise
dispose of (or enter into any transaction which is designed to, or might
reasonably be expected to, result in the disposition (whether by actual
disposition or effective economic disposition due to cash settlement or
otherwise) by the Holder or any affiliate of the Holder or any person in privity
with the Holder or any affiliate of the Holder), directly or indirectly, in the
filing of a registration statement with the Securities and Exchange Commission
in respect of, or establish or increase a put equivalent position or liquidate
or decrease a call equivalent position within the meaning of Section 16 of the
Securities Exchange Act of 1934, as amended, and the rules and regulations of
the Securities and Exchange Commission promulgated hereunder with respect to,
any shares of capital stock of the Company or any securities convertible into,
or exercisable or exchangeable for such capital stock, or publicly announce an
intention to effect any such transaction, for a period of 180 days after the
date of the proposed Underwriting Agreement (the "Underwriting Agreement"),
between the Company, and each of the Underwriters named therein, in connection
with the Company's pending initial public offering, other than shares of Common
Stock disposed of as bona fide gifts approved by Salomon Smith Barney Inc. If
for any reason the Underwriting Agreement shall be terminated prior to the
Closing Date (as defined in the Underwriting Agreement), this provision shall be
of no further effect.

     12. MISCELLANEOUS. This Warrant shall be governed by the laws of the State
of Delaware, as such laws are applied to contracts to be entered into and
performed entirely in Delaware by Delaware residents. The headings in this
Warrant are for purposes of convenience and reference only, and shall not be
deemed to constitute a part hereof. Neither this Warrant nor any term hereof may
be changed or waived orally, but only by an instrument in writing signed by the
Company and the Holder of this Warrant. All notices and other communications
from the Company to the Holder of this Warrant shall be delivered personally or
by facsimile transmission or mailed by first class mail, postage prepaid, to the
address or facsimile number furnished to the Company in writing by the last
Holder of this Warrant who shall have furnished an address or facsimile number
to the Company in writing, and if mailed shall be deemed given three days after
deposit in the United States mail.

                              ISSUED:  August 2, 2000

                                    BEACON POWER CORPORATION

                                    By:      /s/ Maureen Lister
                                             ------------------

                                    Name:    Maureen Lister

                                    Title:   Secretary

                                      -4-
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                                  Attachment 1

NOTICE OF EXERCISE

TO:  BEACON POWER CORPORATION

1.   The undersigned hereby elects to purchase _______________ shares of Warrant
     Stock of Beacon Power Corporation pursuant to the terms of the attached
     Warrant, and tenders herewith payment of the purchase price in full,
     together with all applicable transfer taxes, if any.

2.   Please issue a certificate or certificates representing said shares of
     Warrant Stock in the name of the undersigned or in such other name as is
     specified below:

                         ------------------------------
                                     (Name)

                         -------------------------------
                                    (Address)

---------------------------------------     -----------------------------------
(Date)                                             (Name of Warrant Holder)

                                            By:________________________________

                                            Title:_____________________________

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                                  Attachment 2

                       INVESTMENT REPRESENTATION STATEMENT

     In connection with the purchase of the shares of Warrant Stock upon
exercise of the enclosed Warrant, the undersigned hereby represents to Beacon
Power Corporation (the "Company") as follows:

(a) The securities to be received upon the exercise of the Warrant (the
"Securities") will be acquired for investment for its own account, not as a
nominee or agent, and not with a view to the sale or distribution of any part
thereof, and the undersigned has no present intention of selling, granting
participation in or otherwise distributing the same, but subject, nevertheless,
to any requirement of law that the disposition of its property shall at all
times be within its control. By executing this statement, the undersigned
further represents that it does not have any contract, undertaking, agreement or
arrangement with any person to sell, transfer, or grant participations to such
person or to any third person, with respect to any Securities issuable upon
exercise of the Warrant.

(b) The undersigned understands that the Securities issuable upon exercise of
the Warrant at the time of issuance may not be registered under the Securities
Act of 1933, as amended (the "Securities Act"), and applicable state securities
laws, on the ground that the issuance of such securities is exempt pursuant to
Section 4(2) of the Securities Act and state law exemptions relating to offers
and sales not by means of a public offering, and that the Company's reliance on
such exemptions is predicated on the undersigned's representations set forth
herein.

(c) The undersigned agrees that in no event will it make a disposition of any
Securities acquired upon the exercise of the Warrant unless and until (i) it
shall have notified the Company of the proposed disposition and shall have
furnished the Company with a statement of the circumstances surrounding the
proposed disposition, and (ii) it shall have furnished the Company with an
opinion of counsel satisfactory to the Company and Company's counsel to the
effect that (A) appropriate action necessary for compliance with the Securities
Act and any applicable state securities laws has been taken or an exemption from
the registration requirements of the Securities Act and such laws is available,
and (B) the proposed transfer will not violate any of said laws.

(d) The undersigned acknowledges that an investment in the Company is highly
speculative and represents that it is able to fend for itself in the
transactions contemplated by this statement, has such knowledge and experience
in financial and business matters as to be capable of evaluating the merits and
risks of its investments, and has the ability to bear the economic risks
(including the risk of a total loss) of its investment. The undersigned
represents that it has had the opportunity to ask questions of the Company
concerning the Company's business and assets and to obtain any additional
information which it considered necessary to verify the accuracy of or to
amplify the Company's disclosures, and has had all questions which have been
asked by it satisfactorily answered by the Company

(e) The undersigned acknowledges that the Securities issuable upon exercise or
conversion of the Warrant must be held indefinitely unless subsequently
registered under the Securities Act or an exemption from such registration is
available. The undersigned is aware of the provisions of Rule 144 promulgated
under the Securities Act which permit limited resale of shares purchased in a
private placement subject to the satisfaction of certain conditions, including,
among other things, the existence of a public market for the shares, the
availability of certain current public information about the Company, the resale
occurring not less than one year after a party has purchased and paid for the
security to be sold from the Company or any affiliate of the Company, the sale
being through a "broker's transaction" or in transactions directly with a
"market maker" (as provided by Rule 144(f)) and the number of shares being sold
during any three month period not exceeding specified limitations.

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         Dated:
               ---------------------------------

         ---------------------------------------
         (Typed or Printed Name)

         By:
            ------------------------------------
              (Signature)

         ---------------------------------------
         (Name)

         ---------------------------------------
         (Title)

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                                  Attachment 3

NOTICE OF CONVERSION

TO: BEACON POWER CORPORATION

1. The undersigned hereby elects to acquire _______________ shares of the
Warrant Stock of Beacon Power Corporation pursuant to the terms of the attached
Warrant, by conversion of _________ percent (_____%) of the Warrant.

2. Please issue a certificate or certificates representing said shares of
Warrant Stock in the name of the undersigned or in such other name as is
specified below:

                         ------------------------------
                                     (Name)

                         -------------------------------
                                    (Address)

---------------------------------------     -----------------------------------
(Date)   (Name of Warrant Holder)

         By:____________________________________________

         Title:_________________________________________
              (Title and signature of authorized person)

                                      -3-<PAGE>
                                                       EXHIBIT 10.1.27

                        [Petroleos Mexicanos Letterhead]

25 October 2000

JOHN DOHERTY
Beacon Power
Woborn, MA 01801

PEMEX is very interested in your proposal to use Beacon Flywheel Systems to
support our energy storage needs. As we told you previously, we will require
that this equipment be tested and certified by the Instituto Mexicano Del
Petroleo before we could use it. If this equipment is certified, it would be
our intention to use this system for communications and remote pipeline
monitoring and control. This use will require a minimum of 300 to 500 systems
for the initial install and additional systems as we expand the use.

                               Attention

                       /s/ Jose Montero Gonzalez

                       ING. JOSE MONTERO GONZALEZ
                            Director General

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