Document:

<PAGE>

NUMBER

BPC

BEACON
POWER -TM-

BEACON POWER CORPORATION
THIS CERTIFICATE IS TRANSFERABLE IN CANTON, MA OR NEW YORK, NY
INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

SHARES

COMMON STOCK
$.01 PAR VALUE

CUSIP 073677 10 6

THIS CERTIFIES THAT

IS THE OWNER OF

FULLY PAID AND NON-ASSESSABLE SHARES, $.01 PAR VALUE, OF THE COMMON STOCK OF

BEACON POWER CORPORATION TRANSFERABLE ON THE BOOKS OF THE CORPORATION IN
PERSON OR BY ATTORNEY UPON SURRENDER OF THIS CERTIFICATE PROPERLY ENDORSED.
THIS CERTIFICATE AND THE SHARES REPRESENTED HEREBY ARE SUBJECT TO THE LAWS OF
THE STATE OF DELAWARE AND TO THE CERTIFICATE OF INCORPORATION AND THE BY-LAWS
OF THE CORPORATION AS FROM TIME TO TIME AMENDED.

THIS CERTIFICATE IS NOT VALID UNTIL COUNTERSIGNED AND REGISTERED BY THE
TRANSFER AGENT AND REGISTRAR.

IN WITNESS WHEREOF, BEACON POWER CORPORATION HAS CAUSED ITS FACSIMILE
CORPORATE SEAL AND THE FACSIMILE SIGNATURES OF ITS DULY AUTHORIZED OFFICERS
TO BE HEREUNTO AFFIXED.

DATED:

/S/ MAUREEN A LISTER

Secretary

Beacon Power Corporation
CORPORATE
SEAL
1997
DELAWARE

/S/ WILLIAM E. STANTON

PRESIDENT

SEE REVERSE FOR CERTAIN DEFINITIONS

COUNTERSIGNED AND REGISTERED:

EQUISERVE TRUST COMPANY, N.A.

TRANSFER AGENT AND REGISTRAR

BY

/S/ CHARLES RONIN

AUTHORIZED SIGNATURE

NOTE: LOGO IS CMYK, NOT CONVERTIBLE TO PMS

AMERICAN BANK NOTE COMPANY
55TH & SANSOM STREET
PHILADELPHIA, PA 19139
(215) 764-8600

SALES: D.BURNS 617-786-7600

HOME 46/LIVE JOBS/BEACON/H67855

PRODUCTION COORDINATOR: LISA MARTIN: 215-764-8625
PROOF OF SEPTEMBER 21, 2000
BEACON POWER CORPORATION
H 67855 Fc

OPERATOR: LR/MT/ge

REV.1

<PAGE>

BPC

BEACON
POWER -TM-

BEACON POWER CORPORATION

INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

THIS CERTIFICATE IS TRANSFERABLE IN CANTON, MA OR NEW YORK, NY

COMMON STOCK
$.01 PAR VALUE

CUSIP 073677 10 6

THIS CERTIFIES THAT

IS THE OWNER OF

FULLY PAID AND NON-ASSESSABLE SHARES, $.01 PAR VALUE, OF THE COMMON STOCK OF

BEACON POWER CORPORATION TRANSFERABLE ON THE BOOKS OF THE CORPORATION IN
PERSON OR BY ATTORNEY UPON SURRENDER OF THIS CERTIFICATE PROPERLY ENDORSED.
THIS CERTIFICATE AND THE SHARES REPRESENTED HEREBY ARE SUBJECT TO THE LAWS OF
THE STATE OF DELAWARE AND TO THE CERTIFICATE OF INCORPORATION AND THE BY-LAWS
OF THE CORPORATION AS FROM TIME TO TIME AMENDED.

THIS CERTIFICATE IS NOT VALID UNTIL COUNTERSIGNED AND REGISTERED BY THE
TRANSFER AGENT AND REGISTRAR.

IN WITNESS WHEREOF, BEACON POWER CORPORATION HAS CAUSED ITS FACSIMILE
CORPORATE SEAL AND THE FACSIMILE SIGNATURES OF ITS DULY AUTHORIZED OFFICERS TO
BE HEREUNTO AFFIXED.

DATED:

/S/ MAUREEN A LISTER

SECRETARY

Beacon Power Corporation
CORPORATE
SEAL
1997
DELAWARE

/S/ WILLIAM E. STANTON

PRESIDENT

SEE REVERSE FOR CERTAIN DEFINITIONS

COUNTERSIGNED AND REGISTERED:

EQUISERVE TRUST COMPANY, N.A.

TRANSFER AGENT AND REGISTRAR

BY

/S/ CHARLES RONIN

AUTHORIZED SIGNATURE

NOTE: LOGO IS CMYK, NOT CONVERTIBLE TO PMS

AMERICAN BANK NOTE COMPANY
55TH & SANSOM STREET
PHILADELPHIA, PA 19139
(215) 764-8600

SALES: D.BURNS: 617-786-7600

HOME 46/LIVE JOBS/BEACON/H67855

PRODUCTION COORDINATOR: LISA MARTIN: 215-764-8625
PROOF OF SEPTEMBER 21,2000
BEACON POWER CORPORATION
H 67855 Fc

OPERATOR: LR/MT/ge

REV.1

<PAGE>

BEACON POWER CORPORATION

THE CORPORATION IS AUTHORIZED TO ISSUE MORE THAN ONE CLASS OF STOCK. THE
CORPORATION WILL FURNISH WITHOUT CHARGE TO EACH STOCKHOLDER WHO SO REQUESTS A
COPY OF THE POWERS, DESIGNATIONS, PREFERENCES AND RELATIVE RIGHTS OF THE
SHARES OF EACH OUTSTANDING CLASS OF STOCK OR SERIES THEREOF OF THE
CORPORATION, AND THE QUALIFICATIONS, LIMITATIONS OR RESTRICTIONS OF SUCH
PREFERENCES AND/OR RIGHTS.

The following abbreviations, when used in the inscription on the face of this
certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

TEN COM - as tenants in common
TEN ENT - as tenants by the entireties
JT TEN - as joint tenants with right of survivorship and not as tenants in
common

UNIF GIFT MIN ACT- ______ Custodian _______
                   (Cust)           (Minor)
under Uniform Gifts to Minors
Act  ________
     (State)

Additional abbreviations may also be used though not in the above list.

FOR VALUE RECEIVED _______ HEREBY SELL, ASSIGN AND TRANSFER UNTO

PLEASE INSERT SOCIAL SECURITY OR OTHER
IDENTIFYING NUMBER OF ASSIGNEE
(box)________________________________
_____________________________________

PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS OF ASSIGNEE ______________
_____________________________________________________________________

______SHARES OF THE CAPITAL STOCK REPRESENTED BY THE WITHIN CERTIFICATE, AND DO
HEREBY IRREVOCABLY CONSTITUTE AND APPOINT____________________________
___________ATTORNEY TO TRANSFER THE SAID STOCK ON THE BOOKS OF THE WITHIN-NAMED
CORPORATION WITH FULL POWER OF SUBSTITUTION IN THE PREMISES.

DATED, _____________________

____________________________

NOTICE: THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS
WRITTEN UPON THE FACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT
ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATEVER.

Signature(s) Guaranteed:

_________________________

THE SIGNATURE(S) MUST BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION
(BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH
MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM), PURSUANT TO
S.E.C. RULE 17Ad-15.

AMERICAN BANK NOTE COMPANY
55TH & SANSOM STREET
PHILADELPHIA, PA 19139
(215) 764-8600

SALES: D.BURNS: 617-786-7600

HOME 46/LIVE JOBS/BEACON/H67855

PRODUCTION COORDINATOR: LISA MARTIN: 215-764-8625
PROOF OF SEPTEMBER 19, 2000
BEACON POWER CORPORATION
H 67855 Bk

OPERATOR: MT

NEW<PAGE>

                                                                     Exh 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-1

                                     WARRANT
                            TO PURCHASE COMMON STOCK
                                       OF
                            BEACON POWER CORPORATION

                          (void after January 31, 2001)

      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, 2001 (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.
<PAGE>

      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

                                      -2-
<PAGE>

with 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.    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.

      8.    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.

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

      10.   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.

      11.   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.

                                      -3-
<PAGE>

                                         ISSUED:    August 2, 2000

                                                BEACON POWER CORPORATION

                                                By:      /s/ William E. Stanton

                                                Name:    William E. Stanton

                                                Title:   President

                                      -4-
<PAGE>

                                  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:________________________
<PAGE>

                                  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.

         Dated:________________________
<PAGE>

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

         By:____________________________________
              (Signature)

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

                                      -2-

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