Exhibit 10.4

NEITHER THESE SECURITIES NOR THE SECURITIES FOR WHICH THESE SECURITIES ARE EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OR PURSUANT TO AN AVAILABLE EXEMPTION FROM, OR IN A TRANSACTION NOT SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT AND IN COMPLIANCE WITH APPLICABLE STATE SECURITIES OR BLUE SKY LAWS.  THESE SECURITIES AND THE SECURITIES ISSUABLE UPON EXERCISE OF THESE SECURITIES MAY BE PLEDGED IN CONNECTION WITH A BONA FIDE MARGIN ACCOUNT OR OTHER LOAN SECURED BY SUCH SECURITIES, SUBJECT TO THE TERMS OF THIS LEGEND AND THE SECURITIES ACT.

SATCON TECHNOLOGY CORPORATION

WARRANT B

Warrant B No. [  ]                                                                                                                                          Dated:  July 19, 2006

SatCon Technology Corporation, a Delaware corporation (the “Company”), hereby certifies that, for value received, [Name of Holder] or its registered assigns (the “Holder”), is entitled to purchase from the Company (a) up to a total of [          ] shares of common stock, $0.01 par value per share (the “Common Stock”), of the Company (each such share, a “Warrant Share” and all such shares, the “Warrant Shares”) at an exercise price equal to $1.68 per share (as adjusted from time to time as provided in Section 9, the “Exercise Price”), and (b) only as part of and in connection with the purchase of the Warrant Shares, warrants in the form attached to the Purchase Agreement (as hereinafter defined) as Exhibit B-3 to acquire up to 0.50 shares of Common Stock for each Warrant Share purchased (the “Additional Warrants”), at any time and from time to time from and after the six month anniversary of the Closing Date and through and including the 90th Trading Day following the later of (i) the Effective Date, but not including the Effective Date and (ii) the six month anniversary of the Closing Date (the “Expiration Date”), and subject to the following terms and conditions.  This Warrant (this “Warrant”) is one of a series of similar warrants issued pursuant to that certain Securities Purchase Agreement, dated as of the date hereof, by and among the Company and the Purchasers identified therein (the “Purchase Agreement”).  All such warrants are referred to herein, collectively, as the “Warrants.”  Common Stock issuable upon exercise of the Additional Warrants shall be known herein as the “Additional Warrant Shares”.

1.             Definitions.  In addition to the terms defined elsewhere in this Warrant, capitalized terms that are not otherwise defined herein have the meanings given to such terms in the Purchase Agreement.

2.             Registration of Warrant.  The Company shall register this Warrant, upon records to be maintained by the Company for that purpose (the “Warrant Register”), in the name of the record Holder hereof from time to time.  The Company may deem and treat the registered Holder of this Warrant as the absolute owner hereof for the purpose of any exercise hereof or any distribution to the Holder, and for all other purposes, absent actual notice to the contrary.

3.             Registration of Transfers.  The Company shall register the assignment and transfer of any portion of this Warrant in the Warrant Register, upon surrender of this Warrant, with the Form of Assignment attached hereto on Annex B duly completed and signed, to the Company at its address specified herein.  Upon any such registration or transfer, a new warrant to purchase Common Stock, in substantially the form of this Warrant (any such new warrant, a “New Warrant”), evidencing the portion of this Warrant so transferred shall be issued to the transferee and a New Warrant evidencing the remaining portion of this Warrant not so transferred, if any, shall be issued to the transferring Holder.  The acceptance of the New Warrant by the transferee thereof shall be deemed the acceptance by such transferee of all of the rights and obligations of a holder of a Warrant.

4.             Exercise and Duration of Warrants.

(a)           This Warrant shall be exercisable by the registered Holder at any time and from time to time on or after the six month anniversary of the Closing Date to and including the Expiration Date.  At 6:30 P.M., New York City time on the Expiration Date, the portion of this Warrant not exercised prior thereto shall be and become void and of no value. Notwithstanding anything to the contrary herein, the Expiration Date shall be extended for each day following the Effective Date that the Registration Statement is not effective.

(b)           A Holder may exercise this Warrant by delivering to the Company (i) an exercise notice, in the form attached hereto on Annex A (the “Exercise Notice”), appropriately completed and duly signed, and (ii) payment of the Exercise Price for the number of Warrant Shares and Additional Warrants as to which this Warrant is being exercised, and the date such items are delivered to the Company (as determined in accordance with the notice provisions hereof) is an “Exercise Date.”  The Holder shall not be required to deliver the original Warrant in order to effect an exercise hereunder.  Execution and delivery of the Exercise Notice shall have the same effect as cancellation of the original Warrant and issuance of a New Warrant evidencing the right to purchase the remaining number of Warrant Shares and Additional Warrants.

5.             Delivery of Warrant Shares and Additional Warrants.

(a)           Upon exercise of this Warrant, the Company shall promptly (but in no event later than three Trading Days after the Exercise Date) issue or cause to be issued and cause to be delivered to or upon the written order of the Holder and in such name or names as the Holder may designate, a certificate for the Warrant Shares and Additional Warrants issuable

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upon such exercise.  The Company shall cause the certificate for the Warrant Shares to be issued free of restrictive legends unless a registration statement covering the resale of the Warrant Shares and naming the Holder as a selling stockholder thereunder is not then effective and the Warrant Shares are not freely transferable without volume restrictions pursuant to Rule 144 under the Securities Act.  The Holder, or any Person so designated by the Holder to receive Warrant Shares and Additional Warrants, shall be deemed to have become holder of record of such Warrant Shares and Additional Warrants as of the Exercise Date.  The Company shall, upon request of the Holder, use its best efforts to deliver Warrant Shares hereunder electronically through the Depository Trust Corporation or another established clearing corporation performing similar functions.

(b)           This Warrant is exercisable, either in its entirety or, from time to time, for a portion of the number of Warrant Shares and Additional Warrants.  Upon surrender of this Warrant following one or more partial exercises, the Company shall issue or cause to be issued, at its expense, a New Warrant evidencing the right to purchase the remaining number of Warrant Shares and Additional Warrants.

(c)           In addition to any other rights available to a Holder, if the Company fails to deliver to the Holder a certificate representing Warrant Shares and Additional Warrants by the third Trading Day after exercise of this Warrant in full compliance with Section 4(b), and if after such third Trading Day the Holder purchases (in an open market transaction or otherwise) shares of Common Stock to deliver in satisfaction of a sale by the Holder of the Warrant Shares or Additional Warrant Shares that the Holder anticipated receiving from the Company (a “Buy-In”), then the Company shall, within three Trading Days after the Holder’s request and in the Holder’s discretion, either (i) pay cash to the Holder in an amount equal to the Holder’s total purchase price (including brokerage commissions, if any) for the shares of Common Stock so purchased (the “Buy-In Price”), at which point the Company’s obligation to deliver such certificate (and to issue such Common Stock) shall terminate, or (ii) promptly honor its obligation to deliver to the Holder a certificate or certificates representing such Common Stock and pay cash to the Holder in an amount equal to the excess (if any) of the Buy-In Price over the product of (A) such number of shares of Common Stock, times (B) the Closing Price on the date of the event giving rise to the Company’s obligation to deliver such certificate.

(d)           The Company’s obligations to issue and deliver Warrant Shares and Additional Warrants in accordance with the terms hereof are absolute and unconditional, irrespective of any action or inaction by the Holder to enforce the same, any waiver or consent with respect to any provision hereof, the recovery of any judgment against any Person or any action to enforce the same, or any setoff, counterclaim, recoupment, limitation or termination, or any breach or alleged breach by the Holder or any other Person of any obligation to the Company or any violation or alleged violation of law by the Holder or any other Person, and irrespective of any other circumstance which might otherwise limit such obligation of the Company to the Holder in connection with the issuance of Warrant Shares and Additional Warrants.  Nothing herein shall limit a Holder’s right to pursue any other remedies available to it hereunder, at law or in equity including, without limitation, a decree of specific performance and/or injunctive relief with respect to the Company’s failure to timely deliver certificates representing shares of Common Stock upon exercise of the Warrant  as required pursuant to the terms hereof.

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6.             Charges, Taxes and Expenses.   Issuance and delivery of certificates for shares of Common Stock and Additional Warrants upon exercise of this Warrant shall be made without charge to the Holder for any issue or transfer tax, withholding tax, transfer agent fee or other incidental tax or expense in respect of the issuance of such certificates, all of which taxes and expenses shall be paid by the Company; provided, however, that the Company shall not be required to pay any tax which may be payable in respect of any transfer involved in the registration of any certificates for Warrant Shares or Warrants in a name other than that of the Holder or an Affiliate thereof.  The Holder shall be responsible for all other tax liability that may arise as a result of holding or transferring this Warrant or receiving Warrant Shares and Additional Warrants upon exercise hereof.

7.             Replacement of Warrant.  If this Warrant is mutilated, lost, stolen or destroyed, the Company shall issue or cause to be issued in exchange and substitution for and upon cancellation hereof, or in lieu of and substitution for this Warrant, a New Warrant, but only upon receipt of evidence reasonably satisfactory to the Company of such loss, theft or destruction and customary and reasonable indemnity, if requested.

8.             Reservation of Warrant Shares and Additional Warrant Shares.  The Company covenants that it will at all times reserve and keep available out of the aggregate of its authorized but unissued and otherwise unreserved Common Stock, solely for the purpose of enabling it to issue Warrant Shares upon exercise of this Warrant and Additional Warrants as herein provided or in the Additional Warrant Shares upon exercise of the Additional Warrants as provided in the Additional Warrants, the number of Warrant Shares which are then issuable and deliverable upon the exercise of this entire Warrant and the number of Additional Warrant Shares issuable and deliverable upon the exercise of any Additional Warrants, free from preemptive rights or any other contingent purchase rights of persons other than the Holder (taking into account the adjustments and restrictions of Section 9).  The Company covenants that all Warrant Shares and Additional Warrant Shares so issuable and deliverable shall, upon issuance and the payment of the applicable Exercise Price in accordance with the terms hereof, or the Additional Warrants, be duly and validly authorized, issued and fully paid and nonassessable.  The Company will take all such action as may be necessary to assure that such shares of Common Stock may be issued as provided herein without violation of any applicable law or regulation, or of any requirements of any securities exchange or automated quotation system upon which the Common Stock may be listed.

9.             Certain Adjustments.  The Exercise Price and number of Warrant Shares issuable upon exercise of this Warrant are subject to adjustment from time to time as set forth in this Section 9.  The exercise price and number of Additional Warrant Shares issuable upon exercise of the Additional Warrants shall be subject to adjustment from time to time as set forth in Section 9 of the Additional Warrants.

(a)           Stock Dividends and Splits.  If the Company, at any time while this Warrant is outstanding, (i) pays a stock dividend on its Common Stock or otherwise makes a distribution on any class of capital stock that is payable in shares of Common Stock, (ii) subdivides outstanding shares of Common Stock into a larger number of shares, or (iii) combines outstanding shares of Common Stock into a smaller number of shares, then in each such case the Exercise Price shall be multiplied by a fraction of which the numerator shall be the number of

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shares of Common Stock outstanding immediately before such event and of which the denominator shall be the number of shares of Common Stock outstanding immediately after such event.  Any adjustment made pursuant to clause (i) of this paragraph shall become effective immediately after the record date for the determination of stockholders entitled to receive such dividend or distribution, and any adjustment pursuant to clause (ii) or (iii) of this paragraph shall become effective immediately after the effective date of such subdivision or combination.

(b)           Pro Rata Distributions.  If the Company, at any time while this Warrant is outstanding, distributes to holders of Common Stock (i) evidences of its indebtedness, (ii) any security (other than a distribution of Common Stock covered by the preceding paragraph), (iii) rights or warrants to subscribe for or purchase any security, or (iv) any other asset (in each case, “Distributed Property”), then in each such case the Exercise Price in effect immediately prior to the record date fixed for determination of stockholders entitled to receive such distribution shall be adjusted (effective on such record date) to equal the product of such Exercise Price times a fraction of which the denominator shall be the average of the Closing Prices for the five Trading Days immediately prior to (but not including) such record date and of which the numerator shall be such average less the then fair market value of the Distributed Property distributed in respect of  one outstanding share of Common Stock, as determined by the Company’s independent certified public accountants that regularly examine the financial statements of the Company, (an “Appraiser”).  In such event, the Holder, after receipt of the determination by the Appraiser, shall have the right to select an additional appraiser (which shall be a nationally recognized accounting firm), in which case such fair market value shall be deemed to equal the average of the values determined by each of the Appraiser and such appraiser.  As an alternative to the foregoing adjustment to the Exercise Price, at the request of the Holder delivered to the Company in writing before the 45th day after such record date, the Company will deliver to such Holder, within five Trading Days after such request (or, if later, on the effective date of such distribution), the Distributed Property that such Holder would have been entitled to receive in respect of the Warrant Shares for which this Warrant could have been exercised immediately prior to such record date.  If such Distributed Property is not delivered to a Holder pursuant to the preceding sentence, then upon expiration of or any exercise of the Warrant that occurs after such record date, such Holder shall remain entitled to receive, in addition to the Warrant Shares otherwise issuable upon such exercise (if applicable), such Distributed Property.

(c)           Fundamental Transactions.  If, at any time while this Warrant is outstanding, (i) the Company effects any merger or consolidation of the Company with or into another Person, (ii) the Company effects any sale of all or substantially all of its assets in one or a series of related transactions, (iii) any tender offer or exchange offer (whether by the Company or another Person) is completed pursuant to which holders of Common Stock are permitted to tender or exchange their shares for other securities, cash or property, or (iv) the Company effects any reclassification of the Common Stock or any compulsory share exchange pursuant to which the Common Stock is effectively converted into or exchanged for other securities, cash or property (other than as a result of a subdivision or combination of shares of Common Stock covered by Section 9(a) above) (in any such case, a “Fundamental Transaction”), then the Holder shall have the right thereafter to receive, upon exercise of this Warrant, the same amount and kind of securities, cash or property as it would have been entitled to receive upon the occurrence of such Fundamental Transaction if it had been, immediately prior to such

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Fundamental Transaction, the holder of the number of Warrant Shares then issuable upon exercise in full of this Warrant (the “Alternate Consideration”).  The aggregate Exercise Price for this Warrant will not be affected by any such Fundamental Transaction, but the Company shall apportion such aggregate Exercise Price among the Alternate Consideration in a reasonable manner reflecting the relative value of any different components of the Alternate Consideration.  If holders of Common Stock are given any choice as to the securities, cash or property to be received in a Fundamental Transaction, then the Holder shall be given the same choice as to the Alternate Consideration it receives upon any exercise of this Warrant following such Fundamental Transaction.  In the event of a Fundamental Transaction, the Company or the successor or purchasing Person, as the case may be, shall execute with the Holder a written agreement providing that:

(x)   this Warrant shall thereafter entitle the Holder to purchase the Alternate Consideration in accordance with this section 9(c),

(y)  in the case of any such successor or purchasing Person, upon such consolidation, merger, statutory exchange, combination, sale or conveyance such successor or purchasing Person shall be jointly and severally liable with the Company for the performance of all of the Company’s obligations under this Warrant and the Purchase Agreement, and

(z)   if registration or qualification is required under the Exchange Act or applicable state law for the public  resale by the Holder of shares of stock and other securities so issuable upon exercise of this Warrant, such registration or qualification shall be completed prior to such reclassification, change, consolidation, merger, statutory exchange, combination or sale.

If, in the case of any Fundamental Transaction, the Alternate Consideration includes shares of stock, other securities, other property or assets of a Person other than the Company or any such successor or purchasing Person, as the case may be, in such Fundamental Transaction, then such written agreement shall also be executed by such other Person and shall contain such additional provisions to protect the interests of the Holder as the Board of Directors of the Company shall reasonably consider necessary by reason of the foregoing.  At the Holder’s request, any successor to the Company or surviving entity in such Fundamental Transaction shall issue to the Holder a new warrant consistent with the foregoing provisions and evidencing the Holder’s right to purchase the Alternate Consideration for the aggregate Exercise Price upon exercise thereof.  The terms of any agreement pursuant to which a Fundamental Transaction is effected shall include terms requiring any such successor or surviving entity to comply with the provisions of this paragraph (c) and insuring that the Warrant (or any such replacement security) will be similarly adjusted upon any subsequent transaction analogous to a Fundamental Transaction. If any Fundamental Transaction constitutes or results in a Change of Control, then at the request of the Holder delivered to the Company in writing before the 45th day after such Fundamental Transaction, the Company (or any such successor or surviving entity) will purchase the Warrant from the Holder for a purchase price, payable in cash within five Trading Days after such request (or, if later, on the effective date of the Fundamental Transaction), equal to the Black-Scholes value of the remaining unexercised portion of this Warrant on the date of such request.

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(d)           Subsequent Equity Sales.

(i)            For so long as this Warrant is outstanding, the Company or any Subsidiary shall not issue additional shares of Common Stock or rights, warrants, options or other securities or debt convertible, exercisable or exchangeable for shares of Common Stock or otherwise entitling any Person to acquire shares of Common Stock (collectively, “Common Stock Equivalents”) at an effective price per share of Common Stock (prior to deducting fees, commissions and other expenses related to such issuance) (the “Effective Price”) less than the Conversion Price (as defined in the Notes) (as adjusted to such date) (a “Prohibited Issuance”).  For purposes of this paragraph, in connection with any issuance of any Common Stock Equivalents, (A) the maximum number of shares of Common Stock potentially issuable at any time upon conversion, exercise or exchange of such Common Stock Equivalents (the “Deemed Number”) shall be deemed to be outstanding upon issuance of such Common Stock Equivalents, (B) the Effective Price applicable to such Common Stock shall equal the minimum dollar value of consideration payable to the Company to purchase such Common Stock Equivalents and to convert, exercise or exchange them into Common Stock (prior to deducting any fees, commissions and other expenses related thereto), divided by the Deemed Number, and (C) the actual issuance of Common Stock upon conversion, exercise or exchange of such Common Stock Equivalents shall not be subject again to this Section 9(d)(i).

(ii)           If, at any time while this Warrant is outstanding, the Company or any Subsidiary issues Common Stock Equivalents with an Effective Price or a number of underlying shares that floats or resets or otherwise varies or is subject to adjustment based (directly or indirectly) on market prices of the Common Stock (a “Floating Price Security”), then for purposes of applying the preceding paragraph, whether Section 9(d)(i) has been violated will be determined separately each time such adjustment occurs.

(iii)          In the event the Company breaches Section 9(d)(i), then at the request of the Holder delivered to the Company in writing before the 45th day after such Prohibited Issuance, the Company (or any such successor or surviving entity) will purchase this Warrant from the Holder for a purchase price, payable in cash within five Trading Days after such request, equal to the Black-Scholes value of the remaining unexercised portion of this Warrant on the date of such request.

(iv)          Notwithstanding the foregoing, the Company shall be permitted to issue Excluded Stock.

(e)           Number of Warrant Shares.  Simultaneously with any adjustment to the Exercise Price pursuant to paragraphs (a) or (b) of this Section, the number of Warrant Shares that may be purchased upon exercise of this Warrant shall be increased or decreased proportionately, so that after such adjustment the aggregate Exercise Price payable hereunder for the increased or decreased number of Warrant Shares shall be the same as the aggregate Exercise Price in effect immediately prior to such adjustment.

(f)            Calculations.  All calculations under this Section 9 shall be made to the nearest cent or the nearest 1/100th of a share, as applicable.  The number of shares of Common

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Stock outstanding at any given time shall not include shares owned or held by or for the account of the Company, and the disposition of any such shares shall be considered an issue or sale of Common Stock.

(g)           Notice of Adjustments.  Upon the occurrence of each adjustment pursuant to this Section 9, the Company at its expense will promptly compute such adjustment in accordance with the terms of this Warrant and prepare a certificate setting forth such adjustment, including a statement of the adjusted Exercise Price and adjusted number or type of Warrant Shares or other securities issuable upon exercise of this Warrant (as applicable), describing the transactions giving rise to such adjustments and showing in detail the facts upon which such adjustment is based.  The Company will promptly deliver a copy of each such certificate to the Holder within 10 Trading Days of the occurrence of such adjustment.

(h)           Notice of Corporate Events.  If the Company  (i) declares a dividend or any other distribution of cash, securities or other property in respect of its Common Stock, including without limitation any granting of rights or warrants to subscribe for or purchase any capital stock of the Company or any Subsidiary, (ii) authorizes or approves, enters into any agreement contemplating or solicits stockholder approval for any Fundamental Transaction or (iii) authorizes the voluntary dissolution, liquidation or winding up of the affairs of the Company, then the Company shall deliver to the Holder a notice describing the material terms and conditions of such transaction, at least 20 calendar days prior to the applicable record or effective date on which a Person would need to hold Common Stock in order to participate in or vote with respect to such transaction, and the Company will take all steps reasonably necessary in order to insure that the Holder is given the practical opportunity to exercise this Warrant prior to such time so as to participate in or vote with respect to such transaction; provided, however, that the failure to deliver such notice or any defect therein shall not affect the validity of the corporate action required to be described in such notice.

10.           Payment of Exercise Price.  The Holder shall pay the Exercise Price in cash in immediately available funds.

11.           Limitation on Exercise.

(a)           Notwithstanding anything to the contrary contained herein, the number of shares of Common Stock that may be acquired by the Holder upon any exercise of this Warrant (or otherwise in respect hereof) shall be limited to the extent necessary to insure that, following such exercise (or other issuance), the total number of shares of Common Stock then beneficially owned by such Holder and its Affiliates and any other Persons whose beneficial ownership of Common Stock would be aggregated with the Holder’s for purposes of Section 13(d) of the Exchange Act, does not exceed 4.999%  (the “Threshold Percentage”) or 9.999% (the “Maximum Percentage”) of the total number of issued and outstanding shares of Common Stock (including for such purpose the shares of Common Stock issuable upon such exercise).  For such purposes, beneficial ownership shall be determined in accordance with Section 13(d) of the Exchange Act and the rules and regulations promulgated thereunder.  Each delivery of an Exercise Notice hereunder will constitute a representation by the Holder that it has evaluated the limitations set forth in this paragraph and determined that issuance of the full number of Warrant Shares requested in such Exercise Notice is permitted under this paragraph.  The Company’s

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obligation to issue shares of Common Stock in excess of the limitation referred to in this Section shall be suspended (and shall not terminate or expire notwithstanding any contrary provisions hereof) until such time, if any, as such shares of Common Stock may be issued in compliance with such limitation.  By written notice to the Company, the Holder shall have the right (x) at any time and from time to time to reduce its Maximum Percentage immediately upon notice to the Company in the event and only to the extent that Section 16 of the Exchange Act or the rules promulgated thereunder (or any successor statute or rules) is changed to reduce the beneficial ownership percentage threshold thereunder to a percentage less than 9.999% and (y) at any time and from time to time, to waive the provisions of this Section insofar as they relate to the Threshold Percentage or to increase or decrease its Threshold Percentage (but not in excess of the Maximum Percentage) unless the Holder shall have, by written instrument delivered to the Company, irrevocably waived its rights to so increase or decrease its Threshold Percentage, but (i) any such waiver, increase or decrease will not be effective until the 61st day after such notice is delivered to the Company, and (ii) any such waiver or increase or decrease will apply only to the Holder and not to any other holder of Warrants.

(b)           Notwithstanding anything to the contrary contained herein, the number of shares of Common Stock that may be acquired by the Holder upon any exercise of this Warrant (or otherwise in respect hereof) shall be limited to the extent necessary to insure that, following such exercise (or other issuance), the total number of shares of Common Stock then beneficially owned by such Holder and its Affiliates and any other Persons whose beneficial ownership of Common Stock would be aggregated with the Holder’s for purposes of Section 13(d) of the Exchange Act, does not exceed 19.999% of the total number of issued and outstanding shares of Common Stock (including for such purpose the shares of Common Stock issuable upon such exercise).  For such purposes, beneficial ownership shall be determined in accordance with Section 13(d) of the Exchange Act and the rules and regulations promulgated thereunder.

12.           Fractional Shares.  The Company shall not be required to issue or cause to be issued fractional Warrant Shares or Additional Warrants to purchase fractional Additional Warrant Shares on the exercise of this Warrant.  If any fraction of a Warrant Share or if any Additional Warrant to purchase a fraction of an Additional Warrant Share would, except for the provisions of this Section, be issuable upon exercise of this Warrant, the number of Warrant Shares and/or Additional Warrant Shares issuable upon exercise of the Additional Warrants, as the case may be, to be issued will be rounded up to the nearest whole share or right to purchase the nearest whole share, as the case may be.

13.           Notices.  Any and all notices or other communications or deliveries hereunder (including without limitation any Exercise Notice) shall be in writing and shall be deemed given and effective on the earliest of (i) the date of transmission, if such notice or communication is delivered via facsimile at the facsimile number specified in this Section prior to 6:30 p.m. (New York City time) on a Trading Day, (ii) the next Trading Day after the date of transmission, if such notice or communication is delivered via facsimile at the facsimile number specified in this Section on a day that is not a Trading Day or later than 6:30 p.m. (New York City time) on any Trading Day, (iii) the Trading Day following the date of mailing, if sent by a nationally recognized overnight courier service, or (iv) upon actual receipt by the party to whom such notice is required to be given.  The address for such notices or communications shall be as set forth in the Purchase Agreement.

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14.           Warrant Agent.  The Company shall serve as warrant agent under this Warrant.  Upon 30 days’ notice to the Holder, the Company may appoint a new warrant agent.  Any corporation into which the Company or any new warrant agent may be merged or any corporation resulting from any consolidation to which the Company or any new warrant agent shall be a party or any corporation to which the Company or any new warrant agent transfers substantially all of its corporate trust or shareholders services business shall be a successor warrant agent under this Warrant without any further act.  Any such successor warrant agent shall promptly cause notice of its succession as warrant agent to be mailed (by first class mail, postage prepaid) to the Holder at the Holder’s last address as shown on the Warrant Register.

15.           Call Right.

(a)           If following the Effective Date, the Closing Prices for any 20 consecutive Trading Days exceeds 150% of the Exercise Price (the “Threshold Price”, and such 20 day period, the “Threshold Period”), then the Company will have the right, but not obligation (the “Call Right”), on prior written notice in accordance with Section 15(b) to the Holder, to require the Holder to exercise any unexercised portion of this Warrant for which an Exercise Notice has not yet been delivered (the “Call Amount”); provided that the Call Right must be exercised within 20 Trading Days of the last day of the Threshold Period.

(b)           To exercise this Call Right, the Company shall deliver to the Holder an irrevocable written notice (a “Call Notice”), indicating the Call Amount.  The date that the Company delivers the Call Notice to the Holders will be referred to as the “Call Date.” Within 15 Trading Days of receipt of the Call Notice, the Holder shall exercise this Warrant for the entire Call Amount in accordance with Section 4(b) above.  The date on which the Call Amount is exercised is referred to herein as the “Forced Exercise Date”.  Any unexercised portion of this Warrant to which the Call Notice does not pertain (the “Remaining Portion”) will be unaffected by such Call Notice.  The Company covenants and agrees that it will honor any Exercise Notice with respect to the Call Amount that are tendered from the Call Date through and including 6:30 p.m. (New York City time) on the Forced Exercise Date.

Notwithstanding anything to the contrary set forth in this Warrant, the Company may not require the cancellation of any unexercised Call Amount (and any Call Notice will be void), unless from the beginning of the 20 consecutive Trading Days used to determine whether the Common Stock has achieved the Threshold Price through the Forced Exercise Date (the “Call Period”) (i) the Closing Prices for each Trading Day during such Call Period exceeds the Threshold Price, (ii) the Company shall have honored in accordance with the terms of this Warrant any Exercise Notice delivered by 6:30 p.m. (New York City time) on the Forced Exercise Date, (iii) the Equity Conditions (as defined in the Notes) are satisfied (or waived in writing by the applicable Holder) on each Trading Day with respect to all Underlying Shares issuable upon exercise of the Call Amount, and (iv) the average daily trading volume as reported on Bloomberg, L.P. during such Call Period (determined by calculating the arithmetic average of the daily trading volume for each Trading Day in such Call Period) is greater than 100,000 shares.

(c)           Notwithstanding anything herein to the contrary, (i) in connection with the Company’s exercise of a Call Right, the Threshold Percentage limitation on exercise set forth in

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Section 11 shall not apply and (ii) if after the Call Right is exercised, the stated Expiration Date of this Warrant would occur prior to the Forced Exercise Date, the “Expiration Date” hereof shall be extended to end of the Forced Exercise Date solely to the extent necessary to enable this Warrant to be exercised for the Call Amount on the Forced Exercise Date.

16.           Miscellaneous.

(a)           Subject to the restrictions on transfer set forth on the first page hereof, this Warrant may be assigned by the Holder. This Warrant may not be assigned by the Company except to a successor in the event of a Fundamental Transaction. This Warrant shall be binding on and inure to the benefit of the parties hereto and their respective successors and assigns.  Subject to the preceding sentence, nothing in this Warrant shall be construed to give to any Person other than the Company and the Holder any legal or equitable right, remedy or cause of action under this Warrant.  This Warrant may be amended only in writing signed by the Company and the Holder and their successors and assigns.

(b)           The Company will not, by amendment of its governing documents or through any 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 of this Warrant, but will at all times in good faith assist in the carrying out of all such terms and in the taking of all such action as may be necessary or appropriate in order to protect the rights of the Holder against impairment.  Without limiting the generality of the foregoing, the Company (i) will not increase the par value of any Warrant Shares or Additional Warrant Shares above the amount payable therefor on such exercise, (ii) will take all such action as may be reasonably necessary or appropriate in order that the Company may validly and legally issue fully paid and nonassessable Warrant Shares or Additional Warrant Shares on the exercise of this Warrant and the Additional Warrants, respectively, and (iii) will not close its shareholder books or records in any manner which interferes with the timely exercise of this Warrant.

(c)           GOVERNING LAW; VENUE; WAIVER OF JURY TRIAL.  ALL QUESTIONS CONCERNING THE CONSTRUCTION, VALIDITY, ENFORCEMENT AND INTERPRETATION OF THIS WARRANT SHALL BE GOVERNED BY AND CONSTRUED AND ENFORCED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.  EACH PARTY HEREBY IRREVOCABLY SUBMITS TO THE EXCLUSIVE JURISDICTION OF THE STATE AND FEDERAL COURTS SITTING IN THE CITY OF NEW YORK, BOROUGH OF MANHATTAN, FOR THE ADJUDICATION OF ANY DISPUTE HEREUNDER OR IN CONNECTION HEREWITH OR WITH ANY TRANSACTION CONTEMPLATED HEREBY OR DISCUSSED HEREIN (INCLUDING WITH RESPECT TO THE ENFORCEMENT OF ANY OF THE TRANSACTION DOCUMENTS), AND HEREBY IRREVOCABLY WAIVES, AND AGREES NOT TO ASSERT IN ANY SUIT, ACTION OR PROCEEDING, ANY CLAIM THAT IT IS NOT PERSONALLY SUBJECT TO THE JURISDICTION OF ANY SUCH COURT, THAT SUCH SUIT, ACTION OR PROCEEDING IS IMPROPER.  EACH PARTY HEREBY IRREVOCABLY WAIVES PERSONAL SERVICE OF PROCESS AND CONSENTS TO PROCESS BEING SERVED IN ANY SUCH SUIT, ACTION OR PROCEEDING BY MAILING A COPY THEREOF VIA REGISTERED OR CERTIFIED MAIL OR OVERNIGHT DELIVERY (WITH EVIDENCE OF DELIVERY) TO SUCH PARTY AT THE ADDRESS IN EFFECT FOR NOTICES TO IT UNDER THIS AGREEMENT AND AGREES THAT SUCH SERVICE SHALL CONSTITUTE GOOD AND SUFFICIENT SERVICE OF PROCESS AND NOTICE THEREOF. NOTHING

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CONTAINED HEREIN SHALL BE DEEMED TO LIMIT IN ANY WAY ANY RIGHT TO SERVE PROCESS IN ANY MANNER PERMITTED BY LAW.  THE COMPANY HEREBY WAIVES ALL RIGHTS TO A TRIAL BY JURY.

(d)           The headings herein are for convenience only, do not constitute a part of this Warrant and shall not be deemed to limit or affect any of the provisions hereof.

(e)           In case any one or more of the provisions of this Warrant shall be invalid or unenforceable in any respect, the validity and enforceability of the remaining terms and provisions of this Warrant shall not in any way be affected or impaired thereby and the parties will attempt in good faith to agree upon a valid and enforceable provision which shall be a commercially reasonable substitute therefor, and upon so agreeing, shall incorporate such substitute provision in this Warrant.

[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK,
SIGNATURE PAGE FOLLOWS]

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IN WITNESS WHEREOF, the Company has caused this Warrant B to be duly executed by its authorized officer as of the date first indicated above.

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Annex A

FORM OF EXERCISE NOTICE

(To be executed by the Holder to exercise the right to purchase shares of Common Stock under the foregoing Warrant)

To:  SatCon Technology Corporation

The undersigned is the Holder of Warrant B No. _______ (the “Warrant”) issued by SatCon Technology Corporation, a Delaware corporation (the “Company”).  Capitalized terms used herein and not otherwise defined have the respective meanings set forth in the Warrant.

1.                               The Warrant is currently exercisable to purchase a total of ______________ Warrant Shares.

2.                               The undersigned Holder hereby exercises its right to purchase _________________ Warrant Shares pursuant to the Warrant and Additional Warrants exercisable for _______________ shares of Common Stock.

3.                               In satisfaction of the Exercise Price, the holder shall pay the sum of $____________ to the Company in accordance with the terms of the Warrant.

4.                               Pursuant to this exercise, the Company shall deliver to the holder _______________ Warrant Shares and Additional Warrants exercisable for _______________ shares of Common Stock in accordance with the terms of the Warrant.

5.                               Following this exercise, the Warrant shall be exercisable to purchase a total of _____________ Warrant Shares and Additional Warrants exercisable for _____________ shares of Common Stock.

Annex  B

FORM OF ASSIGNMENT

[To be completed and signed only upon transfer of Warrant]

FOR VALUE RECEIVED, the undersigned hereby sells, assigns and transfers unto ________________________________ the right represented by the within Warrant to purchase  ____________ shares of Common Stock and warrants to purchase shares of the Common Stock of SatCon Technology Corporation to which the within Warrant relates and appoints ________________ attorney to transfer said right on the books of SatCon Technology Corporation with full power of substitution in the premises.