<Page>

                                                                  EXHIBIT 10.39

                                                               February 11, 2002

Mr. Ralph M. Norwood
56 Fox Hill Road
Wellesley Hills, MA 02481

Dear Ralph:

     Pursuant to our discussions regarding your first year of employment with
SatCon Technology Corporation (the "Company"), please be advised that if within
the first year of your employment with the Company, your employment is
terminated without cause, the Company shall continue to pay your salary as in
effect on the date of termination for a period of six (6) months from the date
of termination; PROVIDED, HOWEVER, that as a condition of payment, you execute
and deliver a general release and waiver to the Company in a form reasonably
acceptable to the Company within thirty (30) days of your termination. In
addition, with regard to all stock options which have been granted to you prior
to the date of termination but have not vested, if you are terminated without
cause during your initial year of employment, i) fifty percent (50%) of the
unvested options shall immediately vest; or, ii) if the termination occurs as a
result of a Change of Control Event, as hereinafter defined, then, at your
option, the unvested options shall vest in accordance with the provisions of the
Stock Option Plan from which the option grant was authorized.

     For purposes of this letter, Change in Control Event and Without Cause
shall be defined as follows:

     (a) A "Change in Control Event" shall mean:

     (i)    the acquisition by an individual, entity or group (within the
            meaning of Section 13(d)(3) or 14(d)(2) of the Securities Exchange
            Act of 1934, as amended (the "Exchange Act)) (a "Person") of
            beneficial ownership of any capital stock of the Company if, after
            such acquisition, such Person beneficially owns (within the meaning
            of Rule 13d-3 promulgated under the Exchanged Act) 50% or more of
            either (x) and then-outstanding shares of common stock of the
            Company (the "Outstanding Company Common Stock") or (y) the combined
            voting power of the then-outstanding securities of the Company
            entitled to vote generally in the election of directors (the
            "Outstanding Company Voting Securities"); PROVIDED, HOWEVER, that
            for purposes of this subsection (i), the following acquisitions
            shall not constitute a Change in Control Event: (A) any acquisitions
            directly from the Company (excluding an acquisition pursuant to the
            exercise, conversion or exchange of any security exercisable for,

<Page>

Mr. Ralph M. Norwood
February 11, 2002
Page 2

            convertible into or exchangeable for common stock or voting
            securities of the Company, unless the Person exercising, converting
            or exchanging such security acquired such security directly from the
            Company or an underwriter or agent of the Company), (B) any
            acquisition by any employee benefit plan (or related trust)
            sponsored or maintained by the Company or any corporation controlled
            by the Company, or (C) any acquisition by any corporation pursuant
            to a Business Combination (as defined below) which complies with
            clauses (x) and (y) of subsection (iii) of this definition; or

     (ii)   such time as the Continuing Directors (as defined below) do not
            constitute a majority of the Board (or, if applicable, the Board of
            Directors of a successor corporation to the Company), where the term
            "Continuing Director" means at any date a member of the Board (x)
            who was a member of the Board on the date of this letter or (y) who
            was nominated or elected subsequent to such date by at least
            majority of the directors who were Continuing Directors at the time
            of such nomination or election; provided, however, that there shall
            be excluded from this clause (y) any individual whose initial
            assumption of office occurred as a result of an actual or threatened
            election contest with respect to the election removal of directors
            or other actual or threatened solicitation of proxies consents, by
            or on behalf of a person other than the Board; or

     (iii)  the consummation of a merger, consolidation, reorganization,
            recapitalization or statutory share exchange involving the Company
            or a sale or other disposition of all or substantially all of the
            assets of the Company (a "Business Combination"), unless,
            immediately following such Business Combination, each of the
            following two conditions is satisfied: (x) all or substantially all
            of the individuals and entities who were the beneficial owners of
            the Outstanding Company Stock and Outstanding Company Voting
            Securities immediately prior to such Business Combination
            beneficially own, directly or indirectly, more than 50% of the
            then-outstanding shares of common stock and the combined voting
            power of the then-outstanding securities entitled to vote generally
            in the election of directors, respectively, of the resulting or
            acquiring corporation in such Business Combination (which shall
            include, without limitation, a corporation which as a result of such
            transaction owns the Company or substantially all of the Company's
            assets either directly or through one or more subsidiaries) (such
            resulting or acquiring corporation is referred to herein as the
            "Acquiring Corporation") in substantially the same proportions as
            their ownership of the Outstanding Company Common Stock and
            Outstanding Company Voting Securities respectively, immediately
            prior to such Business Combination and (y) no Person (excluding the
            Acquiring Corporation or any employee benefit plan (or

<Page>

Mr. Ralph M. Norwood
February 11, 2002
Page 2

            related trust) maintained or sponsored by the Company or by the
            Acquiring Corporation) beneficially owns, directly or indirectly,
            50% or more of the then-outstanding shares of common stock of the
            Acquiring Corporation, or of the combined voting power of the
            then-outstanding securities of such corporation entitled to vote
            generally in the election of directors (except to the extent that
            such ownership existed prior to the Business Combination).

     (b) "Without Cause" shall mean that the termination will not have occurred
         as a result of the willful breach or habitual neglect of your duties
         and obligations as an officer and employee of the Company or the
         falseness of any representation made by you to the Company prior to or
         during your employment.

     Also, it is agreed that your duties and obligations, which will serve as
the basis of your performance objectives, will be agreed upon in writing within
sixty (60) days of your initial date of employment.

     If this is in accordance with your understanding, please indicate your
agreement by signing below. This letter shall be void if it is not countersigned
by you and returned to the Company within five (5) days of the date of this
letter.


                                                Sincerely,


                                                /s/ Michael Turmelle
                                                --------------------
                                                Michael Turmelle
                                                Chief Operating Officer


/s/ Ralph M. Norwood
---------------------------
Ralph M. Norwood


February 11, 2002
---------------------------
Date