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                                                                   EXHIBIT 10.1


                              COOPERATION AGREEMENT



         This Agreement is entered into this 25th day of April 2001 by and
between SatCon Technology Corporation, a Delaware corporation ("SatCon") and
Beacon Power Corporation, a Delaware corporation ("Beacon").

         WHEREAS, Beacon develops, manufacturers and sells flywheel energy
storage systems and components thereof; and

         WHEREAS, SatCon, through its Ling subsidiary, is developing an
uninterruptible power supply product ("UPS System") which, among other things,
may use a flywheel energy storage system or components thereof, of the type
being marketed and sold by Beacon; and

         WHEREAS, SatCon also produces electronics, motors and related
electronic and motor assemblies which may be incorporated in Beacon's flywheel
systems; and

         WHEREAS, SatCon and Beacon believe that it is in each of their best
interest to establish, where appropriate, cooperative supply, marketing and
selling arrangements;

         NOW THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged by the parties hereto, Beacon and
SatCon agree as follows:

         1. In connection with Satcon's need for flywheels and components
thereof which are capable of being produced by Beacon (and are not being
produced directly by SatCon) for use in connection with Ling's contemplated
UPS System, SatCon will give Beacon the opportunity to bid on 50% ("Beacon's
Bid Percentage") of all of such flywheel and flywheel component requirements
of SatCon. If in the exercise of SatCon's reasonable judgment, Beacon's bid
is equal or superior to other quotes received by SatCon in terms of meeting
specifications, price, quality of deliverables, delivery times and other
terms required by SatCon, SatCon shall be required to purchase Beacon's Bid
Percentage of its requirements for such items from Beacon. In the event that
in SatCon's reasonable judgment, Beacon's bid is equal or superior to other
quotes received by SatCon in all respects other than price, Beacon will be
given a reasonable time (determined by SatCon under the circumstances) to
meet the lower quoted price.

         2. In connection with Beacon's need for electronics, motors and
related electronic and motor assemblies which are capable of being produced
by SatCon (and are not being produced directly by Beacon) for use in
connection with Beacon's flywheel energy storage system, Beacon will give
SatCon the opportunity to bid on 50% ("SatCon's Bid Percentage") of all such
electronics, motors and related electronic and motor assembly requirements of
Beacon. If in the exercise of Beacon's reasonable judgment, SatCon's bid is
equal or superior to other quotes received by Beacon in terms of meeting
specifications, price, quality of deliverables, delivery times and other
terms required by Beacon, Beacon shall be required to purchase

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SatCon's Bid Percentage of its requirements for such items from SatCon. In the
event that in Beacon's reasonable judgment, SatCon's bid is equal or superior to
other quotes received by Beacon in all respects other than price, SatCon will be
given a reasonable time (determined by Beacon under the circumstances) to meet
the lower quoted price.

         3. Each of Beacon's Bid Percentage and SatCon's Bid Percentage set
forth in Section 1 and Section 2 of this Agreement shall be renegotiated on
an annual basis within sixty (60) days prior to the expiration of each
anniversary of this Agreement. If Beacon and SatCon are not able to agree on
the Beacon Bid Percentage and the SatCon Bid Percentage during such 60-day
period, this Agreement shall terminate upon the expiration of such 60-day
period. If Beacon and SatCon agree on the Beacon Bid Percentage and SatCon
Bid Percentage during such 60-day period, this Agreement shall renew for an
additional term of one year with the Beacon Bid Percentage and SatCon Bid
Percentage being the percentages agreed upon during the 60-day period
preceding the additional term. This Agreement shall continually renew for
additional one-year periods, in perpetuity, for so long as Beacon and SatCon
agree upon the Beacon Bid Percentage and SatCon Bid Percentage during the
applicable 60-day period; provided, however, after the fifth anniversary of
this Agreement, either party may terminate this Agreement at any time by
providing the other party hereto at least 90 days advance written notice of
termination. Any quotes that have been accepted at the time of termination
and any other outstanding contractual arrangements at such time shall remain
in full force and effect.

         4. For so long as this Agreement remains in effect, the head of
sales of Beacon and the head of sales of Ling shall meet at least once
annually to see if there are mutually beneficial opportunities to enable the
sales force of one company to market and sell products of the other company.

SATCON TECHNOLOGY CORPORATION          BEACON POWER CORPORATION



By: /s/ David B. Eisenhaure            By: /s/ William Stanton
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