<Page>

                                                                    EXHIBIT 31.2

                            CERTIFICATION PURSUANT TO
                               SECTION 302 OF THE
                           SARBANES-OXLEY ACT OF 2002

I, Ralph M. Norwood, certify that:

1.   I have reviewed this annual report on Form 10-K of SatCon Technology
     Corporation;

2.   Based on my knowledge, this annual report does not contain any untrue
     statement of a material fact or omit to state a material fact necessary to
     make the statements made, in light of the circumstances under which such
     statements were made, not misleading with respect to the period covered by
     this annual report;

3.   Based on my knowledge, the financial statements, and other financial
     information included in this annual report, fairly present in all material
     respects the financial condition, results of operations and cash flows of
     the registrant as of, and for, the periods presented in this annual report;

4.   The registrant's other certifying officer and I are responsible for
     establishing and maintaining disclosure controls and procedures (as defined
     in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:

     a)   designed such disclosure controls and procedures, or caused such
          disclosure controls and procedures to be designed under our
          supervision, to ensure that material information relating to the
          registrant, including its consolidated subsidiaries, is made known to
          us by others within those entities, particularly during the period in
          which this annual report is being prepared;

     b)   evaluated the effectiveness of the registrant's disclosure controls
          and procedures, and presented in this annual report our conclusions
          about the effectiveness of the disclosure controls and procedures, as
          of the end of the period covered by this report based on such
          evaluation; and

     c)   disclosed in this annual report any change in the registrant's
          internal control over financial reporting that occurred during the
          registrant's fourth fiscal quarter that has materially affected, or is
          reasonably likely to materially affect, the registrant's internal
          control over financial reporting; and

5.   The registrant's other certifying officer and I have disclosed, based on
     our most recent evaluation of internal control over financial reporting, to
     the registrant's auditors and the audit committee of registrant's board of
     directors (or persons performing the equivalent functions):

     a)   all significant deficiencies and material weaknesses in the design or
          operation of internal control over financial reporting which are
          reasonably likely to adversely affect the registrant's ability to
          record, process, summarize and report financial information; and

     b)   any fraud, whether or not material, that involves management or other
     employees who have a significant role in the registrant's internal control
     over financial reporting.

                                                 /s/ RALPH M. NORWOOD
                                        ----------------------------------------
                                                   Ralph M. Norwood
Dated: December 23, 2004                        Chief Financial Officer