Exhibit 10.4


                            UNSECURED PROMISSORY NOTE

$100,000                                                          March 10, 2004

      FOR VALUE RECEIVED, the undersigned, GreenMan Technologies, Inc., 7
Kimball Lane, Lynnfield, MA 01940 (the "Debtor"), hereby promises to pay to the
order of Joyce Ritterhaus, an individual residing at 23 Timothy Drive, Andover,
Massachusetts, 01810 (the "Holder") on March 10, 2006 the principal sum of One
Hundred Thousand Dollars ($100,000) or such lesser principal amount then
outstanding, together with all accrued and unpaid interest thereon. Interest on
the principal amount of this Note will accrue from and including the date hereof
until and including the date such principal amount is paid, at a rate equal to
twelve percent (12%) per annum. Interest only shall be payable, in quarterly
installments commencing on June 1, 2004 in lawful money of the United States of
America, in immediately available funds. Interest shall be computed on the basis
of a 360-day year and a 30-day month.

      The outstanding balance of this Note shall be rendered immediately due and
payable, without the necessity of a Demand Notice, in case of any of the
following acts (individually, an "Event of Default"): (a) entry of any judgment
or order against the Debtor for the payment of money, if the same is not
satisfied or enforcement proceedings are not stayed within sixty (60) days or
if, within sixty (60) days after the expiration of any such stay, the judgment
or order is not dismissed, discharged or satisfied; (b) appointment of a
receiver, trustee, custodian or similar official, for the Debtor or any property
or assets of the Debtor; (c) conveyance of any or all assets to a trustee,
mortgagee or liquidating agent or assignment for the benefit of creditors by the
Debtor; or (d) commencement of any proceeding under any law or any jurisdiction,
now or hereafter in force, relating to bankruptcy, insolvency, renegotiation of
outstanding indebtedness, arrangement or otherwise to the relief of debtors or
the readjustment of indebtedness, by or against the Debtor. Notwithstanding
anything contained herein to the contrary, upon the occurrence of any such Event
of Default, the entire outstanding amount of principal and interest of this Note
shall become immediately due and payable, without presentment, demand, protest
or other notice of any kind, all of which are hereby expressly waived.

      The Debtor may prepay this Note, in whole or in part, at any time prior to
demand or acceleration. Any permitted prepayment of principal by the Debtor will
be accompanied by payment of all accrued and unpaid interest on the principal
sum being repaid plus a prepayment penalty equal to three months interest.

      The Debtor agrees to pay all costs, charges and expenses incurred by the
Holder and its assigns (including, without limitation, costs of collection,
court costs, and reasonable attorneys' fees and disbursements) in connection
with the successful enforcement of the Holder's rights under this Note (all such
costs, charges and expenses being herein referred to as "Costs"). Presentment
for payment, demand, protest, notice of protest and notice of nonpayment are
hereby waived. The Debtor agrees that any delay on the part of the Holder in
exercising any rights hereunder will not operate as a waiver of such rights, and
further agrees that any payments received hereunder will be applied first to
Costs, then to interest, and the balance to principal. The Holder shall not by
any act, delay, omission, or otherwise be deemed to waive any of its rights or
remedies, and no waiver of any kind to enforce this Note shall be valid unless
in writing and signed by the Holder. This Note is payable in any events and is
not subject to offset or reduction because of any other claims of Debtor against
the Holder.
<PAGE>

      This Note applies to, inures to the benefit of, and binds the successors
and assigns of the parties hereto. This Note is not negotiable or transferable
to any other holder without the written consent of the Debtor. This Note is made
under and shall be governed by the internal laws of the Commonwealth of
Massachusetts.

      IN WITNESS WHEREOF, the Debtor has executed this Note as an instrument
under seal as of the date first written above.

DEBTOR


/s/ Charles E. Coppa
--------------------
GreenMan Technologies Inc.
Charles E. Coppa
Chief Financial Officer


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