AMENDMENT NO. 2
TO
UNSECURED PROMISSORY NOTE

This instrument is Amendment No. 2 (this “Amendment”), dated as of April 30,
2014, to the Unsecured Promissory Note dated as of September 17, 2010 (the
“Promissory Note”) issued by American Power Group, Inc. (formerly GreenMan
Technologies, Inc.) (the “Company”) to Charles E. Coppa (the “Holder”). Terms
used in this Amendment without definition which are defined in the Promissory
Note have the same meanings in this Amendment as in the Promissory Note unless
otherwise provided herein.
    
WHEREAS, the Company has previously issued the Promissory Note to the Holder and
amended the Promissory Note on April 27, 2012;

WHEREAS, the Promissory Note shall remain in full force and effect with this
Amendment No. 2; and

WHEREAS, the Company and the Holder now desire to further amend the Promissory
Note;

NOW, THEREFORE, for good and valuable consideration, the receipt and adequacy of
which the Parties hereby acknowledge, the Company and the Holder, intending to
be legally bound, hereby agree as follows:

1.
The first paragraph of the Promissory Note is hereby amended by:

(a)
deleting the reference to “the second anniversary of the Closing (as defined
below)” therein and replacing it with “September 30, 2014”;

(b)
Deleting the reference to “at a rate equal to twelve percent (12%) per annum”
therein and replacing it with “at a rate equal to eight percent (8%) per annum”;
and

(c)
deleting the following sentence at the end of such paragraph:

“Notwithstanding the foregoing, commencing on the sale of at least $7,000,000 of
Convertible Preferred Stock pursuant to that certain Securities Purchase
Agreement by and among the Debtor and certain Purchasers (as defined therein)
and the receipt by the Debtor of $7,000,000 before payment of applicable fees
and expenses (the “Closing”), the interest rate on this Note shall be reduced
from twelve percent (12%) per annum to eight percent (8%) per annum.”

2.    The Holder waives any prior default under the Promissory Note.

3.    Except as otherwise amended by this Amendment, all other terms and
conditions of the Promissory Note shall remain in full force and effect.

4.    This Amendment shall be governed by and construed and interpreted in
accordance with the laws of the Commonwealth of Massachusetts.

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IN WITNESS WHEREOF, the Parties have caused this Amendment to be executed by
their duly authorized representatives as of the date first written above.

American Power Group Corporation
        

By: /s/Maury Needham        
Maury Needham
Chairman

HOLDER:

        
/s/Charles E. Coppa            
Charles E. Coppa