Exhibit 4.1








AMENDMENT NO. 2 TO AMENDMENT AGREEMENT
AND WAIVER


This AMENDMENT
NO. 2 TO AMENDMENT AGREEMENT AND WAIVER (this “Amendment”), dated as of February 27, 2019, is made by and
between Ener-Core, Inc., a Delaware corporation, with headquarters located at 30100 Town Center Dr., Suite O-209, Laguna Niguel,
California 92677 (the “Company”), and the investor listed on the signature page attached hereto (the “Holder”).


RECITALS


A.                
Reference is made to that certain Securities Purchase Agreement dated as of April 22, 2015, by and among the Company, the
Holder (if applicable) and the other investors (the “April 2015 Other Holders”) listed on the signature pages
attached thereto (the “April 2015 SPA”) and, if applicable, the Senior Secured Notes issued to the Holder pursuant
thereto, as amended and restated on December 2, 2016 pursuant to certain amendment agreements (as amended from time to time prior
to the date hereof, the “April 2015 Notes”);


B.                 
Reference is made to that certain Securities Purchase Agreement dated as of May 7, 2015, by and among the Company, the Holder
(if applicable) and the other investors (the “May 2015 Other Holders” and together with the April 2015 Other
Holders, the “Other Holders” and together with the Holder, the “Holders”) listed on the signature
pages attached thereto (the “May 2015 SPA” and together with the April 2015 SPA, individually, an “SPA”
and collectively, the “SPAs”), and, if applicable, the Senior Secured Notes issued to the Holder pursuant thereto,
as amended and restated on December 2, 2016 pursuant to certain amendment agreements (as amended from time to time prior to the
date hereof, the “May 2015 Notes” and together with the April 2015 Notes, the “2015 Notes”);


C.                 
Reference is made to that certain Amendment Agreement and Waiver dated as of December 31, 2018 by and among the Company
and the Holder with respect to the 2015 Notes and the SPAs (the "December Amendment"); and


D.    
In compliance with Section 15 of the 2015 Notes and the SPAs, this Amendment shall only be effective upon the execution
and delivery of this Amendment and agreements in form and substance identical to this Amendment (other than with respect to the
identity of the Holder and any provision regarding the reimbursement of legal fees) (the “Other Agreements”
and together with this Amendment, the “Amendments”) by Other Holders of the 2015 Notes (each an “Other
Holder”) representing on the Closing Date at least the Required Holders (as defined in each of the 2015 Notes) (such
time, the “Effective Time”).


AGREEMENT


NOW THEREFORE,
in consideration of the foregoing mutual premises and the covenants and agreements hereinafter set forth, and for other good and
valuable consideration, the receipt, and legal adequacy of which is hereby acknowledged, the parties hereto, intending to be legally
bound, hereby agree as follows:






    	 		 



     


    

 


ARTICLE I


AMENDMENT


1.                  
Amendment of December Amendment. All references to the date "January 31,
2019" set forth in the December Amendment are hereby amended to instead refer to the date "March 31, 2019", and
all references to the date "February 1, 2019" set forth in the December Amendment are hereby amended to instead refer
to the date "April 1, 2019". Capitalized terms used herein and not otherwise defined herein shall have the respective
meanings set forth in the December Amendment.


article
II

MISCELLANEOUS


 


1.                  
Effect of this Amendment. This Amendment shall form a part of the 2015 Notes and SPAs for all purposes, and each
holder of 2015 Notes and each party to the SPAs shall be bound hereby. This Amendment shall only be deemed to be in full force
and effect from and after both the execution of this Amendment by the parties hereto and the execution of Amendments substantially
identical to this Amendment by the Company and “Holders” holding at least a majority of the aggregate principal amount
of the 2015 Notes outstanding, including the Lead Investor, as well as the Collateral Agent, that, together with undersigned, constitute
the Required Holders under each of the 2015 Notes and SPAs. From and after such effectiveness, any reference to the 2015 Notes
and the SPAs shall be deemed to be a reference to the 2015 Notes and SPAs, as amended hereby. Except as specifically amended as
set forth herein, each term and condition of the 2015 Notes and SPAs shall continue in full force and effect.


 


2.                  
Entire Agreement. This Amendment, together with the SPAs and 2015 Notes, as amended and/or amended and restated to
date, contains the entire agreement of the parties with respect to the matters contemplated hereby and thereby, and supersedes
any prior or contemporaneous written or oral agreements between them concerning the subject matter of this Amendment.


 


3.                  
Governing Law. This Amendment shall be governed by the internal law of the State of New York.


 


4.                  
Counterparts. This Amendment may be executed in any number of counterparts and by different parties hereto in separate
counterparts, each of which when so executed and delivered shall be deemed an original, but all such counterparts together shall
constitute but one and the same instrument; signature pages may be detached from multiple separate counterparts and attached to
a single counterpart so that all signature pages are physically attached to the same document. This Amendment may be executed by
fax or electronic mail, in PDF format, and no party hereto may contest this Amendment’s validity solely because a signature
was faxed or otherwise sent electronically.


 


[Signature Page
Follows]






    	 	2	 



     


    







IN WITNESS WHEREOF,
the Holder and the Company have caused their respective signature pages to this Amendment to be duly executed as of the date first
written above. 


	 	COMPANY:
	 	 
	 	ENER-CORE, INC.
	 	 
	 	By: 	
	 	 	Name: Domonic J. Carney

Title: Chief Financial Officer






 


 


 


 





Signature
Page to amendment no. 2 to Amendment Agreement and Waiver—2015 Notes








    	 	3	 



     


    





 





IN WITNESS WHEREOF,
the Holder and the Company have caused their respective signature pages to this Amendment to be duly executed as of the date first
written above.





 


	 	HOLDER:
	 	 
	 	By: 	
	 	 	Name:
Title:



 















Signature
Page to amendment no. 2 to Amendment Agreement and Waiver—2015 Notes


4