UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No.     )

Quantum Fuel Systems Technologies Worldwide, Inc.

(Name of Issuer)

Common Stock, $0.02 par value

(Title of Class of Securities)

74765E109

(CUSIP Number)

Ryan J. York

Davis Wright Tremaine LLP

1201 Third Avenue, Suite 2200

Seattle, WA 98101

(206) 622-3150

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

September 18, 2013

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f), or 240.13d-1(g), check the following box.  ¨

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See § 240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of Act but shall be subject to all other provisions of the Act (however, see the Notes).

Schedule 13D

This Schedule 13D is being filed by Kevin Douglas, Michelle Douglas, Tim McGaw, K&M Douglas Trust and James Douglas and Jean Douglas Irrevocable Descendants’ Trust (collectively, the “Filers”). This Schedule 13D reflects purchase of senior secured convertible notes (the “Convertible Notes”), with Warrants attached (the “Warrants”) by the Filers from Quantum Fuel Systems Technologies Worldwide, Inc. (the “Issuer”) in a private placement transaction that closed on September 18, 2013. The Convertible Notes can be converted into common stock, par value $0.02 per share, (the “Common Stock”) of the Issuer at a conversion price of $2.3824 per share. The Warrants can be converted into Common Stock of the Issuer at a conversion price of $2.30 per share.

This statement relates to shares of Common Stock of Quantum Fuel Systems Technologies Worldwide, Inc. The principal executive office of the Issuer is located at 25242 Arctic Ocean Drive, Lake Forest, CA 92630.

The persons filing this statement and the persons enumerated in Instruction C of Schedule 13D and, where applicable, their respective places of organization, general partners, directors, executive officers and controlling persons, and the information regarding them are as follows:

125 E. Sir Francis Drake Blvd., Suite 400, Larkspur, CA 94399.

Kevin Douglas is an active securities and commodities investor and is employed by Douglas Telecommunications, Inc., which has the same business address as the Filers. Michelle Douglas participates in nonprofit fund raising and in assisting Kevin Douglas in his investment activities. Tim McGaw is an executive and is employed by Douglas Telecommunications, Inc., which has the same business address as the Filers.

The source and amount of funds used in purchasing the Convertible Notes were as follows:

The Filers purchased the Convertible Notes and attached Warrants in a private placement transaction pursuant to a convertible note and warrant purchase agreement entered into by the Filers and the Issuer on September 15, 2013 (the “Purchase Agreement”), filed herewith as Exhibit 7.2, that closed on September 18, 2013. The acquisition of the Convertible Notes and Common Stock of the Issuer by the Filers was for investment purposes. In pursuing their investment purposes, the Filers may from time to time further purchase, hold, vote, trade, dispose of, engage in option, swap or other derivative securities transactions with respect to, or otherwise deal in the Common Stock at times, and in such manner, as they deem advisable to benefit from changes in the Common Stock’s market price, changes in the Issuer’s operations, business strategy or prospects, or from sale or merger of the Issuer. To evaluate such alternatives, the Filers routinely will monitor the Issuer’s operations, prospects, business development, management, competitive and strategic matters, capital structure and prevailing market conditions, as well as alternative investment opportunities, the Filers’ liquidity requirements and other investment considerations. Consistent with their investment research methods and evaluation criteria, the Filers may discuss such matters with the Issuer’s management, board of directors, other shareholders, industry analysts, existing or potential strategic partners or competitors, investment and financing professionals, sources of credit and other investors. Such factors and discussions may affect materially, and result in, the Filers’ modifying their ownership of the Common Stock. Other than the planned designation of Tim McGaw to serve on the Issuer’s board of directors as permitted under the Purchase Agreement, the Filers do not have any current intent to propose or take any of the actions described in paragraphs (a) through (j) of Item 4 of Schedule 13D, they may reconsider and change their plans or proposals relating to the Common Stock at any time.

The beneficial ownership of the Common Stock by each Filer at the date hereof is reflected on that Reporting Person’s cover page.

Other than the acquisition of the Convertible Notes and attached Warrants discussed above, there were no other transactions effected by the Filers in the Common Stock within the past sixty (60) days.

On September 15, 2013, the Issuer entered into the Purchase Agreement, agreeing to issue and sell Convertible Notes with an aggregate principal amount of up to $11,000,000 and attached Warrants, for an aggregate purchase price of up to $11,000,000. On September 18, 2013, the transactions contemplated by the Purchase Agreement closed, and pursuant thereto, the Filers purchased Convertible Notes in an aggregate principal amount of $10,050,000, along with attached Warrants (such purchases, the “Transaction”).

Pursuant to the Purchase Agreement, for so long as Kevin Douglas beneficially owns at least 5.0% of the Issuer’s Common Stock, he is entitled to designate a person for appointment to the Issuer’s board of directors. Accordingly, pursuant to the terms of the Purchase Agreement, Tim McGaw is expected to be designated for appointment to the Issuer’s board of directors and the Issuer is required to appoint Mr. McGaw within 30 days of notice from Kevin Douglas. Throughout the period between notice of designation and appointment of the designee by the Issuer, Kevin Douglas has the right to have a representative attend board meetings of the Issuer.

Pursuant to the Purchase Agreement, the Convertible Note and the attached Warrant, the Filers are prohibited from converting the Convertible Notes and attached Warrants, if and to the extent that the issuance of shares of Common Stock on such conversion of the Convertible Notes and/or attached Warrants would cause the ownership or voting power of the Filers and their affiliates to exceed 19.99% of the Issuer’s Common Stock. This provision will remain in effect until the Issuer obtains stockholder approval permitting the issuance of shares of Common Stock and voting power in excess of 19.99% of the Issuer’s Common Stock. Under the Purchase Agreement, the Issuer has agreed to solicit approval permitting the issuance of shares of Common Stock and voting power in excess of 19.99% of the Issuer’s Common Stock at the next annual meeting of the Issuer’s stockholders to be held no later than May 31, 2014.

The Issuer has agreed to take all necessary action to render inapplicable any control share acquisition, business combination, poison pill or similar agreements that would limit the rights of the Filers to hold any shares of Common Stock or acquire additional securities of the Issuer.

Pursuant to the Purchase Agreement, the Issuer agreed to file a resale registration statement covering the shares of Common Stock issuable upon conversion of the Convertible Notes and exercise of the Warrants within 90 days following the closing of the Transaction and to use its best efforts to have such registration statement declared effective within 150 days following the closing of the Transaction. The Issuer agreed to pay the holders of the Convertible Notes liquidated damages not to exceed 12% of the gross proceeds received by the Issuer in the event the registration statement is not timely filed or declared effective or if, under certain circumstances, the registration statement is suspended.

The Convertible Notes mature on the fifth anniversary date of the closing of the Transaction; provided, however, during the 30-day period beginning on the three-year anniversary of the closing of the Transaction, and upon notice provided by the holders of a majority of the outstanding principal amount of the Convertible Notes, the holders can put the Convertible Notes to the Issuer and the Issuer would be obligated to redeem the principal and interest then outstanding under the Convertible Notes within 90 days thereafter. In addition, the Convertible Notes are subject to redemption in connection with a change in control transaction. The

Convertible Notes are subordinated in all respects to the Issuer’s obligations to Bridge Bank, National Association, (“Bridge Bank”) and provide for a default if the Issuer’s common stock is not listed on Nasdaq or another national securities exchange as well as other customary events of default.

The Convertible Notes are secured by a second lien on substantially all of the Issuer’s operating assets (excluding the Issuer’s direct and indirect ownership interests in Schneider Power Inc. (“SPI”) and each of SPI’s wholly-owned subsidiaries and Fisker Automotive, Inc.) pursuant to the terms of a subordinated security agreement (the “Subordinated Security Agreement”) between the Company and Kevin Douglas, as collateral agent for all the Convertible Note holders. The lien granted to the collateral agent on behalf of the Convertible Note holders is subordinate in all respects to the first lien position of Bridge Bank.

The foregoing summary does not purport to be complete and is qualified in its entirety by reference to the Purchase Agreement, the form of Convertible Note, the form of Warrant, and the Subordinated Security Agreement, filed herewith as Exhibits 7.2, 7.3, 7.4 and 7.5, respectively, and incorporated herein by reference. Capitalized terms used without definition in this Item 6 have the meanings attributed to them in the foregoing agreements.

None of the Filers is party to any other contracts, arrangements, understandings or relationships with respect to any securities of the Issuer, including but not limited to the transfer or voting of any of the securities, finder’s fees, joint ventures, loan or option agreements, puts or calls, guarantees of profits, division of profits or loss, or the giving or withholding of proxies.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Exhibit 7.1

AGREEMENT REGARDING JOINT FILING

OF STATEMENT ON SCHEDULE 13D

Each of the undersigned hereby acknowledges and agrees, pursuant to the provisions of Rule 13d-1(k)(1) promulgated under the Securities Exchange Act of 1934, as amended, that the Schedule 13D to which this Agreement is attached as an Exhibit, and any amendments thereto, will be filed with the Securities and Exchange Commission jointly on behalf of the undersigned.

Dated: September 25, 2013

Exhibit 7.6

LIMITED POWER OF ATTORNEY FOR

REPORTING OBLIGATIONS UNDER SECTIONS 13(D) AND 13(G) OF THE SECURITIES EXCHANGE ACT OF 1934

The undersigned hereby make, constitute and appoint each of Tim McGaw, Eileen Davis-Wheatman and Kevin Douglas, acting either individually or together, as each of the undersigned’s true and lawful attorneys-in-fact, with full power and authority as hereinafter described on behalf of and in the name, place and stead of each of the undersigned to:

(1) prepare, execute, acknowledge, deliver and file Schedules 13D and 13G (including any amendments thereto) with respect to the securities of Quantum Fuel Systems Technologies Worldwide, Inc., a corporation formed under the laws of the state of Delaware (the “Company”), with the U.S. Securities and Exchange Commission, any national securities exchanges and the Company, as considered necessary or advisable under Sections 13(d) or 13(g) of the Securities Exchange Act of 1934 (the “Exchange Act”) and the rules and regulations promulgated thereunder (including, without limitation, Regulation 13D-G);

(2) seek or obtain, as each of the undersigned’s representative and on each of the undersigned’s behalf, information on transactions in the Company’s securities from any third party, including brokers, employee benefit plan administrators and trustees, in connection with the foregoing, and the undersigned hereby authorizes any such person to release any such information to any of the attorneys-in-fact and approve and ratify any such release of information; and

(3) perform any and all other acts which in the discretion of such attorney-in-fact are necessary or desirable for and on behalf of the undersigned in connection with the foregoing.

The undersigned acknowledge that:

(1) this Limited Power of Attorney authorizes, but does not require, each such attorney-in-fact to act in his or her discretion on information provided to such attorney-in-fact without independent verification of such information;

(2) any documents prepared and/or executed by any such attorney-in-fact on behalf of the undersigned pursuant to this Limited Power of Attorney will be in such form and will contain such information and disclosure as such attorney-in-fact, in his or her discretion, deems necessary or desirable;

(3) none of such attorneys-in-fact assumes (i) any liability for any responsibility of the undersigned to comply with the requirements of the Exchange Act, or (ii) any liability of the undersigned for any failure to comply with such requirements; and

(4) this Limited Power of Attorney does not relieve the undersigned from responsibility for compliance with the obligations of the undersigned under the Exchange Act, including without limitation the reporting requirements under Sections 13(d) and 13(g) of the Exchange Act and Regulation 13D-G promulgated thereunder.

The undersigned hereby give and grant each of the foregoing attorneys-in-fact full power and authority to do and perform all and every act and thing whatsoever requisite, necessary, appropriate or desirable to be done in and about the foregoing matters as fully to all intents and purposes as the undersigned might or could do if present, hereby ratifying all that each such attorney-in-fact of, for and on behalf of the undersigned, shall lawfully do or cause to be done by virtue of this Limited Power of Attorney.

This Limited Power of Attorney shall remain in full force and effect until the undersigned are no longer required to file Schedules 13D or 13G with respect to the undersigned’s holdings of and transactions in securities issued by the Company, unless earlier revoked by the undersigned in a signed writing delivered to each such attorney-in-fact.

The undersigned have caused this Limited Power of Attorney to be executed as of this 25th day of September, 2013.