The principal business address for the Reporting Persons is 875 Third Avenue, 11th Floor, New York, New York 10022.

Each of the Reporting Persons is engaged in the business of investing. This Schedule 13D relates to securities of Eos Energy Enterprises Inc. (the "Issuer") held directly by each of CCM Denali Equity and CCM Frontier. The principal business of Cerberus Capital Management II is providing investment management services to certain investment funds or other investment advisory clients and serving as the sole member of CCM Denali Equity GP. The principal business of CCM Denali Equity is holding certain investments. The principal business of CCM Denali Equity GP is serving as the general partner of CCM Denali Equity. The principal business of CCM Frontier is holding certain investments. The principal business of CCM Frontier LP is serving as the sole member of CCM Frontier. The principal business of CCM Frontier GP is serving as the general partner of CCM Frontier LP. The principal business of Cerberus GP Manager is serving as the sole member of CCM Frontier GP and a control person of other affiliated entities.

None of the Reporting Persons nor, to the best knowledge of the Reporting Persons, any of the Scheduled Persons, have been, during the last five years, convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).

None of the Reporting Persons nor, to the best knowledge of the Reporting Persons, any of the Scheduled Persons, have been, during the last five years, a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Cerberus Capital Management II is a Delaware limited partnership. CCM Denali Equity is a Delaware limited partnership. CCM Denali Equity GP is a Delaware limited liability company. CCM Frontier is a Delaware limited liability company. CCM Frontier LP is a Delaware limited partnership. CCM Frontier GP is a Delaware limited liability company. Cerberus GP Manager is a Delaware limited liability company.

Item 3 is hereby amended and supplemented by the addition of the following: The information in Item 4 is incorporated herein by reference.

Item 4 is hereby amended and supplemented by the addition of the following: Pursuant to the previously disclosed A&R Term Sheet, on August 4, 2026, the Issuer, CCM Frontier, and HBC MSF Capital Solutions Blocker II LLC, an affiliate of Hudson Bay Capital Management LP ("HBC"), consummated the closing of the funding (the "Funding") of Frontier Power USA Parent, LLC (the "JV Company"), a Delaware limited liability company and a joint venture among the Issuer, CCM Frontier and HBC. Pursuant to a Contribution and Warrants Purchase Agreement (the "Contribution and Warrants Purchase Agreement"), dated as of August 4, 2026, by and between CCM Frontier and the JV Company, CCM Frontier (i) caused the JV Company to receive the benefit of certain contracts, contacts, investment opportunities, subject matter expertise and other going concern value with respect to the Frontier power platform developed by affiliates of CCM Frontier and (ii) contributed cash and certain assets to the JV Company as detailed in the Contribution and Warrants Purchase Agreement. In exchange therefor and for certain funds previously contributed by CCM Frontier to the JV Company, the JV Company (A) issued to CCM Frontier 50,000,001 Class A-1 Units of the JV Company and 100,000,000 Class A-2 Units of the JV Company and (B) sold and transferred to CCM Frontier warrants to purchase 20,017,772 shares of Common Stock of the Issuer (the "JV Warrants") that were previously contributed to the JV Company by the Issuer. The foregoing description of the Contribution and Warrants Purchase Agreement is qualified in its entirety by reference to the full text of the Contribution and Warrants Purchase Agreement, which is filed as Exhibit 99.3 and is incorporated herein by reference. The JV Warrants are governed by that certain Warrant Agreement, dated as of August 4, 2026, by and between the Issuer and Continental Stock Transfer & Trust Company, as warrant agent (the "Warrant Agreement"). The JV Warrants are exercisable at an exercise price of $5.481 per share of Common Stock and expire on the tenth anniversary of the date of issuance. The JV Warrants may be exercised for cash or on a cashless basis. The Issuer may lower the exercise price and extend the duration of the JV Warrants under certain conditions described in the Warrant Agreement. The Issuer has certain rights to redeem the JV Warrants beginning five years after the date of issuance of the JV Warrants under certain conditions described in the Warrant Agreement. The JV Warrants are subject to customary anti-dilution adjustments as described in the Warrant Agreement. The foregoing description of the Warrant Agreement is qualified in its entirety by reference to the full text of the Warrant Agreement, the form of which is incorporated by reference as Exhibit 99.4 and is incorporated herein by reference. In connection with the closing of the Funding, on August 4, 2026, the JV Company, the Issuer, CCM Frontier and HBC entered into an Amended and Restated Limited Liability Company Agreement of the JV Company, which provides for the governance, management and operations of the JV Company. In addition, on August 4, 2026, (i) the Issuer, the JV Company and HBC entered into an Exchange Agreement, which, among other things, provides HBC with the right, from time to time, to exchange Class C Units in the JV Company that it holds for shares of Common Stock of the Issuer and (ii) the JV Company, CCM Frontier and the Issuer entered into a letter agreement, which, among other things, provides that if HBC exercises its exchange right, 10% of the Class C Units in the JV Company that the Issuer receives in the exchange are cancelled and reissued to CCM Frontier and CCM Frontier will have the right to purchase up to the remaining 90% of such Class C Units from the Issuer at a price of $1.00 per Class C Unit. Further, on August 4, 2026, the Issuer and CCM Frontier entered into a Registration Rights Agreement (the "Registration Rights Agreement") pursuant to which the Issuer agreed to customary resale registration rights for the shares of Common Stock issuable upon the exercise of the JV Warrants. Pursuant to the Registration Rights Agreement, the Issuer agreed to prepare and, as soon as practicable, but in no event later than the 30th calendar day after August 4, 2026, file with the SEC a registration statement on Form S-3 covering the resale of the shares of Common Stock issuable upon exercise of the JV Warrants. In addition, the Issuer agreed to use its best efforts to have such resale registration statement declared effective by the SEC as soon as practicable, but in no event later than the earlier of the (i) 60th calendar day after August 4, 2026, and (ii) the second business day after the date the Issuer is notified (orally or in writing, whichever is earlier) by the SEC that such registration statement will not be reviewed or will not be subject to further review. The foregoing description of the Registration Rights Agreement is qualified in its entirety by reference to the full text of the Registration Rights Agreement, which is filed as Exhibit 99.5 and is incorporated herein by reference. In addition, CCM Denali Equity has agreed to extend the lock-up restriction of Section 4.1(d) of the previously disclosed Securities Purchase Agreement to December 21, 2026.

The amount of shares of Common Stock issuable upon exercise of the Warrant (as defined in Item 4 in the original Schedule 13D and subject to the limitations as described therein) and issuable upon the conversion Series B-1 Preferred Stock, Series B-2 Preferred Stock, Series B-3 Preferred Stock, and Series B-4 Preferred Stock detailed below reflect antidilution adjustments pursuant to the terms of such securities that were triggered by additional issuances of securities by the Issuer. Each of the Initial Reporting Persons may be deemed to beneficially own 175,829,986 shares of Common Stock, which amount includes 44,435,304 shares of Common Stock of the Issuer issuable upon exercise of the Warrant (as defined in Item 4 in the original Schedule 13D and subject to the limitations as described therein), 36,067,246 shares of Common Stock of the Issuer issuable upon conversion of 31.940063 shares of Series B-1 Preferred Stock, 32,528,734 shares of Common Stock of the Issuer issuable upon conversion of 28.806463 shares of Series B-2 Preferred Stock, 43,203,670 shares of Common Stock of the Issuer issuable upon conversion of 38.259864 shares of Series B-3 Preferred Stock, and 19,595,032 shares of Common Stock of the Issuer issuable upon conversion of 16.150528 shares of Series B-4 Preferred Stock. Such amount of beneficial ownership represents approximately 32.6% of the Common Stock outstanding, based on 364,167,744 shares of Common Stock outstanding as of August 3, 2026, as reported in the Issuer's Form 10-Q filed with the SEC on August 5, 2026. The securities of the Issuer beneficially owned by the Initial Reporting Persons reported herein are directly held and beneficially owned by CCM Denali Equity. CCM Denali Equity GP, as the general partner of CCM Denali Equity, may be deemed to beneficially own the securities of the Issuer held by CCM Denali Equity. Cerberus Capital Management II, as the sole member of CCM Denali Equity GP, may be deemed to beneficially own the securities of the Issuer held by CCM Denali Equity. Each of the JV Reporting Persons may be deemed to beneficially own 20,017,772 shares of Common Stock issuable upon the exercise of the JV Warrants. Such amount of beneficial ownership represents approximately 5.2% of the Common Stock outstanding, based on 364,167,744 shares of Common Stock outstanding as of August 3, 2026, as reported in the Issuer's Form 10-Q filed with the SEC on August 5, 2026. The securities of the Issuer beneficially owned by the JV Reporting Persons reported herein are directly held and beneficially owned by CCM Frontier. CCM Frontier LP, as the sole member of CCM Frontier, may be deemed to beneficially own the securities of the Issuer held by CCM Frontier. CCM Frontier GP, as the general partner of CCM Frontier LP, may be deemed to beneficially own the securities of the Issuer held by CCM Frontier. Cerberus GP Manager, as the sole member of CCM Frontier GP, may be deemed to beneficially own the securities of the Issuer held by CCM Frontier.

Items 7 through 10 of each of the cover pages of this Schedule 13D are incorporated herein by reference. Each of the Initial Reporting Persons may be deemed to have sole voting power and sole dispositive power over 175,829,986 shares of Common Stock. Each of the JV Reporting Persons may be deemed to have sole voting power and sole dispositive power over 20,017,772 shares of Common Stock. The information in Item 5(a) above is incorporated herein by reference.

The disclosure in Item 4 and Item 5(a) is incorporated herein by reference. Except as disclosed in this Schedule 13D, as amended, there have been no transactions by the Reporting Persons or the Scheduled Persons in the securities of the Issuer during the past sixty days.

The disclosure regarding the relationship between the Reporting Persons in Item 2(a) of this Schedule 13D is incorporated herein by reference.

Not applicable.

Item 6 is hereby amended and supplemented by the addition of the following: The disclosure in Item 4 is incorporated herein by reference. The Contribution and Warrants Purchase Agreement is filed as Exhibit 99.3 and is incorporated herein by reference. The form of Warrant is incorporated by reference as Exhibit 99.4 and is incorporated herein by reference. The Registration Rights Agreement is filed as Exhibit 99.5 and is incorporated herein by reference.

99.1 Agreement Regarding the Joint Filing of Schedule 13D by and among the Reporting Persons. 99.2 Control Persons of Cerberus Capital Management II, Control Person of Cerberus GP Manager, and Managers of CCM Denali Equity GP. 99.3 Contribution and Warrants Purchase Agreement, by and between CCM Frontier and the JV Company, dated as of August 4, 2026. 99.4 Form of Warrant Agreement (incorporated by reference to Exhibit 4.2 to the Issuer's Form 8-K, filed with the SEC on July 2, 2026). 99.5 Registration Rights Agreement, by and between the Issuer and CCM Frontier, dated as of August 4, 2026.