Eos Energy Enterprises, Inc. announced that its Eos Z3 battery modules successfully completed independent destructive testing conducted by Energy Safety Response Group (ESRG). The testing, equivalent to large-scale fire testing (LSFT), confirmed that the modules exhibited no thermal runaway, no sustained fire, and no propagation to adjacent live modules under the conditions tested. The results support the safe siting of long-duration storage in dense urban environments and address evolving NFPA 855 fire-test expectations.

To address the 2026 edition of NFPA 855, which requires large-scale fire testing to confirm that system failure does not spread between units, Eos subjected modules to two severe abuse scenarios: direct flame impingement and overcharge. Even with active flame applied, the modules did not enter thermal runaway, did not sustain fire, and did not propagate to adjacent modules. The tests also showed no ignition of off-gas.

The results reflect the inherent safety advantages of Eos’ water-based electrolyte and flame-retardant polymer architecture. "Independent testing using LSFT-equivalent methods turns that design into validated performance," said Francis Richey, Eos Chief Technology Officer. "Under direct flame and overcharge, the Z3 modules did not experience thermal runaway, sustain fire, or propagate failure."

Separately, Eos announced it has achieved ISO 14001 certification, the globally recognized standard for environmental management systems. This certification confirms that Eos maintains robust environmental management practices across its operations and manufacturing facilities.

Test Results Overview

Eos Energy Enterprises, Inc. has secured the first purchase order under its 2 GWh capacity reservation agreement with Frontier Power USA Parent, LLC (FPUSA). This initial order supports FPUSA's Redbird project, which involves a 100 MW / 400 MWh battery energy storage system. The deployment will utilize Eos' Z3™ technology, marking a significant step in the execution of the broader capacity reservation framework.

Project Details

The Redbird project represents a substantial commitment to long-duration energy storage (LDES). By leveraging Eos' zinc-based systems, FPUSA aims to enhance energy storage capabilities. The 100 MW / 400 MWh scale of the project underscores the growing demand for domestically manufactured energy storage solutions in the United States.

Strategic Agreement

The 2 GWh capacity reservation agreement between Eos and FPUSA establishes a structured pathway for future orders. This latest purchase order is the first tangible outcome of that strategic partnership. The agreement is designed to provide FPUSA with access to Eos' Z3™ technology while securing a significant pipeline for Eos's manufacturing operations.

Technology and Manufacturing

Eos Energy Enterprises specializes in zinc-based LDES systems that are sourced and manufactured in the United States. The Z3™ technology is central to the company's offerings, providing a solution for grid-scale energy storage. The Redbird project serves as a validation of this technology's commercial viability at scale.