ESS Tech, Inc.

ESS Tech, Inc. (NYSE: GWH) is a Portland, Oregon-based developer of long-duration iron flow battery systems designed for commercial and utility-scale grid energy storage applications. The company entered the public markets in October 2021 through a merger with ACON S2 Acquisition Corp, a blank-check vehicle sponsored by ACON S2 Partners LLC, an affiliate of Washington, D.C.-based private equity firm ACON Investments. ESS Tech operates in the clean energy and long-duration storage sector, focusing on iron-based battery chemistry as an alternative to lithium-ion solutions. The company filed an 8-K with the SEC on May 7, 2026, under accession number 0001819438-26-000032. For full filing history, deal timelines, and SPAC analytics on GWH, sign up for complete data access at SpacDesk.