Korea's ESS centralized-contract market Round-3 bid (approximately KRW 1 trillion), scheduled for announcement in September 2026, has already shown a decline in bid prices compared to Rounds 1 and 2, intensifying low-price order competition among the three battery makers. This article focuses on the possibility that this low-price order volume will require cell-format mixed-model flow on an existing single-model production line, and quantifies, as a target scenario, the impact of changeover time on takt time and the OEE Availability factor. The verification shows that controlling changeover time within the 216 s target versus exceeding it by 50% produces an OEE gap of approximately 3.8 pp. However, these figures are an…