The study of battery behaviors has become a necessity in order to design efficient battery management systems for large-scale energy storage applications. This paper developed an open-circuit-voltage (OCV) characterization system implemented with sequential-control algorithms to study the OCV characteristics in Mn-type Li-ion batteries and their electrode properties regarding the phase-transition mechanisms. Differential voltage (DV) and incremental capacity (IC) techniques are applied for analyzing the phase-transition behaviors. Based on the changes of DV and IC characteristics for the OCV, the phase-transitions are discussed and evaluated to understand electrochemical changes and deterioration mechanisms in the batteries during cycling operations.