Author: Jenny Börjesson Axén
Title: Modeling of OCV hysteresis in the NiMH battery system
Affiliation: Royal Institute of Technology, KTH
Open circuit voltage (OCV) hysteresis of batteries is a phenomenon that is rarely modeled but plays an important role in some battery systems. Hysteresis is when the properties of a material depends on the path used to attain a certain state. For batteries it depends on the charge/discharge sequence taken to reach a state of charge (SOC), and the property affected is the OCV.
The NiMH battery is significantly affected by OCV hysteresis. The hysteresis window is large, a single OCV value can represent a span of SOCs as wide as 70% of the total SOC window. As a consequence, NiMH battery models without a proper description of the OCV hysteresis often render inaccurate results when simulating the behavior of systems during dynamic charge/discharge patterns. In this study different ways of modeling the OCV hysteresis is compared in a lumped model setting on different dynamic data sets from NiMH battery systems.