A modified equivalent circuit model to capture low temperature effects in Li ion batteries

Among various existing battery models, equivalent circuit model (ECM) is widely employed for real-time battery management applications due to the ease of parametrization and implementation. Most commonly used equivalent circuit model consists of two resistive and capacitive (RC) networks to represent slow and fast dynamics of a cell. Such model works well for temperatures above and equal to 0°C depending on chemistry. However, it does not work well at low temperatures, since it fails to capture the enhanced impedance due to low temperature phenomena such as slow chemical discharge, C-rate dependent diffusivity etc. Here, we have employed C-rate dependent resistance in ECM to include the slow kinetics as well as the effect of C-rates on diffusivity, which is more significant at subzero temperatures than temperatures above 0°C. This modified ECM can be implemented in battery management system to accurately predict the cell behavior at different operating conditions at low temperature.