Internal resistance measurements of Li-ion batteries using AC methods

The internal resistance of Li-ion cells is a quantity for determining the performance such as energy efficiency and state of health (SoH). To combine Li-ion cells as a battery for the solar cell industry as well as electric vehicle (EV), the internal resistance of each cell needs to be consistent otherwise the lifetime will be shortened. However, the internal resistance of Li-Ion cells depends on variables such as operating temperature and state of charge (SoC). In this work, we carried out the internal resistance measurements of individual Li-ion cells based on AC methods. According to an equivalent circuit of Li-ion battery, the measurement frequency was varied to study the effects of influence quantities such as the battery's capacitance and inductance. Two AC methods were compared and discussed for the internal resistance values of Li-ion cells.