Battery heating for lithium-ion batteries based on multi-stage alternative currents

This paper presents a multi-stage alternative current (AC) strategy for internally hearting lithium-ion batteries. To this end, the influence of the amplitude and frequency of ACs is first examined. Electrochemical Impedance Spectroscopy (EIS) tests under different temperatures and frequencies are also conducted to obtain battery impedance spectra that are used to derive the maximum permissible current amplitude under different temperatures. An equivalent circuit model is then proposed and parameterized to predict battery heat generation based on the EIS test datasets. Finally, a multi-stage alternative current strategy is proposed for battery heating, in which the magnitude of the imposed AC is maintained unchanged for a constant time. The effects of different time durations are also examined. The results show that the proposed battery heating strategy can heat the tested battery from -20 °C to above 0 °C in less than 5 minutes without incurring negative impact on battery health and a small current duration is beneficial to reducing the heating time.