Online monitoring of lithium-ion battery aging effects by internal resistance estimation in electric vehicles

In electric and hybrid vehicles, driving performance is strongly influenced by the battery aging effects. For most lithium-ion batteries, the power capability fade caused by battery impedance rise is the main reason for battery end-of-life. In this paper, an online diagnosing method of internal resistance is presented based on equivalent circuit impedance model. Under a special diagnosing signal, voltage response is recorded and the impedance model is parameterized with the help of recursive least square (RLS) algorithm. The values of impedance model are then used for the estimation of power capability and detection of battery end-of-life. The performance of the internal resistance monitoring method is proved in Matlab/Simulink, which shows little error in estimation of battery power capability.