Online Estimation of State of Charge in Li-Ion Batteries Using Impulse Response Concept

Lithium-ion batteries exhibit high levels of energy and power density among electrochemical batteries. These attributes make them suitable as the energy storage system in electric, hybrid electric vehicle, and plug-in vehicles (EV/HEV/PHEV). One of the important requirements in automotive batteries is to monitor their real time state-of-charge (SOC) and state-of-health (SOH). Open circuit voltage, as one parameter used for predicting the SOC in the battery, is not readily available during charge and discharge cycles. In this paper a new method for prediction of the terminal voltage in li-ion batteries based on the impulse response concept has been proposed. By obtaining the impulse response of the li-ion battery, one can use the terminal current to predict the output voltage of the battery. Online comparison of the predicted and measured terminal voltage provides a tool for online monitoring of the SOH and SOC.