Battery Modelling and Impact of Internal Losses on Range and Health Estimation in HEV Application

In order to design a hybrid vehicle equipped with lithium-ion battery packs, it is necessary to comprehend the thermal characteristics of the batteries. This knowledge is crucial for identifying the most optimal cell that takes into account power consumption, capacity, electrical and thermal management, monitoring etc. One of the most crucial issues with lithium-ion batteries is heat control and management because high temperatures reduce charge/discharge efficiency, shorten battery life, and even pose a safety risk. During the HEV application, for a given drive cycle there is a temperature rise observed which needs to be predicted in order to avoid the thermal runaway situation and also to maintain the health of the battery system. This paper shows a good way to make a simulation model by considering empirical parameters of battery equivalent circuit for a lithium cell that works at different temperatures and changes with temperature. A circuit model consisting of a single voltage source, a series resistor, and an RC block leading to the development of equivalent circuit model illustrate the time-varying nature of the charge /discharge behavior for the battery pack. A method for estimating parameters using pulse power characterization tests on high-power lithium cells in a range of operating conditions showed that the equivalent circuit elements changed depending on the temperature, average current, power and state of charge. This method can help to make a very accurate model that can estimate how well electrical current and voltage will work and predict the run-time state of charge.