#### Second-order RC model of lithium-ion power battery

What is the second-order RC model of lithium-ion power battery? Next, the second-order RC model of lithium-ion power battery is introduced.

We have learned How does the lithium ion power battery work.The charge and discharge process of lithium-ion power batteries is a very complex electrochemical process, and its performance parameters are affected by many factors such as charge and discharge depth, current intensity, temperature, and vibration. It takes a lot of time and cost to detect the changes of various parameters of the battery through the method of battery charge and discharge test, and there are potential safety hazards such as fire and explosion. By establishing an accurate battery model to simulate the change state of various performance parameters of the battery during the charging and discharging process, not only can safety be improved, but also a lot of test time and cost can be saved. Therefore, this section studies the establishment of a lithium-ion power battery model..

The battery models commonly used at this stage mainly include equivalent circuit models, mechanism models, empirical models based on experimental data, electrochemical models, neural network models, and random models. Among them, the equivalent circuit model can express the relationship between the output characteristics of the battery and the internal parameters, and can be used to predict the state of charge SOC, the state of health SOH and other parameters of the battery. It can well reflect the working state of the battery. It has a simple structure, easy modeling, Convenient parameter identification and other advantages. Since the order of the second-order RC equivalent circuit model is appropriate, the engineering is easier to realize, and the steady-state and transient characteristics of the battery can be taken into account, so this article chooses the second-order RC model as the lithium-ion power battery model, as shown in Figure Shown.

Among them, VOC represents the ideal voltage source, representing the open circuit voltage of the lithium-ion power battery; R0 represents the ohmic internal resistance; two RC structures are used to represent the polarization reaction of the battery, where RS, and RL are the polarization internal resistance, CS, and CL is the polarization capacitance;
I(t) represents the current, and Vbat represents the measurable battery terminal voltage. Let τ1=Rs. Cs,τ2=RL. CL, τ1 and τ2 respectively represent the short time constant and long time constant in the dynamic response process of the lithium-ion power battery.