One of the most popular approaches for battery modelling is the 'Electric model'.
Understanding the Electric Model:
The electric model is a simplified representation of a battery, that uses electrical circuit elements such as resistors, capacitors, and voltage sources to simulate the complex electrochemical processes occurring within the battery. These elements are arranged in specific configurations to emulate the battery's dynamic behaviour, including its voltage response, charge and discharge characteristics, and thermal behaviour.
Key Components of the Electric Model:
a) Ohmic Resistance (R0):
The ohmic resistance represents the internal resistance of the battery, which is influenced by factors such as electrode material, electrolyte, and current collector. It is responsible for the instantaneous voltage drop (IR drop) when a current passes through the battery. The ohmic resistance has a significant impact on the efficiency and heat generation of the battery during operation.
b) Polarization Resistances (Rp)
Polarization resistances account for the delayed voltage response of the battery due to the slow electrochemical processes at the electrode-electrolyte interface. The polarization resistances are usually modelled as resistor-capacitor (RC) pairs, with each RC pair representing a specific electrochemical process, such as charge transfer or solid-state diffusion.
c) Open Circuit Voltage (OCV)
The open circuit voltage is the battery's voltage when no current is flowing through it, which depends on the battery's state of charge (SOC) and temperature. The OCV is modeled as a voltage source in series with the ohmic and polarization resistances.
d) Thermal Model
The thermal model is an optional component that describes the heat generation and dissipation within the battery during operation. The thermal model can be integrated with the electric model to study the effects of temperature on battery performance and to develop thermal management strategies for improving the battery's safety and longevity.
Applications of the Electric Model in Battery Modelling:
a) Performance Prediction
Predict the battery's voltage response, power capability, and energy capacity under various operating conditions, such as different discharge rates, temperatures, and aging effects.
b) State Estimation
Estimate the battery's state of charge (SOC), state of health (SOH), and other internal states.
c) Control and Optimization
The electric model can serve as the basis for developing advanced battery management systems (BMS) that control and optimize the battery's operation, such as charging and discharging strategies, thermal management, and fault detection.
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