Meaning
Theoretical voltage of an electrochemical cell when the current is so low that the system remains close to its thermodynamic equilibrium. Measuring the quasi equilibrium potential allows the mapping of the state of charge to voltage without the distortions caused by internal resistance or ion diffusion limits. This value is typically obtained through Galvanostatic Intermittent Titration Technique or extremely slow discharge rates.
Thermodynamic Baseline
Data points collected during these tests serve as the reference for all other performance metrics. By isolating the quasi equilibrium potential, engineers can determine how much of the voltage drop during high power operation is due to kinetic losses versus the actual energy state of the materials. This distinction is necessary for developing accurate battery models for electric vehicles.
Pulse Relaxation
Testing involves applying a small current pulse followed by a long rest period for the voltage to stabilize. The stabilized value after this rest is the quasi equilibrium potential for that specific state of charge. Repeating this across the full capacity of the cell generates the open circuit voltage curve used in BMS software.
Model Fidelity
Simulation tools use these values to predict how a battery will respond to complex drive cycles. Calculating the quasi equilibrium potential provides the groundwork for high fidelity digital twin models. This improves accuracy.
