Thermodynamic Hysteresis Mapping for Open Circuit State Estimation
Dynamic thermodynamic hysteresis mapping eliminates up to six percent state of charge error across flat voltage plateaus, protecting storage project revenue.
Pseudo OCV Sweep
Meaning
Characterization procedures that measure the voltage of a battery cell during continuous charging and discharging at extremely low current rates provide an approximation of the thermodynamic open circuit voltage curve. By cycling the cell at rates such as C/25 or C/50, a pseudo ocv sweep reduces the overpotential to negligible levels while avoiding the long rest periods required for step-by-step measurements. This continuous technique allows engineers to capture detailed electrochemical signatures that would be obscured by high current or rapid cycling.
Test Methodology
Laboratory instruments apply a constant, minute current to the cell while monitoring terminal voltage over a full charge and discharge cycle. Conducting a pseudo ocv sweep requires highly stable temperature chambers because small thermal fluctuations can shift the measured voltage and distort the resulting phase transition peaks. Sourcing engineers demand these low-rate datasets during cell qualification to verify the thermodynamic properties of new anode and cathode mixtures.
Diagnostic Value
Differential capacity analysis of the data collected during this test reveals the distinct voltage plateaus that correspond to specific lithium intercalation stages. Analyzing a pseudo ocv sweep over the lifetime of a cell reveals degradation mechanisms like loss of active material or lithium inventory depletion. This diagnostic capability helps buyers evaluate the long-term chemical stability of competing cell designs.
Data Processing
Mathematical algorithms calculate the average of the charge and discharge voltage curves to subtract the remaining resistance and overpotential effects. This processed pseudo ocv sweep represents the closest practical approximation of the true thermodynamic state of the battery.