Solid Phase Diffusion Dynamics Distorting Battery Voltage Lookups
Unrelaxed solid-phase diffusion gradients create particle surface overpotentials that distort battery open-circuit voltage lookups by up to twenty percent.
Overpotential Correction
Meaning
Analytical calculation adjusts the measured cell voltage during active current flow to estimate the underlying equilibrium open circuit voltage. Applying overpotential correction enables the battery management system to calculate the true state of charge even while the battery is discharging or charging. This correction accounts for the voltage drop caused by internal resistance and ion concentration gradients.
Mathematical Adjustment
Internal resistance causes the terminal voltage of a cell to deviate from its thermodynamic equilibrium when current passes through it. The algorithm computes the magnitude of this deviation by multiplying the current by the estimated internal resistance and subtracting this value from the measured voltage. This dynamic overpotential correction ensures that the system does not trigger premature low-voltage cutoffs during high-power discharge events.
Sourcing Benefit
Procurement teams use these correction algorithms to evaluate cells with higher internal resistance without sacrificing usable energy. Accurate correction allows the pack to operate closer to its physical limits, which reduces the need for expensive, low-resistance cell chemistries. This flexibility lowers the overall bill of materials for the energy storage system.
Safety Benefit
Overestimating the voltage of a charging cell can lead to hazardous overcharging. Accurate correction protects the electrodes from lithium plating by monitoring the true potential of the anode. This tracking prevents localized degradation and minimizes the risk of internal short circuits.