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.
Terminal Voltage
Meaning
Electrical potential differences measured directly across the positive and negative contacts of a battery cell under dynamic or static conditions determine the available voltage for external circuits. Unlike the internal thermodynamic open circuit voltage, terminal voltage is affected by the internal resistance and polarization effects of the cell during current flow. This value is the primary measurement used by the battery management system to monitor operation and protect the cell from overcharge and over-discharge.
Operational Variation
During discharge, the measured value drops below the open circuit voltage by an amount proportional to the current and internal resistance. This reduction, known as voltage sag, is caused by ohmic losses and mass transport limitations within the electrolyte and electrodes. Sourcing engineers analyze this behavior to ensure that the terminal voltage remains above the minimum cutoff of the inverter during high-load events.
Sourcing Selection
Cells with low internal resistance maintain a more stable voltage profile throughout their discharge cycles. Sourcing teams compare the terminal voltage curves of different manufacturers to select cells that minimize energy loss and heat generation during operation. This selection process is vital for high-power applications where thermal management is a key cost driver.
Control Application
Safety circuits continuously monitor this potential to trigger cutoff switches before damaging voltage thresholds are breached. In high-voltage packs, the uniformity of terminal voltage across all series-connected cells is the key metric used to trigger cell balancing routines.