Meaning
Performance degradation benchmarks compare the internal resistance of a cell at various stages of its lifecycle to determine end of life status. Periodic pulse tests measure the instantaneous voltage drop and the subsequent recovery to calculate how dcir impedance growth progresses. High resistance values lead to excessive heat generation and reduced power delivery during vehicle acceleration.
Interface Resistance
Thickening of the solid electrolyte interphase is the primary cause of the Interface Resistance of dcir impedance growth. Chemical reactions between the electrolyte and the electrode surface create a resistive film that slows ion transport during every charge cycle. This layer eventually blocks the pores of the electrode and limits the high rate capability of the cell.
Power Delivery
Internal heating increases as the square of the current, which means the Power Delivery of dcir impedance growth directly affects the thermal management requirements. Software limits the maximum current to prevent the terminal voltage from dropping below the safety cutoff as the pack ages. Drivers experience this as a gradual reduction in the available torque during high load events.
Standard Measurement
Consistent temperature and state of charge conditions are required to produce reliable data for the Standard Measurement of dcir impedance growth. Typical laboratory protocols specify a ten second pulse at fifty percent state of charge to ensure repeatability. Variations in these test parameters prevent the comparison of data across different cell batches or manufacturers.
