Meaning
Post-formation manufacturing sorting protocols group finished battery cells into narrow discharge capacity bins to ensure module-level balance. Automated testing equipment subjects charged cells to controlled discharge cycles at specified C-rates and reference temperatures. Executing cell capacity grading prevents weak cells from limiting the usable energy of entire pack assemblies.
Banning mismatched capacity bins from module assembly minimizes early pack degradation caused by cell over-discharge.
Bin Distribution
Statistical grouping places cells into discrete capacity tolerance bands, typically within one percent of nominal values. High-volume production lines route cells into automated sorting lanes based on measured ampere-hour metrics. Matching cell capacities reduces cell balancing currents required during battery management system operation.
Production yield optimization depends on maintaining narrow bin distribution widths.
Measurement Standard
Constant-current discharge testing from full charge down to lower cutoff voltage establishes baseline capacity values. Environmental test chambers maintain ambient temperatures within plus or minus zero point five degrees Celsius during discharge runs. Temperature variations shift measured capacity by altering internal electrochemical reaction rates.
Standardized test conditions enable consistent binning across manufacturing lots.
Pack Imbalance
Stringing unequal cell capacities in series creates early pack capacity truncation during discharge cycles. Lowest capacity cells reach voltage cutoffs first, forcing system shut down while higher capacity cells retain charge. Series imbalance accelerates degradation of weaker cells subjected to deeper depth of discharge.
Automated capacity grading eliminates early string failure modes.
