Modeling changes in the state-of-charge open circuit voltage curve by using regressed parameters in a reduced order physics based model

摘要

A method for modeling changes in the state of charge vs. open circuit voltage (SOC-OCV) curve for a lithium-ion battery cell as it ages. During battery pack charging, voltage and current data are gathered for a battery cell. A set of state equations are used to determine the stoichiometry and state of charge of the cathode half-cell based on the charging current profile over time. The voltage and current data, along with the stoichiometry and state of charge of the cathode half-cell, are then used to estimate maximum and minimum solid concentration values at the anode, using an error function parameter regression/optimization. With stoichiometric conditions at both the cathode and anode calculated, the cell's capacity and a new SOC-OCV curve can be determined.

主权项

1. A method for monitoring performance changes in aging cells in a battery pack, said method comprising:
providing full-cell open circuit voltage data vs. time and current data vs. time for a cell in the battery pack, where the data is obtained by sensors during a plug-in charge event; calculating cathode half-cell stoichiometry using the current data and providing cathode concentration data vs. time and cathode half-cell open circuit voltage data vs. time; determining anode half-cell stoichiometry using the cathode concentration data, the cathode half-cell open circuit voltage data and the full-cell open circuit voltage data; and calculating, using a microprocessor, an updated state of charge vs. open circuit voltage curve (SOC-OCV curve) for the cell based on the cathode half-cell stoichiometry, the anode half-cell stoichiometry and a full-cell capacity.