Method for Estimating State of Charge for Lithium-Ion Batteries

A method for estimating a state of charge (SoC) a lithium-ion (Li+) battery at a time instant, comprising the steps of:

• constructing a model of the Li+ battery, wherein the model is based on a single particle operation of the Li+ battery, where the model describes a relationship between the SoC, a charge current, a discharge current, and an output voltage;
• determining, using a nonlinear optimization, a function expressing a relationship between the SoC and an open circuit voltage, wherein the relationship is based on off-line measurements of the charge current, the discharge current, and the open-circuit voltage;
• and
• estimating the SoC and parameters of the model concurrently, wherein the SoC and the parameters are based on the model, the function, and on-line measurements of the charge current, the discharge current, and the output voltage.