306 Control Lab Prof Kung ChungChun Lithium Battery

306 Control Lab. Prof. Kung, Chung-Chun

Lithium Battery (18650 type)

Lithium Battery Modeling Steps Battery Equivalent Circuit Model Analysis Battery Parameter Identification Battery Parameter Modeling Model-Based State of Charge Estimator

Li-ion Battery Equivalent Circuit Model (I) z(t) State of Charge Voc(z Open-Circuit Voltage (V) ) RI (z) Total Internal Resistance (Ω) I(t) Load Current (A) Vt (t) Terminal Voltage (V) QN State of Charge Equation: Nominal Capacity (Ah) Output Equation: Coulomb Counting Method Total Internal Resistance:

Li-ion Battery Equivalent Circuit Model (II) z(t) State of Charge Voc(z Open-Circuit Voltage (V) ) Vp(t) Polarization Voltage (V) RI Total Internal Resistance (Ω) Rp Polarization Resistance (Ω) Cp Polarization Capacitance (Ω) I(t) Load Current (A) Vt (t) Terminal Voltage (V) State of Charge Equation: Qmax Max available Capacity (Ah) Model Equation:

Li-ion Battery Equivalent Circuit Model (II) “. . . , the useful voltage delivered by the cell is reduced by polarization and the internal IR drop. It is only at very low operating currents, where polarization and the IR drop are small, that the cell may operate close to the open-circuit voltage and deliver most of theoretically available energy. ” From: Thomas B. Reddy, Handbook of Batteries.

Lithium Battery Modeling Steps Battery Equivalent Circuit Model Analysis Battery Parameter Identification Battery Parameter Modeling Model-Based State of Charge Estimator

Li-ion Battery Equivalent Circuit Model (II) Battery Model Parameter (Voc(z)) Estimation :

Li-ion Battery Equivalent Circuit Model (III) Internal Resistance versus State of Charge: Using ICR 18650 H

Li-ion Battery Equivalent Circuit Model (III) Internal Resistance (Normalized) versus Cycle Number: Using ICR 18650 H

Li-ion Battery Equivalent Circuit Model (III) Polarization Resistance versus State of Charge: Using ICR 18650 H

Li-ion Battery Equivalent Circuit Model (III) Polarization Resistance (Normalized) versus Cycle Number: Using ICR 18650 H

Li-ion Battery Equivalent Circuit Model (III) Polarization Capacitance versus State of Charge: Using ICR 18650 H

Li-ion Battery Equivalent Circuit Model (III) Polarization Capacitance (Normalized) versus Cycle Number: Using ICR 18650 H

Lithium Battery Modeling Steps Battery Equivalent Circuit Model Analysis Battery Parameter Identification Battery Parameter Modeling Model-Based State of Charge Estimator

Polynomial Equation:

Lithium Battery Modeling Steps Battery Equivalent Circuit Model Analysis Battery Parameter Identification Battery Parameter Modeling Model-Based State of Charge Estimator

Model-Based State of Charge Estimator (nonlinear observer)