Method and apparatus for online determination of battery state of charge and state of health

• US 9,157,966 B2
• Filed: 11/25/2011
• Issued: 10/13/2015
• Est. Priority Date: 11/25/2011
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Singh, Harmohan N., Kojori, Hassan Ali, Lazarovich, David, Papana, Anki Reddy, Keshri, Subodh
• Primary Examiner(s): Feliciano, Eliseo Ramos
• Assistant Examiner(s): SUAREZ, FELIX E
• Application Number:
  US13/304,596
• Publication Number:
  US 20130138369A1
• Time in Patent Office: 1,418 Days
• Field of Search: 702/57, 702/63, 702/64, 702/179, 702/182, 702/183, 702/189, 320/132, 324/426
• US Class Current: 1/1
• CPC Class Codes: B60L 2240/545 Temperature
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 2260/44 by parameter estimation
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: B60L 58/16 responding to battery ageing, e.g. to the number of charging cycles or the state of health [SoH]
• CPC Class Codes: G01R 31/3644 Constructional arrangements
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

An online method and apparatus for determining state of charge (SoC) and state of health (SoH) of batteries on platforms that present dynamic charge and discharge environments is disclosed. A rested open circuit voltage (OCV) may be estimated online using a battery dynamic model along with measured terminal voltage, current and temperature. The SoC and SoH can then be determined from this estimated OCV. The apparatus and methods may estimate SoC and SoH of a battery in a real-time fashion without the need to a) disconnect the battery system from service; b) wait for a predefined rest time; or c) depolarize the battery.

Claims

1. A system for determining on-line battery'"'"'s state of charge, the system comprising:

a measurement section having a voltage sensor, a current sensor and a temperature sensor, the measurement section adapted to take on-line measurements from the battery;

a computer having a battery dynamic model stored in a non-volatile memory, the battery dynamic model including various values of parameters R_s, C_st, R_st, C_lt and R_lt determined at various temperatures, terminal voltages and currents while the battery is off line, the parameters being elements of a battery model that includes;

a resistance R_s in series with a first and a second RC branch;

the first RC branch representing a polarization phenomenon for short time just after keeping the battery in rest;

the first RC branch including a capacitor C_st connected in parallel with a resistor R_st;

the second RC branch representing the polarization phenomenon for long time just after keeping the battery in rest;

the second RC branch including a capacitor C_lt connected in parallel with a resistor R_lt;

a computer having a processor adapted to receive the on-line measurements from the measurement section and to calculate an open circuit voltage online, using an equation

V_OC=V_BAT+Δ

V_R+Δ

V_P

where V_BAT—

Battery terminal voltage, Δ

V_R—

Voltage drop due to battery resistance, and Δ

V_P—

Voltage drop due to polarization phenomenon;

wherein Δ

V_P is computed using an equation

2. The system of claim 1, further comprising a data acquisition system for collecting the data from the measurement section.

3. The system of claim 1, wherein the non-volatile memory includes a lookup table that correlates open circuit voltage with battery state of charge.

4. A computer implemented method for determining a state of charge of an on-line battery, the method comprising:

determining various values of parameters R_s, C_st, R_s, C_lt and R_lt at various temperatures, terminal voltages and currents while the battery is off line, the parameters being elements of a battery model that includes;

a resistance R_s in series with a first and a second RC branch;

the first RC branch representing a polarization phenomenon for short time just after keeping the battery in rest;

the first RC branch including a capacitor C_st connected in parallel with a resistor R_st;

the second RC branch representing the polarization phenomenon for long time just after keeping the battery in rest;

the second RC branch including a capacitor C_lt connected in parallel with a resistor R_lt;

constructing a battery dynamic model that correlates the various off-line battery temperatures, terminal voltages and currents with the various values of parameters R_s, C_st, R_st, C_lt and R_lt

storing the battery dynamic model in a non-volatile memory of a computer;

receiving, at a processor of the computer, on-line measurements of battery temperature, terminal voltage, and current;

computing, using the processor of the computer, an open circuit voltage online without requiring a battery rest time using an equation

V_OC=V_BAT+Δ

V_R+Δ

V_P

where V_BAT—

Battery terminal voltage, Δ

V_R—

Voltage drop due to battery resistance, and Δ

V_P—

Voltage drop due to polarization phenomenon;

wherein Δ

V_P is computed using an equation

5. The method of claim 4, further comprising periodically updating model parameters for current, state of charge, temperature and battery age.

6. The method of claim 4, further comprising measuring V_BAT using a voltage sensing connected across terminals of the battery.

7. The method of claim 4, further comprising correlating charge or discharge energy with a change in state of charge and extrapolating to get full battery capacity.

8. A computer implemented method for determining a state of health of on-line battery, comprising:

determining various values of parameters R_s, C_st, R_st, C_lt and R_lt at various temperatures, terminal voltages and currents while the battery is off line, the parameters being elements of a battery model that includes;

a resistance R_s in series with a first and a second RC branch;

the first RC branch representing a polarization phenomenon for short time just after keeping the battery in rest;

the first RC branch including a capacitor C_st connected in parallel with a resistor R_st;

the second RC branch representing the polarization phenomenon for long time just after keeping the battery in rest;

the second RC branch including a capacitor C_lt connected in parallel with a resistor R_lt;

constructing a battery dynamic model that correlates the various off-line battery temperatures, terminal voltages and currents with the various values of parameters R_s, C_st, C_lt R_lt;

storing the battery dynamic model in a non-volatile memory of a computer;

estimating, using a processor of a computer, a full capacity of the battery by;

charging or discharging the battery while the battery is on line;

computing, using a processor of a computer, an open circuit voltage of the online battery using an equation

V_OC=V_BAT+Δ

+Δ

V_P

where V_BAT—

Battery terminal voltage, Δ

V_R—

Voltage drop due to battery resistance, and Δ

V_P—

Voltage drop due to polarization phenomenon;

receiving, at a processor of the computer, on-line measurements of battery temperature, terminal voltage, and current;

wherein Δ

V_P is computed using an equation

9. The method of claim 8, further comprising performing trend analysis of the battery'"'"'s full capacity over time to predict the battery'"'"'s end of life.

10. The method of claim 8, further comprising measuring V_BAT using a voltage sensing connected across terminals of the battery.