METHOD AND APPARATUS FOR ONLINE DETERMINATION OF BATTERY STATE OF CHARGE AND STATE OF HEALTH

• US 20130138369A1
• Filed: 11/25/2011
• Published: 05/30/2013
• Est. Priority Date: 11/25/2011
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: KOJORI, HASSAN ALI, LAZAROVICH, DAVID, PAPANA, ANKI REDDY, SINGH, HARMOHAN, KESHRI, SUBODH
• Granted Patent: US 9,157,966 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• 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 a battery'"'"'s state of charge and state of health, the system comprising:

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

a power supply connected to the battery via a power supply switch;

a load connected to the battery via a load switch; and

a computer adapted to receive the measurements from the measurement section, the computer having a control card adapted to open and close the power supply switch and the load switch, the computer adapted to calculate an open circuit voltage online, without requiring a battery rest time.

2. The system of claim 1, wherein the open circuit voltage is calculated by the 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.

3. The system of claim 2, wherein Δ

V_P is

computed using the equation

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

5. The system of claim 2, further comprising a non-volatile memory for storing a lookup table and data.

6. A method for determining a battery open circuit voltage online without requiring a battery rest time, the method comprising:

charging or discharging the battery;

computing the open circuit voltage using the 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; and

determining the state of charge using the computed open circuit voltage and a battery temperature.

7. The method of claim 6, wherein a lookup table is used to determine the state of charge of the battery using the computed open circuit voltage and the battery temperature.

8. The method of claim 6, further comprising initially measuring the open circuit voltage of the battery in a rested state and determining an initial battery state of charge.

9. The method of claim 6, further comprising periodically updating model parameters for current, state of charge, temperature and battery age.

10. The method of claim 6, wherein Δ

V_P is

computed using the equation

11. The method of claim 6, further comprising computing Δ

V_R using the equation

Δ

V_R=I*R_s

where R_s is a battery internal resistance and I is a current through terminals of the battery.

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

13. The method of claim 6, further comprising correlating charge or discharge energy with a change in state of charge and extrapolating to get full battery capacity.

14. A method for determining the state of health of a battery, comprising:

estimating full capacity of the battery by;

charging or discharging the battery;

computing the open circuit voltage using the 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;

determining the state of charge using the computed open circuit voltage and a battery temperature; and

correlating charge or discharge energy with a change in state of charge and extrapolating to get full battery capacity;

tracking the battery'"'"'s full capacity as a function of time; and

determining if the full capacity of the battery has declined a predetermined amount.

15. The method of claim 14, further comprising performing trend analysis of the battery'"'"'s full capacity over time to predict the battery'"'"'s end of life.

16. The method of claim 14, wherein Δ

V_P is

computed using the equation

17. The method of claim 14, further comprising computing Δ

V_R using the equation

Δ

V_R=I*R_s

where R_s is a battery internal resistance and I is a current through terminals of the battery.

18. The method of claim 14, further comprising measuring V_BAT using a voltage sensing connected across terminals of the battery.