Method and Apparatus for Estimating Battery Capacity of a Battery

• US 20120072145A1
• Filed: 09/22/2010
• Published: 03/22/2012
• Est. Priority Date: 09/22/2010
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Zhang, Yilu, Shin, Kwang-Keun, Tang, Xidong, Salman, Mutasim A.
• Granted Patent: US 8,612,168 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3828 using current integration
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method is provided for determining a battery capacity for a vehicle battery. Open circuit voltages of a vehicle battery are measured during ignition startups. A battery parameter is estimated for the vehicle battery that is a function of a present open circuit voltage measurement for a present ignition startup, a function of at least one open circuit voltage observation of a previous ignition startup, a function of a current draw integration over a time period from a previous ignition startup event to a present ignition startup event, and a function of an adjustment factor. A battery parameter is determined based on a new battery. The battery capacity is calculated as function of the battery parameter for the vehicle battery and the battery parameter for the new battery.

Claims

1. A method of determining a battery capacity for a vehicle battery, the method comprising the steps of:

measuring open circuit voltages of a vehicle battery during ignition startups;

estimating a battery parameter for the vehicle battery that is a function of a present open circuit voltage measurement for a present ignition startup, a function of at least one open circuit voltage observation of a previous ignition startup, a function of a current draw integration over a time period from a previous ignition startup event to a present ignition startup event, and a function of an adjustment factor;

determining a battery parameter based on a new battery; and

calculating the battery capacity as function of the battery parameter for the vehicle battery and the battery parameter for the new battery.

2. The method of claim 1 wherein the battery parameter of the vehicle battery is a function of a previous battery parameter observation and a present estimated battery parameter.

3. The method of claim 2 wherein estimating a battery parameter for the vehicle battery is represented by the following formula:

4. The method of claim 3 wherein the adjustment factor for the battery parameter is a function of a time that an ignition key is off and is represented by the following formula:

λ

_θ

=e<sup>−

toff(tk)/τ

θ</sup>

.

5. The method of claim 3 wherein the battery capacity of the battery is determined from the following formula:

Q_actual=Q_new(θ

_new/{circumflex over (θ

)}_k)

where Q_actual is the estimated actual estimated battery capacity of the vehicle battery, Q_new is a battery capacity based on a new battery, θ

_new is a battery parameter based on a new battery, and {circumflex over (θ

)}_k is the estimated battery parameter of the vehicle battery.

6. The method of claim 5 wherein the battery parameter for the vehicle battery, the battery parameter for the new battery, and the charge capacity for the new battery are normalized at a respective temperature.

7. The method of claim 3 wherein the present open circuit voltage measurement, the previous open circuit voltage observation, and the battery parameter are normalized at a respective temperature.

8. The method of claim 1 wherein the battery capacity of the vehicle battery is displayed to user of the vehicle via a display device.

9. The method of claim 1 wherein a representation of the battery capacity of the battery is displayed to user of the vehicle via a display device.

10. A system for determining a battery capacity for a vehicle battery comprising:

a battery;

at least one component for drawing power from the battery;

a voltmeter for measuring an open circuit voltage of the battery at ignition start sequences;

a current sensor for sensing current drawn from the battery; and

a control module for determining a battery parameter for the vehicle battery that is a function of a present open circuit voltage measurement for a present ignition startup, a function of at least one open circuit voltage observation of a previous ignition startup, a function of a current draw integration over a time period from a previous ignition startup event to a present ignition startup event, and a function of an adjustment factor, the control module further determining a battery parameter based on a new battery, the control module calculating the battery capacity as function of the battery parameter for the vehicle battery and a function of the battery parameter for the new battery.

11. The system of claim 11 wherein the control module estimating a battery parameter for the vehicle battery is represented by the following formula:

14. The system of claim 11 wherein the battery capacity of the battery is determined from the following formula:

Q_actual=Q_new(θ

_new/{circumflex over (θ

)}_k)

where Q_actual is the estimated battery capacity of the vehicle battery, Q_current^T is a normalized battery capacity based on a new battery, θ

_new is a battery parameter based on a new battery, and {circumflex over (θ

)}_k is the estimated battery parameter of the vehicle battery.

12. The system of claim 12 wherein the control module determines the adjustment factor for the battery parameter of the vehicle battery as a function of a time that an ignition key is off, wherein the adjustment factor is determined by the following formula:

λ

_θ

=e<sup>−

toff(tk)/τ

θ</sup>

.

13. The system of claim 12 wherein the control module normalizes the present open circuit voltage measurement at the k_th ignition start, the previous open circuit voltage observation, and the battery parameter of the vehicle battery are normalized at a respective temperature.