Battery control apparatus, electric vehicle, and computer-readable medium storing a program that causes a computer to execute processing for estimating a state of charge of a secondary battery

• US 7,893,652 B2
• Filed: 08/31/2007
• Issued: 02/22/2011
• Est. Priority Date: 09/05/2006
• Status: Active Grant

• Current Assignee: Panasonic EV Energy Company, Limited (Toyota Motor Corporation)
• Original Assignee: Panasonic EV Energy Company, Limited (Toyota Motor Corporation)
• Inventors: Suzuki, Masahiko, Kanamaru, Kunio, Uemura, Yukie, Togashi, Kouta
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US11/849,215
• Publication Number:
  US 20080053715A1
• Time in Patent Office: 1,271 Days
• Field of Search: 320/104
• US Class Current: 320/104
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

The present invention can speedily and accurately estimate an SOC of a secondary battery immediately after a charge/discharge operation resumes. A determination unit determines whether a dormant period is longer than a predetermined time in response to an initiation of power supply from a secondary battery to a motor generator. The dormant period is equivalent to the duration from a previous stop of power supply to a present initiation of power supply. If the dormant period is longer than the predetermined time, a state-of-charge estimating unit sets an initial SOC based on a peak battery voltage drop ΔVs and a peak discharge current Is, wherein the peak battery voltage drop ΔVs represents a difference between a battery voltage Vo measured before initiating power supply and a lowest battery voltage Vs measured after initiating power supply and the peak discharge current Is represents a maximum current value measured after initiating power supply. The state-of-charge estimating unit estimates a state of charge of the secondary battery 30 based on the initial SOC as a value effective immediately after initiating power supply.

Claims

1. A battery control apparatus comprising:

a determination unit configured to determine whether a secondary battery generates a polarization voltage in response to resuming power supply from the secondary battery to a load; and

a state-of-charge estimating unit configured to estimate a present state of charge indicating a state of charge of the secondary battery immediately after resuming power supply, in response to the determination unit determining that the secondary battery generates no polarization voltage,

wherein the state-of-charge estimating unit calculates the present state of charge by measuring a battery voltage Vo measured before resuming power supply, a peak discharge current Is representing a maximum current value appearing within a predetermined short period of time after resuming power supply, and a lowest battery voltage Vs corresponding to the peak discharge current Is, and by referring to an SOC estimating map illustrating a relationship between a peak battery voltage drop Δ

Vs and the peak discharge current Is, wherein the peak battery voltage drop Δ

Vs represents a difference between the battery voltage Vo and the lowest battery voltage Vs, and

wherein the state-of-charge estimating unit sets an initial value based on the estimated present state of charge and estimates a state of charge of the secondary battery based on the initial value as a value effective immediately after resuming power supply.

2. The battery control apparatus according to claim 1, wherein the determination unit determines that the secondary battery generates no polarization voltage when a dormant period is longer than a predetermined time and determines that the secondary battery generates a polarization voltage when the dormant period is shorter than or equal to the predetermined time, wherein the dormant period is equivalent to the duration from a previous stop of the power supply to a present resuming of the power supply.

3. The battery control apparatus according to claim 1, wherein the state-of-charge estimating unit sets the initial value based on a previous state of charge estimated immediately before a previous stop of the power supply, in response to the determination unit determining that the secondary battery generates a polarization voltage.

4. The battery control apparatus according to claim 1, further comprising a control unit configured to prevent the state-of-charge estimating unit from estimating the present state of charge and prohibit resuming the power supply, in response to the determination unit determining that the secondary battery generates a polarization voltage.

5. The battery control apparatus according to claim 1, wherein the state-of-charge estimating unit determines whether the present state of charge is higher than a previous state of charge estimated immediately before a previous stop of the power supply, and sets the initial value based on the previous state of charge instead of using the present state of charge.

6. The battery control apparatus according to claim 1, furthermore comprising a control unit configured to execute predetermined anti-overdischarge processing for the secondary battery in response to a determination that the present state of charge is less than a predetermined value.

7. The battery control apparatus according to claim 1, wherein the state-of-charge estimating unit estimates the present state of charge based on a battery temperature of the secondary battery in addition to the peak battery voltage drop Δ

Vs and the peak discharge current Is.

8. A computer-readable medium storing a program for causing a computer to perform processing for estimating a state of charge of a secondary battery, the processing comprising:

determining whether the secondary battery generates a polarization voltage in response to resuming power supply from the secondary battery to a load;

estimating a present state of charge indicating a state of charge of the secondary battery immediately after resuming power supply, in response to a determination that the secondary battery generates no polarization voltage, by measuring a battery voltage Vo measured before resuming power supply, a peak discharge current Is representing a maximum current value appearing within a predetermined short period of time after resuming power supply, and a lowest battery voltage Vs corresponding to the peak discharge current Is, and by referring to an SOC estimating map illustrating a relationship between a peak battery voltage drop Δ

Vs and the peak discharge current Is, wherein the peak battery voltage drop Δ

Vs represents a difference between the battery voltage Vo and the lowest battery voltage Vs;

setting an initial value based on the estimated present state of charge; and

estimating a state of charge of the secondary battery based on the initial value as a value effective immediately after resuming power supply.

9. An electric vehicle comprising:

a motor generator configured to generate a driving power;

a secondary battery configured to supply electric power to the motor generator;

a determination unit configured to determine whether a dormant period is longer than a predetermined time when the secondary battery resumes power supply to the motor generator in response to a turning-on operation of an ignition switch, wherein the dormant period is equivalent to the duration from a previous stop of the power supply to a present resuming of the power supply; and

a state-of-charge estimating unit configured to estimate a present state of charge indicating a state of charge of the secondary battery immediately after resuming power supply, in response to a determination by the determination unit that the dormant period is longer than a predetermined time,

wherein the state-of-charge estimating unit calculates the present state of charge by measuring a battery voltage drop Vo measured before resuming power supply, a peak discharge current Is representing a maximum current value appearing within a predetermined short period of time after resuming power supply, and a lowest battery voltage Vs corresponding to the peak discharge current Is, and by referring to an SOC estimating map illustrating a relationship between a peak battery voltage drop Δ

Vs and the peak discharge current Is, wherein the peak battery voltage drop Δ

Vs represents a difference between the battery voltage Vo and the lowest battery voltage Vs, and

wherein the state-of-charge estimating unit sets an initial value based on the estimated present state of charge and estimates a state of charge of the secondary battery based on the initial value as a value effective immediately after resuming power supply.