Method of controlling battery condition of self-generation electric vehicle

• US 6,232,744 B1
• Filed: 02/24/2000
• Issued: 05/15/2001
• Est. Priority Date: 02/24/1999
• Status: Expired due to Term

• Current Assignee: DENSO Corporation, Nippon Soken, Inc. (DENSO Corporation)
• Original Assignee: DENSO Corporation, Nippon Soken, Inc. (DENSO Corporation)
• Inventors: Yamashita, Takashi, Kobayashi, Tetsuya, Kawai, Toshiyuki
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US09/512,275
• Time in Patent Office: 446 Days
• Field of Search: 320/134, 320/136, 320/162, 180/165, 180/65.3, 180/65.4, 180/65.8, 307/10.1, 307/10.7, 361/437
• US Class Current: 320/132
• CPC Class Codes: B60K 6/28 characterised by the electric energy storing means, e.g. batteries or capacitors
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 50/61 by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• 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 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: H02J 7/1415 with a generator driven by a prime mover other than the motor of a vehicle
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y10S 903/907 Electricity storage, e.g. battery, capacitor

Abstract

This invention provides a method of controlling condition of an assembled battery mounted in a self-generation electric vehicle. The method is comprised of the following steps: detecting battery voltage and battery current repeatedly; estimating a constant-power voltage on the basis of the battery voltage and the battery current; setting a target voltage; comparing the constant-power-discharge voltage with the target voltage to provide a difference therebetween; and charging or discharging the battery to reduce the difference when the battery is not operated. The constant-power voltage is set as a function of a remaining capacity of the battery when a preset constant power is charged to or discharged from the battery.

Claims

1. A method of controlling condition of a battery of a self-generation electric vehicle, the method comprising the steps of:

detecting battery voltage and battery current repeatedly;

estimating a constant-power voltage on the basis of said battery voltage and battery current, said constant-power voltage being a function of a remaining capacity of said battery when a preset constant power is charged to or discharged from said battery;

setting a target voltage;

comparing said constant-power voltage with said target voltage to provide a difference therebetween; and

charging or discharging said battery to reduce said difference.

2. The method as claimed in claim 1, further comprising the steps of:

setting a maximum-normal voltage and a minimum-normal voltage between a voltage level of said battery that is fully charged and a voltage level of said battery that is completely discharged; and

stopping said battery current if said constant-power voltage level becomes out of a range between said maximum-normal voltage and said minimum-normal voltage.

3. The method as claimed in claim 2, wherein said target voltage is set at the middle of said maximum-normal voltage and said minimum-normal voltage.

4. The method as claimed in claim 3, further comprising the steps of:

estimating said remaining capacity of said battery by summing up said battery current; and

correcting said estimated remaining capacity to said target remaining capacity when said constant-power-discharge voltage approaches said target voltage.

5. The method as claimed in claim 1, said battery is a nickel-hydrogen battery.

6. The method as claimed in claim 3, further comprising a step of resetting battery condition.

7. The method as claimed in claim 6, wherein said step of resetting battery charge-discharge condition comprises the steps of:

setting a reference condition range that is defined by a preset voltage range and a preset remaining capacity range;

setting an operation condition defined by said constant-power-discharge voltage and said estimated remaining capacity; and

if said operation condition is found to be out of said reference condition range, controlling said battery current to change said operation condition to be out of a boundary defined by said maximum-normal voltage and said minimum-normal voltage and, subsequently controlling said battery current to return said constant-power voltage to said target voltage.

8. The method as claimed in claim 7, wherein if said operation condition is found to be lower than said reference condition range, said step of controlling said battery current comprises a step of charging battery with an amount of power less than the power corresponding to a difference in remaining capacity between said preset remaining capacity and said estimated capacity.

9. A method of controlling condition of a battery of a self-generation electric vehicle, said method comprising the steps of:

detecting battery voltage and battery current;

calculating constant-power voltage of said battery on the basis of said battery voltage and said battery current, said constant-power voltage being a function of a remaining capacity of said battery when a preset constant power is charged to or discharged from said battery;

setting a minimum remaining capacity and a maximum remaining capacity;

setting a target voltage between a voltage level corresponding to said minimum remaining capacity and a voltage level corresponding to said maximum remaining capacity; and

controlling said constant-power voltage to approach said target voltage, wherein said step of controlling comprises the steps of;

charging said battery so that said constant power voltage becomes approximately said maximum normal voltage and subsequently discharging said battery so that said constant power voltage approaches approximately said target voltage, if said constant power voltage is found to be lower than said voltage level corresponding to said minimum normal capacity.

10. The method as claimed in claim 9, wherein said step of controlling said battery current comprises a step of charging said battery so that said remaining capacity does not exceed said maximum normal capacity by a difference between said minimum normal capacity and a remaining capacity corresponding to said constant-power voltage.

11. The method as claimed in claim 9, wherein said battery comprises a nickel-hydrogen battery.

12. A method of controlling condition of a battery of a self-generation electric vehicle, said method comprising the steps of:

detecting battery voltage and battery current;

calculating constant-power voltage of said battery on the basis of said battery voltage and said battery current, said constant-power voltage being a function of a remaining capacity of said battery when a preset constant power is charged to or discharged from said battery;

setting a minimum normal capacity and a maximum normal capacity;

setting a target voltage between a voltage level corresponding to said minimum normal capacity and a voltage level corresponding to said maximum normal capacity; and

controlling said constant-power voltage to approach said target voltage, wherein said step of controlling comprises the steps of;

comparing said constant-power voltage with said voltage level corresponding to said minimum normal capacity; and

fully charging said battery and subsequently to discharging said battery so that said constant-power voltage becomes approximately said voltage level corresponding to said minimum normal capacity and discharge said battery again below said target voltage before said constant-power voltage is controlled to approach said target value, if said constant power voltage is found to be lower than said voltage level corresponding to said minimum normal capacity.

13. The method as claimed in claim 12, wherein

said step of fully charging comprises a plurality of steps of uniform charging.

14. A method of operating an assembled battery of a self-generation electric vehicle, said method comprising the steps of:

detecting voltage and current of said battery;

calculating a constant-power voltage of said battery at its discharging a maximum normal power on the basis of said detected voltage and current, said constant-power voltage being a function of a remaining capacity of said battery when a preset constant power is charged to or discharged from said battery;

;

setting a minimum normal capacity;

setting a minimum normal voltage that correspond to said minimums normal remaining capacity; and

reducing power to be discharged from said battery if said constant-power voltage approaches said minimum normal voltage.

15. The method as claimed in claim 14, wherein said minimum normal voltage is set to correspond to an SOC ratio between 5-20%.

16. The method as claimed in claim 14, further comprising the steps of:

comparing said constant-power voltage with said minimum normal voltage; and

fully charging said battery before said constant-power voltage is controlled to approach said target value, if said constant power voltage is found to be lower than said minimum normal voltage, wherein

said step of fully charging comprises a plurality of steps of uniform charging.