Battery control method for hybrid vehicle

• US 6,608,482 B2
• Filed: 02/12/2002
• Issued: 08/19/2003
• Est. Priority Date: 02/14/2001
• Status: Expired due to Term

• Current Assignee: DENSO Corporation, Nippon Soken, Inc.
• Original Assignee: DENSO Corporation, Nippon Soken, Inc.
• Inventors: Kobayashi, Tetsuya, Sakai, Shoji
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US10/073,026
• Publication Number:
  US 20020113595A1
• Time in Patent Office: 553 Days
• Field of Search: 324/426, 324/427, 324/429, 324/430, 324/433, 320/132, 320/149, 320/DIG.21
• US Class Current: 324/426
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/006 on road vehicles, e.g. automobiles or trucks testing of ignition installations peculiar to internal combustion engines F02P17/00
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3828 using current integration
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/0049 Detection of fully charged condition
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/14 for charging batteries from dynamo-electric generators driven at varying speed, e.g. on 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: Y10S 903/903 having energy storing means, e.g. battery, capacitor

Abstract

A battery control system is provided which charges or discharges a storage battery installed in a hybrid vehicle to bring a state-of-charge of the storage battery into agreement with a target one. The system determines whether the state-of-charge lies within a given narrower range defined around the target state-of-charge and corrects the state-of-charge based on an open-circuit voltage of the battery when the state-of-charge lies within the given narrower range, thereby eliminating a cumulative error in calculating the state-of-charge of the battery caused by a variation in charge/discharge efficiency of the battery.

Claims

1. A battery control method of charging or discharging a storage battery installed in a hybrid vehicle to bring a calculated state-of-charge of the storage battery into agreement with a target state-of-charge, comprising the steps of:

determining an open-circuit voltage of the storage battery installed in the hybrid vehicle using a voltage developed across the storage battery and a current flowing into or out of the storage battery in a given voltage-to-current relation of the storage battery;

totalizing an amount of current flowing into or out of the storage battery in a cycle to calculate a state-of-charge of the storage battery;

comparing the open-circuit voltage with a reference voltage which corresponds to a reference state-of-charge predetermined in a state-of-charge correction range defined around a target state-of-charge of the storage battery; and

correcting the state-of-charge of the storage battery when the state-of-charge lies within the state-of-charge correction range by brining the state-of-charge close to the reference state-of-charge based on a result of comparison between the open-circuit voltage and the reference voltage.

2. A battery control method as set forth in claim 1, further comprising the step of prohibiting said correction step when it is determined that a discharge-caused polarization of the storage battery becomes greater than a given value.

3. A battery control method as set forth in claim 1, wherein said correcting step increases the state-of-charge when the open-circuit voltage is greater than the reference voltage and decreases the state-of-charge when the open-circuit voltage is smaller than the reference voltage.

4. A battery control method as set forth in claim 1, further comprising the step of prohibiting said correction step for a preselected period of time when the storage battery has been discharged so that the state-of-charge decreases by a given amount out of the state-of-charge correction range.

5. A battery control method as set forth in claim 1, further comprising the step of determining whether the open-circuit voltage has exceeded a high open-circuit voltage higher than said reference voltage or not and the step of correcting said reference voltage by a preselected value when it is determined that the open-circuit voltage has exceeded the high open-circuit voltage.

6. A battery control method as set forth in claim 1, wherein instead of the open-circuit voltage, a voltage developed across terminals of the storage battery when the storage battery is charged or discharged with a given current is used.

7. A battery control method as set forth in claim 1, wherein said correction step changes the state-of-charge of the storage battery by a preselected correction value in a cycle when the state-of-charge lies within the state-of-charge correction range, and further comprising the step of determining that the storage battery has undergone a drop in state-of-charge due to self discharge when a cumulative value of the correction value exceeds a given value, and the open-circuit voltage remains below a given voltage lower than said reference voltage.

8. A battery control method of charging or discharging a storage battery installed in a hybrid vehicle to bring a calculated state-of-charge of the storage battery into agreement with a target state-of-charge, comprising the steps of:

determining an open-circuit voltage of the storage battery installed in the hybrid vehicle using a voltage developed across the storage battery and a current flowing into or out of the storage battery in a given voltage-to-current relation of the storage battery;

totalizing an amount of current flowing into or out of the storage battery in a cycle to calculate a state-of-charge of the storage battery;

determining whether the storage battery has been charged so that the state-of-charge of the storage battery increases out of a preselected state-of-charge range defined around the target state-of-charge or not;

determining whether the open-circuit voltage has reached a high open-circuit voltage higher than a reference voltage which corresponds to a reference state-of-charge predetermined in the state-of-charge range or not; and

discharging the storage battery until the state-of-charge reaches a given value smaller than the preselected state-of-charge range by a given amount when it is determined that the open-circuit voltage has reached the high open-circuit voltage.

9. A battery control method as set forth in claim 8, further comprising the step of prohibiting the storage battery from being charged when it is determined that the open-circuit voltage has reached the high open-circuit voltage.

10. A battery control method as set forth in claim 8, further comprising the step of, when the storage battery has been charged so that the state-of-charge is greater than a high state-of-charge higher than the preselected state-of-charge range, determining a maximum value of the state-of-charge calculated in a cycle and the step of discharging the storage battery by a given amount determined as a function of the maximum value of the state-of-charge after the storage battery is discharged, and the state-of-charge falls within the preselected state-of-charge range.

11. A battery control methods as set forth in claim 10, wherein the maximum value is reset each time the storage battery is discharged by said given amount.

12. A battery control method as set forth in claim 8, further comprising the step of charging the storage battery until the open-circuit voltage reaches the high open-circuit voltage when the open-circuit voltage remains below the high open-circuit voltage for a given period of time.

13. A battery control method as set forth in claim 8, wherein instead of the open-circuit voltage, a voltage developed across terminals of the storage battery when the storage battery is charged or discharged with a given current is used.

14. A battery control method of charging or discharging a storage battery installed in a hybrid vehicle to bring a calculated state-of-charge of the storage battery into agreement with a target state-of-charge, comprising the steps of:

totalizing an amount of current flowing into or out of the storage battery in a cycle to calculate a state-of-charge of the storage battery;

determining whether the storage battery has been discharged until the state-of-charge of the storage battery decreases by a given amount out of a preselected state-of-charge range defined around the target state-of-charge or not; and

charging the storage battery until the state-of-charge reaches a given value higher than the preselected state-of-charge range by a predetermined amount when it is determined that the storage battery has been discharged until the state-of-charge of the storage battery decreases by the given amount.

15. A battery control method as set forth in claim 14, further comprising the step of prohibiting the storage battery from being discharged further when it is determined that the storage battery has been discharged until the state-of-charge of the storage battery decreases by the given amount.

16. A battery control method as set forth in claim 15, further comprising the steps of:

determining an open-circuit voltage of the storage battery using a voltage developed across the storage battery and a current flowing into or out of the storage battery in a given voltage-to-current relation of the storage battery;

comparing the open-circuit voltage with a reference voltage which corresponds to a reference state-of-charge predetermined in the preselected state-of-charge range;

correcting the state-of-charge of the storage battery only when the state-of-charge lies within the preselected state-of-charge range by brining the state-of-charge close to the reference state-of-charge based on a result of comparison between the open-circuit voltage and the reference voltage; and

prohibiting said correction step for a preselected period of time when the storage battery has been discharged so that the state-of-charge decreases by a given amount out of the preselected state-of-charge range.

17. A battery control method as set forth in claim 14, wherein instead of the open-circuit voltage, a voltage developed across terminals of the storage battery when the storage battery is charged or discharged with a given current is used.

18. A battery control method of charging or discharging a storage battery installed in a hybrid vehicle to bring a calculated state-of-charge of the storage battery into agreement with a target state-of-charge, comprising the steps of:

determining an open-circuit voltage of the storage battery installed in the hybrid vehicle using a voltage developed across the storage battery and a current flowing into or out of the storage battery in a given voltage-to-current relation of the storage battery;

totalizing an amount of current flowing into or out of the storage battery in a cycle to calculate a state-of-charge of the storage battery;

determining whether the storage battery has been charged so that the state-of-charge of the storage battery increases out of a preselected state-of-charge range defined around the target state-of-charge or not;

determining whether the open-circuit voltage has exceeded a high open-circuit voltage higher than a reference voltage which corresponds to a reference state-of-charge predetermined in the preselected state-of-charge range or not; and

correcting said reference voltage by a preselected value when it is determined that the open-circuit voltage has exceeded the high open-circuit voltage.

19. A battery control method as set forth in claim 18, further comprising the step of determining whether the state-of-charge has exceeded a high state-of-charge higher than the preselected state-of-charge range or not, and wherein said correction step corrects said reference voltage when it is determined that the state-of-charge has exceeded the high state-of-charge.

20. A battery control method as set forth in claim 18, further comprising the step of charging the storage battery until the open-circuit voltage reaches the high open-circuit voltage when the open-circuit voltage remains below the high open-circuit voltage for a given period of time.

21. A battery control method as set forth in claim 18, wherein instead of the open-circuit voltage, a voltage developed across terminals of the storage battery when the storage battery is charged or discharged with a given current is used.