Method of detecting residual capacity of battery for use on electric vehicle

• US 5,614,804 A
• Filed: 12/27/1994
• Issued: 03/25/1997
• Est. Priority Date: 12/27/1993
• Status: Expired due to Fees

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Kayano, Morio, Watanabe, Kazunori
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Law, Patrick B.
• Application Number:
  US08/364,654
• Time in Patent Office: 819 Days
• Field of Search: 320/13, 320/48, 320/43, 324/426, 324/427, 324/428, 324/429, 324/431, 324/432, 324/433
• US Class Current: 320/134
• CPC Class Codes: G01R 31/3647 for determining the ability of a battery to perform a critical function, e.g. cranking
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• 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: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10S 320/21 State of charge of battery

Abstract

Based on the difference between a battery voltage immediately after the battery is left to stand and the battery voltage upon elapse of the period of time after the battery has been left to stand, it is determined whether the battery has been in a charge mode or a discharge mode immediately before the battery is left to stand. If the battery has been in the charge mode, then a residual capacity is determined from the battery voltage at a predetermined time. When the battery is being discharged, then a maximum battery output is calculated based on a discharge current. If the residual capacity of the battery is determined as being virtually zero based on the maximum output, then the residual capacity is corrected with a corrective capacity for correcting for a change in the residual capacity due to a degradation of the battery, thus determining the residual capacity of the required charge quantity is calculated from the detected residual capacity and a stored rated capacity of the battery, and a temperature corrective coefficient for correcting the required charge quantity is determined. The residual capacity of the battery is determined based on an actual charge quantity indicative of an integrated average charging current at predetermined periods and the charging efficiency based on battery voltage during charging.

Claims

1. A method of detecting the residual capacity of a battery for energizing an electric motor to propel an electric vehicle while the battery is being discharged, based on an initial value of the residual capacity of the battery upon a transition of the battery to a discharging condition and a discharge current at predetermined periods from said battery after said transition, said method comprising the steps of:

(a) calculating a maximum output which can be produced from said battery based on the discharge current from said battery and a battery voltage while the battery is being discharged;

(b) calculating a maximum output density by dividing said maximum output by a weight of said battery and determining whether the residual capacity of the battery is virtually zero or not based on the maximum output density;

(c) calculating a degradation error corrective capacity for correcting for a change in the residual capacity due to a degradation of the battery when the residual capacity of said battery is virtually zero; and

(d) correcting the residual capacity of said battery which has been calculated based on the initial value of the residual capacity of the battery and the discharge current from said battery, with said degradation error corrective capacity, for thereby calculating the residual capacity of said battery while the battery is being discharged.

3. A method according to claim 1, wherein said step (c) includes the step of calculating said degradation error corrective capacity based on whether an integration error of the discharge current from said battery has been canceled or not.

5. A method according to claim 1, wherein said step (d) includes the steps of calculating a discharge current corrective capacity to correct for a change in the residual capacity due to an average discharge current, and correcting the residual capacity of said battery with said discharge current corrective capacity.

7. A method according to claim 1, wherein said step (d) includes the steps of calculating a temperature corrective capacity to correct for a change in the residual capacity due to a battery temperature based on said battery temperature, and correcting the residual capacity of said battery with said temperature corrective capacity.

2. A method of detecting the residual capacity of a battery for energizing an electric motor to propel an electric vehicle while the battery is being discharged, based on an initial value of the residual capacity of the battery upon a transition of the battery to a discharging condition and a discharge current at predetermined periods from said battery after said transition, said method comprising the steps of:

(a) detecting a battery voltage at predetermined periods while the battery is being discharged;

(b) determining whether the detected battery voltage while the battery is being discharged is lower than a preset value or not;

(c) determining the residual capacity of the battery as being virtually zero when the detected battery voltage while the battery is being discharged is determined as being lower than said preset value, to calculate a degradation error corrective capacity for correcting for a change in the residual capacity due to a degradation of the battery; and

(d) correcting the residual capacity of said battery which has been calculated based on the initial value of the residual capacity of the battery and the discharge current from said battery, with said degradation error corrective capacity, for thereby calculating the residual capacity of said battery while the battery is being discharged.

4. A method according to claim 2, wherein said step (c) includes the step of calculating said degradation error corrective capacity based on whether a integration error of the discharge current from said battery has been canceled or not.

6. A method according to claim 2, wherein said step (d) includes the steps of calculating a discharge current corrective capacity to correct for a change in the residual capacity due to an average discharge current, and correcting the residual capacity of said battery with said discharge current corrective capacity.

8. A method of detecting the residual capacity of a battery for energizing an electric motor to propel an electric vehicle upon a transition of the battery to a charging condition, comprising the steps of:

(a) detecting a residual capacity of the battery based on a battery voltage at the time the battery starts being charged, and calculating a required charge quantity from the detected residual capacity and a stored rated capacity of the battery;

(b) detecting a battery temperature, and determining a temperature corrective coefficient to correct said required charge quantity with the battery temperature, based on said battery temperature;

(c) calculating a target charge quantity at said battery temperature from said required charge quantity and said temperature corrective coefficient;

(d) determining a charging efficiency representative of a proportion of a charging current supplied to the battery which is converted into a residual capacity, based on the battery voltage while the battery is being charged; and

(e) determining an actual charge quantity from an integrated charge quantity indicative of an integrated average charging current and said charging efficiency.

9. A method according to claim 8, further comprising the step of outputting a signal to stop supplying the charging current to the battery when the actual charge quantity has reached at least one of either said target charge quantity or a fully charged capacity of the battery.

10. A method according to claim 9, further comprising the step of setting a fully charged flag to provide information indicating that the residual capacity of the battery has reached said target charge quantity when a change in the battery voltage is lower than a preset value or a change in the battery temperature is higher than a preset value.

11. A method of detecting the residual capacity of a battery for energizing an electric motor to propel an electric vehicle when the battery is left to stand after the battery has been either charged or discharged, comprising the steps of:

(a) detecting a first battery voltage immediately after the battery is left to stand and a second battery voltage upon elapse of a predetermined time after the battery is left to stand, and calculating the difference between said first battery voltage and said second battery voltage;

(b) determining whether the battery has been in a charging condition or a discharging condition immediately before the battery is left to stand, based on said calculated difference;

(c) reading a third battery voltage corresponding to said second battery voltage from first memory means which stores said third battery voltage as a voltage which is expected to be in a stable state of the battery voltage in a manner to correspond to said second battery voltage, when the battery is determined as having been in the charging condition; and

(d) reading a residual capacity of the battery corresponding to the read third battery voltage from second memory means which stores said residual capacity in a manner to correspond to said third battery voltage.

13. A method according to claim 11, wherein said step (d) includes a step of correcting the residual capacity of the battery with a corrective value for correcting a battery capacity based on at least one of a degradation of the battery and a corrective value for correcting a battery capacity based on an integration error which occurs when the residual capacity is calculated while the battery is in the charging condition, thereby producing a corrected residual capacity.

15. A method according to claim 13, wherein said step of correcting the residual capacity of the battery includes a step of correcting the residual capacity of the battery with a battery temperature.

12. A method of detecting the residual capacity of a battery for energizing an electric motor to propel an electric vehicle when the battery is left to stand after the battery has been either charged or discharged, comprising the steps of:

(a) detecting a first battery voltage immediately after the battery is left to stand and a second battery voltage upon elapse of a predetermined time after the battery is left to stand, and calculating the difference between said first battery voltage and said second battery voltage;

(b) determining whether the battery has been in a charging condition or a discharging condition immediately before the battery is left to stand, based on said calculated difference; and

(c) reading a residual capacity of the battery corresponding to said second battery voltage from memory means which stores said residual capacity in a manner to correspond to said second battery voltage, when the battery is determined as having been in the discharging condition immediately before the battery is left to stand.

14. A method according to claim 12, wherein said step (c) includes a step of correcting the residual capacity of the battery with a corrective value for correcting a battery capacity based on at least one of degradation of the battery and a corrective value for correcting a battery capacity based on an integration error which occurs when the residual capacity is calculated while the battery is in the charged condition, thereby producing a corrected residual capacity.

16. A method according to claim 14, wherein said step of correcting the residual capacity of the battery includes a step of correcting the residual capacity of the battery with a battery temperature.

17. A method of detecting the residual capacity of a battery for energizing an electric motor to propel an electric vehicle while the battery is being discharged, based on an initial value of the residual capacity of the battery upon a transition of the battery to a discharging condition and a discharge current at predetermined periods from said battery after said transition, said method comprising the steps of:

(a) calculating a maximum output which can be produced from said battery based on the discharge current from said battery and a battery voltage while the battery is being discharged;

(b) calculating a maximum output density by dividing said maximum output by a weight of said battery and determining whether the residual capacity of the battery is virtually zero or not based on the maximum output density;

(c) calculating an integration error corrective capacity for correcting for an integration error of the discharged current from said battery, when the residual capacity of said battery is virtually zero; and

(d) correcting the residual capacity of said battery which has been calculated based on the initial value of the residual capacity of the battery and the discharge current from said battery, with said integration error corrective capacity, for thereby calculating the residual capacity of said battery while the battery is being discharged.

18. A method according to claim 17, wherein said step (c) includes the step of calculating said integration error corrective capacity based on whether an integration error of the discharge current from said battery has been cancelled or not.

19. A method according to claim 17, wherein said step (d) includes the steps of calculating a discharge current corrective capacity to correct for a change in the residual capacity due to an average discharge current, and correcting the residual capacity of said battery with said discharge current corrective capacity.

20. A method according to claim 17, wherein said step (d) includes the steps of calculating a temperature corrective capacity to correct for a change in the residual capacity due to a battery temperature based on said battery temperature, and correcting the residual capacity of said battery with said temperature corrective capacity.

21. A method according to claim 17 further including a step of calculating a degradation error corrective capacity for correcting for a change in the residual capacity of the battery due to degradation of the battery when the residual capacity of the battery is virtually zero, a step of determining when an error in the residual capacity of the battery is caused by said degradation error corrective capacity, and then cancelling the calculated integration error corrective capacity and correcting the residual capacity of the battery with said degradation error corrective capacity.

22. A method according to claim 17 further including a step of calculating a degradation error corrective capacity for correcting for a change in the residual capacity of the battery due to degradation of the battery when the residual capacity of the battery is virtually zero, a step of determining when an error in the residual capacity of the battery is caused by said integration error corrective capacity, and then cancelling the calculated degradation error corrective capacity and correcting the residual capacity of the battery with said integration error corrective capacity.

23. A method according to claim 17 further including a step of calculating a degradation error corrective capacity for correcting for a change in the residual capacity of the battery due to degradation of the battery when the residual capacity of the battery is virtually zero, and selectively correcting the residual capacity of the battery with said degradation error corrective capacity and said integration error corrective capacity.

24. A method of detecting the residual capacity of a battery for energizing an electric motor to propel an electric vehicle while the battery is being discharged, based on an initial value of the residual capacity of the battery upon a transition of the battery to a discharging condition and a discharge current at predetermined periods from said battery after said transition, said method comprising the steps of:

(a) detecting a battery voltage at predetermined periods while the battery is being discharged;

(b) determining whether the detected battery voltage while the battery is being discharged is lower than a preset value or not;

(c) determining the residual capacity of the battery as being virtually zero when the detected battery voltage while the battery is being discharged is determined as being lower than said preset value, to calculate an integration error corrective capacity for correcting for an integration error of the discharge current from said battery; and

(d) correcting the residual capacity of said battery which has been calculated based on the initial value of the residual capacity of the battery and the discharge current from said battery, with said integration error corrective capacity, for thereby calculating the residual capacity of said battery while the battery is being discharged.

25. A method according to claim 24, wherein said step (c) includes the step of calculating said integration error corrective capacity based on whether an integration error of the discharge current from said battery has been cancelled or not.

26. A method according to claim 24, wherein said step (d) includes the steps of calculating a discharge current corrective capacity to correct for a change in the residual capacity due to an average discharge current, and correcting the residual capacity of said battery with said discharge current corrective capacity.