Method for charging and discharging battery based on charging capacity

• US 6,756,767 B2
• Filed: 10/22/2002
• Issued: 06/29/2004
• Est. Priority Date: 10/23/2001
• Status: Active Grant

• Current Assignee: Burcon NutraScience (MB) Corp., HTC Corporation
• Original Assignee: NEC Corporation
• Inventors: Kawai, Toshimichi
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US10/274,866
• Publication Number:
  US 20030076074A1
• Time in Patent Office: 616 Days
• Field of Search: 320/124, 320/125, 320/130, 320/135, 320/150, 320/160
• US Class Current: 320/125
• CPC Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

A nonaqueous-electrolyte secondary battery charging/discharging method that provides a prolonged cyclic life. In the charging/discharging method, a secondary battery is continuously charged unconditionally until a charging capacity exceeds 20% of a full charging capacity. The charging is completed when the charging capacity exceeds 70% of a full charging capacity. A maintenance charging/discharging operation is performed to avoid the full charging capacity being in an error state when dV/dt exceeds a specified value “a” before a charging current exceeds 70% of the full charging capacity. Likewise, the maintenance charging/discharging operation is performed to avoid the full charging capacity being in an error state when dT/dt exceeds a specified value “b” before a charging current exceeds 70% of the charging capacity.

Claims

1. An apparatus for charging and discharging a nonaqueous electrolyte secondary battery, said apparatus comprising:

a first switch for connecting or disconnecting a secondary battery and a charging power source;

a second switch for connecting or disconnecting the secondary battery and a load;

a full charging capacity memory for storing a full charging capacity value of the secondary battery;

means for detecting a charging capacity of the secondary battery during charging, for connecting the secondary battery and the charging power source by controlling said first switch when the detected charging capacity is less than a first predetermined ratio of the full charging capacity, and for disconnecting the secondary battery and the charging power source by controlling said first switch when the detected charging capacity is a second predetermined ratio or more of the full charging capacity;

means for calculating a voltage variation dV/dt of the secondary battery during charging;

means for calculating a temperature variation dT/dt of the secondary battery during charging;

means for determining whether or not the voltage variation dV/dt exceeds a first specified value, determining whether or not the temperature variation dT/dt exceeds a second specified value, detecting whether or not the secondary battery is in a full charging state during charging based on the voltage and the temperature of the secondary battery during charging when at least one of the voltage variation dV/dt and the temperature variation dT/dt exceeds the associated specified value, and controlling said second switch when the secondary battery is in a full charging state, thus connecting the secondary battery and the load to permit discharging of the secondary battery; and

means for detecting completion of discharging of the secondary battery, computing a full charging capacity based on a discharging current when discharging is completed, and updating the full charging capacity value stored in said full charging capacity memory.

2. The apparatus defined in claim 1, wherein the secondary battery comprises a nickel-hydrogen battery.

3. A method for charging and discharging a nonaqueous electrolyte secondary battery, comprising:

calculating a voltage variation dV/dt of said secondary battery during charging;

calculating a temperature variation dT/dt of said secondary battery during charging;

detecting a charging capacity of said secondary battery during charging and then, when the detected charging capacity is less than a first predetermined ratio of a stored full charging capacity, determining whether or not a detected voltage variation dV/dt exceeds a first previously specified value and determining whether or not a detected temperature variation dT/dt exceeds a second previously specified value;

when at least one of said detected voltage variation dV/dt and said detected temperature variation dT/dt exceeds the associated previously specified value, detecting whether or not said secondary battery during charging is in a full charging state based on the voltage and the temperature of said secondary battery during charging;

discharging said secondary battery when a full charging state is detected;

detecting completion of discharging of said secondary battery;

computing, upon completion of discharging, a full charging capacity based on a discharging current of said secondary battery, and updating said stored full charging capacity; and

completing charging of said secondary battery when said stored charging capacity is a predetermined ratio or more of a stored full charging capacity.

4. The method defined in claim 3, further comprising charging said secondary battery unconditionally in initial charging thereof until a current charging capacity reaches to 20% of said stored full charging capacity value.

5. A method for charging and discharging a nonaqueous electrolyte secondary battery, comprising:

re-charging a battery, which is discharged, to less than a full charging amount of said battery;

performing a maintenance charging/discharging operation to avoid the possibility of an erroneous full charging capacity when dV/dt exceeds a specific value “

a”

before said charging capacity exceeds 70% of said full charging capacity; and

supplying a re-charging amount to a load.

6. The method defined in claim 5, wherein said re-charging amount is set to 70% of said full charging amount.

7. The method defined in claim 5, further comprising continuously charging said battery unconditionally in initial charging thereof until a current charging capacity reaches 20% of a reference charging amount.

8. The method defined in claim 5, wherein said battery comprises a nickel-hydrogen battery.

11. The method defined in claim 5, further comprising performing a maintenance charging/discharging operation to avoid the possibility of an erroneous full charging capacity when dT/dt exceeds a specific value “

b”

before said charging capacity exceeds 70% of said full charging capacity.

9. A method for charging and discharging a nonaqueous electrolyte secondary battery, comprising:

continuously charging said secondary battery unconditionally until a charging capacity exceeds 20% of a full charging capacity to avoid the temperature and the voltage of said battery becoming unstable in initial charging;

ending the charging operation when said charging capacity exceeds 70% of said full charging capacity;

performing a maintenance charging/discharging operation to avoid the possibility of an erroneous full charging capacity when dV/dt exceeds a specific value “

a”

before said charging capacity exceeds 70% of said full charging capacity; and

performing a maintenance charging/discharging operation to avoid the possibility of an erroneous full charging capacity when dT/dt exceeds a specific value “

b”

before said charging capacity exceeds 70% of said full charging capacity.

10. The method defined in claim 9, further comprising, with a controller:

acquiring a voltage of said battery from a voltage measuring section and a temperature of said battery from a temperature measuring section and thus detecting full charging;

when full charging is detected, turning on a switch and supplying power from said battery to a load;

simultaneously acquiring a discharging current from a charge/discharge current measuring section and integrating a discharging capacity; and

simultaneously acquiring a battery voltage of said battery from a voltage measuring section, ending discharging and capacity integration by turning off the switch when the battery voltage becomes empty, and updating said full charging capacity.

12. A method for charging and discharging a nonaqueous electrolyte secondary battery, comprising:

re-charging a battery, which is discharged, to less than a full charging amount of said battery;

performing a maintenance charging/discharging operation to avoid the possibility of an erroneous full charging capacity when dT/dt exceeds a specific value “

b”

before said charging capacity exceeds 70% of said full charging capacity; and

supplying a re-charging amount to a load.

13. An apparatus for charging and discharging a battery, said apparatus comprising:

a first switch for connecting or disconnecting a battery and a charging power source;

a second switch for connecting or disconnecting the battery and a load;

a full charging capacity memory for storing a full charging capacity value of the battery; and

a controller, wherein;

said controller is responsive to the charging capacity of the battery during charging being less than a first predetermined ratio of the full charging capacity, for controlling said first switch to connect the battery and the charging power source, and responsive to the charging capacity of the battery being at least a second predetermined ratio of the full charging capacity for controlling said first switch to disconnect the battery and the charging power source;

said controller is further responsive to at least one of the voltage variation dV/dt exceeding a first specified value and the temperature variation dT/dt exceeding a second associated specified value for detecting whether or not the battery is in a full charging state during charging based on the voltage and the temperature of the battery;

said controller is further responsive to the battery being in a full charging state for controlling said second switch to connect the battery and the load; and

said controller is further responsive to discharging of the battery being completed for computing a full charging capacity based on a discharging current.

14. The apparatus defined in claim 13, wherein said controller is further responsive to discharging of the battery being completed for updating the full charging capacity value stored in said full charging capacity memory.

15. A method for charging and discharging a battery, said method comprising:

calculating a voltage variation dV/dt of said battery during charging;

calculating a temperature variation dT/dt of said battery during charging;

when said battery is completely discharged, computing a full charging capacity based on a discharging current of said battery

detecting a charging capacity of said battery;

when the detected charging capacity is less than a first predetermined ratio of the full charging capacity, charging the battery, determining whether or not a detected voltage variation dV/dt exceeds a first previously specified value, and determining whether or not a detected temperature variation dT/dt exceeds a second previously specified value;

when at least one of said detected voltage variation dV/dt and said detected temperature variation dT/dt exceeds the associated previously specified value, detecting whether or not said battery is fully charged based on the voltage and the temperature of said battery.

16. The method defined in claim 15, further comprising storing the full charging capacity.

17. A method for charging and discharging a battery, comprising:

re-charging a battery, which is discharged, to less than a full charging amount of said battery;

performing a maintenance charging/discharging operation when dV/dt exceeds a specific value “

a”

before said charging capacity exceeds 70% of said full charging capacity; and

supplying a re-charging amount to a load.

18. The method defined in claim 17, further comprising performing a maintenance charging/discharging operation when dT/dt exceeds a specific value “

b”

before said charging capacity exceeds 70% of said full charging capacity.

19. A method for charging and discharging a battery, comprising:

charging said battery until a charging capacity exceeds 20% of a full charging capacity;

ending the charging operation when said charging capacity exceeds 70% of said full charging capacity;

performing a maintenance charging/discharging operation when dV/dt exceeds a specific value “

a”

before said charging capacity exceeds 70% of said full charging capacity; and

performing a maintenance charging/discharging operation when dT/dt exceeds a specific value “

b”

before said charging capacity exceeds 70% of said full charging capacity.

20. The method defined in claim 19, further comprising:

acquiring a voltage of said battery so as to detect full charging;

when full charging is detected, supplying power from said battery to a load;

acquiring a discharging current of said battery;

integrating a discharging capacity; and

when the battery voltage becomes empty, ending discharging.

21. A method for charging and discharging a battery, comprising:

re-charging a battery, which is discharged, to less than a full charging amount of said battery;

performing a maintenance charging/discharging operation when dT/dt exceeds a specified value “

b”

said charging capacity exceeds 70% of said full charging capacity; and

supplying a re-charging amount to a load.