Method for charging and discharging a nonaqueous electrolyte secondary battery

• US 20030076074A1
• Filed: 10/22/2002
• Published: 04/24/2003
• Est. Priority Date: 10/23/2001
• Status: Active Grant

• Current Assignee: Burcon NutraScience (MB) Corp., HTC Corporation
• Original Assignee: NEC Corporation
• Inventors: Kawai, Toshimichi
• Granted Patent: US 6,756,767 B2
• Time in Patent Office: Days
• US Class Current: 320/136
• 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 is provided that has a prolonged cyclic life. In the charging/discharging method, a secondary battery is continuously charging a battery unconditionally until a charging capacity exceeds 20% of a full charging capacity because the battery voltage and the battery temperature are unstable in an initial charging stage (step S11). The charging is completed when the charging capacity exceeds 70% of a full charging capacity (step S12). A maintenance charging/discharging operation is performed because the full charging capacity is in an error state if dV/dt exceeds a specified value “a” before a charging current exceeds 70% of the full charging capacity (step S13). A maintenance charging/discharging operation performed because the full charging capacity is in an error state if dT/dt exceeds a specified value “b” before a charging current exceeds 70% of the full charging capacity (step S14).

Claims

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

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

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

a full charging capacity memory for storing a full charging capacity of said secondary battery;

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

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

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

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

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

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

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

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 charging capacity detected is less than a predetermined ratio of a full charging capacity stored, deciding whether or not at least one of a detected voltage variation dV/dt and a detected temperature variation dT/dt exceeds a previously specified value;

when at least one of said detected voltage variation dV/dt and said detected temperature variation dT/dt exceeds the 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 a stored full charging capacity.

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

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

re-charging a battery, which is cyclically charged and discharged, periodically and to less than a full charging amount of said battery; 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 the step of continuously charging said battery unconditionally in initial charging thereof until a current charging capacity reaches to 20% of a reference charging amount.

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

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

continuously charging said secondary battery unconditionally until a charging capacity exceeds 20% of a full charging capacity because the temperature and the voltage of said battery become 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 because there is 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 because there is 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, the steps of, by means of 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;

turning, when a full charging is detected, 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.