Method for charging secondary battery and charger used therefor

• US 5,576,608 A
• Filed: 05/03/1994
• Issued: 11/19/1996
• Est. Priority Date: 05/14/1993
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Akiho, Hitoshi, Nagai, Tamimi
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Toatley, Gregory J.
• Application Number:
  US08/237,299
• Time in Patent Office: 931 Days
• Field of Search: 320/19, 320/20, 320/30, 320/31
• US Class Current: 320/159
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: H02J 7/0024 Parallel/serial switching of connection of batteries to charge or load circuit
• CPC Class Codes: H02J 7/0071 with a programmable schedule
• CPC Class Codes: H02J 7/007182 in response to battery voltage

Abstract

A secondary battery charging method and a charger used therefor, in which the method uses a constant current and a constant voltage such that the secondary battery is first charged with the constant current until the terminal voltage of the battery becomes a reference voltage higher than the full charging voltage for the battery and then further charged with the constant voltage which is equal to the full charging voltage. These two charging operations are switched by using various kinds of detection and control circuits so that the secondary battery is properly charged in a short time. Further, the charger of the present invention is provided with a circuit for charging a plurality of battery cells simultaneously or separately.

Claims

1. A method for charging a secondary battery wherein the secondary battery is charged with a constant current and then additionally charged with a constant voltage equal to a full charging voltage, said method comprising the steps of:

detecting a voltage across said secondary battery while said secondary battery is being charged with said constant current;

starting a timer when said detected voltage is equal to said full charging voltage;

charging said secondary battery with said constant current until a predetermined period of time lapses in the timer from the time when said detected voltage becomes equal to said full charging voltage; and

further charging said secondary battery with said constant voltage after a lapse of said predetermined period of time.

2. A method for charging a secondary battery wherein a voltage applied to the secondary battery is controlled by a constant voltage source supplying to the secondary battery a constant voltage equal to a full charging voltage and said secondary battery is charged with a current supplied from a constant current source, said method comprising the steps of:

detecting an amount of decrease in the current supplied to said secondary battery when the voltage applied to said secondary battery is controlled by said constant voltage source;

comparing the detected amount of decrease in the current with a predetermined reference value;

continuing a charging operation when the comparison indicates the detected amount of decrease in the current exceeds the reference value; and

charging said secondary battery with said constant current for a predetermined period of time when the comparison indicates the detected amount of decrease in the current is less than the reference value.

3. A charger for performing a charging operation on a secondary battery in such a manner that the secondary battery is first charged with a constant current supplied from a constant current source and then charged with a constant voltage supplied from a constant voltage source equal to a full charging voltage, said charger comprising:

detecting means connected to said secondary battery for detecting a voltage across said secondary battery;

means for determining when the detected voltage is higher than a predetermined reference voltage higher than said full charging voltage; and

switching means connected to said detecting means, said current source and said voltage source for switching from a constant current charging operation to a constant voltage charging operation when the voltage detected across said secondary battery by said detecting means is determined to equal said predetermined reference voltage higher than said full charging voltage.

4. A charger for performing a charging operation on a secondary battery in such a manner that the secondary battery is first charged with a constant current supplied from a constant current source and is then charged with a constant voltage supplied from a constant voltage source equal to a full charging voltage, said charger comprising:

detecting means connected to said secondary battery for detecting a voltage across said secondary battery while said secondary battery is being charged with said constant current;

means for determining when the detected voltage is equal to said full charging voltage;

timing means connected to said means for for determining for measuring a predetermined period of time from a time when the voltage detected by said detecting means is determined to be equal to said full charging voltage; and

switching means connected to said timing means, said current source and said voltage source for switching the charging operation through said constant current source to the charging operation through said constant voltage source after said predetermined period of time.

5. A method for performing a charging operation on a secondary battery, comprising the steps of:

charging the secondary battery with a constant current;

detecting a charging voltage across said secondary battery;

comparing the detected voltage to first and second predetermined reference values;

supplying said constant current intermittently to said secondary battery when said charging voltage reaches the first predetermined reference voltage; and

stopping the charging operation during an interval in which said constant current is not supplied to said secondary battery when said charging voltage becomes equal to the second predetermined reference voltage.

6. A method for performing a charging operation on a secondary battery, comprising the steps of:

charging said secondary battery with a constant current;

detecting a charging voltage across said secondary battery;

supplying said constant current intermittently to said secondary battery when said charging voltage reaches a predetermined reference voltage; and

stopping the charging operation after a lapse of a predetermined period of time from the time during an interval in which said constant current is not supplied to said secondary battery when said charging voltage reaches a second predetermined reference voltage.

7. A charger for performing a charging operation on a secondary battery, comprising:

constant current means connected to said secondary battery for charging said secondary battery with a constant current;

constant voltage means connected to said secondary battery for charging said secondary battery with a constant voltage;

detecting means connected to said secondary battery for detecting said charging voltage across said secondary battery;

means for comparing the detected charging voltage with a predetermined value;

switching means connected to said constant current means and said constant voltage means for switching a charging operation with said constant current to a charging operation with said constant voltage after continuing said constant current charging operation for a predetermined period of time from the time when said means for comparing determines said charging voltage reaches the predetermined value; and

detecting means connected to said secondary battery for detecting the charging current through said secondary battery at the time of charging with said constant voltage.