Charging method of a secondary battery

• US 5,684,386 A
• Filed: 10/18/1995
• Issued: 11/04/1997
• Est. Priority Date: 10/20/1994
• Status: Expired due to Term

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Okada, Tetsuya
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): SHIN, KYUNG E
• Application Number:
  US08/544,795
• Time in Patent Office: 748 Days
• Field of Search: 320/21, 320/22-24, 320/48, 320/30, 320/31, 320/35, 320/36, 320/39, 320/40
• US Class Current: 320/139
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A secondary battery is charged in alternating charging and pulse-charging periods in which the secondary battery is continuously charged during the charging periods and the secondary battery is charged in a series of charging pulses during the pulse-charging periods. The terminal voltage or the temperature of the secondary battery may be sampled during at least one interval between the pulses in a pulse-charging period to detect a full charge level or an excessive temperature, respectively. Such an arrangement can reduce charging time and facilitate accurate monitoring of the terminal voltage or the temperature.

Claims

1. A method for charging a secondary battery, the method comprising:

charging the secondary battery in alternating continuous charging periods and pulse-charging periods in which the secondary battery is continuously charged during each continuous charging period and the secondary battery is charged by a series of charging pulses during each pulse-charging period;

sampling a terminal voltage of the secondary battery during at least one interval between the pulses during a pulse-charging period; and

modifying the charging step based on the sampled terminal voltage.

2. A method according to claim 1, the method further including:

sampling the terminal voltage of the secondary battery during at least two intervals in each of the pulse-charging periods; and

calculating an average of the sampled terminal voltages during the at least two intervals.

3. A method according to claim 1, the method further including modifying the charging step when the sampled terminal voltage exhibits at least one of a predetermined peak value and a decrease of a predetermined voltage Δ

V after the peak value.

4. A method according to claim 1, wherein the step of charging includes applying a charging current and the step of modifying the charging step comprises one of shutting off the charging current and reducing the charging current to a lower level.

5. A method according to claim 1, the method further including:

setting the ratio of the duration of each pulse to the duration of each continuous charging period to less than 1/10; and

setting the ratio of the duration of each interval between pulses to the duration of each pulse to less than 1/2.

6. A method according to claim 1, the method further comprising:

sampling a temperature of the secondary battery; and

modifying the charging if the temperature exceeds a predetermined maximum.

7. A method of charging a secondary battery, the secondary battery having terminals, by supplying a current through the terminals of the second battery, the method comprising:

charging the secondary battery in alternating continuous charging periods and pulse-charging periods in which the secondary battery is continuously charged during each continuous charging period and the secondary battery is charged by a series of charging pulses during each pulse-charging period;

sampling a temperature of the secondary battery during at least one interval between the pulses during a pulse-charging period to provide a sampled temperature; and

modifying the charging based on the sampled temperature.

8. A method according to claim 7, wherein in the step of sampling includes sampling the temperature during an interval in each of the pulse charging periods.

9. A method according to claim 7, wherein the step of sampling a temperature comprises sampling a voltage of a temperature detecting element which is thermally coupled to the secondary battery and has a terminal electrically coupled to the secondary battery.

10. A method according to claim 9, wherein the temperature detecting element is a thermistor.

11. A method according to claim 7, the method further including modifying the charging when the sampled temperature exceeds a predetermined temperature value.

12. A method according to claim 7, wherein the step of charging includes supplying a charging current to the secondary battery and the step of modifying the charging comprises one of shutting off the charging current and reducing the charging current to a lower level.

13. A method according to claim 7, the method further comprising:

setting the ratio of the duration of each pulse to the duration of the continuous charging period to less than 1/10; and

setting the ratio of the duration of each interval between pulses to the duration of each pulse is set to less than 1/2.

14. A charging apparatus for charging a secondary battery, the apparatus comprising:

a circuit for charging the secondary battery in alternating continuous charging periods and pulse-charging periods in which the secondary battery is continuously charged during each continuous charging period and the secondary battery is charged by a series of charging pulses during each pulse-charging period;

a circuit for sampling the terminal voltage of the secondary battery during at least one interval between the pulses during a pulse-charging period; and

a circuit for modifying the charging based on the sampled terminal voltage.

15. A charging apparatus for charging a secondary battery, comprising:

a circuit for charging the secondary battery in alternating continuous charging periods and pulse-charging periods in which the secondary battery is continuously charged during each continuous charging period and the secondary battery is charged by a series of charging pulses during each pulse-charging period;

a circuit for sampling a temperature of the secondary battery during at least one interval between the pulses during a pulse-charging period to provide a sampled temperature; and

a circuit for modifying the charging based on the sampled temperature.