Battery charger

• US 6,211,655 B1
• Filed: 02/09/2000
• Issued: 04/03/2001
• Est. Priority Date: 02/11/1999
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Hardie, Jonathan Owen
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/501,152
• Time in Patent Office: 419 Days
• Field of Search: 320/150
• US Class Current: 320/150
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

A battery charger measures an average battery temperature at a pre-determined timing for a first fixed period after start of charging. If the number of consecutive positive second derivatives of battery temperature is four, charging is discontinued. If the number of consecutive positive second derivatives of battery temperature is not four, the charging is carried out continuously for a pre-determined secondary period.

Claims

1. A battery charger assembly comprising:

a battery to be charged; and

a control unit for measuring an averaged battery temperature at pre-determined times in a first fixed period after start of charging, for ending charging of said battery if the measurements meet pre-determined conditions after the first fixed period, and for causing continuous charging of said battery for a secondary period so long as the measurements do not meet the pre-determined conditions.

2. A battery charger according to claim 1, wherein said pre-determined conditions comprise consecutive positive second derivatives of the battery temperature at the predetermined times being a predetermined number.

3. A battery charger according to claim 2, wherein said number of consecutive positive second derivatives of battery temperature is four.

4. A battery charger according to claim 1, wherein said first fixed period is 2.5 minutes.

5. A battery charger according to claim 1, wherein said secondary period is 7.5 minutes.

6. A battery charger according to claim 1, wherein the temperature of said battery is measured by a thermistor.

7. A battery charger according to claim 1, wherein the start of charging is prevented when measured battery temperatures are beyond one of an upper and a lower predetermined threshold.

8. A battery charger according to claim 1, wherein said battery is installed in a mobile phone.

9. A battery charger according to claim 8, further comprising:

an ambient temperature indicator for measuring the temperature of the inside of the mobile phone;

wherein start of charging is prevented when a difference greater than a predetermined threshold value exists between a battery temperature measurement and an ambient temperature measured by said ambient temperature indicator.

10. A battery charger according to claim 1 further comprising:

a charge switch for controlling supply of current to said battery, said switch controlled by said control unit.

11. A battery charger according to claim 1 further comprising:

a display unit for displaying the state of charge of said battery.

12. A battery charger according to claim 1, wherein said pre-determined conditions comprise a temperature of said battery being within a range of temperatures about an ambient temperature.

13. A battery charger assembly comprising:

a battery to be charged; and

a control unit operative to;

measure a temperature of said battery at predetermined intervals from a start of charging said battery, and record an average of the temperature measurements for predetermined portions of a first fixed period;

compute a second derivative for each average, and determine whether the second derivative is positive;

count a number of positive second derivatives and reset the count when the second derivative is negative;

determine whether a temperature and a voltage of said battery are outside predetermined limits and, if so, generate a first event;

generate a second event when the count reaches a predetermined number.

14. A battery charger assembly as claimed in claim 13, wherein said control unit further comprises a timer that generates said second event when a timer time has expired, the timer time being greater than or equal to the first fixed period.

15. A battery charger assembly as claimed in claim 13, wherein said second event is an enablement of a charge termination system.

16. A battery charger assembly as claimed in claim 13, wherein said first event is an enablement of a charge termination system.

17. A battery charger assembly comprising:

a battery to be charged; and

a control unit for measuring a battery temperature at pre-determined times in a first fixed period after start of charging, for ending charging of said battery if the measurements meet predetermined conditions after the first fixed period, and for causing continuous charging of said battery for a secondary period so long as the measurements do not meet the pre-determined conditions.

18. A battery charger according to claim 17, wherein said pre-determined conditions comprise consecutive positive second derivatives of the battery temperature at the predetermined times being a predetermined number.

19. A battery charger according to claim 18, wherein said number of consecutive positive second derivatives of battery temperature is four.

20. A battery charger according to claim 17, wherein said first fixed period is 2.5 minutes.

21. A battery charger according to claim 17, wherein said secondary period is 7.5 minutes.

22. A battery charger according to claim 17, wherein the temperature of said battery is measured by a thermistor.

23. A battery charger according to claim 17, wherein the start of charging is prevented when measured battery temperatures are beyond one of an upper and a lower predetermined threshold.

24. A battery charger according to claim 17, wherein said battery is installed in a mobile phone.

25. A battery charger according to claim 24, further comprising:

an ambient temperature indicator for measuring the temperature of the inside of the mobile phone;

wherein start of charging is prevented when a difference greater than a predetermined threshold value exists between a battery temperature measurement and an ambient temperature measured by said ambient temperature indicator.

26. A battery charger according to claim 17, further comprising:

a charge switch for controlling supply of current to said battery, said switch controlled by said control unit.

27. A battery charger according to claim 17, further comprising a display unit for displaying the state of charge of said battery.