Battery charger and battery charging method

• US 6,476,584 B2
• Filed: 04/25/2001
• Issued: 11/05/2002
• Est. Priority Date: 03/25/1999
• Status: Expired due to Fees

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: Sakakibara, Kazuyuki
• Primary Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US09/842,324
• Publication Number:
  US 20010048289A1
• Time in Patent Office: 559 Days
• Field of Search: 320/150, 320/151, 320/152, 320/153
• US Class Current: 320/150
• CPC Class Codes: H01M 10/345 Gastight metal hydride accumulators
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H02J 7/0071 with a programmable schedule
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A temperature rise pattern is retrieved from charging time based on the difference between a battery temperature at the beginning of battery charge and a target temperature value which a battery is intended to reach (in S116). The battery is charged while adjusting a current value so that a temperature rise value becomes the temperature rise pattern (in S118 and S120). Thus, by optimizing the temperature rise pattern, it is possible to charge the battery so that the temperature at the time of the completion of battery charge becomes the target temperature value (the lowest temperature value).

Claims

1. An apparatus comprising:

a battery pack comprising at least a first block of battery cells, a second block of battery cells, a first battery temperature sensor in communication with the first block of battery cells and a second battery temperature sensor in communication with the second block of battery cells, and

a battery charger comprising a current supply arranged and constructed to supply charging current to the battery pack and a processor arranged and constructed to (i) calculate battery temperature increase rates based upon signals from the first and second battery temperature sensors, (ii) select charging currents that will be supplied by the current supply to the first and second blocks of battery cells based upon battery temperature and the calculated battery temperature increase rate, and (iii) alternately supply the selected charging currents to the respective first and second block of battery cells.

2. An apparatus as in claim 1, wherein the processor is further arranged and constructed to terminate the supply of charging current to the respective first and second blocks of batteries based upon a determination that relatively low charging currents have been repeatedly supplied to the respective first and second blocks of batteries over a series of intervals.

3. An apparatus as in claim 1, wherein the first and second blocks of battery cells comprise at least one battery selected from the group consisting of nickel metal hydride batteries and nickel cadmium batteries.

4. The method for charging a battery pack comprising at least a first block of battery cells and a second block of battery cells, comprising:

supplying a first charging current to the first block of battery cells while monitoring battery temperature and battery temperature increase rate of the first block of battery cells,

adjusting the first charging current based upon the battery temperature and the battery temperature increase rate of the first block of battery cells in order to avoid overheating the first block of battery cells,

supplying a second charging current to the second block of battery cells while monitoring battery temperature and battery temperature increase rate of the second block of battery cells, and

adjusting the second charging current based upon the battery temperature and the battery temperature increase rate of the second block of battery cells in order to avoid overcharging the second block of battery cells.

5. A method as in claim 4, further comprising:

terminating the supply of the first charging current to the first block of battery cells based upon a determination that relatively low charging currents have been repeatedly supplied to the first block of battery cells over a series of intervals, and

terminating the supply of the second charging current to the second block of battery cells based upon a determination that relatively low charging currents have been repeatedly supplied to the second block of battery cells over a series of intervals.

6. A method for charging a battery pack comprising at least a first block of battery cells and a second block of battery cells, comprising:

independently monitoring battery temperature and battery temperature increase rate of the respective first and second block of battery cells,

selecting a first charging current from a look up table using the battery temperature and battery temperature increase rate of the first block of battery cells as indices for the look up table,

selecting a second charging current from the look up table using the battery temperature and battery temperature increase rate of the second block of battery cells as indices for the look up table,

alternately supplying the selected charging currents to the first block of battery cells and the second block of battery cells while continuing to monitor the battery temperature and battery temperature increase rate of the first and second blocks of battery cells at frequent intervals,

selecting a first new charging current from the look up table when the battery temperature and/or the battery temperature increase rate of the first block of battery cells changes, and

selecting a second new charging current from the look up table when the battery temperature and/or the battery temperature increase rate of the second block of battery cells changes.

7. A method as in claim 6, further comprising

terminating charging of the first block of battery cells when the battery temperature increase rate of the first block of battery cells is relatively high and relatively low charging current has been supplied to the first block of battery cells at a relatively high frequency, and

terminating charging of the second block of battery cells when the battery temperature increase rate of the second block of battery cells is relatively high and relatively low charging current has been supplied to the second block of battery cells at a relatively high frequency.

8. A method as in claim 7, wherein the new charging current selection steps further comprise selecting a lower charging current when the battery temperature and/or battery temperature increase rate increases.

9. A method as in claim 8, wherein the new charging current selection steps further comprise selecting a higher charging current when the battery temperature increase rate decreases.

10. A method as in claim 9, wherein the first and second blocks of battery cells comprise at least one battery selected from the group consisting of nickel metal hydride batteries and nickel cadmium batteries.

11. An apparatus adapted to charge a removable battery pack comprising at least a first block of battery cells, a second block of battery cells, a first battery temperature sensor coupled to the first block of battery cells, a second battery temperature sensor coupled to the second block of battery cells, and at least one charging terminal comprising:

a controller arranged and constructed to couple to the first and second battery temperature sensors and the at least one charging terminal of the removable battery pack, wherein the controller comprises a memory storing a program containing instructions to;

calculate battery temperature and battery temperature increase rate of the first and second blocks of battery cells based upon signals received from the respective first and second temperature sensors,

select a first charging current based upon the battery temperature and the battery temperature increase rate of the first block of battery cells and supplying the first charging current to the first block of battery cells, and

select a second charging current based upon the battery temperature and the battery temperature increase rate of the second block of battery cells and supplying the second charging current to the second block of battery cells, wherein the first and second blocks of battery cells are alternately charged.

12. An apparatus as in claim 11, wherein the stored program further comprises instructions to:

terminate the supply of the first charging current to the first block of battery cells based upon a determination that relatively low charging current has been repeatedly supplied to the first block of battery cells over a series of intervals, and

terminate the supply of the second charging current to the second block of battery cells based upon a determination that relatively low charging current has been repeatedly supplied to the second block of battery cells over a series of intervals.

13. An apparatus as in claim 12, wherein the stored program further comprises instructions to terminate the supply of current to the first block of battery cells if the current being supplied to the first block of battery cells falls below a predetermined current value over a series of consecutive intervals.

14. An apparatus as in claim 13, further comprising a look up table comprising a set of allowable charging current values and having battery temperature and battery temperature increase rates as indices, wherein the stored program further comprises instructions to select allowable charging current values based upon the detected battery temperature and the calculated battery temperature increase rate.

15. A battery charger adapted to supply current to a rechargeable battery pack comprising a first block of battery cells, a second block of battery cells, a first temperature sensor coupled to the first block of battery cells, a second temperature sensor coupled to the second block of battery cells, a first charging terminal and a second charging terminal, comprising:

a source of charging current,

a first terminal arranged and constructed to couple to the first battery temperature sensor,

a second terminal coupled to the source of charging current and arranged and constructed to conduct charging current via the first charging terminal to the first block of battery cells,

a third terminal arranged and constructed to couple to the second battery temperature sensor,

a fourth terminal coupled to the source of charging current and arranged and constructed to conduct charging current via the second charging terminal to the second block of battery cells, and

a controller coupled to the first and third terminals and the source of charging current, the controller being arranged and constructed to select the amount of charging current supplied to the second and fourth terminals based at least upon battery temperature signals received from the first and third terminals.

16. An apparatus as in claim 15, wherein the controller is further arranged and constructed to independently terminate the supply of charging current to the respective first and second blocks of battery cells based upon a determination that relatively low charging currents have been repeatedly supplied to the respective first and second blocks of battery cells over a series of intervals.

17. An apparatus as in claim 16, further comprising a look up table comprising a set of allowable charging current values, wherein battery temperature and battery temperature increase rates serve as indices to the look up table, and wherein the controller further comprises instructions for selecting allowable charging current values based upon detected battery temperature and a calculated battery temperature increase rate.

18. An apparatus as in claim 17, wherein the controller comprises instructions for stopping the supply of current to the first block of battery cells when the charging current being supplied to the first block of battery cells is repeatedly below a predetermined current value over a plurality of consecutive intervals.

19. A battery charging system for charging a detachable battery pack comprising at least a first block of battery cells and a second block of battery cells, comprising:

first means for detecting a battery temperature and battery temperature increase rate of the first block of battery cells and the second block of battery cells,

second means for storing a map of allowable current values based upon the detected battery temperatures and battery temperature increase rates,

third means for selecting an allowable charging current from the second means based upon the detected battery temperatures and battery temperature increase rates, and

fourth means for alternately supplying the selected allowable charging currents to the respective first and second blocks of battery cells.

20. A battery charging system as in claim 19, further comprising fifth means for terminating the supply of charging current to the first block of battery cells based upon a determination that relatively low charging current has been repeatedly supplied to the first block of battery cells over a series of intervals.

21. A method for charging a battery pack comprising at least a first block of battery cells and a second block of battery cells, comprising:

independently monitoring respective battery temperatures of the first and second block of battery cells,

using a processor to select allowable charging currents based upon detected battery temperatures of the respective first and second blocks of battery cells,

alternately supplying selected charging currents to the respective first and second blocks of battery cells while continuing to independently monitor the battery temperatures of the respective first and second blocks of battery cells, and

independently adjusting the selected charging currents based upon changes in the detected battery temperatures of the respective first and second blocks of battery cells.

22. A method as in claim 21, further comprising terminating the supply of charging currents to the first block of battery cells when the battery temperature of the first block of battery cells is relatively high and a relatively low charging current has been supplied to the first block of battery cells over a plurality of consecutive intervals.

23. A method as in claim 22, further comprising independently terminating the supply of charging currents to the second block of battery cells when the battery temperature of the second block of battery cells is relatively high and a relatively low charging current has been supplied to the second block of battery cells over a plurality of consecutive intervals.

24. An apparatus for charging a battery pack comprising at least a first block of battery cells and a second block of battery cells, comprising:

means for independently monitoring respective battery temperatures of the first and second block of battery cells,

a processor for selecting allowable charging currents based upon detected battery temperatures of the respective first and second blocks of battery cells,

means for alternately supplying selected charging currents to the respective first and second blocks of battery cells while continuing to independently monitor the battery temperatures of the respective first and second blocks of battery cells, and

means for independently adjusting the selected charging currents based upon changes in the detected battery temperatures of the respective first and second blocks of battery cells.

25. An apparatus as in claim 24, further comprising means for terminating the supply of charging currents to the first block of battery cells when the battery temperature of the first block of battery cells is relatively high and a relatively low charging current has been supplied to the first block of battery cells over a plurality of consecutive intervals.

26. An apparatus as in claim 25, further comprising means for independently terminating the supply of charging currents to the second block of battery cells when the battery temperature of the second block of battery cells is relatively high and a relatively low charging current has been supplied to the second block of battery cells over a plurality of consecutive intervals.