Methods and apparatuses rechargeable battery pack chargers

• US 20020070709A1
• Filed: 08/07/2001
• Published: 06/13/2002
• Est. Priority Date: 03/30/1999
• Status: Active Grant

• Current Assignee: Brian Farley, David Small, James Mckeefery
• Original Assignee: Brian Farley, David Small, James Mckeefery
• Inventors: Small, David, Farley, Brian, McKeefery, James
• Granted Patent: US 6,489,751 B2
• Time in Patent Office: Days
• US Class Current: 320/150
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 2200/10 Temperature sensitive devices
• CPC Class Codes: H01M 2200/30 Preventing polarity reversal
• CPC Class Codes: H01M 50/213 adapted for cells having curved cross-section, e.g. round or elliptic H01M50/209, H01M50/216 take precedence
• CPC Class Codes: H01M 6/42 Grouping of primary cells into batteries H01M6/40 takes precedence
• CPC Class Codes: H02J 7/0029 with safety or protection devices or circuits
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0045 concerning the insertion or the connection of the batteries
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A system, method and apparatus for charging rechargeable battery packs having redundant safety systems. A battery charger has a temperature sensor at a negative charging terminal for determining the charge condition of a rechargeable battery pack and controlling a charging current. The battery charger has a microcontroller to control the charging of the rechargeable battery pack using a fast charge current or a trickle charge current. Independent safety systems provide safe operation of the battery charger if the microcontroller operation fails. A rechargeable battery pack has a pair of openings to allow direct contact to a positive pole and a negative pole of the end batteries for improved temperature sensing by a battery charger.

Claims

1. A rechargeable battery pack for providing electrical capacity to portable electrical devices and for coupling to a battery charger to receive a charging current, the rechargeable battery pack comprising:

a plurality of batteries coupled in series to generate the electrical capacity of the rechargeable battery pack and to receive the charging current from the battery charger, the plurality of batteries having a first battery with a negative terminal having a negative pole and a last battery with a positive terminal having a positive pole, the negative terminal and the positive terminal to couple to the battery charger to receive the charging current and the negative pole to couple to the battery charger to sense a battery temperature; and

a battery pack housing, coupled to the plurality of batteries, to protect and hold together the plurality of batteries coupled in series, the battery pack housing having a polarity protection slot to prevent reverse polarity charging, a first battery terminal opening to provide access to the positive pole of the positive terminal of the last battery to couple to a positive charging terminal of the battery charger, and a second battery terminal opening to provide access to the negative pole of the negative terminal of the first battery to couple to a negative charging terminal of the battery charger having a temperature sensor to sense the battery temperature at the negative pole of the negative terminal of the first battery.

2. The rechargeable battery pack of claim 1 for coupling to a battery charger wherein,

the temperature sensor of the battery charger is a thermistor to sense the battery temperature at the negative pole of the negative terminal of the first battery.

3. The rechargeable battery pack of claim 1 for coupling to a battery charger, the rechargeable battery pack further comprising:

a first locking tab coupled to a bottom edge of a back side of the battery pack housing, the first locking tab to couple to a receiving hook of the battery charger when the rechargeable battery back is inserted into the battery charger; and

a finger grip tab coupled to the back side of the battery pack housing.

4. The rechargeable battery pack of claim 3 for coupling to a battery charger, the rechargeable battery pack further comprising:

a second locking tab coupled to the bottom edge of the back side of the battery pack housing opposite the first locking tab, the second locking tab to couple to the receiving hook of the battery charger when the rechargeable battery back is inserted into the battery charger.

5. The rechargeable battery pack of claim 4 for coupling to a battery charger wherein,

the first locking tab is near a left edge of the back side of the battery pack housing and the second locking tab is near a right edge of the back side of the battery pack housing.

6. The rechargeable battery pack of claim 5 for coupling to a battery charger wherein,

the polarity protection slot is in a bottom side of the battery pack housing near a front side of the battery pack housing.

7. The rechargeable battery pack of claim 5 for coupling to a battery charger wherein,

the first battery terminal opening and the second battery terminal opening are in a front side of the battery pack housing opposite the back side of the battery pack housing.

8. The rechargeable battery pack of claim 5 for coupling to a battery charger, the rechargeable battery pack further comprising,

a first sealing washer coupled to the first battery terminal opening and the positive terminal of the last battery to provide access to the positive pole of the positive terminal of the last battery to couple to a positive charging terminal of the battery charger and to protect the plurality of batteries from environmental elements;

and

a second sealing washer coupled to the second battery terminal opening and the negative terminal of the first battery to provide access to the negative pole of the negative terminal of the first battery to couple to a negative charging terminal of the battery charger and to protect the plurality of batteries from environmental elements.

9. A battery charger for charging a rechargeable battery pack having a plurality of rechargeable batteries coupled in series, the battery charger comprising:

a power supply to provide a DC voltage across a positive node and a negative node and a DC current into the positive node, the DC current to fast charge the rechargeable battery pack;

a charge switch to selectively couple the DC current into the rechargeable battery pack in response to a charge control signal;

a controller to measure the battery temperature and voltage of the rechargeable battery pack to determine a charge condition of the rechargeable battery pack, the controller generating the charge control signal in response to the charge condition of the rechargeable battery pack; and

a safety cutoff switch coupled between the power supply and the charge switch to selectively switch the DC current OFF in response to a safety signal generated independent of the controller, the safety signal being generated when it is unsafe to utilize the DC current to fast charge the rechargeable battery pack, the safety cutoff switch to control the DC current independent of the controller to increase the operational safety of the battery charger.

10. The battery charger of claim 9 for charging a rechargeable battery pack, the battery charger further comprising:

a positive charging terminal coupled to the charge switch to receive the DC current, the positive charging terminal to couple to a positive terminal of a last battery in the rechargeable battery pack and to charge the rechargeable battery pack;

a negative charging terminal coupled to the negative node of the power supply, the negative charging terminal to couple to a negative terminal of a first battery in the rechargeable battery pack and to charge the rechargeable battery pack; and

a temperature sensor coupled to the negative charging terminal, the temperature sensor to sense the battery temperature at the negative pole of the negative terminal of the first battery in the rechargeable battery pack.

11. The battery charger of claim 10 for charging a rechargeable battery pack wherein,

the temperature sensor is a thermistor to sense the battery temperature at the negative pole of the negative terminal of the first battery.

12. The battery charger of claim 11 for charging a rechargeable battery pack wherein,

the thermistor is coupled to a backside of the negative charging terminal;

and

the negative charging terminal has a front side to couple to the negative pole of the negative terminal of the first battery.

13. The battery charger of claim 9 for charging a rechargeable battery pack, the battery charger further comprising:

a temperature sensor to sense the battery temperature at the negative pole of the negative terminal of the first battery in the rechargeable battery pack, the temperature sensor generating an electrical heat level, the electrical heat level a function of the battery temperature; and

a temperature sense converter coupled to the temperature sensor to receive the electrical heat level and coupled to the processor to receive an electrical reference level, the temperature sense converter comparing the electrical heat level with the electrical reference level to generate a comparison output indicating which level is greater than the other, the comparison output coupled to the processor.

14. The battery charger of claim 13 for charging a rechargeable battery pack wherein,

the electrical heat level is an analog signal in the form of a current or a voltage.

15. The battery charger of claim 13 for charging a rechargeable battery pack wherein,

the electrical heat level is a digital signal coupled between the temperature sensor and the temperature sense converter.

16. The battery charger of claim 9 for charging a rechargeable battery pack wherein,

the safety signal is generated when the battery temperature is greater than a maximum fast charge battery temperature.

17. The battery charger of claim 9 for charging a rechargeable battery pack wherein,

the safety signal is generated when the battery temperature is less than a minimum fast charge battery temperature.

18. The battery charger of claim 9 for charging a rechargeable battery pack wherein,

the safety signal is generated when the voltage of the rechargeable battery pack is less than a minimum fast charge battery voltage level.

19. The battery charger of claim 9 for charging a rechargeable battery pack wherein,

the controller generates a charge control signal to turn OFF the DC current in response to the battery temperature exceeding a fast charge battery temperature range.

20. The battery charger of claim 9 for charging a rechargeable battery pack wherein,

the controller generates a charge control signal to turn OFF the DC current in response to the battery voltage of the rechargeable battery pack exceeding a fast charge battery voltage range.

21. The battery charger of claim 9 for charging a rechargeable battery pack wherein,

the controller generates a charge control signal to turn OFF the DC current in response to the battery temperature increasing logarithmically under charging by the DC current.

22. The battery charger of claim 9 for charging a rechargeable battery pack wherein,

the controller generates a charge control signal to turn OFF the DC current in response to the battery temperature rising at a rate greater than a maximum safe rate of temperature increase under charging by the DC current.

23. The battery charger of claim 9 for charging a rechargeable battery pack, the battery charger further comprising:

a trickle charge current regulator coupled to the power supply to generate a trickle charge current to couple to the rechargeable battery pack.

24. The battery charger of claim 9 for charging a rechargeable battery pack, the battery charger further comprising:

a comparator to generate the safety signal independent of the controller when the comparison indicates that an electrical level representing the battery temperature is greater than an electrical level representing a maximum fast charge battery temperature.

25. The battery charger of claim 9 for charging a rechargeable battery pack, the battery charger further comprising:

a comparator to generate the safety signal independent of the controller when the comparison indicates that an electrical level representing the battery temperature is less than an electrical level representing a minimum fast charge battery temperature.

26. The battery charger of claim 9 for charging a rechargeable battery pack, the battery charger further comprising:

a comparator to generate the safety signal independent of the controller when the comparison indicates that the voltage of the rechargeable battery pack is less than an electrical level representing a minimum fast charge battery voltage level.

28. The method of claim 27 of controlling the charging of a rechargeable battery pack wherein,

the first temperature sensor is a thermistor coupled to a negative charging terminal of the battery charger to measure the battery temperature at the negative pole of the negative terminal of a battery in the rechargeable battery pack.

29. The method of claim 27 of controlling the charging of a rechargeable battery pack, the method further comprising:

providing a predetermined period of time between measuring the battery temperature of the rechargeable battery pack to determine the rate of increase in battery temperature.

30. The method of claim 27 of controlling the charging of a rechargeable battery pack, the method further comprising:

comparing a voltage of the rechargeable battery pack with a first reference voltage prior to the fast charging of the rechargeable battery pack to determine if it is safe to charge the rechargeable battery pack.

31. The method of claim 30 of controlling the charging of a rechargeable battery pack wherein,

the first reference voltage is a minimum chargeable voltage level, and

the comparing of the voltage of the rechargeable battery pack with the minimum chargeable voltage level determines that it is below the minimum chargeable voltage level indicating that it is unsafe to charge the rechargeable battery pack with the fast charging current and skipping the fast charging of the rechargeable battery pack and trickle charging the rechargeable battery pack by providing a trickle charging current to the rechargeable battery pack.

32. The method of claim 30 of controlling the charging of a rechargeable battery pack wherein,

the first reference voltage is a minimum chargeable voltage level, and

the comparing of the voltage of the rechargeable battery pack with the minimum chargeable voltage level determines that it is above the minimum chargeable voltage level.

33. The method of claim 27 of controlling the charging of a rechargeable battery pack, the method further comprising:

comparing the battery temperature of the rechargeable battery pack with a reference level prior to the fast charging of the rechargeable battery pack to determine if it is safe to charge the rechargeable battery pack.

34. The method of claim 33 of controlling the charging of a rechargeable battery pack wherein,

the reference level is a maximum battery temperature level, and

the comparing of the battery temperature of the rechargeable battery pack with the maximum battery temperature level determines that it is over the maximum battery temperature level indicating that it is unsafe to charge the rechargeable battery pack with the fast charging current.

35. The method of claim 33 of controlling the charging of a rechargeable battery pack wherein,

the reference level is a minimum battery temperature level, and

the comparing of the battery temperature of the rechargeable battery pack with the minimum battery temperature level determines that it is under the minimum battery temperature level indicating that it is unsafe to charge the rechargeable battery pack with the fast charging current

27. A method of controlling the charging of a rechargeable battery pack, the method comprising:

(a) coupling the rechargeable battery pack to a battery charger;

(b) fast charging the rechargeable battery pack by providing a fast charging current to the rechargeable battery pack;

(c) measuring a battery temperature of the rechargeable battery pack by coupling a temperature sensor to a negative pole of a negative terminal of a battery within the rechargeable battery pack;

(d) determining a rate of increase in battery temperature during the providing of the fast charging current to determine a charge condition of the rechargeable battery pack; and

(e) terminating the fast charging when it is determined that the rate of increase in battery temperature is greater than a maximum rate of increase or when it is determined that the increase in battery temperature is rising non-logarithmically either of which may indicate that the charge condition of the rechargeable battery pack is substantially full.