Protection methods, protection circuits and protective devices for secondary batteries, a power tool, charger and battery pack adapted to provide protection against fault conditions in the battery pack

• US 20050077878A1
• Filed: 10/07/2004
• Published: 04/14/2005
• Est. Priority Date: 10/14/2003
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Francis, Jeffrey J., Trinh, Danh Thanh, Brotto, Daniele C., Seman, Andrew E. Jr., Yahnker, Christopher R., Phillips, Steve, Bailey, R. Roby, Carrier, Dave
• Granted Patent: US 7,508,171 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: B25F 5/00 Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
• CPC Class Codes: B60L 53/18 Cables specially adapted for charging electric vehicles
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: H01M 10/488 Cells or batteries combined with indicating means for external visualization of the condition, e.g. by change of colour or of light density
• CPC Class Codes: H01M 2200/106 PTC
• 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 50/247 specially adapted for portable devices, e.g. mobile phones, computers, hand tools or pacemakers
• CPC Class Codes: H01M 50/581 in response to temperature
• CPC Class Codes: H01M 50/583 in response to current, e.g. fuses
• CPC Class Codes: H01M 6/42 Grouping of primary cells into batteries H01M6/40 takes precedence
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/00308 Overvoltage 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: Y02E 60/10 : Energy storage using batteries
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/12 : Electric charging stations
• CPC Class Codes: Y02T 90/14 : Plug-in electric vehicles

Abstract

In a cordless power tool system, protection methods, circuits and devices are provided to protect against fault conditions within a battery pack that is operatively attached to a power tool or charger, so as to prevent internal or external damage to the battery pack or attached tool or charger. The exemplary methods, circuits and devices address fault conditions such as over-charge, over-discharge, over-current, over-temperature, etc.

Claims

1. A protection arrangement within a battery pack for protecting against a fault condition in the battery pack, the battery pack adapted to power a cordless power tool and including a plurality of battery cells, comprising:

a plurality of distinct protection devices, each cell having a corresponding protection device adapted to perform a current limiting function.

2. The arrangement of claim 1, wherein each protection device is embodied as a thermistor.

3. The arrangement of claim 1, wherein

the cells are serially connected to form a string of cells, and

each protection device is embodied as a positive temperature coefficient (PTC) that increases in resistance to limit the current through the entire string, when its corresponding cell reaches a fault condition.

4. The arrangement of claim 1, wherein the battery pack is a lithium-ion battery pack.

5. The arrangement of claim 4, wherein the lithium-ion battery pack has a nominal voltage rating of at least 18 volts.

6. A battery pack adapted to power a cordless power tool and including a plurality of serially-connected battery cells, the battery pack including a protection arrangement adapted to limit or interrupt current in the battery pack upon a fault condition that is sensed in the battery pack.

7. The battery pack of claim 6, the arrangement further comprising:

at least one protection circuit sensing a given battery parameter to determine the fault condition in one or more of the cells and to generate a control signal based on an indication of a fault condition; and

a master device having a current limiting or current interrupting function adapted to limit or interrupt current based on the control signal received from the protection circuit.

8. The battery pack of claim 6, the arrangement further comprising:

a temperature sensor for sensing pack temperature to generate a first signal;

a current sensor for sensing pack current to generate a second signal; and

a battery control circuit adapted to receive said first and second signals to determine a fault condition in the battery pack and generate a control signal.

9. The battery pack of claim 8, wherein

the battery electronic control unit sends the control signal to a semiconductor device operatively connected thereto, and

the semiconductor device has a current limiting or current interrupting function to limit or interrupt current based on the control signal.

10. The battery pack of claim 6, the arrangement further comprising:

a current sensor for sensing pack current to generate a control signal based on a sensed over-current fault condition; and

a semiconductor device having a current limiting or current interrupting function and operatively connected to the current sensor, the semiconductor device adapted to limit or interrupt current based on the control signal received from the current sensor.

11. The battery pack of claim 10, wherein the over-current fault condition exists if the sensed pack current exceeds a given threshold.

12. The battery pack of claim 11, wherein the current threshold is based on temperature of the cells.

13. The battery pack of claim 6, the arrangement further comprising:

a battery control circuit configured to monitor battery voltage, battery current and battery temperature so as to generate a control signal, and

a semiconductor device operatively controlled by the battery control circuit, the semiconductor device adapted to limit or interrupt current based on the control signal.

14. The battery pack of claim 13, the arrangement further comprising:

a temperature sensor for sensing cell temperature to output a sensed signal to the battery control circuit;

a current sensor for sensing battery current to output a sensed signal to the battery control circuit; and

a voltage monitor circuit for sensing one of individual cell voltage and total pack voltage of the pack to output a sensed signal to the battery control circuit.

15. The battery pack of claim 6, the arrangement further comprising:

at least one communication terminal for communicating information to, and sensing information from, an attached external component.

16. The battery pack of claim 6, the arrangement further comprising:

at least one protection circuit monitoring pack voltage for a potential over-discharge fault condition in the pack and adapted to perform an automatic shutdown of current flow in the pack if the monitored voltage reaches a given voltage threshold.

17. The battery pack of claim 6, the arrangement further comprising:

at least one protection circuit monitoring pack voltage for a potential over-discharge fault condition in the pack and adapted to perform an automatic shutdown of current flow in the pack if the monitored voltage reaches a given dynamic voltage threshold,

wherein the dynamic voltage threshold is varied by subtracting a proportion of instant discharge current from an absolute threshold level to compensate for impedance of the battery pack and to avoid a spurious automatic shutdown of current flow, if monitored voltage momentarily drops below the threshold.

18. The battery pack of claim 6, the arrangement further comprising:

a single PTC device placed in series with the serially-connected cells within the battery pack as a protection against an over-current fault condition, the PTC device adapted to increase total pack impedance with increasing current in the pack.

19. The battery pack of claim 6, the arrangement further comprising:

a plurality of PTC devices placed in parallel with each other within the pack to form a parallel PTC string, the parallel PTC string placed in series with the serially-connected cells as a protection against an over-current fault condition, the parallel PTC string adapted to increase total pack impedance with increasing current in the pack.

20. The battery pack of claim 6, the arrangement further comprising:

at least one fuse arranged between the cells and a terminal of the battery pack, wherein the physical placement of the fuse is nearer in proximity to the terminal than to the cells, thereby isolating the cells and associated electronics of the pack from a connected charger or power tool in the event of an over-current casualty in the pack.

21. The battery pack of claim 6, wherein the battery pack is a lithium-ion battery pack.

22. The battery pack of claim 21, wherein the lithium-ion battery pack has a nominal voltage rating of at least 18 volts.

23. The battery pack of claim 6, the arrangement further comprising an audible warning mechanism configured to alert the user of the battery pack of an impending or present fault condition in the battery pack.

24. The battery pack of claim 6, the arrangement further comprising a visual warning mechanism configured to alert the user of the battery pack of an impending or present fault condition in the battery pack.

25. A method of providing over-voltage protection in a battery pack removably attachable to a cordless power tool and a charger, the battery pack operatively attached to the charger charging the pack, comprising:

sensing an over-voltage fault condition in the pack; and

terminating charge current in the battery pack or charger based on the sensed fault condition.

26. The method of claim 25, wherein terminating includes generating a control signal in the pack to turn off a semiconductor device in the pack that is adapted to limit or interrupt current in a charge path of the pack.

27. The method of claim 25, wherein terminating further includes

generating a control signal in the pack, and

communicating the control signal to the charger to turn off a semiconductor device in the charger that is adapted to limit or interrupt current in a charge path of the charger to terminate current flow in the battery pack.

28. A watchdog circuit of a charger, the charger operatively attached to a battery pack for charging the battery pack, the watchdog circuit monitoring parameters in both the battery pack and the charger for one or more control signals from the battery pack or charger to terminate current flow in the battery pack.

29. The watchdog circuit of claim 28, wherein the parameters include one or more of battery pack temperature, individual cell voltages, battery stack voltage, a charge current reset pulse from the battery pack, and a clock reset pulse from the battery pack, and/or a charge current reset pulse from the charger.

30. In a charger adapted to charge a battery pack, the charger and battery pack part of a cordless power tool system, the charger comprising:

a charge current interruption circuit monitoring parameters in both the battery pack and the charger for one or more control signals from the battery pack or charger to terminate current flow in the battery pack.

31. The charge current interruption circuit of claim 30, wherein the parameters include one or more of battery pack temperature, individual cell voltages, battery stack voltage, a charge current reset pulse from the battery pack, a clock reset pulse from the battery pack, and/or a charge current reset pulse from the charger.

32. A battery pack adapted to power a cordless power tool and to be charged by a charger, the pack including a plurality of battery cells, the battery pack comprising:

a device that terminates an over-temperature condition in the pack based on pack temperature or an individual cell temperature exceeding a given temperature threshold.

33. The battery pack of claim 32, wherein the device further includes

a thermal switch, and

a plurality of high current contacts,

wherein the thermal switch opens the high current contacts when pack or cell temperature exceeds the given threshold.

34. In a battery pack operatively attachable to a charger, the battery pack adapted to power a cordless power tool, a device for providing over-temperature protection in the pack during charging, comprising:

a thermistor;

a first thermistor lead connecting the thermistor to a positive terminal shared by the pack and charger; and

a second thermistor lead connecting the thermistor to a negative terminal shared by the pack and charger.

35. The device of claim 34, wherein the positive and negative terminals connected to the first and second leads interface to temperature monitoring circuitry in the charger to enable monitoring of pack temperature while maintaining the thermistor isolated from the charge path in the pack.

36. A battery pack, the pack operatively attached to a cordless power tool for powering a motor of the power tool, the battery pack comprising:

a motor control unit for determining at least one measurable parameter in the battery pack that would indicate a fault condition; and

a pair of transistors in communication with the motor control circuit, the motor control circuit controlling the pair of transistors to provide one of audible or tactile feedback to the user of the tool.

37. In a cordless power tool system including a battery pack removably attached to a power tool, a method of providing an audible warning in the motor of the power tool to alert an operator of the tool of an impending fault condition in the pack or tool, comprising:

determining at least one measurable parameter in one of the battery pack or tool, and

providing one of audible or tactile feedback to the user of the tool based on the at least one determined measurable parameter.

38. The method of claim 37, wherein providing includes adjusting motor current switching frequency based on the at least one determined parameter to produce an audible tone in the motor of the tool that warns the tool operator of the impending fault condition.

39. The method of claim 37, wherein providing includes adjusting a desired PWM duty cycle of at least one semiconductor device in the battery pack to produce a warble effect in the motor speed that warns the tool operator of the impending fault condition.

40. The method of claim 39, wherein adjusting further includes reducing the PWM duty cycle to produce a weakening of the tool as felt by the tool user to warn the user of an impending fault condition.

41. A battery pack having over-charge protection, comprising:

a housing,

a plurality of serially-connected cells therein, and

a current interrupt mechanism to interrupt current in the cells that is triggered upon swelling of at least one cell during an over-charge event.

42. The battery pack of claim 41, wherein

the cells are serially connected between power terminals of the pack and interconnected to each other via tab connectors, the tab connectors of adjacent cells connected to each other.

43. The battery pack of claim 42, wherein the current interrupt mechanism is embodied as at least one tab connector of a swelling cell being pull apart from at least one tab connector of an adjacent cell to interrupt current.

44. The battery pack of claim 41, wherein the current interrupt mechanism comprises:

a plunger, and

a spring, the plunger restrained between the serially-connected cells and a sidewall of the battery housing under a counterforce provided by the spring, the plunger including a portion that extends partially into a recess between formed an intermediate wall and an outer sidewall of the battery pack housing, the recess including a lead wire from the pack electrically connecting the cells of the pack to a charger,

wherein swelling of the at least one cell assists the plunger to overcome spring pressure to sever the lead wire in the recess to interrupt current.

45. The battery pack of claim 44, wherein the cells are serially connected between power terminals of the pack and interconnected to each other via tab connectors, the tab connectors of adjacent cells connected to each other, and the current interrupt mechanism further includes at least one tab connector of the at least one swelling cell pulling apart from at least one tab connector of an adjacent cell to interrupt current.

46. The battery pack of claim 41, wherein the current interrupt mechanism comprises:

a plunger, and

a spring, the plunger restrained between the serially-connected cells and a sidewall of the battery housing under a counterforce provided by the spring, the plunger including a portion that extends partially into a recess, the recess extending through a sidewall of the battery pack housing and a sidewall of a charger housing,

wherein a charger lead wire electrically connecting the charger to a corresponding lead wire of the battery pack extends longitudinally along a face of the charger housing sidewall and over the recess, and

wherein swelling of the at least one cell assists the plunger to overcome spring pressure to sever the charger lead wire extending over the recess to interrupt current.

47. The battery pack of claim 46, wherein the cells are serially connected between power terminals of the pack and interconnected to each other via tab connectors, the tab connectors of adjacent cells connected to each other, and the current interrupt mechanism further includes at least one tab connector of the at least one swelling cell pulling apart from at least one tab connector of an adjacent cell to interrupt current.

48. The battery pack of claim 41, wherein the current interrupt mechanism comprises:

a plunger, and

a spring, the plunger restrained between the serially-connected cells and a sidewall of the battery housing under a counterforce provided by the spring, the plunger including a portion that extends partially into a recess between formed a sidewall of the battery pack housing and a housing of the charger,

wherein a lead wire from the cells is electrically connected to a corresponding lead wire of the charger at a contact interface, and

wherein swelling of the at least one cell assists the plunger to overcome spring pressure to eject the pack housing from the charger housing, causing a break in the contact interface to interrupt current.

49. The battery pack of claim 48, wherein the cells are serially connected between power terminals of the pack and interconnected to each other via tab connectors, the tab connectors of adjacent cells connected to each other, and the current interrupt mechanism further includes at least one tab connector of the at least one swelling cell pulling apart from at least one tab connector of an adjacent cell to interrupt current.