Battery pack for cordless power tools

• US 7,728,553 B2
• Filed: 11/20/2006
• Issued: 06/01/2010
• Est. Priority Date: 10/28/2005
• Status: Expired due to Fees

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Carrier, David A., Brotto, Daniele C., Seman, Andrew E. Jr., Watts, Fred S., Choksi, Snehal S., Howard, Geoffrey S., Zhang, Qiang J., Trinh, Danh T.
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): BOATENG, ALEXIS ASIEDUA
• Application Number:
  US11/552,832
• Publication Number:
  US 20080238370A1
• Time in Patent Office: 1,289 Days
• Field of Search: 320/134, 320/114, 320/119, 320/115, 320/124, 320/135, 320/136, 320/137, 320/117, 320/116, 320/127, 320/161, 320/162
• US Class Current: 320/119
• CPC Class Codes: H01M 50/204 Racks, modules or packs for multiple batteries or multiple cells
• CPC Class Codes: H01M 50/247 specially adapted for portable devices, e.g. mobile phones, computers, hand tools or pacemakers
• CPC Class Codes: H02J 7/00036 Charger exchanging data with battery
• CPC Class Codes: H02J 7/00047 with provisions for charging different types of batteries
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery pack which includes a battery pack electronic control circuit adapted to control an attached power tool and/or an attached charger. The battery pack includes additional protection circuits, methodologies and devices to protect against fault conditions within the pack, as the pack is operatively attached to and providing power to the power tool, and/or as the pack is operatively attached to and being charged by the charger.

Claims

1. A battery pack of a cordless power tool system including a power tool and a charger, the pack removably attachable to the tool and charger, the battery pack comprising:

a housing,

a plurality of battery cells within the housing,

a battery electronic control unit within the housing for controlling the charger during a charge of the cells, and for controlling a field effect transistor (FET) during discharge operations to control current to a motor of the power tool,

a first voltage monitoring unit for monitoring one or both of individual cell voltages and total stack voltage in the pack during charge and discharge operations, and

a second voltage monitoring circuit for separately monitoring individual cell voltage to detect any cell reaching an over-voltage condition during a charge, wherein, upon detecting any cell reaching an over-voltage condition, the second voltage monitoring circuit, without interfacing with the battery electronic control unit, sends a signal to the charger to generate a disable signal in the charger for terminating charge current to the pack.

2. The battery pack of claim 1, wherein the first voltage monitoring unit provides a signal representing one of a measured individual cell voltage or stack voltage to the battery electronic control unit during charge and discharge operations, and the battery electronic control unit controls balancing of each of the cell voltages during a charge based on signals received from the first voltage monitoring unit.

3. The battery pack of claim 2, wherein the second voltage monitoring circuit provides backup protection where cell balancing functionality becomes corrupted during charge or the first voltage monitoring unit becomes inoperative.

4. The battery pack of claim 1, further comprising:

a fuse in a charge return line within the pack acting as additional protection in a case where the battery electronic control circuit in the pack or a current control circuit in the charger becomes inoperative and current exceeds normal levels during charge.

5. A battery pack of a cordless power tool system including a power tool and a charger, the pack removably attachable to the tool and charger, the battery pack comprising:

a housing,

a plurality of battery cells within the housing,

a battery electronic control unit within the housing for controlling the charger during a charge of the cells, and for controlling a field effect transistor (FET) during discharge operations to control current to a motor of the power tool,

a first voltage monitoring unit for monitoring one or both of individual cell voltages and total stack voltage in the pack during charge and discharge operations, and

a second voltage monitoring circuit for separately monitoring individual cell voltage to detect any cell reaching an over-voltage condition during a charge and sends a signal to the charger to generate a disable signal in the charger for terminating charge current to the rack without interfacing with the battery electronic control unit, wherein a sense line is provided between each of the cells and the first voltage monitoring unit to sense individual cell voltage, and each sense line includes a fuse or a fuse-able link therein.

6. The battery pack of claim 1, further comprising a plurality of serial data paths between the battery electronic control unit and one of the charger and power tool for exchanging data and control information there between.

7. The battery pack of claim 6, wherein, if the pack is connected to a charger, the battery electronic control unit receives information including one or more of a digital ID of the charger, charger current, total stack voltage of the cells as read by the charger, temperature conditions of the charger, and AC mains level of the charger.

8. The battery pack of claim 6, wherein the battery electronic control unit controls charger output or charging decisions for its cells based on charger fault data received over the serial data paths from an attached charger.

9. The battery pack of claim 6, wherein the battery electronic control unit controls output voltage to a tool motor based on information received from the tool.

10. The battery pack of claim 9, wherein

the information includes an analog trigger signal received over the serial data paths and representing a degree of trigger retraction by a user of the tool, and

the battery electronic control unit issues a PWM control signal to cause the discharge FET to switch at a desired duty cycle so as to create a desired motor speed.

11. The battery pack of claim 1, wherein

the battery electronic control unit provides pulse width modulation (PWM) control of the FET so as to control tool motor current, and

the battery pack further includes current limit processing circuitry for evaluating pack current during each switching period of the FET and for selectively limiting power out of the pack based on the evaluation.

12. The battery pack of claim 1,

further comprising a driver circuit that supplies a drive signal for switching the FET based on a control signal received from the battery electronic control unit,

wherein the battery electronic control unit periodically monitors a supply voltage of the driver circuit for comparison against a reference voltage level and inhibits the drive signal sent to the driver circuit so that the FET is turned off if the supply voltage falls below the reference voltage level.

13. The battery pack of claim 1, wherein the battery electronic control unit is configured to detect a stall condition in an attached power tool during tool operations and to limit the length of time of the stall condition.

14. The battery pack of claim 13, wherein the stall condition is intentionally caused by a user of the power tool.

15. The battery pack of claim 13, wherein the battery electronic control unit maintains a stall counter that increments a count upon a current limit in the pack being exceeded and a duty cycle being less than a threshold, and detects a stall condition if the stall count exceeds a count threshold.

16. The battery pack of claim 13, wherein upon detection of the stall condition, the battery electronic control unit controls the FET so as to pulse the tool motor.

17. The battery pack of claim 16, wherein the battery electronic control unit controls on and off timing of the FET so that the FET remains off for a period of time after stall detection to enable the motor to decelerate in an opposite rotational direction to take up backlash in a gear train of the power tool and mesh gears so that motor torque due to deceleration is transferred to an output shaft of the power tool, and thereafter to turn the FET back on to provide current to the tool motor which, in combination with the torque applied to the output shaft, generates a torque pulse in excess of stall torque.

18. The battery pack of claim 16, wherein the battery electronic control unit controls on and off timing of the FET to achieve a resonance in the tool, wherein resonance is achieved by timing motor activation and motor relaxation to maximize backlash within gear play of the tool so as to create a desired output torque pulse using a minimum amount of battery energy.

19. The battery pack of claim 1, wherein, upon the pack being placed in the tool, the battery electronic control unit detects whether or not there is a short circuit in the power tool.

20. The battery pack of claim 1, wherein the power tool includes a power diode between power terminals in the tool and in parallel with the tool motor, and the pack includes a detection circuit for protecting the FET in the pack if the power diode fails opens or becomes disconnected during power operations.

21. The battery pack of claim 1, wherein the cells are lithium-ion cells.

22. The battery pack of claim 1, wherein the cells are lithium-ion cells and the nominal voltage rating of the battery pack is at least 18V.

23. A battery pack of a cordless power tool system including a power tool and a charger, the battery pack comprising:

a housing;

a plurality of battery cells within the housing;

a battery electronic control unit within the housing for controlling the charger during a charging operation and for controlling current output from the pack during discharge operations;

a first voltage monitoring unit within the housing that monitors one or both of individual cell voltages and total stack voltage in the pack and in data communication with the battery electronic control unit for reporting voltage measures thereto; and

a second voltage monitoring circuit distinct from the first voltage monitoring unit that monitors individual cell voltages and, without interfacing with the battery electronic control unit, generates a disable signal in the charger when any cell reaches an over-voltage condition during a charging operation.

24. The battery pack of claim 23, wherein the first voltage monitoring unit provides a signal representing one of a measured individual cell voltage or stack voltage to the battery electronic control unit during charge and discharge operations, and the battery electronic control unit controls balancing of each of the cell voltages during a charge based on signals received from the first voltage monitoring unit.

25. The battery pack of claim 23, further comprising:

a fuse in a charge return line within the pack acting as additional protection in a case where the battery electronic control circuit in the pack or a current control circuit in the charger becomes inoperative and current exceeds normal levels during charge.

26. The battery pack of claim 23, wherein a sense line is provided between each of the cells and the first voltage monitoring unit to sense individual cell voltage, and each sense line includes a fuse or a fuse-able link therein.

27. The battery pack of claim 23, further comprising a plurality of serial data paths between the battery electronic control unit and one of the charger and power tool for exchanging data and control information there between.

28. The battery pack of claim 27, wherein the battery electronic control unit controls charger output based on cell conditions detected by the first voltage monitoring unit.

29. The battery pack of claim 27, wherein the battery electronic control unit controls output voltage to a tool motor based on information received over the serial data paths from the tool.

30. The battery pack of claim 29, wherein the information includes an analog trigger signal received over the serial data paths and representing a degree of trigger retraction by a user of the tool, and the battery electronic control unit issues a PWM control signal to cause a discharge FET to switch at a desired duty cycle so as to create a desired motor speed.

31. The battery pack of claim 23 wherein the second voltage monitoring circuit includes a fuse in a serial data path connecting the second voltage monitoring circuit to a disable circuit in the charger, wherein the fuse creates an open circuit in the data path when any cell reaches an over-voltage condition during a charging operation.

32. The battery pack of claim 31 wherein the disable circuit includes a transistor having a control terminal connected to the data path and operable to generate the disable signal when the data path having an open circuit.

33. A battery pack of a cordless power tool system including a power tool and a charger, the battery pack comprising:

a housing;

a plurality of battery cells within the housing;

a first voltage monitoring circuit interfaced directly with the plurality of battery cells to measure cell voltages of each battery cell;

a battery electronic control unit configured to receive cell voltage measurements from the first voltage monitoring circuit and control the charger output based on the cell voltage measurements from the first voltage monitoring circuit; and

a second voltage monitoring circuit that is distinct from the first voltage monitoring circuit and interfaced directly with the plurality of battery cells to measure individual cell voltages and control the charger output based on the individual cell voltages measurements and without interfacing with the battery electronic control unit.