Signal for pre-charge selection in lithium charging and discharge control/pre-charge function

• US 8,154,248 B2
• Filed: 10/07/2008
• Issued: 04/10/2012
• Est. Priority Date: 10/07/2008
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Cruise, Nathan, Aydin, Tarek, Flaharty, Keith D., Qin, Fugen, Phillips, Steven J.
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): Chung, Steve T
• Application Number:
  US12/247,086
• Publication Number:
  US 20100085012A1
• Time in Patent Office: 1,281 Days
• Field of Search: 320/134, 320/112, 320/113, 320/114, 320/115, 320/149, 320/155, 320/160, 320/162, 324/426, 340/636.1, 340/636.21, 200/43.17
• US Class Current: 320/112
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: H02J 7/04 Regulation of charging current or voltage
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A rechargeable battery pack for a power tool can have a data terminal that provides a signal that is indicative of whether the voltage is below a threshold and can serve as both a pre-charge signal for a charger and as a stop-discharge signal for a power tool. A charger can include a power supply circuit and a voltage detection circuit. A charger control module can receive a signal indicative of the voltage of the battery pack and determine a pre-charge time based on the voltage and can monitor a change in the voltage of the battery pack during the pre-charge operation and stop the pre-charge operation based on the change in voltage and the time period.

Claims

1. A battery charger operable to charge a battery pack having a plurality of battery cells and at least one data terminal providing an under voltage signal indicative of a voltage of the battery cells relative to a low voltage threshold, the charger comprising:

a power supply circuit operable to supply a first charge current of a first value and a second charge current of a second value substantially less than the first value; and

a charger control module adapted to receive the under voltage signal from the data terminal of the battery pack and operable to direct the power supply circuit to supply the first and second charge currents based on the under voltage signal,

wherein the power supply circuit supplies the first charge current when the under voltage signal is indicative of every one of the battery cells being at or above the low voltage threshold, and the power supply circuit supplies the second charge current when the under voltage signal is indicative of any one of the battery cells being below the low voltage threshold.

2. The charger of claim 1, wherein the power supply circuit supplies the first charge current when the under voltage signal is at a first state and the power supply circuit supplies the second charge current when the under voltage signal is at a second state different than the first state.

3. The charger of claim 1, further comprising a voltage detection circuit operable to detect an aggregate voltage of the battery cells of the battery pack and the charger control module is operable to cease the supplying of the charger current based on the detected aggregate voltage.

4. The charger of claim 1, wherein the power supply circuit is operable to charge battery cells that include lithium.

5. The charger of claim 1, wherein the power supply circuit supplies the second charge current for no longer than a threshold time period.

6. The charger of claim 5, wherein the threshold time period is a fixed time period.

7. The charger of claim 5, wherein the charger control module monitors the time duration for which the power supply circuit supplies the second charge current and causes the power supply circuit to stop supplying the second charge current and to start supplying the first charge current when the under voltage signal switches to indicating that every one of the battery cells is at or above the low voltage threshold and the time duration is less than the threshold time period.

8. The charger of claim 5, wherein the charger control module monitors the time duration for which the power supply circuit supplies the second charge current and causes the power supply circuit to stop supplying the second charge current and prevents the power supply circuit from supplying the first charge current when the under voltage signal continues to indicate that any one of the battery cells is below the low voltage threshold and the time duration exceeds the threshold time period.

9. A power tool battery pack charger comprising:

a charger operable to engage with the battery pack having at least one battery cell and to supply a charge current, the charger including;

a power supply circuit operable to supply a charge current of first and second values, the second value being substantially less than the first value;

a voltage detection circuit operable to detect a voltage of an engaged battery pack; and

a charger control module adapted to receive a signal from the voltage detection circuit indicative of the voltage of the battery pack and operable to control supplying of the charge current from the power supply circuit to the battery pack, the charger control module adapted to determine a time period for a pre-charge operation based on the voltage of the battery pack, the charger control module adapted to monitor a change in the voltage of the battery pack during the pre-charge operation, and the charger control module operable to stop the pre-charge operation as a function of the change in voltage and the time period,

wherein the pre-charge operation is characterized by the supplying of the charge current at the second value.

10. The power tool battery pack charger of claim 9, wherein the charger control module determines the time period from a look-up table.

11. The power tool battery pack charger of claim 9, wherein the charger control module calculates the time period as a function of an initial detected voltage of the battery pack.

12. The power tool battery pack charger of claim 9, wherein the charger control module determines a rate of change of the voltage of the battery pack and compares the range of change to a threshold and conducts the pre-charge operation based on the comparison.

13. The power tool battery pack charger of claim 12, wherein the threshold is a minimum rate of voltage change and the charger control module terminates the pre-charge operation when the rate is below the threshold.

14. The power tool battery pack charger of claim 9, wherein the time period is based on an initial voltage of the battery pack prior to the initiation of the pre-charge operation.

15. The power tool battery pack charger of claim 9, wherein the charger control module is adapted to receive a signal from the battery pack indicative of a need to conduct a pre-charge operation and the charger control module only implements the pre-charge operation so long as the signal from the battery pack indicates the need for the pre-charge operation.

16. A method of operating a system of power tools having a cordless power tool, a rechargeable battery pack, and a charger, the method comprising:

(a) charging the battery pack with the charger, the charging including;

engaging a first pair of terminals of the battery pack with the charger, the first pair of terminals communicating with battery cells of the battery pack;

engaging a data terminal of the battery pack with the charger;

receiving an under voltage signal with the charger at the data terminal, the under voltage signal being indicative of whether a voltage of any one of the battery cells is below a low voltage threshold without identifying any particular battery cell;

supplying a charge current of a first value to the battery pack with the power supply circuit in the charger when the low voltage signal is indicative of the voltage of every one of the battery cells being at or above the low voltage threshold and supplying a charge current of a second value substantially less than the first value to the battery pack with the power supply circuit in the charger when the low voltage signal is indicative of the voltage of any one of the battery cells being below the low voltage threshold, the power supply circuit communicating with the first pair of terminals; and

(b) powering the power tool with the battery pack, the powering including;

engaging a second pair of terminals of the battery pack with the power tool, the second pair of terminals communicating with the battery cells of the battery pack;

engaging the data terminal with the power tool;

receiving the under voltage signal with the power tool at the data terminal; and

supplying a discharge current from the battery cells to a motor of the power tool based on the under voltage signal received by the power tool, the motor communicating with the second pair of terminals.

17. The method of claim 16, wherein supplying a discharge current includes supplying the discharge current when the under voltage signal is indicative of the voltage of every one of the battery cells being at or above the low voltage threshold and preventing the flow of a discharge current when the low voltage signal is indicative of the voltage of any one of the battery cells being below the low voltage threshold.

18. The method of claim 16, further comprising generating the low voltage signal at the data terminal with a battery management unit in the battery pack.

19. The method of claim 16, further comprising controlling the supplying of the charge current with a charger control module in the charger and controlling the supplying of the discharge current with a tool control module in the power tool.

20. A method of charging a power tool battery pack having at least one battery cell with a charger adapted to engage with the battery pack, the method comprising:

determining whether to implement a first charging operation using a charge current of a first value or a second charging operation using a charge current of a second value substantially less than the first value;

implementing the second charging operation when a voltage of the battery pack is below a low voltage threshold, implementing the second charging operation including;

detecting an initial voltage of the at least one battery cell with a voltage detection circuit;

determining a time period for the second charging operation as a function of the detected initial voltage;

supplying the charge current of the second value to the at least one battery cell with a power supply circuit in the charger;

monitoring a voltage of the at least one battery cell;

determining a change in the voltage of the at least one battery cell over time during the second charging operation;

terminating the second charging operation based on the determined time period and the change in the voltage; and

implementing the first charging operation when the voltage of the battery pack is at or above the low voltage threshold.

21. The method of claim 20, wherein terminating the second charging operation includes comparing the determined change in voltage to a threshold and terminating the second charging operation if the change in voltage is less than the threshold.

22. The method of claim 21, wherein determining a change in voltage includes determining a rate of change of the voltage as a function of time and the threshold is a minimum rate of voltage increase as a function of time.

23. The method of claim 20, wherein determining a time period includes calculating the time period based on a formula and the initial voltage.

24. The method of claim 20, wherein determining a time period includes retrieving the time period from a look-up table based on the initial voltage.

25. The method of claim 20, further comprising monitoring a low voltage signal provided by the battery pack which is indicative of a voltage of the at least one battery cell relative to the low voltage threshold and wherein terminating the second charging operation includes terminating the second charging operation if the low voltage signal is indicative of the voltage of the at least one battery cell being at or above the low voltage threshold.

26. The method of claim 20, wherein detecting an initial voltage includes detecting the initial voltage with a voltage detection circuit in the charger.

27. The method of claim 20, wherein determining whether to implement the first or second charging operation includes receiving a low voltage signal provided by the battery pack which is indicative of a voltage of the at least one battery cell relative to the low voltage threshold and implementing the first charging operation if the low voltage signal is indicative of the voltage of the at least one battery cell being at or above the low voltage threshold, and implementing the second charging operation if the low voltage signal is indicative of the voltage of the at least one battery cell being below the low voltage threshold.

28. A method of charging a power tool battery pack having at least one battery cell with a charger adapted to engage with the battery pack, the method comprising:

monitoring a signal from the battery pack indicative of either the voltage of any one cell being below a low voltage threshold or the voltage of every cell being at or above the low voltage threshold;

determining whether to implement a first charging operation using a charge current of a first value or a second charging operation using a charge current of a second value substantially less than the first value based on the signal from the battery pack;

implementing the second charging operation when the signal indicates that the voltage of any cell of the battery pack is below the low voltage threshold, implementing the second charging operation including;

supplying the charge current of the second value to the at least one battery cell with a power supply circuit in the charger;

monitoring a time duration that the charge current of the second value is supplied;

terminating the second charging operation based on the time duration and the signal.

29. The method of claim 28, wherein terminating the second charging operation includes preventing the implementation of the first charging operation when the time duration exceeds a threshold and the signal continues to indicate that the voltage of any cell of the battery pack is below the low voltage threshold.

30. The method of claim 28, wherein terminating the second charging operation includes implementing the first charging operation when the signal indicates that the voltage of every cell is at or above the low voltage threshold and the time duration is below a threshold.