Methods of discharge control for a battery pack of a cordless power tool system, a cordless power tool system and battery pack adapted to provide over-discharge protection and discharge control

• US 20080203995A1
• Filed: 04/28/2008
• Published: 08/28/2008
• Est. Priority Date: 10/03/2003
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Trinh, Danh Thanh, Carrier, David A., Brotto, Daniele C., Gorti, Bhanuprasad V., Watts, Fred S., Bailey, R. Roby, Seman, Andrew E.
• Granted Patent: US 7,719,234 B2
• Time in Patent Office: Days
• US Class Current: 323/351
• 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: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• 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 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 50/204 Racks, modules or packs for multiple batteries or multiple cells
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

In a cordless power tool system, a battery pack which may removably attachable to a cordless power tool and to a charger may include at least one battery cell and a power limiting device. The power limiting device may be arranged in series with the at least one battery cell for limiting power output of the battery pack based on the component that is connected to the pack. Current and hence power out of the battery pack may be controlled as a function of total internal impedance in the battery pack, which may be adjusted depending on the component that is connected to the pack.

Claims

1. A battery pack adapted to power a first type of power tool and a second type of power tool configured to operate at a higher power than the first type of power tool, comprising:

a positive terminal;

a negative terminal;

a third terminal adapted to receive a sense signal from the first type of power tool;

a control circuit operable to identify the type of power tool attached thereto based on a sense signal received via the third terminal; and

a discharge control circuit operably coupled to the control circuit and operable to selectively control voltage output by the battery pack based on the identified type of power tool.

2. The battery pack of claim 1 wherein the discharge control circuit controls a duty cycle of a semiconductor device disposed in series with a plurality of battery cells.

3. The battery pack of claim 2 wherein the semiconductor device is pulse width modulated field-effect transistor.

4. The battery pack of claim 1 wherein the third terminal senses a signal from the first type of power tool when the pack is connected to the first type of power tool and the third terminal is open when the pack is connected to the second type of power tool.

5. The battery pack of claim 2 wherein the discharge control circuit controls two semiconductor devices operating in parallel to form a parallel combination in series with the plurality of battery cells.

6. A power tool system comprising:

a first power tool being of a first type;

a second power tool being of a second type configured to operate at a higher power than the first type of power tool;

a battery pack having a plurality of serially-connected battery cells therein and configured to attach to the first power tool and the second power tool, the battery pack including a control circuit operable to identify the type of power tool attached thereto based on an input from an attached power tool and a discharge control circuit operably coupled to the control circuit and operable to selectively control voltage output by the battery pack based on the identified type of power tool.

7. The power tool system of claim 6 wherein the battery pack further includes a positive terminal;

a negative terminal; and

a third terminal adapted to receive a sense signal from the first type of power tool.

8. The power tool system of claim 6 wherein the discharge control circuit controls a duty cycle of a semiconductor device disposed in series with the plurality of battery cells.

9. The power tool system of claim 8 wherein the semiconductor device is pulse width modulated field-effect transistor.

10. The power tool system of claim 7 wherein the third terminal senses a signal from the first type of power tool when the pack is connected to the first type of power tool and the third terminal is open when the pack is connected to the second type of power tool.

11. A cordless power tool system, comprising:

a power tool including a tool motor, and

a battery pack having a plurality of cells and removably attached to the power tool for providing power to the motor, wherein a control signal

related to speed control information for the motor of the tool is an input for controlling the current output from the cells for powering the tool.

12. The system of claim 11, wherein discharge control for current out of the pack and speed control for controlling speed of the tool resides in the battery pack.

13. The system of claim 11,

wherein the battery pack further includes:

a positive terminal,

a negative terminal,

a control terminal,

at least one semiconductor device between the negative terminal and at least one cell for providing variable speed control for the tool motor,

a discharge control circuit operatively connected to the positive terminal and control terminal, and operatively connected to the semiconductor device for controlling the semiconductor device, wherein the power tool further includes;

a pair of power terminals, one power terminal connected to the positive terminal and the other to the negative terminals of the pack,

a voltage sense device between the power terminals for sensing a voltage value corresponding to a given tool motor speed to generate the control signal, and

a third terminal connecting the voltage sense device to the control terminal of the pack, and

as the voltage sense device sends the control signal via the third terminal and control terminal to the discharge control device, the discharge control device controls the semiconductor device based on the control signal to control current out of the pack and speed of the tool motor.