METHOD AND SYSTEM FOR DETERMINING BATTERY CELL VOLTAGE

• US 20090160452A1
• Filed: 02/09/2009
• Published: 06/25/2009
• Est. Priority Date: 11/22/2002
• Status: Active Grant

• Current Assignee: Milwaukee Electric Tool Corporation (Techtronic Industries Company Limited)
• Original Assignee: Milwaukee Electric Tool Corporation (Techtronic Industries Company Limited)
• Inventors: Meyer, Gary D.
• Granted Patent: US 8,228,036 B2
• Time in Patent Office: Days
• US Class Current: 324/434
• CPC Class Codes: H01M 50/209 adapted for prismatic or rectangular cells H01M50/216 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: Y02E 60/10 Energy storage using batteries

Abstract

Embodiments of the invention relate to a method and system of determining over-voltage and under-voltage conditions for cells in a battery pack. The method includes combining the cells in a battery pack into groups, detecting each cell group'"'"'s voltage, and calculating ratios of cell group voltages to determine over-voltage and under-voltage conditions.

Claims

1. A battery pack comprising:

a housing;

a first group of cells positioned within the housing, wherein the first group of cells includes at least two cells;

a second group of cells positioned within the housing, wherein the second group of cells includes at least two cells; and

at least two tap connections, wherein the at least two tap connections are positioned with respect to the first and second groups of cells to provide a plurality of voltages related to the first and second groups of cells, the at least two tap connections connected to a detection circuit that is operable to calculate at least one voltage ratio between the first group of cells and the second group of cells.

2. The battery pack of claim 1, further comprising an interface for connecting the at least two tap connections to the detection circuit.

3. The battery pack of claim 1, wherein the detection circuit is located external to the battery pack.

4. The battery pack of claim 3, wherein the detection circuit is located within a power tool.

5. The battery pack of claim 1, wherein the detection circuit compares the at least one voltage ratio to a predetermined voltage ratio.

6. The battery pack of claim 1, further comprising a display for providing an indication of a voltage level of the battery pack.

7. The battery pack of claim 1, wherein the detection circuit determines if the battery pack is in an over-voltage condition, an under-voltage condition, or neither.

8. A battery pack comprising:

an outer casing;

a first group of cells positioned within the outer casing, the first group of cells including at least two cells;

a second group of cells positioned within the outer casing, the second group of cells including at least two cells; and

at least two tap connections, wherein the at least two tap connections are positioned at respective ends of the first or second group of cells, and

wherein the at least two tap connections are connected to a detection circuit, the detection circuit operable to calculate at least one voltage ratio between the first group of cells and the second group of cells.

9. The battery pack of claim 8, further comprising an interface for connecting the at least two tap connections to the detection circuit.

10. The battery pack of claim 8, wherein the detection circuit is located external to the battery pack.

11. The battery pack of claim 10, wherein the detection circuit is located within a power tool.

12. The battery pack of claim 8, wherein the detection circuit compares the at least one voltage ratio to a predetermined voltage ratio.

13. The battery pack of claim 8, further comprising a display for providing an indication of a voltage level of the battery pack.

14. The battery pack of claim 8, wherein the detection circuit determines if the battery pack is in an over-voltage condition, an under-voltage condition, or neither.

15. A method for determining over-voltage and under-voltage conditions of a battery pack, the method comprising:

grouping at least two of a plurality of cells in a first group of cells;

grouping at least two of the plurality of cells in a second group of cells;

positioning at least two tap connections with respect to the first and second groups of cells;

connecting the at least two tap connections to a detection circuit;

providing a plurality of voltages related to the first and second groups of cells to the detection circuit; and

calculating at least one voltage ratio between the first group of cells and the second group of cells.

16. The method of claim 15, wherein the detection circuit is located external to the battery pack.

17. The method of claim 16, wherein the detection circuit is located within a power tool.

18. The method of claim 15, further comprising comparing the at least one voltage ratio to a predetermined voltage ratio.

19. The method of claim 15, further comprising providing an indication of a voltage level of the battery pack.

20. The method of claim 15, further comprising determining if the battery pack is in an over-voltage condition, an under-voltage condition, or neither.