Autonomous charge balancing circuit and method for battery pack

• US 9,302,595 B2
• Filed: 01/16/2013
• Issued: 04/05/2016
• Est. Priority Date: 01/16/2013
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Tabatowski-Bush, Benjamin A., Tran, Tuyen Quoc
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): Dhillon, Jagdeep
• Application Number:
  US13/742,437
• Publication Number:
  US 20140197682A1
• Time in Patent Office: 1,175 Days
• Field of Search: 307/9.1, 307/10.1, 307/10.2, 307/82, 307/66, 307/80, 320/136, 320/134, 320/112, 320/116
• US Class Current: 1/1
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 58/10 for monitoring or controlling batteries
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: B60R 16/0315 using multiplexing techniques multiplexing for transmission of signals G08C15/00; multiplexing for electrical communication in general H04J
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

Systems and methods for controlling a vehicle having a traction battery with a plurality of cell groups each having a plurality of serially connected battery cells include balancing each cell of each cell group with a corresponding autonomous cell balancing circuit, and coupling a single output associated with each cell group to an associated battery monitoring circuit. An integrated driver and switch circuit adapts the voltage from an associated cell group for powering battery monitoring integrated circuits with a voltage range corresponding to a single cell voltage range to facilitate use of an existing battery monitoring integrated circuit design and subsequent input to a microprocessor-based battery controller. Cell balancing is performed at each cell with a battery monitor circuit associated with each group of cells.

Claims

1. A method for controlling a traction battery having a plurality of cell groups each having a plurality of serially connected cells, comprising:

balancing each of the cells with a corresponding autonomous cell balancing circuit by, as a difference between a reference voltage and a detected voltage across the cell increases, increasing via analog circuitry a duty cycle of a transistor gate signal to enable a resistor to shunt excess current before overcharge occurs.

2. The method as described in claim 1, comprising:

coupling a plurality of the cell groups in series to form a stack; and

coupling a single output from each of the stacks to a battery controller.

3. The method as described in claim 2, wherein the battery controller comprises a microprocessor.

4. The method as described in claim 1 further comprising:

coupling a voltage divider circuit to each of the cell groups and coupling a single output associated with each of the cell groups to an associated battery monitoring circuit, wherein each of the single outputs comprises an output from one of the voltage divider circuits.

5. The method as described in claim 4, wherein each of the cell balancing circuits and an associated one of the voltage divider circuits are formed on a single substrate.

6. A system for a plurality of battery cell groups each having a plurality of cells coupled in series, comprising:

a plurality of autonomous cell balancing circuits each electrically connected across one of the cells and including analog circuitry configured to increase a duty cycle of a transistor gate signal to enable a resistor to shunt excess current before overcharge occurs as a difference between a reference voltage and a detected voltage across the cell increases.

7. The system of claim 6, wherein each of the cell balancing circuits further comprises a temperature sensor coupled to the analog circuitry and wherein the analog circuitry is further configured to alter the duty cycle based on a temperature of the cell.

8. The system of claim 6 further comprising:

a plurality of battery monitor circuits each connected to a single output from at least one of the cell groups.

9. The system of claim 8, wherein each of the battery monitor circuits includes multiple channels and wherein each of the multiple channels is connected to one of the cell groups.

10. The system of claim 6, wherein the cell groups are connected in series, further comprising a microprocessor-based battery controller connected to the cell groups.

11. A system for controlling a vehicle, comprising:

a traction battery having a plurality of cell groups each having an associated plurality of cells connected in series;

an autonomous cell balancing circuit connected across each of the cells, each of the cell balancing circuits including analogy circuitry configured to increase a duty cycle of a transistor gate signal to enable a resistor to shunt excess current before overcharge occurs as a difference between a reference cell voltage and a measured voltage across the cell increases;

an interface circuit having inputs connected across an associated one of the cell groups and providing an output voltage in a range corresponding to a voltage range of a single one of the cells;

a battery monitor circuit coupled to each interface circuit; and

a battery controller coupled to the battery monitor circuit.

12. The system of claim 11, wherein each of the cell balancing circuits comprises a temperature sensor and wherein the analog circuitry is further configured to alter the duty cycle in response to a signal from the temperature sensor.

13. The system of claim 11, wherein the cell balancing circuits and the interface circuit are formed on a common integrated circuit substrate.

14. The system of claim 11, wherein the battery comprises a lithium-ion battery.

15. The system of claim 11, wherein the interface circuit comprises a voltage divider circuit.