Circuit and method for detection of battery cell drain

• US 9,381,824 B2
• Filed: 09/30/2014
• Issued: 07/05/2016
• Est. Priority Date: 09/30/2014
• 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., Keramidas, Ai
• Primary Examiner(s): Badii, Behrang
• Assistant Examiner(s): BERNS, MICHAEL ANDREW
• Application Number:
  US14/502,419
• Publication Number:
  US 20160089999A1
• Time in Patent Office: 644 Days
• Field of Search: 701/22, 320/116
• US Class Current: 1/1
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• 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
• CPC Class Codes: Y02T 10/92 Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles
• CPC Class Codes: Y10S 903/907 Electricity storage, e.g. battery, capacitor

Abstract

A vehicle includes a traction battery and a battery management system. The battery management system includes a controller programmed to output a drained cell diagnostic indicator. The drained cell diagnostic indicator is based on a magnitude of a difference between an average cell state of charge at a start of a battery rest period and a cell state of charge estimated at predetermined intervals during the battery rest period being greater than a predetermined value. A response to the drained cell diagnostic indicator depends on the magnitude of the cell drain rate and may include operating the traction battery at a reduced power level and notifying an operator of the diagnostic condition.

Claims

1. A battery management system comprising:

at least one controller programmed to, in response to a magnitude of a difference between an average cell state of charge at a start of a battery rest period and at least one of a plurality of cell states of charge estimated at predetermined intervals during the battery rest period being greater than a predetermined value, output a drained cell diagnostic indicator.

2. The battery management system of claim 1 wherein the at least one controller is further programmed to output the drained cell diagnostic indicator in response to a magnitude of a difference between an average rate of change in cell state of charge over the predetermined intervals and a rate of change in cell state of charge between the predetermined intervals being less than a predetermined threshold for each of the predetermined intervals.

3. The battery management system of claim 1 wherein the at least one controller is further programmed to output the drained cell diagnostic indicator in response to a magnitude of a difference between a cell state of charge estimated at the predetermined intervals and a cell state of charge at the start of the battery rest period being greater than a predetermined difference.

4. The battery management system of claim 1 wherein the at least one controller is further programmed to operate a traction battery during a period of battery usage according to a cell drain rate that is based on the cell state of charge at the predetermined intervals and a cell state of charge at the start of the battery rest period.

5. The battery management system of claim 4 wherein the at least one controller is further programmed to operate the traction battery according to a battery power limit that is a predetermined minimum value when the cell drain rate is greater than a predetermined threshold.

6. The battery management system of claim 4 wherein the at least one controller is further programmed to operate the traction battery according to a battery power limit that is a predetermined percentage of a base battery power limit when the cell drain rate is greater than a predetermined threshold.

7. The battery management system of claim 4 wherein the at least one controller is further programmed to operate the traction battery according to a zero battery power limit when the drain rate is greater than a predetermined threshold and the cell state of charge at the predetermined intervals is outside of a predetermined range.

8. The battery management system of claim 1 wherein the average cell state of charge at the start of the battery rest period is an average of all of the cell states of charge at the start of the battery rest period.

9. The battery management system of claim 1 wherein the battery rest period is a period of time in which a magnitude of a battery current is less than a predetermined current.

10. A vehicle comprising:

a traction battery including a plurality of cells; and

at least one controller programmed to reduce a maximum power requested from the traction battery by a predetermined percentage in response to a cell drain rate that is based on a cell state of charge at a start of a battery rest period and cell states of charge at predetermined intervals during the battery rest period being greater than a redetermined rate.

11. The vehicle of claim 10 wherein the at least one controller is further programmed to output a drained cell diagnostic indicator in response to a magnitude of a difference between an average cell state of charge at a start of the battery rest period and a cell state of charge estimated at predetermined intervals during the battery rest period being greater than a predetermined value.

12. The vehicle of claim 11 wherein the at least one controller is further programmed to output a drained cell diagnostic indicator in response to a magnitude of a difference between an average change in cell state of charge between the predetermined intervals and a change in cell state of charge between the predetermined intervals being less than a predetermined threshold for each of the predetermined intervals.

13. The vehicle of claim 10 wherein the cell drain rate is further based on a battery capacity and an elapsed time since the start of the battery rest period.

14. The vehicle of claim 10 wherein the at least one controller is further programmed to operate the traction battery according to a battery power limit that is a predetermined minimum value when the cell drain rate is greater than a predetermined threshold.

15. A method of operating a traction battery comprising:

outputting, by a controller, a drained cell diagnostic in response to a cell state of charge estimated at predetermined intervals during a battery rest period being outside of a predetermined range about an average cell state of charge computed at a start of the battery rest period; and

operating, by the controller, the traction battery according to the drained cell diagnostic and a cell drain rate.

16. The method of claim 15 wherein the drain rate is based on a difference between the cell state of charge at the start of the battery rest period and the cell state of charge at the predetermined intervals.

17. The method of claim 15 wherein operating the traction battery includes limiting battery power to a predetermined minimum value when the cell drain rate is greater than a predetermined threshold.

18. The method of claim 15 wherein operating the traction battery includes limiting battery power to a predetermined percentage of a base battery power limit when the cell drain rate is greater than a predetermined threshold.

19. The method of claim 15 wherein outputting the drained cell diagnostic is further based on a rate of change of the cell state of charge between the predetermined intervals being within a predetermined range about an average rate of change of the cell state of charge over the predetermined intervals.