Battery open-circuit voltage measurement using reverse current pulse

• US 9,676,288 B2
• Filed: 03/20/2015
• Issued: 06/13/2017
• Est. Priority Date: 03/20/2015
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Chang, Xiaoguang, Ho, Szushen, Wang, Xu, He, Chuan
• Primary Examiner(s): TSO, EDWARD H
• Application Number:
  US14/664,343
• Publication Number:
  US 20160272080A1
• Time in Patent Office: 816 Days
• Field of Search: 320107, 320127, 320128, 320130, 320131, 320132, 320139, 320141, 320150
• CPC Class Codes: B60L 53/62 in response to charging parameters, e.g. current, voltage or electrical charge
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

A battery management system for a vehicle includes a controller programmed to apply a current pulse to reverse a current flow through a battery to reduce or remove cell polarization. After the current pulse, an open-circuit voltage is measured as the terminal voltage of the battery. The settling time for the terminal voltage to approach the open-circuit voltage is reduced after the current pulse. The magnitude of the current pulse is based on a battery state of charge, a battery temperature, and a current magnitude prior to the current pulse.

Claims

1. A battery management system comprising:

a controller programmed to, in response to an error of a state of charge of a battery being greater than a predetermined error magnitude in a presence of conditions indicative of a terminal voltage of the battery and the open-circuit voltage being different, apply a current pulse to reverse a current flow in the battery followed by a rest period such that cell polarization of the battery is reduced.

2. The battery management system of claim 1 wherein the conditions include charging the battery for greater than a predetermined time.

3. The battery management system of claim 1 wherein the conditions include discharging the battery for greater than a predetermined time.

4. The battery management system of claim 1 wherein the rest period is defined by a time period of approximately zero current.

5. The battery management system of claim 1 wherein a magnitude of the current pulse is based on a state of charge of the battery.

6. The battery management system of claim 1 wherein a magnitude of the current pulse is based on a temperature of the battery.

7. The battery management system of claim 1 wherein a magnitude of the current pulse is based on a magnitude of the current flow in the battery.

8. The battery management system of claim 1 wherein a duration of the current pulse is based on parameters of the battery.

9. The battery management system of claim 1 wherein the current pulse is a charge pulse when the current flow is a discharge current and the current pulse is a discharge pulse when the current flow is a charge current.

10. The battery management system of claim 1 wherein the controller is further programmed to apply the current pulse in response to an elapsed time from an immediately preceding application of the current pulse being greater than a predetermined period of time.

11. A vehicle comprising:

a battery including cells that acquire a cell polarization when a current flows through the battery such that an open-circuit voltage of the battery and a terminal voltage of the battery become different; and

a controller programmed to, in response to a request to measure the open-circuit voltage triggered by an error of a state of charge being greater than a predetermined error magnitude, apply a current pulse to reverse the current followed by a rest period to the battery to reduce the cell polarization.

12. The vehicle of claim 11 wherein the rest period is defined by a time period of approximately zero current.

13. The vehicle of claim 11 wherein a magnitude of the current pulse is based on one or more of a state of charge of the battery, a temperature of the battery, and a magnitude of the current flowing through the battery.

14. The vehicle of claim 11 wherein the current pulse is a charge current pulse when the current flows from the battery.

15. The vehicle of claim 11 wherein the current pulse is a discharge current pulse when the current flows to the battery.

16. The vehicle of claim 11 wherein the controller is further programmed to filter measured values of the current to generate a magnitude of the current pulse such that the magnitude increases as a current magnitude increases and increases as a current duration increases.

17. A method comprising:

reversing, by a controller, a current through a battery according to a current pulse profile that includes a rest period to reduce cell polarization of the battery in response to an error of a state of charge of the battery exceeding a predetermined magnitude; and

outputting, by the controller, a state of charge for the battery based on a measurement of a terminal voltage of the battery taken after the rest period.

18. The method of claim 17 wherein a magnitude associated with the current pulse profile is based on one or more of the state of charge, a temperature of the battery, and a magnitude of current flowing through the battery prior to reversing the current.

19. The method of claim 17 wherein a duration of the current pulse is based on parameters of the battery.