Method for battery state of charge estimation

• US 9,533,598 B2
• Filed: 08/29/2014
• Issued: 01/03/2017
• Est. Priority Date: 08/29/2014
• Status: Expired due to Fees

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Lee, Tae-Kyung
• Primary Examiner(s): Olszewski, John R
• Assistant Examiner(s): Worden, Tommy
• Application Number:
  US14/473,286
• Publication Number:
  US 20160059727A1
• Time in Patent Office: 858 Days
• US Class Current: 1/1
• CPC Class Codes: B60L 53/14 Conductive energy transfer
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: B60L 58/21 having the same nominal voltage
• CPC Class Codes: G01R 31/007 using microprocessors or computers
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• 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 90/14 Plug-in electric vehicles
• CPC Class Codes: Y10S 903/903 having energy storing means, e.g. battery, capacitor

Abstract

A battery management system includes at least one controller programmed to, in response to a battery current becoming approximately zero, output an open-circuit voltage based on a sequence of battery terminal voltages measured during a time interval in which the battery current remains approximately zero and while a charge polarization voltage is decreasing. The open-circuit voltage may be further based on a non-linear regression of the sequence of battery terminal voltages. The non-linear regression may minimize a mean-squared error between the battery terminal voltages and corresponding battery terminal voltage estimates. The at least one controller may command the battery current to zero for the time interval. The battery management system may be included in a vehicle with a traction battery.

Claims

1. A vehicle comprising:

a battery;

and

a controller, coupled to sensors that periodically measure a terminal voltage and a current of the battery, programmed to, in response to the current during operation falling below a predetermined threshold for a duration lasting until the terminal voltage gradient magnitude decreases below a predetermined value, control the terminal voltage during charging to exceed an open-circuit voltage derived from a sequence of terminal voltages measured during the duration.

2. The vehicle of claim 1, wherein the controller is further programmed to command the current to be less than the predetermined threshold for the duration.

3. The vehicle of claim 1, wherein the open-circuit voltage is further based on a non-linear regression of the sequence of terminal voltages.

4. The vehicle of claim 3, wherein the non-linear regression minimizes a mean-squared error between the terminal voltages and corresponding terminal voltage estimates.

5. The vehicle of claim 1, wherein the controller is further programmed to output a state of charge of the battery based on the open-circuit voltage to a display.

6. The vehicle of claim 1, wherein the controller is further programmed to output a charge polarization voltage estimate associated with a time at which the current falls below the predetermined threshold to a memory of the controller.

7. The vehicle of claim 1, wherein the controller is further programmed to limit the open-circuit voltage to be between a maximum voltage and a minimum voltage that are based on predetermined thresholds.