Method to estimate battery open-circuit voltage based on transient resistive effects

• US 9,205,750 B2
• Filed: 07/23/2013
• Issued: 12/08/2015
• Est. Priority Date: 07/23/2013
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Bernardi, Dawn, Coupar, Thomas J., Moore, William T., Lee, Josephine S., Taenaka, Robert
• Primary Examiner(s): GARBOWSKI, LEIGH M
• Application Number:
  US13/948,214
• Publication Number:
  US 20150028808A1
• Time in Patent Office: 868 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: B60L 2240/545 Temperature
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 2250/16 by display
• CPC Class Codes: B60L 53/00 Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
• CPC Class Codes: B60L 58/13 Maintaining the SoC within a determined range
• CPC Class Codes: B60L 58/20 having different nominal voltages
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: G01R 31/00 Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere measuring superconductive properties G01R33/1238; testing or measuring semiconductors or solid state devices during manufacture H01L22/00; testing line transmission systems H04B3/46
• 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: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/00712 the cycle being controlled or terminated in response to electric parameters
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• 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

Abstract

A vehicle is disclosed that includes a battery and a controller programmed to calculate a battery voltage characteristic from previously measured charge and discharge data. The battery voltage characteristic is based on differences between the previously measured values when state of charge falls in a range in which the differences are approximately equal. Outside of the range, the charge and discharge voltage data are corrected based on a square root of time to obtain the battery voltage characteristic. The characterization may be performed with a high-rate continuous charge and discharge cycle. Also disclosed is an apparatus for generating the battery characteristic that includes a bi-directional power supply. The battery voltage characteristic is obtained based on the differences of the charge and discharge voltage data and corrected data based on the square root of time. A method is also disclosed based on the same.

Claims

1. A vehicle comprising:

at least one battery cell; and

at least one controller programmed to, in response to a state of charge of the at least one battery cell falling within a range of states of charge for which differences between charge and discharge voltage values previously measured during charging and discharging at each of the states of charge are approximately equal, charge and discharge the at least one battery cell based on the differences.

2. The vehicle of claim 1 wherein the at least one controller is further programmed to charge and discharge the at least one battery cell based on at least one of a charge time of the previously measured charge voltage values and a discharge time of the previously measured discharge voltage values in response to the state of charge falling outside of the range of states of charge.

3. The vehicle of claim 1 wherein the at least one controller is further programmed to charge and discharge the at least one battery cell based on a square root of charge time of the previously measured charge voltage values in response to the state of charge falling outside of the range of states of charge.

4. The vehicle of claim 1 wherein the at least one controller is further programmed to charge and discharge the at least one battery cell based on a square root of discharge time of the previously measured discharge voltage values in response to the state of charge falling outside of the range of states of charge.

5. The vehicle of claim 1 wherein the previously measured charge and discharge voltage values result from charging and discharging the at least one battery cell at a generally constant current such that the differences between the measured charge and discharge voltage values exceed a predetermined amount.

6. An apparatus comprising:

a bi-directional power supply electrically connected to at least one battery cell; and

at least one controller programmed to generate output representing a relationship between voltage and state of charge for the at least one battery cell based on differences between measured charge and discharge voltage values of the at least one battery cell while a state of charge of the at least one battery cell falls within a range of states of charge for which the differences at each state of charge within the range are approximately equal.

7. The apparatus of claim 6 wherein the at least one controller is further programmed to generate output representing the relationship between voltage and state of charge for the at least one battery cell based on a charge time while charging and a discharge time while discharging when the state of charge falls outside of the range of states of charge.

8. The apparatus of claim 6 wherein the bi-directional power supply is commanded to charge and discharge the at least one battery cell with a generally constant current based on a rated current capacity of the at least one battery cell.

9. The apparatus of claim 6 wherein the at least one controller is further programmed to generate output representing the relationship between voltage and state of charge for the at least one battery cell based on a square root of charge time when charging at a state of charge outside of the range of states of charge.

10. The apparatus of claim 6 wherein the at least one controller is further programmed to generate output representing the relationship between voltage and state of charge for the at least one battery cell based on a square root of discharge time when discharging at a state of charge outside of the range of states of charge.

11. A method comprising:

measuring voltage values across a battery during charging and discharging;

calculating a relationship between voltage and state of charge based on differences between the measured charging and discharging voltage values while a state of charge of the battery falls within a range of states of charge for which the differences at each of the states of charge within the range are approximately equal; and

outputting the relationship.

12. The method of claim 11 further comprising calculating the relationship between voltage and state of charge based on a charge time while charging and a discharge time while discharging when the state of charge falls outside of the range of states of charge.

13. The method of claim 11 further comprising calculating the relationship between voltage and state of charge for the battery based on a square root of charge time when charging at a state of charge outside of the range of states of charge.

14. The method of claim 11 further comprising calculating the relationship between voltage and state of charge for the battery based on a square root of discharge time when discharging at a state of charge outside of the range of states of charge.

15. The method of claim 11 wherein the differences between the voltage values measured during charging and the voltage values measured during discharging are averaged over the range of states of charge.

16. The method of claim 11 wherein the charging and discharging is at a generally constant current such that differences between the measured charge and discharge voltage values exceed a predetermined amount.