BATTERY STATE OF HEALTH ESTIMATION USING CHARGING RESISTANCE EQUIVALENT

• US 20150362561A1
• Filed: 06/11/2014
• Published: 12/17/2015
• Est. Priority Date: 06/11/2014
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: DU, Xinyu, ZHANG, YILU, RYCHLINSKI, MARK J.
• Granted Patent: US 10,042,006 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

Abstract

A number of illustrative variations may include a method of estimating battery health including using a charging resistance equivalent.

Claims

1. A method of estimating the state of health of a battery comprising:

calculating a number of charging equivalents for a number of healthy batteries of a particular type and rating in a vehicle;

determining a charging current threshold value Th_Ic, a lower bound voltage Th_V, and an upper bound current Th_I from the calculated charging equivalents;

collecting readings including but not limited to a state of charge (SOC) reading, an open circuit voltage (OCV) reading, and ten groups of terminal voltage readings and associated current readings from a vehicle battery after the vehicle ignition is on;

identifying values that are terminal voltage readings and placing them in a data structure V which can be iterated through;

identifying values that are current readings and placing them in a data structure I which can be iterated through;

identifying all of the current readings (BatIc) and associated terminal voltage readings (BatVc) which are less than Th_Ic;

using at least some of the ten groups of terminal voltage and associated current readings and OCV to determine the value of the charging resistance equivalent ρ

_c; and

using a controller to estimate the health of the battery using ρ

_c.

2. The method of claim 1 wherein determining a charging current threshold value Th_Ic, a lower bound voltage Th_V, and an upper bound current Th_I from the calculated charging resistance equivalents comprises:

providing a number of charging current threshold values within a range of charging current threshold values;

determining a ratio of a number of healthy batteries having charging resistance equivalents falling above each value within a number of values within the range of charging current threshold values to a number of healthy batteries charging resistance equivalents falling below each value within the number of values within the range of charging current values;

determining a standard deviation of a charging resistance equivalent ρ

_c amongst the batteries having a charging current less than each value within a number of values within the range of charging current threshold values;

selecting a threshold value Th_Ic within the number of values within the range of charging current threshold values which is associated with both a high ratio and a small standard deviation; and

using the selected threshold value as a cut-off value for disabling ρ

_c estimation when the battery current is lower than the selected threshold.

3. The method of claim 2 wherein a visual indication of reasonable charging current threshold choices is formed, comprising:

plotting the standard deviation over the range of charging current threshold values with a range of standard deviation values as a Y-axis; and

plotting each determined ratio over the range of charging current threshold values with a ranged of ratio values as a Y-axis;

4. The method of claim 1 wherein determining the value of the charging resistance equivalent ρ

_c comprises;

using all of the identified current readings and associated terminal voltage readings >

Th_Ic to solve for ρ

_c according to;

5. The method of claim 1 wherein determining the value of the charging resistance equivalent ρ

_c comprises;

setting ρ

_c equal to a preset value P_default if the mean value of BatV is less than Th_V and 0 is less than the mean value of BatI when the mean value of BatI is less than Th_I, and SOC is equal to Th_SOC or OCV is equal to Th_OCV.

6. The method of claim 1 wherein determining the value of the charging resistance equivalent ρ

_c comprises;

setting ρ

_c equal to a preset value P default if the mean value of BatV is not less than Th_V or 0 is not less than the mean value of BatI, or the mean value of BatI is not less than Th_I, or SOC is not equal to Th_SOC and CTCV is not equal to Th_OCV, then ρ

_c equals a preset value P_NA.