System and method for determining battery state-of-health

• US 20010033169A1
• Filed: 12/22/2000
• Published: 10/25/2001
• Est. Priority Date: 01/12/2000
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Original Assignee: Honeywell International Inc.
• Inventors: Hovey, William C., Palanisamy, Thirumalai G., Singh, Harmohan, Huykman, Richard B.
• Granted Patent: US 6,469,512 B2
• Time in Patent Office: Days
• US Class Current: 324/426
• CPC Class Codes: G01R 31/3647 for determining the ability of a battery to perform a critical function, e.g. cranking
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A system and method for accurate and in real time determination of factors relating to the state of health of a storage battery. The system measures the values of battery temperature, voltage and current flow into and out of the battery. This data is multiplexed into a computer and the battery'"'"'s internal resistance (IR), polarization resistance (PR), state of charge (SOC) and its cold cranking amp (CCA) capability are computed and displayed. The presence of shorted and mismatched cells also can be determined and displayed. The state of health of the battery is related to these displayed measured values and calculated factors which are made known to the user of the battery.

Claims

1. A method for monitoring and displaying to a user of a vehicle or a system on a real time basis the state of health (SOH) of a storage battery on which said vehicle or system relies, said method comprising the steps of:

measuring battery voltage and current under one of load and no load conditions for the battery;

computing from the data of the measured battery voltage and current the battery internal resistance and polarization resistance;

determining from said measured battery voltage and current and said computed battery internal resistance and polarization resistance a plurality of the factors of battery state of charge, cold cranking hours, the presence of a shorted cell and the presence of a mismatched cell; and

displaying to the user of said battery said plurality of determined factors.

2. The method of

claim 1

wherein the step of determining comprises determining all of said factors and said step of displaying comprises displaying all of said determined factors.

3. The method of

claim 2

further comprising displaying to the user of said battery at least one of the measured battery voltage and battery current and the computer internal resistance.

4. The method of

claim 1

wherein the step of computing the battery internal resistance is on a DC basis and comprises:

applying one of a voltage (V) and current (I) of known amount to the battery;

determining the change in battery current (dl) in response to the voltage of known amount and the change in battery voltage (dV) in response to the current of known amount; and

computing the battery internal resistance (IR) using the formula dV/dl.

5. The method of

claim 1

wherein the step of computing the battery internal resistance is on an AC basis and comprises:

applying an alternating current voltage or current to the battery;

measuring the corresponding battery current and voltage response; and

calculating the resistance from the applied voltage or current and the measured response.

6. The method of

claim 1

wherein the step of computing the polarization resistance comprises:

computing the battery internal resistance on a direct current basis, computing the battery internal resistance on an alternating current basis, and subtracting the internal resistance computed on an alternating basis from the internal resistance computed on a direct current basis.

7. The method of

claim 1

wherein said step of determining the state of charge (SOC) comprises applying the formula

8. The method of

claim 1

wherein the battery is a lead acid storage battery and the step of determining the cold cranking (CCA) factor comprises computing the battery internal resistance and applying the formal

CCA=950.2−

18616.6*IR.

9. The method of

claim 8

wherein the step of computing the battery internal resistance comprises applying a pulse of known current value and measuring the change in voltage in response to the current pulse.

10. The method of

claim 1

wherein the step of determining the factor of a shorted cell comprises:

charging the battery to full capacity;

measuring the battery terminal voltage over a period of time during which the voltage drops to a predetermined level; and

measuring the battery capacity at the end of the time period to determine if there has been a change in the capacity.

11. The method of

claim 1

wherein the step of determining the factor of a mismatched cell comprises one of:

discharging the battery and determining if the battery voltage goes through two voltage plateaus during discharge; and

charging the battery and determining if the rate of charge of battery voltage with respect top time has passed through a maximum.

12. A system for monitoring and displaying to a user of a vehicle on a real time basis the state of health (SOH) of a storage battery on which said vehicle relies, said system comprising a circuit module mounted to the battery with a connection to at least one of the battery terminals and said circuit module including

means for measuring the battery voltage and current under one of load and no load conditions and for producing voltage and current data values in digital form;

means for computing from the data values of the measured battery voltage and current the battery internal resistance and polarization resistance and for computing from the battery voltage, current, internal resistance (IR) and polarization resistance at least one of the factors of battery state of charge, cold cranking hours, the presence of a shorted cell and the presence of a mismatched cell; and

a display for displaying each of said computed factors to the user of said battery.

13. The system in accordance with

claim 12

wherein said display is mounted on said battery.

14. The system in accordance with

claim 12

wherein the battery is a lead acid storage battery and said means for computing the cold cranking hour (CCAS) factor computes on the basis of

CCA=950.2−

18616.6*IR.