DETECTION AND MITIGATION OF RAPID CAPACITY LOSS FOR AGING BATTERIES

• US 20200132777A1
• Filed: 10/30/2018
• Published: 04/30/2020
• Est. Priority Date: 10/30/2018
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: K, Raghunathan, YING, Ramona Y.
• Granted Patent: US 10,884,062 B2
• Time in Patent Office: Days
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/371 with remote indication, e.g. on external chargers
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A battery control system for a vehicle includes a battery state estimator configured to obtain a battery cell open circuit voltage (OCV) of a battery in response to a charging system charging the battery to a maximum charging voltage. The system includes a negative voltage determination module configured to determine a negative OCV of the battery based on the obtained cell or battery OCV. The system includes a voltage shift determination module configured to identify a difference between the negative OCV of the battery and a previous negative OCV of the battery. The system also includes a charge voltage module configured to selectively reduce the maximum charging voltage to a reduced maximum charging voltage based on the difference and transmit the reduced maximum charging voltage to the charging system. The charging system is instructed to charge the battery such that the battery does not exceed the reduced maximum charging voltage.

Claims

1. A battery control system for a vehicle, the battery control system comprising:

a battery state estimator configured to obtain a battery cell open circuit voltage (OCV) of a battery in response to a charging system charging the battery to a maximum charging voltage;

a negative voltage determination module configured to determine a negative OCV of the battery based on the obtained battery cell OCV;

a voltage shift determination module configured to identify a difference between the negative OCV of the battery and a previous negative OCV of the battery; and

a charge voltage module configured to selectively reduce the maximum charging voltage to a reduced maximum charging voltage based on the difference and transmit the reduced maximum charging voltage to the charging system, wherein the charging system is instructed to charge the battery such that the battery does not exceed the reduced maximum charging voltage.

2. The battery control system of claim 1 wherein the battery state estimator is configured to store the obtained battery cell OCV of the battery in response to the obtained battery cell OCV being measured a predetermined period after the charging system charges the battery to the maximum charging voltage.

3. The battery control system of claim 1 further comprising a voltage sensor configured to measure the voltage of the battery, wherein the charging system receives a measured voltage from the voltage sensor and reduces a charging current supplied to the battery in response to the measured voltage from the voltage sensor reaching at least one of:

(i) the maximum charging voltage and (ii) a reduced maximum voltage.

4. The battery control system of claim 1 further comprising an overpotential identification module configured to:

obtain the OCV of the battery a predetermined period after the charging system charges the battery to the maximum charging voltage; and

determine a cell overpotential of the battery associated with the OCV of the battery.

5. The battery control system of claim 4 wherein the charging voltage module is configured to selectively reduce the maximum charging voltage by the determined cell overpotential or an amount based on the determined cell overpotential.

6. The battery control system of claim 1 wherein the battery state estimator is configured to obtain the OCV of the battery a predetermined period following the battery reaching full charge or the maximum charging voltage.

7. The battery control system of claim 6 wherein the battery is under zero load during the predetermined period.

8. A vehicle comprising:

the battery control system of claim 1; and

a display, wherein the voltage shift determination module transmits a cell capacity alert to the display, and wherein, in response to receiving the cell capacity alert, the display produces at least one of;

a visual alert, an audible alert, and a haptic feedback alert.

9. The battery control system of claim 1 wherein the maximum charging voltage is reduced by an amount based on the difference between the negative OCV of the battery and the previous negative OCV of the battery.

10. The battery control system of claim 9 further comprising a negative OCV history, wherein the previous negative OCV of the battery is an original negative OCV of the battery included in the negative OCV history.

11. The battery control system of claim 1 wherein the charge voltage module selectively reduces the maximum charging voltage of the battery in response to the difference exceeding a threshold value.

12. The battery control system of claim 11 wherein the charge voltage module sets the previous negative OCV of the battery equal to the negative OCV of the battery.

13. A battery control system for a vehicle, the battery control system comprising:

an overpotential identification module configured to obtain an open circuit voltage (OCV) of a battery a predetermined period after a charging system charges the battery to a maximum charging voltage;

a cell overpotential change determination module configured to determine a cell overpotential of the battery based on the obtained OCV;

a voltage shift determination module configured to determine a slope of the cell overpotential using the cell overpotential of the battery and a previous cell overpotential of the battery; and

a charge voltage module configured to selectively reduce the maximum charging voltage to a reduced maximum charging voltage based on the slope and transmit the reduced maximum charging voltage to the charging system, wherein the charging system is instructed to charge the battery such that the battery does not exceed the reduced maximum charging voltage.

14. The battery control system of claim 13 wherein the overpotential identification module includes a voltage sensor configured to measure the OCV across terminals of the battery.

15. A battery control method for a vehicle, the battery control method comprising:

obtaining an open circuit voltage (OCV) of a battery in response to charging the battery to a maximum charging voltage;

determining a negative OCV of the battery based on the obtained OCV;

identifying a difference between the negative OCV of the battery and a previous negative OCV of the battery;

selectively reducing the maximum charging voltage to a reduced maximum charging voltage based on the difference;

transmitting the reduced maximum charging voltage to a charging system; and

instructing the charging system to charge the battery such that the battery does not exceed the reduced maximum charging voltage.

16. The battery control method of claim 15 wherein the obtaining the OCV of the battery occurs a predetermined period after charging the battery to the maximum charging voltage.

17. The battery control method of claim 16 furthering comprising determining a cell overpotential of the battery corresponding to the OCV of the battery and selectively reducing the maximum charging voltage by an amount based on the cell overpotential.

18. The battery control method of claim 15 wherein the obtaining the OCV of the battery occurs while the battery is under zero load.

19. The battery control method of claim 15 wherein the maximum charging voltage is reduced by an amount based on the difference between the negative OCV of the battery and the previous negative OCV of the battery.

20. The battery control method of claim 15 wherein the maximum charging voltage of the battery is selectively reduced in response to the difference exceeding a threshold value.