US-20260126496-A1 - DEVICE FOR DIAGNOSING A STATE OF A BATTERY AND METHOD THEREOF

US20260126496A1US 20260126496 A1US20260126496 A1US 20260126496A1US-20260126496-A1

Abstract

A device and a method for diagnosing a state of a battery are capable of accurately diagnosing the state of a battery and the state of each cell constituting the battery by: monitoring the charging current of the battery to determine a diagnosing time interval in which a preset current change value is maintained; determining a first voltage and a second voltage in the diagnosing time interval; determining a time taken for each cell voltage of each cell of the battery to reach the second voltage from the first voltage within the diagnosing time interval; and diagnosing the state of the battery based on the time corresponding to each cell.

Inventors

Yo Han BAEK

Assignees

HYUNDAI MOTOR COMPANY
KIA CORPORATION

Dates

Publication Date: 20260507
Application Date: 20250225
Priority Date: 20241104

Claims (18)

1 . A device for diagnosing a state of a battery, the device comprising: a current sensor configured to determine a charging current of the battery; a voltage sensor configured to determine a voltage of the battery; and a controller configured to monitor the charging current of the battery to determine a diagnosing time interval in which a preset current change value is maintained, determine a first voltage and a second voltage as a voltage range of the diagnosing time interval, determine a time taken for each cell voltage of each cell of a plurality of cells of the battery to reach the second voltage from the first voltage within the diagnosing time interval, and diagnose the state of the battery based on the time corresponding to each cell.
2 . The device of claim 1 , wherein the controller is further configured to determine a maximum voltage and a minimum voltage of each cell in the diagnosing time interval, determine a highest value among minimum voltages of the plurality of cells as the first voltage of the diagnosing time interval, and determine a lowest value among maximum voltages of the plurality of cells as the second voltage of the diagnosing time interval.
3 . The device of claim 1 , wherein the controller is further configured to determine a standard deviation of times corresponding to the plurality of cells, and diagnose the state of the battery based on the standard deviation.
4 . The device of claim 1 , wherein the controller is further configured to determine a plurality of diagnosing time intervals, determine a first voltage and a second voltage in each diagnosing time interval, determine a time taken for each cell voltage to reach the second voltage from the first voltage within each diagnosing time interval, and diagnose the state of the battery based on the time corresponding to each cell in each diagnosing time interval of the plurality of diagnosing time intervals.
5 . The device of claim 4 , wherein the controller is further configured to determine a standard deviation of times corresponding to the plurality of cells in each diagnosing time interval, and diagnose the state of the battery based on the standard deviation of each diagnosing time interval.
6 . The device of claim 1 , wherein the controller is further configured to divide the voltage range into a plurality of voltage segments, determine a voltage segment time taken for each cell voltage to reach a maximum voltage from a minimum voltage within each voltage segment, and diagnose the state of the battery based on the voltage segment time corresponding to each cell in each voltage segment.
7 . The device of claim 6 , wherein the controller is further configured to determine a standard deviation of voltage segment times corresponding to the plurality of cells in each voltage segment, and diagnose the state of the battery based on the standard deviation of each voltage segment.
8 . The device of claim 1 , wherein the controller is further configured to monitor the charging current of the battery in all time intervals other than a time interval of a state transition between a closed circuit voltage (CCV) and an open circuit voltage (OCV).
9 . The device of claim 1 , wherein the controller is further configured to determine a time interval of a constant current in which a current change value is 0 (zero) as the diagnosing time interval.
10 . A method of diagnosing a state of a battery, the method comprising: determining, by a controller, a diagnosing time interval in which a preset current change value is maintained, by monitoring a charging current of the battery; determining, by the controller, a first voltage and a second voltage as a voltage range of the diagnosing time interval; determining, by the controller, a time taken for each cell voltage of each cell of a plurality of cells of the battery to reach the second voltage from the first voltage within the diagnosing time interval; and diagnosing, by the controller, the state of the battery based on the time corresponding to each cell.
11 . The method of claim 10 , wherein determining the first voltage and the second voltage includes: determining a maximum voltage and a minimum voltage of each cell in the diagnosing time interval; determining a highest value among minimum voltages of the plurality of cells as the first voltage of the diagnosing time interval; and determining a lowest value among maximum voltages of the plurality of cells as the second voltage of the diagnosing time interval.
12 . The method of claim 10 , wherein diagnosing the state of the battery includes: determining a standard deviation of times corresponding to the plurality of cells; and diagnosing the state of the battery based on the standard deviation.
13 . The method of claim 10 , wherein diagnosing the state of the battery includes diagnosing the state of the battery based on a time corresponding to each cell in each diagnosing time interval of a plurality of diagnosing time intervals based on determining the plurality of diagnosing time intervals.
14 . The method of claim 13 , wherein diagnosing the state of the battery includes: determining a standard deviation of times corresponding to each cell in each diagnosing time interval; and diagnosing the state of the battery based on the standard deviation of each diagnosing time interval.
15 . The method of claim 10 , wherein diagnosing the state of the battery includes: diagnosing the state of the battery based on a voltage segment time corresponding to each cell in each of a plurality of voltage segments based on dividing the voltage range into the plurality of voltage segments.
16 . The method of claim 15 , wherein diagnosing the state of the battery includes: determining a standard deviation of times corresponding to the plurality of cells in each voltage segment; and diagnosing the state of the battery based on the standard deviation of each voltage segment.
17 . The method of claim 10 , wherein determining the diagnosing time interval includes monitoring the charging current of the battery in all time intervals other than a time interval of a state transition between a closed circuit voltage (CCV) and an open circuit voltage (OCV).
18 . The method of claim 10 , wherein determining the diagnosing time interval includes determining a time interval of a constant current in which a current change value is 0 (zero) as the diagnosing time interval.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of and priority to Korean Patent Application No. 10-2024-0154580, filed in the Korean Intellectual Property Office on Nov. 4, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a technology for diagnosing the state of a battery installed in an electric vehicle with high accuracy. BACKGROUND In general, an electric vehicle, which is a vehicle driven by electric energy, is equipped with a battery including a plurality of battery cells that store electric energy. Such battery cells convert chemical energy into electrical energy to supply electrical energy (discharge), or convert electrical energy supplied from an outside into chemical energy to store it (charge). Because an electric vehicle is driven using electrical energy stored in a battery as a power source, the performance of the vehicle is significantly affected by the performance of the battery. Therefore, in order to improve the performance of an electric vehicle, it is required to manage the battery to maximize the performance. In recent years, because battery cells with excellent performance are used to improve the power source of a vehicle, and the number of battery cells increases gradually, it is more required to manage a battery. Such battery management is generally performed by a battery management system (BMS). The battery management system measures cell state information including a voltage, a current, a temperature, and the like of a battery cell from a battery module provided in an electric vehicle, uses the cell state information and option values for controlling battery cells to manage the battery cells, and performs cell balancing to maintain balance between the battery cells. The cell balancing is one of the control operations of a battery management system that equalizes the voltages or charge amounts of battery cells. Each battery cell of a battery module may have differences in electrical characteristics even when the battery cells are manufactured under the same manufacturing conditions and environment. Each battery cell of a battery module may also have differences in electrical characteristics even when the battery cells are mounted and operated in an electric vehicle. Due to such differences in electrical characteristics, even when battery cells are charged and discharged with the same current, voltage imbalance or residual charge imbalance may occur between interconnected battery cells, and the voltage imbalance or residual charge imbalance between battery cells may cause the available voltage range of battery cells to decrease or the charging and discharging cycle to be shorter. Recently, fires have occurred frequently in electric vehicles while charging their batteries. This is caused by an abnormal state of the battery. In order to prevent such fires, technology that can accurately diagnose the state of a battery installed in an electric vehicle is required. The matters described in this background section are intended to promote an understanding of the background of the disclosure and may include matters that are not already known to those of ordinary skill in the art. SUMMARY In some cases, for diagnosing the state of a battery, the voltage change of the battery is monitored in a first transition section (or time interval) from a closed circuit voltage (CCV) to an open circuit voltage (OCV) and a second transition section (or time interval) from the OCV to the CCV, and the state of the battery is diagnosed based on the monitoring result. However, because the voltage change of the battery is to be monitored only during the first and second transition sections, which are very short in time, it is impossible to sufficiently monitor the voltage change of the battery. Therefore, the battery state may not be diagnosed with high accuracy. The present disclosure has been made to solve the above-mentioned problems while advantages achieved by the prior art are maintained intact. One aspect of the present disclosure provides a device for diagnosing a state of a battery and a method thereof, which are capable of accurately diagnosing not only the state of a battery but also the state of each cell constituting the battery by: monitoring the charging current of the battery to determine or detect a current section (i.e., a diagnosing time interval) in which a preset current change value is maintained; determining a first voltage and a second voltage in the current section; determining or detecting the time taken for each cell voltage of each cell of a plurality of cells of the battery to reach the second voltage from the first voltage within the current section; and diagnosing the state of the battery based on the time corresponding to each cell. Another aspect of the present disclosure provides a device for diagnosing a state of a battery and a method thereof, which are capable of accurately d