Method and apparatus for correcting SOC, battery management system and storage medium

Patent metadata

Field	Value
Publication number	US-11262406-B2
Application number	US-202016856642-A
Country	US
Kind code	B2
Filing date	Apr 23, 2020
Priority date	May 24, 2019
Publication date	Mar 1, 2022
Grant date	Mar 1, 2022

Abstract

A method and apparatus for correcting a state of charge (SOC), a battery management system and a storage medium are provided. The method includes: acquiring state data of a battery cell in a case where the battery cell meets a preset standing condition; determining, according to the state data of the battery cell, a near-steady-state battery model for characterizing a change in an open circuit voltage (OCV) over time in a near-steady-state and a steady-state time period threshold for characterizing whether a standing time period is sufficient; processing the steady-state time period threshold by using the near-steady-state battery model to obtain an estimated steady-state OCV value; determining a SOC corresponding to the estimated steady-state OCV value by using a preset correspondence between steady-state OCVs and SOCs; and correcting a current SOC by using the SOC corresponding to the estimated steady-state OCV value.

First claim

What we claimed is:

1. A method for correcting a state of charge (SOC), the method comprising:
recording state of health (SOH), a voltage sequence, a current sequence, a temperature sequence and a time sequence of a battery cell and accumulating a standing time period when the battery cell is under a preset standing condition, wherein the preset standing condition is that a current of the battery cell is less than a preset current threshold;
determining an estimated steady-state open circuit voltage (OCV) value based on the time sequence, the voltage sequence and a steady-state time period threshold when the standing time period reaches the steady-state time period threshold, wherein steady-state time period threshold is determined based on SOH and temperature of the battery cell at current time;
determining an SOC corresponding to the estimated steady-state OCV value by looking up a first preset correspondence between steady-state OCVs and SOCs; and
correcting a current SOC by using the SOC corresponding to the estimated steady-state OCV value, wherein the current SOC is obtained by using an open circuit voltage method.

2. The method according to claim 1 , further comprising:
determining whether a preset trustable parameter condition is met; and
the estimated steady-state OCV value is calculated when the preset trustable parameter condition is met;
wherein the preset trustable parameter condition comprises: a change in voltage of the battery cell during the standing time period is greater than a preset change threshold, a temperature of the battery cell during the standing time period is within a preset temperature range, and the standing time period of the battery cell is greater than a first preset length of time period.

3. The method according to claim 2 , wherein the determining whether the preset trustable parameter condition is met is performed when the battery cell does not meet the preset standing condition and/or each time when the battery cell meet the preset standing condition for a second preset length of time period.

4. The method according to claim 2 , wherein the method further comprises:
calculating, when the preset trustable parameter condition is not met, an unsteady-state OCV, wherein the unsteady-state OCV is a difference between a voltage of the battery cell at an ending moment of the standing time period and a polarization voltage compensation value, wherein the polarization voltage compensation value is determined by looking up a preset correspondence between currents, temperatures and polarization voltage compensation values based on a current and a temperature of the battery cell at the ending moment of the standing time period, or determined by looking up a preset correspondence between statistical characteristics of voltages and temperatures and polarization voltage compensation values based on statistical characteristics of voltages and temperatures of the battery cell during the standing time period;
determining an SOC corresponding to the unsteady-state OCV by looking up a second preset correspondence between unsteady-state OCVs and SOCs; and
correcting the current SOC by using the SOC corresponding to the unsteady-state OCV.

5. The method according to claim 4 , wherein the correcting the current SOC by using the SOC corresponding to the unsteady-state OCV comprises:
determining a voltage rebound direction of the battery cell during the standing time period;
correcting the current SOC by using the SOC corresponding to the unsteady-state OCV when the voltage rebound direction indicates a voltage increase and the SOC corresponding to the unsteady-state OCV is greater than the current SOC; and
correcting the current SOC by using the SOC corresponding to the unsteady-state OCV when the voltage rebound direction indicates a voltage decrease and the SOC corresponding to the unsteady-state OCV is smaller than the current SOC.

6. The method according to claim 4 , wherein the correcting the current SOC by using the SOC corresponding to the unsteady-state OCV comprises:
calculating a difference between the SOC corresponding to the unsteady-state OCV and the current SOC; and
correcting the current SOC by using the SOC corresponding to the unsteady-state OCV when an absolute value of the difference is greater than a preset difference threshold.

7. The method according to claim 4 , wherein the correcting the current SOC by using the SOC corresponding to the unsteady-state OCV comprises:
performing a weighting process on the SOC corresponding to the unsteady-state OCV and the current SOC, and
correcting the current SOC by using the weighted SOC.

8. An apparatus for correcting a state of charge (SOC), the apparatus comprising:
a processor;
a memory storing a program;
wherein the processor is configured to:
record state of health (SOH), a voltage sequence, a current sequence, a temperature sequence and a time sequence of a battery cell and accumulating a standing time period when the battery cell is under a preset standing condition, wherein the preset standing condition is that a current of the battery cell is less than a preset current threshold;
determine an estimated steady-state open circuit voltage (OCV) value based on the time sequence, the voltage sequence and a steady-state time period threshold when the standing time period reaches the steady-state time period threshold, wherein steady-state time period threshold is determined based on SOH and temperature of the battery cell at current time;
determine a state of charge (SOC) corresponding to the estimated steady-state OCV value by looking up a first preset correspondence between OCVs and SOCs; and
correct a current SOC by using the SOC corresponding to the estimated steady-state OCV value, wherein the current SOC is obtained by using an open circuit voltage method.

9. The apparatus according to claim 8 , wherein the processor is further configured to:
determine whether a preset trustable parameter condition is met; and
the estimated steady-state OCV value is calculated when the preset trustable parameter condition is met;
wherein the preset trustable parameter condition comprises: a change in voltage of the battery cell during the standing time period is greater than a preset change threshold, a temperature of the battery cell during the standing time period is within a preset temperature range, and the standing time period of the battery cell is greater than a first preset length of time period.

10. The apparatus according to claim 9 , wherein the processor is further configured to:
calculate, when the preset trustable parameter condition is not met, an unsteady-state OCV, wherein the unsteady-state OCV is a difference between a voltage of the battery cell at an ending moment of the standing time period and a polarization voltage compensation value, wherein the polarization voltage compensation value is determined by looking up a preset correspondence between currents, temperatures and polarization voltage compensation values based on a current and a temperature of the battery cell at the ending moment of the standing time period, or determined by looking up a preset correspondence between statistical characteristics of voltages and temperatures and polarization voltage compensation values based on statistical characteristics of voltages and temperatures of the battery cell during the standing time period;
determine an SOC corresponding to the unsteady-state OCV by looking up a second preset correspondence between unsteady-state OCVs and SOCs; and
correct the current SOC by using the SOC corresponding to the unsteady-state OCV.

11. The apparatus according to claim 10 , wherein the proce

Assignees

• Contemporary Amperex Technology Co Ltd

Inventors

• Du Mingshu
• Li Shichao
• Ruan Jian
• Tang Shenzhi
• Lu Yanhua
• Zhang Wei

Classifications

• G01R31/392

  Determining battery ageing or deterioration, e.g. state of health · CPC title

• H01M2010/4271

  Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing · CPC title

• G01R31/396

  Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery · CPC title

• G01R31/3842

  combining voltage and current measurements · CPC title

• G01R31/367 Primary

  Software therefor, e.g. for battery testing using modelling or look-up tables · CPC title