CN115575838A

CN115575838A - Method, apparatus and storage medium for acquiring SOC-OCV curve of secondary battery

Info

Publication number: CN115575838A
Application number: CN202211188126.7A
Authority: CN
Inventors: 陈新虹
Original assignee: Suzhou Yilai Kede Technology Co ltd
Current assignee: Suzhou Yilai Kede Technology Co ltd
Priority date: 2022-09-28
Filing date: 2022-09-28
Publication date: 2023-01-06

Abstract

The invention discloses a method, a device and a storage medium for acquiring a full-battery SOC-OCV curve of a secondary battery, comprising the following steps: respectively obtaining discharge curves of the full battery under different discharge rates; selecting an electric quantity value corresponding to the DOD value of the discharging curve at the minimum discharging current, setting the electric quantity value as a reference value, adjusting the DOD values of other discharging curves by taking the reference value as a reference, and drawing the adjusted discharging curve; drawing a discharging current-voltage curve based on the obtained multiple groups of discharging current and voltage data of the full battery; determining target voltage data based on the drawn discharge current-voltage curve; based on the given depth of discharge and the target voltage data, an SOC-OCV curve is obtained. According to the method, the open-circuit voltage OCV can be quickly and accurately determined only by drawing a plurality of groups of discharge current-voltage curves based on large discharge current and voltage data.

Description

Method, apparatus and storage medium for acquiring SOC-OCV curve of secondary battery

Technical Field

The invention relates to the field of secondary batteries, in particular to a method and a device for acquiring a secondary battery SOC-OCV curve.

Background

In the using process of the lithium ion battery, the state of charge (battery SOC) is an important index, represents the percentage of the remaining available electric quantity of the battery to the total electric quantity, is one of the most important states in a battery management system, and provides important reference for the functions of battery safety management, charge and discharge control, whole vehicle energy management and the like of the electric vehicle. Therefore, performing SOC estimation with high accuracy is a problem that all electric vehicle BMS software development must face. Accurate calibration of the battery SOC will affect the service life of the battery, as well as the dynamic and safety performance of the electric vehicle. At present, most of the finished vehicle SOC calibration is carried out by combining an ampere-hour integration method with a voltage method, and a power battery manufacturer is required to provide an accurate state of charge (SOC) -Open Circuit Voltage (OCV) meter for charging and discharging before the calibration is carried out. The method for calibrating the SOC-OCV curve in the prior art often has the problem that the SOC calibration error is large and the OCV is large in deviation due to deviation of electric quantities under different currents.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a method, a device and a storage medium for acquiring a secondary battery SOC-OCV curve.

In order to achieve the purpose, the invention adopts the technical scheme that:

in a first aspect, there is provided a method of acquiring a full-battery SOC-OCV curve of a secondary battery, including the steps of:

respectively obtaining discharge curves of the full battery under different discharge rates;

selecting an electric quantity value corresponding to the DOD value of any one discharge curve, setting the electric quantity value as a reference value, adjusting the DOD values of other discharge curves by taking the reference value as a reference, and drawing the adjusted discharge curve;

drawing a discharge current-voltage curve based on the obtained multiple groups of discharge current and voltage data;

obtaining target voltage data based on the drawn discharge current-voltage curve;

based on the given depth of discharge and the target voltage data, an SOC-OCV curve is obtained.

In the present application, SOC is a State of Charge (State of Charge) of the battery, and OCV is an Open Circuit Voltage (Open Circuit Voltage) of the battery. Generally, according to the Tafel formula, when the current approaches 0, the internal resistance of the battery is basically unchanged, so the voltage of the battery at this time is the OCV of the battery. By the method, the measurement mode of long period and great difficulty in measuring the OCV of the battery at a small current (when the current approaches to 0) is avoided. And drawing a target discharge current-voltage curve based on a plurality of groups of large discharge current, composite Tafel linear stages and voltage data according to a linear fitting mode. And then, determining a region with basically unchanged internal resistance through the curve, thereby quickly and accurately determining open-circuit voltage OCV data.

Further, selecting an electric quantity value corresponding to the DOD value of any one discharge curve, setting the electric quantity value as a reference value, adjusting the DOD values of other discharge curves by taking the reference value as a reference, and drawing the adjusted discharge curve, wherein the method comprises the following steps of:

acquiring a reference electric quantity value, wherein the reference electric quantity value is a battery electric quantity value corresponding to a specific DOD value of any one discharge curve;

obtaining a comparison electric quantity value, wherein the comparison electric quantity value is a battery electric quantity value corresponding to the specific DOD value of the discharge curve;

obtaining an adjustment parameter of a discharge curve, wherein the adjustment parameter is as follows: comparing the electric quantity value with a reference electric quantity value;

obtaining an adjusted DOD value, wherein the adjusted DOD value is as follows: adjusting parameters for the initial DOD value;

and drawing an adjusted discharge curve based on the adjusted DOD value.

Here, it should be noted that the electric quantity corresponding to the DOD of the battery is different at different discharge rates, for example: under different discharge rates of 0.3C,1C,2C and 3C, the larger the discharge rate is, the smaller the absolute value of the electric quantity corresponding to the DOD (DOD = 1-SOC) of the battery is. Therefore, the present invention needs to adjust the discharge curves after acquiring a plurality of different discharge curves. For example, after two discharge curves of 0.3C and 0.5C are obtained, if the absolute value of the electric quantity corresponding to the battery DOD at the discharge rate of 0.3C is set as the reference value, the DOD value needs to be adjusted by the other discharge curves based on the reference value.

By adjusting the SOC value, the problem that the finally obtained SOC-OCV curve has larger error due to the difference of battery capacities under different discharge rates can be avoided. The invention recognizes the problems, and further adjusts DOD values of different discharge curves by the method of the invention, so that the obtained SOC-OCV curve can describe the performance of the secondary battery more accurately.

In the application, the Discharge curve is a DOD-V curve, the DOD is Depth of Discharge (Depth of Discharge), the DOD-V is Depth of Discharge-voltage, the data of the Depth of Discharge and the voltage can be obtained through the Discharge curves under different Discharge multiplying powers, the data are data conventionally provided by battery manufacturers, and the data are very convenient to obtain.

Further wherein the target voltage data is determined based on the plotted discharge current-voltage curve, comprising the steps of:

extending the drawn discharge current-voltage curve to a position where the discharge current is less than or equal to 0.020C according to a curve extension trend to obtain a target curve;

based on the target curve, obtaining target voltage data of the corresponding position of the target curve when the discharge current is less than or equal to 0.020C;

the target voltage data is the OCV of the full battery.

Specifically, the manner in which the curve extending tendency is extended may be a linear fit or other various manners. The target curve obtained by the above method can be used to obtain an OCV quickly without direct measurement by simply searching a voltage point at which the discharge current is 0.020C or less based on the target curve to obtain an equivalent usable target voltage (equivalent to an OCV). Of course, considering the influence of polarization, the optimum voltage point is when the discharge current is equal to 0C, and the resulting voltage is the most accurate OCV.

In a second aspect, an apparatus for acquiring a secondary battery SOC-OCV curve is provided.

In a third aspect, a computer storage medium having at least one program instruction stored therein is provided, the at least one program instruction being loaded by a processor and performing any of the methods described above.

In order to make the aforementioned and other objects, features and advantages of the invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a DOD-V curve of full cell depth of discharge for the present invention;

FIG. 2 is a full cell discharge current-voltage curve of the present invention;

fig. 3 is a full cell SOC-OCV curve of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example (b):

a method for acquiring a full-cell SOC-OCV curve of a secondary battery includes the following steps:

as shown in fig. 1, discharge curves (DOD-V curves) of the secondary batteries at discharge rates of 0.3c,1c,2c, and 3C were obtained, respectively;

selecting the DOD value of any discharge curve as a reference value, for example, selecting the electric quantity value corresponding to the DOD value under the discharge rate of 0.3C as the reference value, adjusting the DOD values of 1C,2C and 3C discharge curves by taking the reference value as a reference, and drawing the adjusted discharge curve;

specifically, assume that a battery has a battery capacity of 100Ah at 0.3C discharge rate, and 92Ah at 1C discharge rate. At this time, if the battery electric quantity value is set as the reference electric quantity value at the 0.3C discharge rate, the battery electric quantity value is the comparative electric quantity value at the 1C discharge rate, and therefore, at the 1C discharge rate, the adjustment parameters of the DOD value are: 92Ah/100ah =0.92. After the adjustment, when the DOD maximum value of the discharge curve at 0.3C is 1, the DOD maximum value of the discharge curve at 1C is adjusted to 1 × 0.92=0.92. Adjustment of DOD values for other discharge curves, and so on.

It should be noted that the battery power may be adjusted by selecting the total power when the DOD is 0 or the power at any other DOD value. For example, when the DOD is 0.5, the electric quantity value at any discharge rate is the reference electric quantity value, and the electric quantity value at the DOD of 0.5 at the rest of the discharge depths is the comparative electric quantity value, so that the adjusted DOD value can be obtained.

Based on the obtained discharge curve (DOD-V curve), a plurality of sets of discharge current and voltage data at a given depth of discharge are obtained.

Based on the acquired sets of discharge current and voltage data, a discharge current-voltage curve as shown in fig. 2 is plotted.

And extending the drawn discharge current-voltage curve to a position where the discharge current is 0C according to a linear fitting mode to obtain a target curve. Wherein the target curve is a discharge current-voltage curve with the current increasing from 0C.

Based on the target curve, the target voltage data of the corresponding position of the target curve can be determined when the discharge current is 0C;

the target voltage data is the OCV of the full cell;

finally, based on the given depth of discharge and the target voltage data, the SOC-OCV curve as shown in fig. 3 is obtained.

The DOD-V data can be obtained through discharge curves under different discharge multiplying powers, and the data is data conventionally provided by battery manufacturers and is very convenient to obtain.

In addition, the target curve obtained by the method just needs to find a voltage point with the discharge current of 0.020C or less based on the target curve, so that the usable target voltage (equivalent to the OCV) is obtained equivalently, and the OCV can be obtained quickly without direct measurement. Of course, considering the influence of polarization, the optimum voltage point is when the discharge current is equal to 0C, and the resulting voltage is the most accurate OCV.

Claims

1. A method for obtaining a full-cell SOC-OCV curve of a secondary battery, comprising the steps of:

drawing a discharge current-voltage curve based on the adjusted multiple groups of discharge current and voltage data of the full battery;

determining target voltage data based on the drawn discharge current-voltage curve;

2. The method of acquiring a secondary battery full cell SOC-OCV curve according to claim 1, characterized in that: the method comprises the following steps of selecting an electric quantity value corresponding to the DOD value of any one discharge curve, setting the electric quantity value as a reference value, adjusting the DOD values of other discharge curves by taking the reference value as a reference, and drawing the adjusted discharge curve:

acquiring a comparative electric quantity value which is a battery electric quantity value corresponding to the specific DOD value of the discharge curve;

and drawing an adjusted discharge curve based on the adjusted DOD value.

3. The method of claim 1, wherein determining the target voltage data based on the plotted discharge current-voltage curve comprises the steps of:

extending the drawn discharge current-voltage curve to a position where the current is less than or equal to 0.020C according to the curve extension trend to obtain a target curve;

obtaining target voltage data of corresponding positions of the target curve when the current is less than or equal to 0.020C based on the target curve;

the target voltage data is the OCV of the full battery.

4. An apparatus for acquiring a secondary battery SOC-OCV curve, characterized in that: the device comprises a memory and a processor, wherein at least one program instruction is stored in the memory, and the processor is used for realizing the method for acquiring the SOC-open circuit voltage OCV curve of the secondary battery according to any one of claims 1-3 by loading and executing the at least one program instruction.

5. A computer storage medium, characterized in that: the computer storage medium has stored therein at least one program instruction that is loaded and executed by a processor to implement the method of any of claims 1 to 3.