CN104833856A - Method and device for estimating internal resistance of battery - Google Patents

Abstract

Disclosed is a method for estimating the internal resistance of a battery. The method comprises the following steps: measuring the terminal voltage and the charging current of the battery at the start of performing constant current charging of the battery; obtaining an initial residual electric quantity when the battery is subjected to the constant current charging; finding an initial open-circuit voltage corresponding to the initial residual electric quantity from relation contrasting data recording corresponding relationship of the residual electric quantity and the open-circuit voltage of the battery; and calculating the internal resistance of the battery according to the initial open-circuit voltage, the terminal voltage, and the charging current. The invention further relates to a device for estimating the internal resistance of the battery.

Description

Battery internal resistance estimation method and device

technical field

The invention relates to rechargeable battery technology, in particular to a battery internal resistance estimation method and device.

Background technique

The performance of batteries currently on the market will gradually age over time, and the most direct impact of aging is the decrease in capacitance, which is also accompanied by an increase in the internal impedance of the battery. In order to improve the accuracy of State of Charge (SOC) estimation, it is necessary to accurately estimate the State of Health (SOH) of the battery. One of the methods for estimating SOH is to establish the relationship between battery internal resistance and SOH into a table through experiments, and then estimate the current SOH of the battery by measuring the internal resistance and looking up the table. For lithium-ion batteries, battery internal resistance generally includes ohmic internal resistance and polarization internal resistance. Ohmic internal resistance is composed of electrode material, electrolyte, diaphragm resistance and contact resistance of various parts. Polarization internal resistance refers to the resistance caused by polarization during electrochemical reaction, including the resistance caused by electrochemical polarization and concentration polarization. The internal resistance of the battery will vary with different output currents, battery usage times, temperature and aging conditions.

An existing method of measuring internal resistance is to extract the voltage, current and temperature information of the battery under a certain preset current change to calculate the internal resistance value, and this method can only be used when the battery undergoes a specific current change , so it is limited in use, and it is necessary to wait for the battery to reach the preset condition before estimating the SOH.

Contents of the invention

In view of the above problems, it is necessary to provide a more convenient method for estimating the internal resistance of the battery.

In addition, it is also necessary to provide a relatively convenient battery internal resistance estimation device.

A method for estimating battery internal resistance, the method comprising the steps of:

When the battery is charged with a constant current, measure the terminal voltage and charging current of the battery;

Obtain the initial residual capacity when the battery starts charging with a constant current;

According to the initial residual capacity, find out the value of the initial open circuit voltage corresponding to the initial residual capacity from a relationship comparison data that records the corresponding relationship between the residual capacity of the battery and the open circuit voltage; and

Calculate the internal resistance of the battery according to the values of the initial open circuit voltage, terminal voltage and charging current.

A battery internal resistance estimating device, used to estimate the internal resistance of a battery, the battery internal resistance estimating device comprising:

The storage module is used to store a relationship comparison data that records the corresponding relationship between the residual capacity of the battery and the open circuit voltage;

The measurement module is used to measure the terminal voltage and charging current of the battery when the battery is charged with a constant current;

The processing module is used to obtain the initial residual power when the battery starts charging with a constant current; the processing module includes:

A search unit, configured to find an initial open-circuit voltage value corresponding to the initial residual capacity from the relationship comparison data according to the initial residual capacity; and

The calculating unit calculates the internal resistance of the battery according to the values of the initial open circuit voltage, the terminal voltage and the charging current.

The battery internal resistance estimation device and method estimate the internal resistance of the battery by using various parameters such as voltage and current in the constant current charging state of the battery, because the battery has stable battery characteristics and simplified Therefore, the internal resistance of the battery can be estimated conveniently and accurately through the device and method for estimating the internal resistance of the battery.

Description of drawings

FIG. 1 is a functional block diagram of a device for estimating battery internal resistance according to a preferred embodiment of the present invention.

FIG. 2 is a schematic diagram of a preferred embodiment of relational comparison data stored in the memory module of the battery internal resistance estimation device shown in FIG. 1 .

Fig. 3 is a model diagram of an equivalent circuit of a Thevenin battery.

FIG. 4 and FIG. 5 are flowcharts of a method for estimating battery internal resistance according to a preferred embodiment of the present invention.

Explanation of main component symbols

Battery internal resistance estimation device 100 Measurement module 10 processing module 20 storage module 30 Power Measuring Unit twenty one lookup unit twenty two computing unit twenty three

The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings.

Detailed ways

Please refer to FIG. 1 , a battery internal resistance estimating device 100 according to a preferred embodiment of the present invention is used for estimating the internal resistance of a battery in a constant current charging mode of the battery. The internal resistance estimation device 100 includes a measurement module 10 , a processing module 20 and a storage module 30 . The storage module 30 stores a relationship comparison data, and the relationship comparison data records the corresponding relationship between the remaining capacity of the battery and the open circuit voltage. That is to say, if you know the value of the battery's residual capacity, you can find out the open circuit voltage value of the battery under the residual capacity by comparing the data through this relationship; on the contrary, if you know the open circuit voltage value of the battery, you can find out the Calculate the residual capacity of the battery at the open circuit voltage. The relational control data can be made by collecting the battery in experiments in advance. In this embodiment, the relationship comparison data is presented in the form of a coordinate curve, as shown in FIG. 2 . In other implementation manners, it may also be presented in the form of a table. The functions of each module of the internal resistance estimation device 100 will be described in detail in FIG. 3 .

The internal resistance estimation principle of the battery internal resistance estimation device and method of the present invention will be described below.

Please refer to Figure 3, which shows the equivalent circuit model of a Thevenin battery. From Figure 2, the terminal voltage equation of the battery can be deduced as: V(t)=E(t)+R ₀ I+u(t). Among them, V(t) is the terminal voltage of the battery; E(t) is the open circuit voltage of the battery, R ₀ is the ohmic internal resistance of the battery, and I is the current flowing through the battery. u(t) is the voltage across the polarization internal resistance R1 _of the battery. During the constant current charging process of the battery, that is, the constant current charging process with a predetermined current value, the capacitor C connected in parallel with the polarization internal resistance R1 in FIG. ₂ can be regarded as an open circuit. Therefore, the terminal voltage V(t) of the battery at this time is: V(t)=E(t)+(R ₀ +R ₁ )I. In this way, if the terminal voltage V(t), open circuit voltage E(t) and current I of the battery can be obtained, the internal resistance R=R ₀ +R ₁ of the battery can be calculated.

Please refer to Fig. 4, the method for estimating the internal resistance of a battery in a preferred embodiment of the present invention includes the following steps:

Step S1: The measurement module 10 measures the terminal voltage V(t) and the charging current I of the battery when the battery is charged with a constant current.

Step S2: The processing module 20 acquires the residual capacity of the battery when the battery starts to be charged with a constant current, that is, the initial residual capacity Q ₁ .

Step S3: The search unit ₂₂ finds out the initial open circuit voltage E1 corresponding to the initial residual capacity Q1 according to the initial residual capacity and the relation comparison data.

Step S4: the calculation unit 23 calculates the internal resistance of the battery according to the initial open circuit voltage E1, the terminal voltage V(t), the charging current I and the formula V(t)=E(t)+(R ₀ +R ₁ )I, E(t)=E1 in the aforementioned formula.

Please refer to Fig. 5, wherein, step S2 includes following sub-steps:

Step S21: The power metering unit 21 calculates the charging power ΔQ obtained by the battery during the entire constant current charging process according to the charging current I. The electricity metering unit 21 may be a coulomb calculation device or circuit, and the charging electricity ΔQ is obtained by performing coulomb integration on the charging current I.

Step S22: The measurement module 10 measures the open circuit voltage E2 of the battery after charging. That is, the open circuit voltage E2 after the entire charging process is completed. In this embodiment, in order to obtain more accurate measurement results, the measurement module 10 measures the open circuit voltage value E2 again after the battery is charged at a constant current and left for a period of time.

Step S23: The search unit 22 finds out the residual capacity corresponding to the open circuit voltage value E2 from the relationship comparison data, that is, the total capacity Q ₂ of the battery.

Step S24: The calculation unit 23 calculates the initial residual power Q ₁ according to the charging power ΔQ, the total power Q ₂ and the formula ΔQ=Q ₂ −Q ₁ .

The battery internal resistance estimation device and method estimate the internal resistance of the battery by using various parameters such as voltage and current in the constant current charging state of the battery, because the battery has stable battery characteristics and simplified Therefore, the internal resistance of the battery can be estimated conveniently and accurately through the device and method for estimating the internal resistance of the battery.

Claims (6)

1. an internal resistance of cell estimating and measuring method, the method comprises the steps:

Battery carry out constant-current charge start time, measure the terminal voltage of battery and charging current;

Acquisition battery starts initial residual electricity when carrying out constant-current charge;

According to described initial residual electricity, record the comparison data of the residual electricity of battery and the corresponding relation of open-circuit voltage from one, find out the value of the initial open circuit voltage corresponding with described initial residual electricity; And

The internal resistance of battery is calculated according to the value of described initial open circuit voltage, terminal voltage and charging current.

2. internal resistance of cell estimating and measuring method as claimed in claim 1, is characterized in that, the step obtaining the initial residual electricity that battery starts when carrying out constant-current charge comprises following sub-step:

According to the charge capacity that described charging current calculating battery obtains in whole constant-current charge process;

Measure the open-circuit voltage of battery after charging complete;

From comparison data, find out the residual electricity corresponding with this open-circuit voltage, this residual electricity is called total electricity; And

Described initial residual electricity is calculated according to described charge capacity and total electricity.

3. internal resistance of cell estimating and measuring method as claimed in claim 2, it is characterized in that: calculating in the step of the charge capacity that battery obtains in whole constant-current charge process according to described charging current, obtain described charge capacity by carrying out Coulomb integral to described charging current.

4. an internal resistance of cell estimating apparatus, for estimating the internal resistance of a battery, is characterized in that, described internal resistance of cell estimating apparatus comprises:

Memory module, for the comparison data of the corresponding relation of the residual electricity and open-circuit voltage that store a record battery;

Measurement module, for carry out at battery constant-current charge start time, measure the terminal voltage of battery and charging current;

Processing module, for obtaining the initial residual electricity that battery starts when carrying out constant-current charge; Described processing module comprises:

Search unit, for according to described initial residual electricity, from described comparison data, find out the value of the initial open circuit voltage corresponding with described initial residual electricity; And

Computing unit, calculates the internal resistance of battery according to the value of described initial open circuit voltage, terminal voltage and charging current.

5. internal resistance of cell estimating apparatus as claimed in claim 4, it is characterized in that, described processing module also comprises:

Electric quantity metering unit, for calculating the charge capacity that battery obtains in whole constant-current charge process according to described charging current;

Described measurement module is also for measuring the open-circuit voltage of battery after charging complete;

Describedly search unit also for finding out the residual electricity corresponding with this open-circuit voltage from comparison data, this residual electricity is called total electricity; And

Described computing unit is also for calculating described initial residual electricity according to described charge capacity and total electricity.

6. internal resistance of cell estimating apparatus as claimed in claim 5, is characterized in that: described electric quantity metering unit obtains described charge capacity by carrying out Coulomb integral to described charging current.