CN108061858A - Lithium battery SOC appraisal procedures based on ohmic internal resistance - Google Patents

Abstract

The invention provides a lithium battery SOC evaluation method based on ohmic internal resistance, which is characterized in that it comprises the following steps: evaluating the state of charge of the lithium ion battery of the lithium ion battery; obtaining the ohmic internal resistance of the lithium ion battery; The state of charge and ohmic internal resistance obtain the effective maximum capacity of the lithium-ion battery in the current state; correct the OCV-SOC curve of the lithium-ion battery according to the effective maximum capacity; and repeatedly correct the OCV-SOC curve. The invention obtains the effective maximum capacity of the current lithium-ion battery through the ohmic internal resistance characteristics of the battery, and then optimizes the OCV-SOC curve of the lithium-ion battery to obtain accurate SOC evaluation results. The method is simple, has strong practicability and high SOC precision, and can be directly applied to a lithium-ion battery management system.

Description

Lithium battery SOC evaluation method based on ohmic internal resistance

technical field

The invention relates to a method for evaluating the state of charge of a lithium-ion battery for a lithium-ion battery.

Background technique

The state of charge (SOC) of lithium-ion batteries is an important parameter of lithium-ion batteries. Since the SOC cannot be directly measured in the working state of the battery, this parameter needs to be obtained through algorithm evaluation.

Various current algorithms mainly use the open circuit voltage of the lithium battery and the corresponding curve OCV-SOC of the SOC as a reference curve, and obtain the SOC parameters of the lithium battery according to the equivalent circuit model of the lithium battery. However, the OCV-SOC curve is not static in actual situations. Previous studies have shown that the OCV-SOC curve changes with the effective maximum capacity of the battery. If accurate lithium battery SOC results are to be obtained, changes in the OCV-SOC curve due to changes in the current maximum capacity of the lithium battery must be considered. At present, the effective maximum capacity of lithium batteries is mainly obtained through electrochemical methods, which is very difficult in practical applications.

Contents of the invention

The purpose of the present invention is to correct the OCV-SOC curve, so as to obtain a more accurate lithium battery SOC.

In order to achieve the above object, the technical solution of the present invention is to provide a lithium battery SOC evaluation method based on ohmic internal resistance, which is characterized in that it includes the following steps:

Step 1. According to the lithium-ion battery OCV-SOC curve and voltage parameter detection and evaluation of the lithium-ion battery state of charge of the lithium-ion battery;

Step 2, obtaining the ohmic internal resistance of the lithium-ion battery;

Step 3. Obtain the effective maximum capacity of the lithium-ion battery in the current state according to the state of charge of the lithium-ion battery obtained in step 1 and the ohmic internal resistance obtained in step 2;

Step 4. Correct the OCV-SOC curve of the lithium-ion battery according to the effective maximum capacity;

Step 5. Repeat steps 1-4.

Preferably, the ohmic internal resistance in step 2 is obtained by measurement or calculation.

Preferably, the state of charge of the lithium-ion battery described in step 1 is the state of charge of the lithium-ion battery at a certain moment, or the state of charge of the lithium-ion battery for a certain period of time; the ohmic internal resistance described in step 2 is a certain The ohmic internal resistance at a moment, or the ohmic internal resistance for a certain period of time.

The invention obtains the effective maximum capacity of the current lithium-ion battery through the ohmic internal resistance characteristics of the battery, and then optimizes the OCV-SOC curve of the lithium-ion battery to obtain accurate SOC evaluation results. The method is simple, has strong practicability and high SOC precision, and can be directly applied to a lithium-ion battery management system.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Detailed ways

In order to make the present invention more comprehensible, preferred embodiments are described in detail below with accompanying drawings.

In the classic lithium battery equivalent circuit model, the battery internal resistance includes two parts: ohmic internal resistance and polarization internal resistance. Among them, the ohmic internal resistance is related to the temperature, aging degree and SOC of the lithium-ion battery and changes regularly. At the same time, the effective maximum capacity of the lithium battery is also related to the temperature and aging of the battery and changes regularly. For example, when the temperature of the lithium battery drops, the effective maximum capacity of the lithium battery decreases, and the ohmic internal resistance of the battery increases; when the aging degree of the lithium battery increases, the effective maximum capacity of the lithium battery decreases, and the ohmic internal resistance of the battery increases. The ohmic internal resistance of a lithium-ion battery is related to the effective maximum capacity of the battery.

According to the related characteristics of lithium-ion battery ohmic internal resistance and effective maximum capacity, the present invention obtains the current effective maximum capacity of lithium-ion batteries through the ohmic internal resistance value in a specific SOC state, and corrects the current OCV-SOC curve according to the effective maximum capacity of the battery , and then obtain the accurate lithium battery SOC at the next moment through this curve. In conjunction with Fig. 1, the concrete steps of the present invention are as follows:

Step 1. According to the lithium-ion battery OCV-SOC curve and voltage parameter detection and evaluation of the lithium-ion battery state of charge of the lithium-ion battery, the state of charge of the lithium-ion battery is the state of charge of the lithium-ion battery at a certain moment, or a certain time Segment Li-ion battery state of charge.

Step 2. Obtain the ohmic internal resistance of the lithium-ion battery. The ohmic internal resistance is the ohmic internal resistance at a certain moment, or the ohmic internal resistance at a certain time period. The ohmic internal resistance can be obtained by measurement or by calculation.

Step 3. Obtain the effective maximum capacity of the lithium-ion battery in the current state according to the state of charge of the lithium-ion battery obtained in step 1 and the ohmic internal resistance obtained in step 2;

Step 4. Correct the OCV-SOC curve of the lithium-ion battery according to the effective maximum capacity;

Step 5. Repeat steps 1-4.

The present invention obtains the current effective maximum capacity of the battery through the current ohmic internal resistance and SOC, and feeds back and corrects the current OCV-SOC curve, which can effectively improve the accuracy of SOC evaluation.

Claims (3)

1. a kind of lithium battery SOC appraisal procedures based on ohmic internal resistance, which is characterized in that comprise the following steps：

Step 1, the lithium ion battery lotus according to lithium ion battery OCV-SOC curves and voltage parameter check and evaluation lithium ion battery Electricity condition；

Step 2, the ohmic internal resistance for obtaining lithium ion battery；

The ohmic internal resistance that step 3, the charge states of lithium ion battery obtained according to step 1 and step 2 obtain obtains current state Effective maximum capacity of lower lithium ion battery；

Step 4 corrects lithium ion battery OCV-SOC curves according to effective maximum capacity；

Step 5 repeats step 1-4.

2. a kind of lithium battery SOC appraisal procedures based on ohmic internal resistance as described in claim 1, which is characterized in that in step 2 The ohmic internal resistance is obtained by measuring or obtained by calculating.

3. a kind of lithium battery SOC appraisal procedures based on ohmic internal resistance as described in claim 1, which is characterized in that in step 1 The charge states of lithium ion battery for a certain moment charge states of lithium ion battery or be certain time period lithium-ion electric Pond state-of-charge；Ohmic internal resistance described in step 2 for a certain moment ohmic internal resistance or be certain time period ohmic internal resistance.