Lithium battery health assessment method and system based on BMS communication detection technology

Abstract

The present invention discloses a lithium battery health assessment method and system based on BMS communication detection technology, which relates to the technical field of lithium battery health assessment. First, the total voltage, total current, and temperature real-time data of the lithium battery detected by the lithium battery BMS system during the entire charge and discharge cycle are obtained, and the AC internal resistance and DC internal resistance of the lithium battery are detected; the total voltage change curve, total current change curve, and temperature change curve of the lithium battery during the entire charge and discharge cycle are fitted; the first health value is determined based on the total voltage change curve; the second health value is determined based on the total current change curve; the third health value is determined based on the temperature change curve; the fourth health value is determined based on the AC internal resistance and DC internal resistance of the lithium battery; the weighted summation after normalization using the several health values ​​is used to determine the final lithium battery health assessment result. The calculation method of the present invention is simple, the assessment result is more accurate, and a comprehensive assessment of the health of the lithium battery can be performed.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery health assessment, and more specifically to a lithium battery health assessment method and system based on BMS communication detection technology. Background Art

[0002] Electric bicycles mainly use lithium batteries as their power source. Lithium batteries have good performance in the beginning, but as time goes by, battery performance continues to decline, and the performance differences between batteries continue to increase. When battery performance deteriorates, it cannot meet usage requirements, and the battery needs to be replaced.

[0003] The SOH of lithium batteries reflects the safety performance and capacity attenuation of lithium battery packs. The main descriptive parameters include the attenuation of total capacity and the change of internal resistance of lithium batteries. Since unexpected lithium battery health often leads to the failure of the overall function of the lithium battery system, scientific estimation and prediction of the health status of lithium batteries from the perspective of application, further guiding the operation and maintenance of lithium batteries, building a lithium battery status monitoring and health management system, preventing lithium batteries from overcharging and over-discharging, and estimating the health status of lithium batteries are important parameters for achieving long-term and reliable operation of lithium batteries. At present, the methods for evaluating the health status of lithium batteries are relatively complex, usually requiring feature extraction and calculation of data, and only considering single factors such as battery voltage and current. Therefore, how to more accurately and simply evaluate the health of lithium batteries is a problem that technicians in this field urgently need to solve. Summary of the invention

[0004] In view of this, the present invention provides a lithium battery health assessment method and system based on BMS communication detection technology.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A lithium battery health assessment method based on BMS communication detection technology includes the following steps:

[0007] Step 1: Obtain the real-time data of the total voltage, total current, and temperature of the lithium battery detected by the lithium battery BMS system during the entire charge and discharge cycle, and detect the AC internal resistance and DC internal resistance of the lithium battery;

[0008] Step 2: fitting to obtain the total voltage change curve, total current change curve, and temperature change curve of the lithium battery during the entire charge and discharge cycle;

[0009] Step 3: Determine the first health value according to the total voltage change curve; determine the second health value according to the total current change curve; and determine the third health value according to the temperature change curve;

[0010] Step 4: Determine the fourth health value according to the AC internal resistance and DC internal resistance of the lithium battery;

[0011] Step 5: Use the first health value, the second health value, the third health value, and the fourth health value to perform normalization and weighted summation to determine the final lithium battery health assessment result.

[0012] Optionally, in step 1, an AC internal resistance meter is used to collect the AC internal resistance ACR of the lithium battery;

[0013] The DC internal resistance DCR is determined based on the difference between the open circuit voltage of the battery and the voltage of the lithium battery after charge / discharge, and the charge / discharge current value.

[0014] Optionally, in step 3, the first health value is determined according to the total voltage change curve, and the specific method is:

[0015] According to the total voltage change curve, the maximum voltage and the maximum voltage change rate during the charging process, as well as the maximum voltage and the maximum voltage change rate during the discharging process are obtained respectively;

[0016] The maximum voltage value and the maximum voltage change rate during the charging process and the maximum voltage value and the maximum voltage change rate during the discharging process are compared with the corresponding preset threshold values ​​and the differences are taken, and the first health value is determined according to the differences.

[0017] Optionally, in step 3, the second health value is determined according to the total current change curve, and the specific method is:

[0018] According to the total current change curve, the maximum current value and the maximum current change rate during the charging process, as well as the maximum current value and the maximum current change rate during the discharging process are obtained respectively;

[0019] The maximum current value and the maximum current change rate during the charging process and the maximum current value and the maximum current change rate during the discharging process are compared with the corresponding preset thresholds and the difference is determined, and the second health value is determined according to the difference.

[0020] Optionally, in step 3, the third health value is determined according to the temperature change curve, and the specific method is:

[0021] According to the temperature change curve, the maximum temperature and the maximum temperature change rate during the charging process, as well as the maximum temperature and the maximum temperature change rate during the discharging process are obtained respectively;

[0022] The maximum temperature and the maximum temperature change rate during the charging process and the maximum temperature and the maximum temperature change rate during the discharging process are compared with the corresponding preset thresholds and the differences are taken, and the third health value is determined according to the differences.

[0023] Optionally, the preset thresholds are all average values ​​of working status parameter values ​​of several normal lithium batteries under normal operation.

[0024] Optionally, in step 4, the fourth health value is determined according to the AC internal resistance and DC internal resistance of the lithium battery, and the specific method is:

[0025] Comparing the AC internal resistance with the initial value of the AC internal resistance to obtain a first comparison result: if the ratio is less than or equal to a first preset threshold, the AC internal resistance is determined to be normal; otherwise, the AC internal resistance is determined to be abnormal;

[0026] Comparing the DC internal resistance with the AC internal resistance to obtain a second comparison result: if the ratio is less than or equal to a second preset threshold, the DC internal resistance is determined to be normal; otherwise, the DC internal resistance is determined to be abnormal;

[0027] A fourth health value is determined based on the first comparison result and the second comparison result.

[0028] Optionally, in step 5, after obtaining the final lithium battery health assessment result, the final lithium battery health assessment result is compared with a pre-stored health grading system to determine the health status of the lithium battery, including healthy, sub-healthy, faulty, and severe faulty.

[0029] A lithium battery health assessment system based on BMS communication detection technology, including:

[0030] The lithium battery data acquisition unit is used to obtain the real-time data of the total voltage, total current, and temperature of the lithium battery detected by the lithium battery BMS system during the entire charge and discharge cycle, and detect the AC internal resistance and DC internal resistance of the lithium battery;

[0031] The curve fitting unit is used to fit the total voltage change curve, total current change curve and temperature change curve of the lithium battery during the entire charge and discharge cycle;

[0032] The first scoring unit is used to determine a first health value according to a total voltage change curve; determine a second health value according to a total current change curve; and determine a third health value according to a temperature change curve;

[0033] A second scoring unit, used to determine a fourth health value according to the AC internal resistance and the DC internal resistance of the lithium battery;

[0034] The health assessment unit is used to use the first health value, the second health value, the third health value, and the fourth health value to perform normalization and weighted summation to determine a final lithium battery health assessment result.

[0035] It can be seen from the above technical solutions that the present invention provides a lithium battery health assessment method and system based on BMS communication detection technology, which has the following beneficial effects compared with the prior art:

[0036] The present invention takes into account factors such as lithium battery voltage, current, temperature, and battery internal resistance, and conducts a comprehensive assessment of the health of the lithium battery. There is no need to calculate or extract characteristic points. The calculation method is simple, the assessment results are more accurate, and the credibility of the results is increased, providing a data basis for improving the safety of lithium battery use. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0038] Figure 1 It is a schematic diagram of the method steps of the present invention;

[0039] Figure 2 It is a schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The embodiment of the present invention discloses a lithium battery health assessment method based on BMS communication detection technology, see Figure 1 , including the following steps:

[0042] Step 1: Obtain the real-time data of the total voltage, total current, and temperature of the lithium battery detected by the lithium battery BMS system during the entire charge and discharge cycle, and detect the AC internal resistance and DC internal resistance of the lithium battery.

[0043] The voltage, current and other data of lithium batteries can be obtained directly through the BMS system.

[0044] The AC internal resistance and DC internal resistance of lithium batteries are obtained as follows:

[0045] Use an AC internal resistance meter to collect the AC internal resistance ACR of the lithium battery; according to the difference between the open circuit voltage of the battery and the lithium battery voltage after charging / discharging, and the charge / discharge current value, divide the difference and the current value to obtain the DC internal resistance DCR.

[0046] Step 2: fitting to obtain the total voltage change curve, total current change curve, and temperature change curve of the lithium battery during the entire charge and discharge cycle;

[0047] Step 3: Determine the first health value according to the total voltage change curve;

[0048] According to the total voltage change curve, the maximum voltage and the maximum voltage change rate during the charging process, as well as the maximum voltage and the maximum voltage change rate during the discharging process are obtained respectively;

[0049] The maximum voltage value and the maximum voltage change rate during the charging process and the maximum voltage value and the maximum voltage change rate during the discharging process are compared with the corresponding preset thresholds and the differences are taken, and the first health value L1 is determined according to the differences.

[0050] For example, for the maximum voltage V during charging 充max and the corresponding preset threshold V' 充max ,S1=|V 充max -V' 充max | / V' 充max , use the same method to get v 充max Corresponding S2, V 放max Corresponding S3,v 放max Corresponding to S4, then let L1=1-(S1+S2+S3+S4) / 4.

[0051] In other embodiments, the ratio of the number of parameters that meet the preset threshold range to the total number of parameters may also be calculated as the first health value L1.

[0052] Determine a second health value L2 according to the total current change curve;

[0053] According to the total current change curve, the maximum current value and the maximum current change rate during the charging process, as well as the maximum current value and the maximum current change rate during the discharging process are obtained respectively;

[0054] The maximum current value and the maximum current change rate during the charging process and the maximum current value and the maximum current change rate during the discharging process are compared with the corresponding preset thresholds and the difference is taken, and the second health value L2 is determined according to the difference.

[0055] Determine a third health value L3 according to the temperature change curve;

[0056] According to the temperature change curve, the maximum temperature and the maximum temperature change rate during the charging process, as well as the maximum temperature and the maximum temperature change rate during the discharging process are obtained respectively;

[0057] The maximum temperature and the maximum temperature change rate during the charging process and the maximum temperature and the maximum temperature change rate during the discharging process are compared with the corresponding preset thresholds and the differences are taken, and the third health value L3 is determined according to the differences.

[0058] When determining the third health value L3, not only the overall temperature of the lithium battery may be taken into consideration, but further, since a lithium battery is usually composed of a plurality of battery cells, in a specific embodiment, a health value determination may be performed on each battery cell to comprehensively obtain the third health value L3.

[0059] The preset thresholds are all the average values ​​of the working status parameter values ​​of several normal lithium batteries under normal operation. For example, 10 normal lithium batteries are charged and discharged 20 times under normal conditions, and the parameter values ​​during each operation (including total voltage, total current, real-time temperature data, AC internal resistance and DC internal resistance, etc.) are collected, and the average is calculated to obtain the relevant thresholds, including the threshold corresponding to the maximum voltage during the charging process, the threshold corresponding to the maximum rate of change of voltage during the charging process, the threshold corresponding to the maximum voltage during the discharging process, etc.

[0060] Step 4: Determine a fourth health value L4 according to the AC internal resistance and the DC internal resistance of the lithium battery;

[0061] Comparing the AC internal resistance with the initial value of the AC internal resistance to obtain a first comparison result: if the ratio is less than or equal to a first preset threshold, the AC internal resistance is determined to be normal; otherwise, the AC internal resistance is determined to be abnormal;

[0062] Comparing the DC internal resistance with the AC internal resistance to obtain a second comparison result: if the ratio is less than or equal to a second preset threshold, the DC internal resistance is determined to be normal; otherwise, the DC internal resistance is determined to be abnormal;

[0063] The fourth health value L4 is determined according to the first comparison result and the second comparison result. For example, when both comparison results are normal, L4 takes a value of 1, when only one comparison result is normal, takes a value of 0.5, otherwise takes a value of 0.

[0064] In a specific embodiment, the first preset threshold may be 1.8, and the second preset threshold may be 2.0.

[0065] Step 5: Use the first health value, the second health value, the third health value, and the fourth health value to perform normalization and weighted summation to determine the final lithium battery health assessment result. In a specific embodiment, the weight corresponding to each health value can be determined by principal component analysis.

[0066] After obtaining the final lithium battery health assessment result, the final lithium battery health assessment result is compared with the pre-stored health grading system to determine the health status of the lithium battery, including healthy, sub-healthy, faulty, and severe faulty.

[0067] During the specific implementation process, relevant warnings can also be issued for each health value. For example, when the third health value L3 is too large and exceeds the warning line, a battery high temperature warning is required to prompt the user to stop charging and discharging operations in time.

[0068] Another embodiment also discloses a lithium battery health assessment system based on BMS communication detection technology, see Figure 2 ,include:

[0069] The lithium battery data acquisition unit is used to obtain the real-time data of the total voltage, total current, and temperature of the lithium battery detected by the lithium battery BMS system during the entire charge and discharge cycle, and detect the AC internal resistance and DC internal resistance of the lithium battery;

[0070] The curve fitting unit is used to fit the total voltage change curve, total current change curve and temperature change curve of the lithium battery during the entire charge and discharge cycle;

[0071] The first scoring unit is used to determine a first health value according to a total voltage change curve; determine a second health value according to a total current change curve; and determine a third health value according to a temperature change curve;

[0072] A second scoring unit, used to determine a fourth health value according to the AC internal resistance and the DC internal resistance of the lithium battery;

[0073] The health assessment unit is used to use the first health value, the second health value, the third health value, and the fourth health value to perform normalization and weighted summation to determine a final lithium battery health assessment result.

[0074] The method and system for health assessment of lithium batteries of the present invention can be applied to health assessment of lithium batteries of electric bicycles, providing an important basis for the normal use of electric bicycles, especially for user safety protection.

[0075] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0076] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A lithium battery health assessment method based on BMS communication detection technology, characterized in that: The following steps are involved: Step 1: Obtain the real-time data of the total voltage, total current, and temperature of the lithium battery detected by the lithium battery BMS system during the entire charge and discharge cycle, and detect the AC internal resistance and DC internal resistance of the lithium battery; Step 2: fitting to obtain the total voltage change curve, total current change curve, and temperature change curve of the lithium battery during the entire charge and discharge cycle; Step 3: Determine the first health value according to the total voltage change curve; determine the second health value according to the total current change curve; and determine the third health value according to the temperature change curve; Wherein, the first health value is determined according to the total voltage change curve, and the specific method is as follows: According to the total voltage change curve, the maximum voltage and the maximum voltage change rate during the charging process, as well as the maximum voltage and the maximum voltage change rate during the discharging process are obtained respectively; Compare the maximum voltage and the maximum voltage change rate during the charging process and the maximum voltage and the maximum voltage change rate during the discharging process with the corresponding preset thresholds, and determine the first health value according to the difference; According to the total current change curve, the second health value is determined. The specific method is as follows: According to the total current change curve, the maximum current value and the maximum current change rate during the charging process, as well as the maximum current value and the maximum current change rate during the discharging process are obtained respectively; The maximum current value and the maximum current change rate during the charging process and the maximum current value and the maximum current change rate during the discharging process are compared with the corresponding preset threshold values, and a second health value is determined according to the difference; According to the temperature change curve, the third health value is determined. The specific method is as follows: According to the temperature change curve, the maximum temperature and the maximum temperature change rate during the charging process, as well as the maximum temperature and the maximum temperature change rate during the discharging process are obtained respectively; The maximum temperature and the maximum temperature change rate during the charging process and the maximum temperature and the maximum temperature change rate during the discharging process are compared with the corresponding preset thresholds and the difference is determined according to the difference. A third health value; Step 4: Determine the fourth health value based on the AC internal resistance and DC internal resistance of the lithium battery: Comparing the AC internal resistance with the initial value of the AC internal resistance to obtain a first comparison result: if the ratio is less than or equal to a first preset threshold, the AC internal resistance is determined to be normal; otherwise, the AC internal resistance is determined to be abnormal; Comparing the DC internal resistance with the AC internal resistance to obtain a second comparison result: if the ratio is less than or equal to a second preset threshold, the DC internal resistance is determined to be normal; otherwise, the DC internal resistance is determined to be abnormal; Determining a fourth health value according to the first comparison result and the second comparison result; Step 5: Use the first health value, the second health value, the third health value, and the fourth health value to perform normalization and weighted summation to determine the final lithium battery health assessment result.

2. According to claim 1, a lithium battery health assessment method based on BMS communication detection technology is characterized in that: In the step 1, an AC internal resistance meter is used to collect the AC internal resistance ACR of the lithium battery; The DC internal resistance DCR is determined based on the difference between the open circuit voltage of the battery and the voltage of the lithium battery after charge / discharge, and the charge / discharge current value.

3. According to claim 1, a lithium battery health assessment method based on BMS communication detection technology is characterized in that: The preset thresholds are all average values ​​of working state parameter values ​​of several normal lithium batteries under normal operation.

4. A lithium battery health assessment method based on BMS communication detection technology according to claim 1, characterized in that: In step 5, after obtaining the final lithium battery health assessment result, the final lithium battery health assessment result is compared with a pre-stored health grading system to determine the health status of the lithium battery, including healthy, sub-healthy, faulty, and severe faulty.

5. A lithium battery health assessment system based on BMS communication detection technology, characterized in that: include: The lithium battery data acquisition unit is used to obtain the real-time data of the total voltage, total current, and temperature of the lithium battery detected by the lithium battery BMS system during the entire charge and discharge cycle, and detect the AC internal resistance and DC internal resistance of the lithium battery; The curve fitting unit is used to fit the total voltage change curve, total current change curve and temperature change curve of the lithium battery during the entire charge and discharge cycle; The first scoring unit is used to determine a first health value according to a total voltage change curve; determine a second health value according to a total current change curve; and determine a third health value according to a temperature change curve; Wherein, the first health value is determined according to the total voltage change curve, and the specific method is as follows: According to the total voltage change curve, the maximum voltage and the maximum voltage change rate during the charging process, as well as the maximum voltage and the maximum voltage change rate during the discharging process are obtained respectively; Compare the maximum voltage and the maximum voltage change rate during the charging process and the maximum voltage and the maximum voltage change rate during the discharging process with the corresponding preset thresholds, and determine the first health value according to the difference; According to the total current change curve, the second health value is determined. The specific method is as follows: According to the total current change curve, the maximum current value and the maximum current change rate during the charging process, as well as the maximum current value and the maximum current change rate during the discharging process are obtained respectively; The maximum current value and the maximum current change rate during the charging process and the maximum current value and the maximum current change rate during the discharging process are compared with the corresponding preset threshold values, and a second health value is determined according to the difference; According to the temperature change curve, the third health value is determined. The specific method is as follows: According to the temperature change curve, the maximum temperature and the maximum temperature change rate during the charging process, as well as the maximum temperature and the maximum temperature change rate during the discharging process are obtained respectively; The maximum temperature and the maximum temperature change rate during the charging process and the maximum temperature and the maximum temperature change rate during the discharging process are compared with the corresponding preset thresholds and the difference is determined according to the difference. A third health value; The second scoring unit is used to determine a fourth health value according to the AC internal resistance and the DC internal resistance of the lithium battery: Comparing the AC internal resistance with the initial value of the AC internal resistance to obtain a first comparison result: if the ratio is less than or equal to a first preset threshold, the AC internal resistance is determined to be normal; otherwise, the AC internal resistance is determined to be abnormal; Comparing the DC internal resistance with the AC internal resistance to obtain a second comparison result: if the ratio is less than or equal to a second preset threshold, the DC internal resistance is determined to be normal; otherwise, the DC internal resistance is determined to be abnormal; Determining a fourth health value according to the first comparison result and the second comparison result; The health assessment unit is used to use the first health value, the second health value, the third health value, and the fourth health value to perform normalization and weighted summation to determine a final lithium battery health assessment result.

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