CN112834940B - High-low temperature charging test system for new energy automobile and evaluation optimization method - Google Patents

Abstract

The invention provides a high-low temperature charging test system and an evaluation optimization method for a new energy automobile, comprising the following steps: the power output end of the charging pile is connected with the power input end of the new energy automobile, the new energy automobile is placed on the chassis dynamometer to consume energy, the new energy automobile is completely consumed in the high-low temperature environment cabin, and then the charging pile is used for completing the charging test at high temperature and low temperature.

Description

High and low temperature charging test system and evaluation optimization method for new energy vehicles

Technical Field

The present invention relates to the field of new energy vehicle testing, and in particular to a high and low temperature charging test system and an evaluation optimization method for new energy vehicles.

Background Art

Charging is one of the most important links in the life cycle of electric vehicles. The charging safety of power batteries directly affects the service life and safe operation of electric vehicles. According to the current accident investigation and occurrence scenarios, spontaneous combustion during driving, parking and charging account for the highest proportion, and accidents directly caused by charging account for 25% of all accidents. During the charging process, there may be phenomena such as excessive battery temperature rise, excessive temperature difference in the battery system, overcharging, fast charging or micro-short circuit caused by low-temperature lithium precipitation. These phenomena will cause irreversible damage to the battery or even out of control. For example, excessive temperature rise may cause the decomposition of the solid electrolyte membrane inside the battery, the reaction of the electrolyte with embedded lithium or deposited lithium, etc.; excessive temperature difference will increase the inconsistency of the battery system, affect the service life of the battery, and reduce the safety of the battery system; and low-temperature lithium precipitation will also reduce the intrinsic safety of the battery and shorten the battery life, and there is a risk of causing internal short circuits in the battery. In order to ensure the safety of electric vehicles during and after charging, an evaluation method is urgently needed to evaluate the intrinsic safety, thermal management and charging strategy of the battery system during the charging process of new energy vehicles. Currently, there are few evaluation procedures for high and low temperature charging, which urgently requires technical personnel in this field to solve the corresponding technical problems.

Summary of the invention

The present invention aims to at least solve the technical problems existing in the prior art, and in particular innovatively proposes a high and low temperature charging test system and an optimization method.

In order to achieve the above-mentioned object of the present invention, the present invention provides a high and low temperature charging test system for new energy vehicles, comprising:

The power output end of the charging pile is connected to the power input end of the new energy vehicle. The new energy vehicle is placed on the chassis dynamometer to consume energy. The power of the new energy vehicle is consumed in the high and low temperature environment chamber, and then the high and low temperature charging tests are completed through the charging pile.

Preferably, the high and low temperature environment chamber is a walk-in environmental test chamber.

The present invention also discloses a high and low temperature charging test evaluation optimization method for new energy vehicles, comprising the following steps:

S1, a test pretreatment process is performed on the new energy vehicle, the new energy vehicle is discharged, and after the discharge is completed, a high temperature charging test process is performed;

S2, setting charging conditions during the high-temperature charging test, and conducting a comprehensive evaluation of the state changes of new energy vehicles during the high-temperature charging stage according to different charging conditions;

S3, after the comprehensive evaluation of high-temperature charging, the new energy vehicle is discharged, and after the discharge is completed, the low-temperature charging test process is carried out;

S4, setting charging conditions during the low-temperature charging test, and conducting a comprehensive evaluation of the state changes of new energy vehicles during the low-temperature charging stage according to different charging conditions;

S5, checks the high-temperature charging comprehensive evaluation data and the low-temperature charging comprehensive evaluation data, so as to optimize the comprehensive performance of the new energy vehicle.

Preferably, the S1 comprises:

S1-1, after the new energy vehicle is driven at a stable speed at room temperature, the vehicle is continuously discharged, and after the discharge is completed, preliminary charging is performed at room temperature;

S1-2, placing the new energy vehicle in a high and low temperature environment chamber, keeping it in a high temperature environment for a certain period of time, and then conducting a charging test;

S1-3, charging through the shortest charging time strategy, recording the communication messages between the charging pile and the new energy vehicle;

S1-4, according to the pre-set termination condition of charging, if the condition is met, the charging of the new energy vehicle is terminated under high temperature state.

Preferably, S2 includes:

S2-1, in the charging thermal management state, when the current exceeds the 1/6C current value range during the entire charging process, the high temperature charging is classified into the temperature rise state and the extreme temperature difference state. In the temperature rise state, the maximum temperature of the charging process is defined. When the maximum temperature of the new energy vehicle battery system during the charging process is T≥45℃, the evaluation score and weighted score in the high temperature charging evaluation process are qualified. When the maximum temperature of the new energy vehicle battery system during the charging process is 45℃＜T＜T ₁ , the evaluation score in the high temperature charging evaluation process is and weighted scores When the highest temperature of the new energy vehicle battery system during charging is _T≤T1 , the evaluation score and weighted score during the high temperature charging evaluation process are unqualified;

S2-2, define the maximum and minimum temperature extreme value difference in the extreme temperature difference state. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is ΔT≤2℃, the evaluation score and weighted score in the high temperature charging evaluation process are qualified. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is 2℃＜ΔT＜10℃, the evaluation score in the high temperature charging evaluation process is and weighted scores When the maximum temperature difference ΔT of the battery system during the charging process of a new energy vehicle is ≤10°C, the evaluation score and weighted score during the high-temperature charging evaluation process will be unqualified.

S2-3, under the charging efficiency state, the calculation is performed from the initial charging to the end interval of 80% state of charge, and the high-temperature charging is classified into the charging rate state, the charging power ratio state and the charging economy state. In the charging rate state, the charging power per unit time is defined. When the charging power per unit time P'≥40kw, the evaluation score and weighted score in the high-temperature charging evaluation process are qualified. When the charging power per unit time is 20kw＜P'＜40kw, the evaluation score in the high-temperature charging evaluation process is and the weighted score is When the charging capacity per unit time P'≤20kw, the evaluation score and weighted score in the high temperature charging evaluation process are unqualified; when the ratio of high temperature charging time to normal temperature charging time is greater than 2, the evaluation score in the high temperature charging evaluation process is -25 and the weighted score is -10; when the charging capacity per unit time P'≥60kw, the evaluation score in the high temperature charging evaluation process is +12.5 and the weighted score is +5;

S2-4, in the charging power ratio state, defines the ratio of the high temperature battery charging power to the normal temperature battery charging power. When the ratio of the high temperature battery charging power E _high to the normal temperature battery charging power E _nor is When the evaluation score and weighted score are qualified in the high-temperature charging evaluation process, the ratio of the high-temperature battery charging capacity E _high to the normal-temperature battery charging capacity E _nor is When the high temperature charging evaluation process is and the weighted score is When the ratio of the high temperature battery charge E _high to the normal temperature battery charge E _nor is When the high temperature battery charging capacity E _high and the normal temperature battery charging capacity E nor are equal, the evaluation score and weighted score are unqualified in the high temperature charging evaluation process; when the high temperature battery charging capacity E high and the normal temperature battery charging capacity E _nor are equal When the battery is charged at high temperature, the evaluation score is considered unqualified during the high temperature charging evaluation process, and the weighted score is not calculated;

S2-5, define the ratio of the battery charging power E _bat to the charging pile output power E _cha under the charging economy state. When the ratio of the battery charging power E _bat to the charging pile output power E _cha is When the battery charging capacity _Ebat and the charging pile output capacity _Echa are equal, the evaluation score and weighted score are qualified in the high temperature charging evaluation process; when ... When the high temperature charging evaluation process is and the weighted score is When the ratio of battery charging capacity _Ebat to charging pile output capacity _Echa is When the electric vehicle is in the terminal charging state for more than 30 minutes at the end of the charging process or at the end of the charging process, the evaluation score and weighted score will be unqualified during the high temperature charging evaluation process.

Preferably, S3 includes:

S3-1, after the new energy vehicle is driven at a stable speed at room temperature, the vehicle is continuously discharged, and after the discharge is completed, it is preliminarily charged at room temperature;

S3-2, placing the new energy vehicle in a high and low temperature environment chamber, keeping it in a low temperature environment for a certain period of time, and then conducting a charging test;

S3-3, charging through the shortest charging time strategy, recording the communication messages between the charging pile and the new energy vehicle;

S3-4, according to the pre-set termination conditions for charging, if the conditions are met, the charging of the new energy vehicle is terminated in the low temperature state.

Preferably, S4 includes:

S4-1, in the charging thermal management state, when the current exceeds the 1/6C current value range during the entire charging process, the low-temperature charging is classified into the lowest temperature average temperature state and the highest and lowest temperature extreme temperature difference state. In the lowest temperature average temperature state, when the lowest average temperature of the new energy vehicle battery system during the charging process T'≥0℃, the evaluation score and weighted score in the low-temperature charging evaluation process are qualified. When the lowest average temperature of the new energy vehicle battery system during the charging process is -7℃<T'<0℃, the evaluation score in the low-temperature charging evaluation process is and weighted scores When the lowest average temperature T'≤-7℃ during the charging process of the new energy vehicle battery system, the evaluation score and weighted score in the low temperature charging evaluation process are unqualified. If the lowest average temperature T'<0℃ during the charging process of the new energy vehicle battery system, the battery charging current exceeds 1/3C and is maintained for more than 15 minutes, the evaluation score in the low temperature charging evaluation process is -25 and the weighted score is -10.

S4-2, define the maximum and minimum temperature extreme value difference in the extreme temperature difference state. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is ΔT≤2℃, the evaluation score and weighted score in the low temperature charging evaluation process are qualified. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is 2℃＜ΔT＜10℃, the evaluation score in the low temperature charging evaluation process is and weighted scores When the maximum temperature difference ΔT of the battery system during the charging process of a new energy vehicle is ≤10°C, the evaluation score and weighted score during the low-temperature charging evaluation process are unqualified;

S4-3, in the charging efficiency state, the calculation is performed from the initial charging to the end interval of 80% state of charge, and the low-temperature charging is classified into the charging rate state, the charging power ratio state and the charging economy state. In the charging rate state, the charging power per unit time is defined. When the charging power per unit time P'≥35kw, the evaluation score and weighted score in the high-temperature charging evaluation process are qualified. When the charging power per unit time is 15kw＜P'＜35kw, the evaluation score in the high-temperature charging evaluation process is and the weighted score is When the charging capacity per unit time P'≤20kw, the evaluation score and weighted score in the high temperature charging evaluation process are unqualified; when the ratio of high temperature charging time to normal temperature charging time is greater than 3, the evaluation score in the high temperature charging evaluation process is -25 and the weighted score is -10; when the charging capacity per unit time P'≥50kw, the evaluation score in the high temperature charging evaluation process is +12.5 and the weighted score is +5;

S4-4, in the charging power ratio state, defines the ratio of the low temperature battery charging power to the normal temperature battery charging power. When the ratio of the low temperature battery charging power E _low to the normal temperature battery charging power E _nor is When the low-temperature battery charging capacity E _low and the normal temperature battery charging capacity E nor are equal, the evaluation score and weighted score are qualified in the low-temperature charging evaluation process; when the ratio of the low-temperature battery charging capacity E low to the normal temperature battery charging capacity E _nor is equal to When the high temperature charging evaluation process is and the weighted score is When the ratio of the low temperature battery charging capacity E _low to the normal temperature battery charging capacity E _nor is When the ratio of the low-temperature battery charging capacity E _low to the normal-temperature battery charging capacity E _nor is When the battery is charged at high temperature, the evaluation score is considered unqualified during the high temperature charging evaluation process, and the weighted score is not calculated;

S4-5, under the charging economy state, define the ratio of the battery charging power E _bat to the charging pile output power E _cha . When the ratio of the battery charging power E _bat to the charging pile output power E _cha is When the battery charging capacity _Ebat and the charging pile output capacity _Echa are equal, the evaluation score and weighted score are qualified in the high temperature charging evaluation process; when ... When the high temperature charging evaluation process is and the weighted score is When the ratio of battery charging capacity _Ebat to charging pile output capacity _Echa is When the electric vehicle is in the terminal charging state for more than 30 minutes at the end of the charging process or at the end of the charging process, the evaluation score and weighted score will be unqualified during the high temperature charging evaluation process.

Preferably, S5 includes:

The judgment matrix can be set to obtain values through the following hierarchical relationship, where i and j refer to the high temperature charging index and the low temperature charging index respectively:

1. a _ij = 1, high temperature charging index i and low temperature charging index j have the same importance to the previous level index;

2. a _ij = 3, high temperature charging index i is more important than low temperature charging index j;

3. a _ij = 5, high temperature charging index i is more important than low temperature charging index j;

4. a _ij = 7, high temperature charging index i is more important than low temperature charging index j;

5. a _ij = 9, high temperature charging index i is more important than low temperature charging index j;

Let C represent the judgment matrix, and then calculate the maximum eigenvalue and corresponding eigenvector of C, which are 5.3866, -0.6958, -0.2132, -0.6751, -0.1113, and -0.0467 respectively. After standardization, the eigenvector becomes 0.39 0.120.390.06 0.02, and a consistency test is performed: Where n is the matrix order, λ _max is the maximum eigenvalue, and D is the matrix.

Preferably, S5 includes:

The charging capacity of the new energy vehicle battery system is calculated based on the integration of the battery system charging current I and the battery system charging voltage U from the beginning of charging to charging to 80% SOC. The changing trends of I and U when charging to 80% SOC at high temperature, according to the integration of voltage and current at the corresponding time, the charging capacity at high temperature is 41.21kWh, the time consumed is 4562.2s, and the average charging power of the battery system is 32.52kW; the time consumed by the new energy vehicle to charge to 80% SOC at room temperature, the ratio of high temperature charging time to normal temperature charging time is 1.32, the changing trends of I and U when charging to 80% SOC at room temperature, the charging capacity at room temperature is calculated to be 40.97kW/h, so it can be known that the charging capacity ratio is 1.01, the output current and output voltage curve of the charging pile when charging to 80% SOC at high temperature, according to the integration, the output energy of the charging pile is 43.50kWh, and the proportion of charging economy is 0.95.

In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

The present invention discloses a low-temperature charging evaluation method, which mainly compares the charging time of a car charged to 80% SOC in an extremely cold environment with the charging time at normal temperature, and evaluates the low-temperature charging performance of different models by the time ratio between the two. The evaluation optimization method can simply compare the low-temperature charging capabilities of different models. This evaluation optimization method mainly evaluates the high and low temperature charging of electric vehicles from the two aspects of battery thermal management and charging efficiency. This method can comprehensively evaluate the thermal management system, charging strategy and battery performance of different models from the perspective of safety and performance and provide optimization suggestions.

Data is collected on charging of different vehicle models in high and low temperature environments, and the evaluation data is directly evaluated by intercepting communication messages.

Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

Fig. 1 is a schematic diagram of the system of the present invention;

FIG2 is a temperature and time curve diagram of charging at high temperature tested in the present invention;

FIG3 is a graph showing charging current and charging voltage of a rechargeable battery system under high temperature tested by the present invention;

FIG4 is a graph showing charging current and charging voltage of a rechargeable battery system at room temperature tested by the present invention;

FIG5 is a graph showing the output current and output voltage of a charging pile under high temperature tested by the present invention;

FIG. 6 is a temperature and time curve diagram of charging at low temperature tested by the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

As shown in FIG1 , the present invention discloses a high and low temperature charging test evaluation optimization method for new energy vehicles, comprising the following steps:

S1, a test pretreatment process is performed on the new energy vehicle, the new energy vehicle is discharged, and after the discharge is completed, a high temperature charging test process is performed;

S2, setting charging conditions during the high-temperature charging test, and conducting a comprehensive evaluation of the state changes of new energy vehicles during the high-temperature charging stage according to different charging conditions;

S3, after the comprehensive evaluation of high-temperature charging, the new energy vehicle is discharged, and after the discharge is completed, the low-temperature charging test process is carried out;

S4, setting charging conditions during the low-temperature charging test, and conducting a comprehensive evaluation of the state changes of new energy vehicles during the low-temperature charging stage according to different charging conditions;

S5, checks the high-temperature charging comprehensive evaluation data and the low-temperature charging comprehensive evaluation data, so as to optimize the comprehensive performance of the new energy vehicle.

Charging under extreme conditions such as high and low temperatures has a great impact on the battery. By statistically analyzing the temperature characteristics of most parts of the country, finding cities with certain representative maximum temperatures in summer and minimum temperatures in winter in China, and calculating the average temperature and weighted average temperature, we decided to use (39±2)℃ and (-11±2)℃ as the high and low temperature test temperatures for this procedure.

In order to simulate the charging method with the lowest safety factor when charging electric vehicles, this test procedure uses the charging strategy with the shortest charging time. The charging pile uses a Teladian charging pile with a charging power of 120kW, which meets the charging power requirements of almost all electric vehicles at present.

1. Test conditions

1) The charging pile should be a commercial DC charging pile whose charging power meets the maximum charging power required by the vehicle;

2) At the beginning of the test, all protective devices that affect the function of the test object and are related to the test results should be in normal operating condition, such as the relevant relays contained in the battery system circuit should be closed.

2. Experimental Pretreatment

According to the requirements of 4.4.4.2 of GB/T 18386-2017, the test vehicle is driven at a stable speed of (70±5)% of the maximum speed for 30 minutes at room temperature (20℃～30℃) to discharge the vehicle's power battery. The test ends when the speed cannot reach 65% of the maximum speed for 30 minutes. After pretreatment, the vehicle is left at room temperature for 1 hour.

The test sequence is: first charge at normal temperature (10℃～30℃), then charge at high temperature, and finally charge at low temperature.

3. High temperature charging test steps

1) Before charging the vehicle, place the vehicle in a (39±2)℃ environment for 12 hours and test it in this environment;

2) Connect to the charging pile and charge using the charging strategy that takes the shortest time;

3) During the charging process, the communication messages between the charging pile and the electric vehicle are recorded, including the maximum and minimum temperatures of the single cell, the charging capacity of the charging pile, the charging voltage, current, battery state of charge and charging time, etc.

4) Charging is terminated when one of the following conditions is met:

a. The charging vehicle automatically terminates charging;

b. The charging vehicle does not automatically terminate charging, and the temperature of the test object exceeds the maximum operating temperature defined by the battery system manufacturer by more than 10°C;

c. The charging vehicle does not automatically terminate charging and the battery state of charge exceeds 100% SOC;

d. At the end of charging, the electric vehicle is in the terminal charging state (not less than 97%) for more than 30 minutes.

5) After completing the above test steps, if the charging termination conditions in step b or c in the previous step occur, the test is considered abnormal charging termination and this test item ends. Otherwise, observe the vehicle for 1 hour at the test ambient temperature, record whether the vehicle and charging pile have fault alarms, the vehicle's charge status, and check whether the vehicle can start and drive normally after charging is completed.

4. Low temperature charging test steps

1) Before charging the vehicle, place the vehicle in an environment of (-11±2)℃ for 12 hours and test it in this environment;

2) Connect to the charging pile and charge using the charging strategy that takes the shortest time;

3) During the charging process, the communication messages between the charging pile and the electric vehicle are recorded, including the maximum and minimum temperatures of the single cell, the charging capacity of the charging pile, the charging voltage, current, battery state of charge and charging time, etc.

4) Charging is terminated when one of the following conditions is met:

a. The charging vehicle automatically terminates charging;

b. The charging vehicle does not automatically terminate charging, and the temperature of the test object exceeds the maximum operating temperature defined by the battery system manufacturer by more than 10°C;

c. The charging vehicle does not automatically terminate charging and the battery state of charge exceeds 100% SOC;

d. At the end of charging, the electric vehicle is in the terminal charging state (not less than 97%) for more than 30 minutes.

5) After completing the above test steps, if the charging termination conditions in step b or c in the previous step occur, the test is considered abnormal charging termination and this test item ends. Otherwise, observe the vehicle for 1 hour at the test ambient temperature, record whether the vehicle and charging pile have fault alarms, the vehicle's charge status, and check whether the vehicle can start and drive normally after charging is completed.

The high and low temperature charging evaluation of the whole vehicle can be divided into two parts: high temperature charging score and low temperature charging score. The high temperature score accounts for 60% of the total high and low temperature charging score, and the low temperature score accounts for 40%. The high and low temperature charging score is comprehensively scored from the two aspects of charging thermal management and charging efficiency. Charging thermal management is calculated based on the current value interval exceeding 1/6C during the entire charging process, and the charging efficiency is calculated from the initial charging to the end of the 80% state of charge.

Evaluation method for high temperature charging of whole vehicle

S2-1, in the charging thermal management state, when the current exceeds the 1/6C current value range during the entire charging process, the high temperature charging is classified into the temperature rise state and the extreme temperature difference state. In the temperature rise state, the maximum temperature of the charging process is defined. When the maximum temperature of the new energy vehicle battery system during the charging process is T≥45℃, the evaluation score and weighted score in the high temperature charging evaluation process are qualified. When the maximum temperature of the new energy vehicle battery system during the charging process is 45℃＜T＜T ₁ , the evaluation score in the high temperature charging evaluation process is and weighted scores When the highest temperature of the new energy vehicle battery system during charging is _T≤T1 , the evaluation score and weighted score during the high temperature charging evaluation process are unqualified;

S2-2, define the maximum and minimum temperature extreme value difference in the extreme temperature difference state. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is ΔT≤2℃, the evaluation score and weighted score in the high temperature charging evaluation process are qualified. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is 2℃＜ΔT＜10℃, the evaluation score in the high temperature charging evaluation process is and weighted scores When the maximum temperature difference ΔT of the battery system during the charging process of a new energy vehicle is ≤10°C, the evaluation score and weighted score during the high-temperature charging evaluation process will be unqualified.

S2-3, under the charging efficiency state, the calculation is performed from the initial charging to the end interval of 80% state of charge, and the high-temperature charging is classified into the charging rate state, the charging power ratio state and the charging economy state. In the charging rate state, the charging power per unit time is defined. When the charging power per unit time P'≥40kw, the evaluation score and weighted score in the high-temperature charging evaluation process are qualified. When the charging power per unit time is 20kw＜P'＜40kw, the evaluation score in the high-temperature charging evaluation process is and the weighted score is When the charging capacity per unit time P'≤20kw, the evaluation score and weighted score in the high temperature charging evaluation process are unqualified; when the ratio of the high temperature charging time t _high to the normal temperature charging time t _nor is greater than 2, the evaluation score in the high temperature charging evaluation process is -25 and the weighted score is -10; when the charging capacity per unit time P'≥60kw, the evaluation score in the high temperature charging evaluation process is +12.5 and the weighted score is +5;

S2-4, in the charging power ratio state, defines the ratio of the high temperature battery charging power to the normal temperature battery charging power. When the ratio of the high temperature battery charging power E _high to the normal temperature battery charging power E _nor is When the evaluation score and weighted score are qualified in the high-temperature charging evaluation process, the ratio of the high-temperature battery charging capacity E _high to the normal-temperature battery charging capacity E _nor is When the high temperature charging evaluation process is and the weighted score is When the ratio of the high temperature battery charge E _high to the normal temperature battery charge E _nor is When the high temperature battery charging capacity E _high and the normal temperature battery charging capacity E nor are equal, the evaluation score and weighted score are unqualified in the high temperature charging evaluation process; when the high temperature battery charging capacity E high and the normal temperature battery charging capacity E _nor are equal When the battery is charged at high temperature, the evaluation score is considered unqualified during the high temperature charging evaluation process, and the weighted score is not calculated;

S2-5, define the ratio of the battery charging power E _bat to the charging pile output power E _cha under the charging economy state. When the ratio of the battery charging power E _bat to the charging pile output power E _cha is When the battery charging capacity _Ebat and the charging pile output capacity _Echa are equal, the evaluation score and weighted score are qualified in the high temperature charging evaluation process; when ... When the high temperature charging evaluation process is and the weighted score is When the ratio of battery charging capacity _Ebat to charging pile output capacity _Echa is When the electric vehicle is in the terminal charging state for more than 30 minutes at the end of the charging process or at the end of the charging process, the evaluation score and weighted score will be unqualified during the high temperature charging evaluation process.

1: If two abnormal charging terminations occur, the battery system is overcharged, or the battery temperature exceeds the maximum operating temperature without an alarm or automatic charging termination, no points will be awarded for this test item.

2: T is the maximum temperature of the battery system during the charging process, _T0 is the initial maximum temperature of the battery system, _T1 is the maximum operating temperature or alarm temperature of the battery in the user manual provided by the vehicle; ΔT is the maximum temperature difference of the battery system during the charging process; t _{high is} the high-temperature charging time; t _{nor is} the normal-temperature charging time; E _{high is} the high-temperature battery charging capacity; E _{nor is} the normal-temperature battery charging capacity; E _bat is the battery charging capacity; E _cha is the charging pile output capacity.

3: The linear difference region of the weighted score item does not include the endpoint value;

Evaluation method for low temperature charging of whole vehicle

S4-1, in the charging thermal management state, when the current exceeds the 1/6C current value range during the entire charging process, the low-temperature charging is classified into the lowest temperature average temperature state and the highest and lowest temperature extreme temperature difference state. In the lowest temperature average temperature state, when the lowest average temperature of the new energy vehicle battery system during the charging process T'≥0℃, the evaluation score and weighted score in the low-temperature charging evaluation process are qualified. When the lowest average temperature of the new energy vehicle battery system during the charging process is -7℃<T'<0℃, the evaluation score in the low-temperature charging evaluation process is and weighted scores When the lowest average temperature T'≤-7℃ during the charging process of the new energy vehicle battery system, the evaluation score and weighted score in the low temperature charging evaluation process are unqualified. If the lowest average temperature T'<0℃ during the charging process of the new energy vehicle battery system, the battery charging current exceeds 1/3C and is maintained for more than 15 minutes, the evaluation score in the low temperature charging evaluation process is -25 and the weighted score is -10.

S4-2, define the maximum and minimum temperature extreme value difference in the extreme temperature difference state. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is ΔT≤2℃, the evaluation score and weighted score in the low temperature charging evaluation process are qualified. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is 2℃＜ΔT＜10℃, the evaluation score in the low temperature charging evaluation process is and weighted scores When the maximum temperature difference ΔT of the battery system during the charging process of a new energy vehicle is ≤10°C, the evaluation score and weighted score during the low-temperature charging evaluation process are unqualified;

S4-3, in the charging efficiency state, the calculation is performed from the initial charging to the end interval of 80% state of charge, and the low-temperature charging is classified into the charging rate state, the charging power ratio state and the charging economy state. In the charging rate state, the charging power per unit time is defined. When the charging power per unit time P'≥35kw, the evaluation score and weighted score in the high-temperature charging evaluation process are qualified. When the charging power per unit time is 15kw＜P'＜35kw, the evaluation score in the high-temperature charging evaluation process is and the weighted score is When the charging capacity per unit time P'≤20kw, the evaluation score and weighted score in the high temperature charging evaluation process are unqualified; when the ratio of the high temperature charging time t _high to the normal temperature charging time t _nor is greater than 3, the evaluation score in the high temperature charging evaluation process is -25 and the weighted score is -10; when the charging capacity per unit time P'≥50kw, the evaluation score in the high temperature charging evaluation process is +12.5 and the weighted score is +5;

S4-4, in the charging power ratio state, defines the ratio of the low temperature battery charging power to the normal temperature battery charging power. When the ratio of the low temperature battery charging power E _low to the normal temperature battery charging power E _nor is When the low-temperature battery charging capacity E _low and the normal temperature battery charging capacity E nor are equal, the evaluation score and weighted score are qualified in the low-temperature charging evaluation process; when the ratio of the low-temperature battery charging capacity E low to the normal temperature battery charging capacity E _nor is equal to When the high temperature charging evaluation process is and the weighted score is When the ratio of the low temperature battery charging capacity E _low to the normal temperature battery charging capacity E _nor is When the ratio of the low-temperature battery charging capacity E _low to the normal-temperature battery charging capacity E _nor is When the battery is charged at high temperature, the evaluation score is considered unqualified during the high temperature charging evaluation process, and the weighted score is not calculated;

S4-5, under the charging economy state, define the ratio of the battery charging power E _bat to the charging pile output power E _cha . When the ratio of the battery charging power E _bat to the charging pile output power E _cha is When the battery charging capacity _Ebat and the charging pile output capacity _Echa are equal, the evaluation score and weighted score are qualified in the high temperature charging evaluation process; when ... When the high temperature charging evaluation process is and the weighted score is When the ratio of battery charging capacity _Ebat to charging pile output capacity _Echa is When the electric vehicle is in the terminal charging state for more than 30 minutes at the end of the charging process or at the end of the charging process, the evaluation score and weighted score will be unqualified during the high temperature charging evaluation process.

1. If there are two abnormal charging terminations, the battery system is overcharged, or the battery temperature exceeds the maximum operating temperature without an alarm or automatic charging termination, no points will be awarded for this test item.

2.ΔT is the maximum temperature difference of the battery system during the charging process; T' is the minimum average temperature; t _{high is} the high-temperature charging time; t _nor is the normal-temperature charging time; E _{low is} the low-temperature battery charging capacity; E _{nor is} the normal-temperature battery charging capacity.

3: The linear difference region of the weighted score item does not include the endpoint value;

Due to the high and low temperature charging process of the battery system, there is a mutual constraint between battery temperature management and charging. In terms of battery temperature management and charging capabilities under high and low temperatures, this evaluation procedure mainly conducts a comprehensive evaluation from two aspects: charging thermal management and charging efficiency. These two aspects can be further divided into five sub-indicators: temperature rise, temperature difference, charging rate, charging power ratio and charging economy. For the weights of these five sub-indicators, we can use the hierarchical analysis method to obtain them.

The judgment matrix can be used to determine the value through the following hierarchical relationship (where i and j refer to the high temperature charging index and the low temperature charging index respectively):

1. a _ij = 1, high temperature charging index i and low temperature charging index j have the same importance to the previous level index;

2. a _ij = 3, high temperature charging index i is more important than low temperature charging index j;

3. a _ij = 5, high temperature charging index i is more important than low temperature charging index j;

4. a _ij = 7, high temperature charging index i is more important than low temperature charging index j;

5. a _ij = 9, high temperature charging index i is more important than low temperature charging index j;

According to the importance of the five sub-indicators, the following judgment matrix can be obtained:

A B C D E A 1 5 1 8 9 B 1/5 1 1/5 3 7 C 1 5 1 7 9 D 1/8 1/3 1/7 1 5 E 1/9 1/7 1/9 1/5 1

Largest eigenvalue and eigenvector:

Let C represent the judgment matrix:

The maximum eigenvalue and corresponding eigenvector of C are 5.3866 and (-0.6958-0.2132-0.6751-0.1113-0.0467), respectively. After standardization, the eigenvector becomes (0.39 0.12 0.39 0.06 0.02).

Consistency test:

Where n is the matrix order, λ _max is the maximum eigenvalue, and D is the matrix;

Then CI = (5.3866-5)/(5-1) = 0.09665, and looking up the RI table we get RI = 1.12.

n 1 2 3 4 5 6 7 8 9 RI 0 0 0.58 0.9 1.12 1.24 1.32 1.41 1.45

The random consistency ratio CR of C is:

Substituting the calculation results into CR = 0.08629 < 0.1, so it is considered that C has satisfactory consistency and the judge has good fairness. The percentage system of each indicator can be obtained as follows: A: 40 B: 12 C: 39 D: 6 E: 3. After rounding and correction, the weight of each indicator can be taken as: A: 40% B: 10% C: 40% D: 6% E: 4%. The weights of high temperature test and low temperature test are 60% and 40% respectively.

The experimental test is as follows:

This regulation test will use a chassis dynamometer (150kW×2, 200km/h, China Automotive Research Institute), a walk-in environmental test chamber (Galaxy), and a DC charging pile (120kW, Teld) to conduct high and low temperature charging tests on 6 models.

This invention discusses how to use charging data at high and low temperatures to score specific vehicle models in terms of charging thermal management and charging efficiency:

Figure 2 shows the temperature-time curve of the vehicle when charging at high temperature, starting from the current greater than 1/6C. For the charging thermal management in the evaluation index, the maximum temperature of the charging process in this example is 41°C, and the corresponding score is 40 points. The extreme temperature difference between the highest and lowest temperatures refers to the extreme value of the difference between the two temperatures during this time period. In this example, the value is 5°C. According to the interpolation score, this part scores 7.5 points.

For the charging efficiency in the evaluation index, the charging capacity per unit time is obtained by calculating the ratio of the battery system charging capacity to the time consumed when charging to 80% SOC. As shown in formula (1), the battery system charging capacity is calculated by integrating the battery system charging current I and the battery system charging voltage U from the beginning of charging to charging to 80% SOC. Figure 3 shows the changing trend of I and U when charging to 80% SOC at high temperature. According to the integration of voltage and current over the corresponding time, the charging capacity at high temperature is 41.21kWh, the time consumed is 4562.2s, the average charging power of the battery system is 32.52kW, and the corresponding score is 20.03 points. It takes 3469.3s for this model to charge to 80% SOC at normal temperature. The ratio of high temperature charging time to normal temperature charging time is 1.32, which does not exceed 2, and no points are deducted for this item. Figure 4 shows the trend of I and U when charging to 80% SOC at room temperature. The calculated charging capacity at room temperature is 40.97 kWh, so the charging capacity ratio is 1.01, and the score is 6 points. Figure 5 shows the output current and output voltage curve of the charging pile when charging to 80% SOC at high temperature. According to the integral, the output energy of the charging pile is 43.50 kWh, so the ratio of charging economy is 0.95, and the score is 4 points. In summary, the total score of this model at high temperature is 76.28 points.

FIG3 is a charging current and charging voltage curve of a rechargeable battery system under high temperature;

Figure 4 shows the charging current and charging voltage curves of the rechargeable battery system at room temperature; used to compare the baseline with the high temperature charging curve and the low temperature charging curve. By analyzing the data of the curve, we can obtain our index values of charging rate, charging power ratio and charging economy. The image is the charging process, the red line represents the voltage, and the voltage will definitely rise during the charging process. The black line represents the current. During the charging process, the current is determined by the charging strategy set by the vehicle, so it is expressed in different curve forms.

Figure 5: Output current and output voltage curve of charging pile under high temperature; the following table shows the scores of high temperature charging

Figure 6 shows the temperature-time curve when charging at low temperature. It shows the temperature-time curve when charging at low temperature, starting from the current greater than 1/6C. Different from the high temperature evaluation index, in the charging thermal management index, we use the lowest average temperature to replace the highest temperature rise in high temperature. The lowest average temperature is obtained by integrating the lowest temperature within the corresponding time and comparing it with the time difference. The lowest temperature average value is: The remaining indicators are calculated in the same way as in high temperature conditions. _Tmin represents the lowest temperature, and δt represents the integral of the lowest temperature during that time. The following table shows the scores for low temperature charging.

The rating of the whole vehicle charging in high and low temperature environments can be divided into 5 levels, among which 90-100 points are 5 stars, 80-90 points are 4 stars, 70-80 points are 3 stars, 60-70 points are 2 stars, and below 60 points are 1 star. The final score and rating are shown in the table. High and low temperature charging score and rating summary table

Model Rating Sample car 1 ☆☆☆ Sample 2 ☆☆☆☆ Sample 3 ☆☆☆☆☆ Sample car 4 ☆ Sample car 5 ☆☆ Sample car 6 ☆☆☆☆☆

Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims (2)

1. A high and low temperature charging test evaluation optimization method for new energy vehicles, characterized in that it includes the following steps: S1, a test pretreatment process is performed on the new energy vehicle, the new energy vehicle is discharged, and after the discharge is completed, a high temperature charging test process is performed; S1-1, after the new energy vehicle is driven at a stable speed at room temperature, the vehicle is continuously discharged, and after the discharge is completed, preliminary charging is performed at room temperature; S1-2, placing the new energy vehicle in a high and low temperature environment chamber, keeping it in a high temperature environment for a certain period of time, and then conducting a charging test; S1-3, charging through the shortest charging time strategy, recording the communication messages between the charging pile and the new energy vehicle; S1-4, according to the pre-set termination charging condition, if the condition is met, the new energy vehicle is terminated from charging under high temperature state; S2, setting charging conditions during the high-temperature charging test, and conducting a comprehensive evaluation of the state changes of new energy vehicles during the high-temperature charging stage according to different charging conditions; S2-1, in the charging thermal management state, when the current exceeds the 1/6C current value range during the entire charging process, the high temperature charging is classified into the temperature rise state and the extreme temperature difference state. In the temperature rise state, the maximum temperature of the charging process is defined. When the maximum temperature of the new energy vehicle battery system during the charging process is T≥45℃, the evaluation score and weighted score in the high temperature charging evaluation process are qualified. When the maximum temperature of the new energy vehicle battery system during the charging process is 45℃＜T＜T ₁ , the evaluation score in the high temperature charging evaluation process is and weighted scores When the highest temperature of the new energy vehicle battery system during charging is _T≤T1 , the evaluation score and weighted score during the high temperature charging evaluation process are unqualified; S2-2, define the maximum and minimum temperature extreme value difference in the extreme temperature difference state. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is ΔT≤2℃, the evaluation score and weighted score in the high temperature charging evaluation process are qualified. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is 2℃＜ΔT＜10℃, the evaluation score in the high temperature charging evaluation process is and weighted scores When the maximum temperature difference ΔT of the battery system during the charging process of a new energy vehicle is ≤10°C, the evaluation score and weighted score during the high-temperature charging evaluation process are unqualified; S2-3, under the charging efficiency state, the calculation is performed from the initial charging to the end interval of 80% state of charge, and the high-temperature charging is classified into the charging rate state, the charging power ratio state and the charging economy state. In the charging rate state, the charging power per unit time is defined. When the charging power per unit time P'≥40kw, the evaluation score and weighted score in the high-temperature charging evaluation process are qualified. When the charging power per unit time is 20kw＜P'＜40kw, the evaluation score in the high-temperature charging evaluation process is and the weighted score is When the charging capacity per unit time P'≤20kw, the evaluation score and weighted score in the high temperature charging evaluation process are unqualified; when the ratio of high temperature charging time to normal temperature charging time is greater than 2, the evaluation score in the high temperature charging evaluation process is -25 and the weighted score is -10; when the charging capacity per unit time P'≥60kw, the evaluation score in the high temperature charging evaluation process is +12.5 and the weighted score is +5; S2-4, in the charging power ratio state, defines the ratio of the high temperature battery charging power to the normal temperature battery charging power. When the ratio of the high temperature battery charging power E _high to the normal temperature battery charging power E _nor is When the evaluation score and weighted score are qualified in the high-temperature charging evaluation process, the ratio of the high-temperature battery charging capacity E _high to the normal-temperature battery charging capacity E _nor is When the high temperature charging evaluation process is and the weighted score is When the ratio of the high temperature battery charge E _high to the normal temperature battery charge E _nor is When the high temperature battery charging capacity E _high and the normal temperature battery charging capacity E nor are equal, the evaluation score and weighted score are unqualified in the high temperature charging evaluation process; when the high temperature battery charging capacity E high and the normal temperature battery charging capacity E _nor are equal When the battery is charged at high temperature, the evaluation score is considered unqualified during the high temperature charging evaluation process, and the weighted score is not calculated; S2-5, define the ratio of the battery charging power E _bat to the charging pile output power E _cha under the charging economy state. When the ratio of the battery charging power E _bat to the charging pile output power E _cha is When the battery charging capacity _Ebat and the charging pile output capacity _Echa are equal, the evaluation score and weighted score are qualified in the high temperature charging evaluation process; when ... When the high temperature charging evaluation process is and the weighted score is When the ratio of battery charging capacity _Ebat to charging pile output capacity _Echa is When the electric vehicle is in the terminal charging state for more than 30 minutes at the end of charging or at the end of charging, the evaluation score and weighted score in the high temperature charging evaluation process are unqualified; S3, after the comprehensive evaluation of high-temperature charging, the new energy vehicle is discharged, and after the discharge is completed, the low-temperature charging test process is carried out; S3-1, after the new energy vehicle is driven at a stable speed at room temperature, the vehicle is continuously discharged, and after the discharge is completed, it is preliminarily charged at room temperature; S3-2, placing the new energy vehicle in a high and low temperature environment chamber, keeping it in a low temperature environment for a certain period of time, and then conducting a charging test; S3-3, charging through the shortest charging time strategy, recording the communication messages between the charging pile and the new energy vehicle; S3-4, according to the pre-set termination charging condition, if the condition is met, the new energy vehicle is terminated from charging in a low temperature state; S4, setting charging conditions during the low-temperature charging test, and conducting a comprehensive evaluation of the state changes of new energy vehicles during the low-temperature charging stage according to different charging conditions; S4-1, in the charging thermal management state, when the current exceeds the 1/6C current value range during the entire charging process, the low-temperature charging is classified into the lowest temperature average temperature state and the highest and lowest temperature extreme temperature difference state. In the lowest temperature average temperature state, when the lowest average temperature of the new energy vehicle battery system during the charging process T'≥0℃, the evaluation score and weighted score in the low-temperature charging evaluation process are qualified. When the lowest average temperature of the new energy vehicle battery system during the charging process is -7℃<T'<0℃, the evaluation score in the low-temperature charging evaluation process is and weighted scores When the lowest average temperature of the new energy vehicle battery system during charging is T'≤-7℃, the evaluation score and weighted score in the low temperature charging evaluation process are unqualified. If the lowest average temperature of the new energy vehicle battery system during charging is T'<0℃, the battery charging current exceeds 1/3C and is maintained for more than 15 minutes, the evaluation score in the low temperature charging evaluation process is -25 and the weighted score is -10; S4-2, define the maximum and minimum temperature extreme value difference in the extreme temperature difference state. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is ΔT≤2℃, the evaluation score and weighted score in the low temperature charging evaluation process are qualified. When the maximum temperature difference of the battery system during the charging process of the new energy vehicle is 2℃＜ΔT＜10℃, the evaluation score in the low temperature charging evaluation process is and weighted scores When the maximum temperature difference ΔT of the battery system during the charging process of a new energy vehicle is ≤10°C, the evaluation score and weighted score during the low-temperature charging evaluation process are unqualified; S4-3, in the charging efficiency state, the calculation is performed from the initial charging to the end interval of 80% state of charge, and the low-temperature charging is classified into the charging rate state, the charging power ratio state and the charging economy state. In the charging rate state, the charging power per unit time is defined. When the charging power per unit time P'≥35kw, the evaluation score and weighted score in the high-temperature charging evaluation process are qualified. When the charging power per unit time is 15kw＜P'＜35kw, the evaluation score in the high-temperature charging evaluation process is and the weighted score is When the charging capacity per unit time P'≤20kw, the evaluation score and weighted score in the high temperature charging evaluation process are unqualified; when the ratio of high temperature charging time to normal temperature charging time is greater than 3, the evaluation score in the high temperature charging evaluation process is -25 and the weighted score is -10; when the charging capacity per unit time P'≥50kw, the evaluation score in the high temperature charging evaluation process is +12.5 and the weighted score is +5; S4-4, in the charging power ratio state, defines the ratio of the low temperature battery charging power to the normal temperature battery charging power. When the ratio of the low temperature battery charging power E _low to the normal temperature battery charging power E _nor is When the low-temperature battery charging capacity E _low and the normal temperature battery charging capacity E nor are equal, the evaluation score and weighted score are qualified in the low-temperature charging evaluation process; when the ratio of the low-temperature battery charging capacity E low to the normal temperature battery charging capacity E _nor is equal to When the high temperature charging evaluation process is and the weighted score is When the ratio of the low temperature battery charging capacity E _low to the normal temperature battery charging capacity E _nor is When the ratio of the low-temperature battery charging capacity E _low to the normal-temperature battery charging capacity E _nor is When the battery is charged at high temperature, the evaluation score is considered unqualified during the high temperature charging evaluation process, and the weighted score is not calculated; S4-5, under the charging economy state, define the ratio of the battery charging power E _bat to the charging pile output power E _cha . When the ratio of the battery charging power E _bat to the charging pile output power E _cha is When the battery charging capacity _Ebat and the charging pile output capacity _Echa are equal, the evaluation score and weighted score are qualified in the high temperature charging evaluation process; when ... When the high temperature charging evaluation process is and the weighted score is When the ratio of battery charging capacity _Ebat to charging pile output capacity _Echa is When the electric vehicle is in the terminal charging state for more than 30 minutes at the end of charging or at the end of charging, the evaluation score and weighted score in the high temperature charging evaluation process are unqualified; S5, testing the high-temperature charging comprehensive evaluation data and the low-temperature charging comprehensive evaluation data, thereby optimizing the comprehensive performance of the new energy vehicle; The judgment matrix can be set to obtain values through the following hierarchical relationship, where i and j refer to the high temperature charging index and the low temperature charging index respectively: (1) aij = 1, high temperature charging index i and low temperature charging index j have the same importance to the previous level index; (2) aij = 3, high temperature charging index i is more important than low temperature charging index j; (3) aij = 5, high temperature charging index i is more important than low temperature charging index j; (4) aij = 7, high temperature charging index i is more important than low temperature charging index j; (5) aij = 9, high temperature charging index i is more important than low temperature charging index j; Let C represent the judgment matrix, and then calculate the maximum eigenvalue and corresponding eigenvector of C, which are 5.3866 and -0.6958, -0.2132, -0.6751, -0.1113, -0.0467 respectively. After standardization, the eigenvector becomes 0.39 0.12 0.390.06 0.02, and the consistency test is performed: Where n is the matrix order, λ _max is the maximum eigenvalue, and D is the matrix. 2. The high and low temperature charging test evaluation optimization method for new energy vehicles according to claim 1, characterized in that S5 comprises: The charging capacity of the new energy vehicle battery system is calculated based on the integration of the battery system charging current I and the battery system charging voltage U from the beginning of charging to charging to 80% SOC. The changing trends of I and U when charging to 80% SOC at high temperature, according to the integration of voltage and current at the corresponding time, the charging capacity at high temperature is 41.21kWh, the time consumed is 4562.2s, and the average charging power of the battery system is 32.52kW; the time consumed by the new energy vehicle to charge to 80% SOC at room temperature, the ratio of high temperature charging time to normal temperature charging time is 1.32, the changing trends of I and U when charging to 80% SOC at room temperature, the charging capacity at room temperature is calculated to be 40.97kW/h, so it can be known that the charging capacity ratio is 1.01, the output current and output voltage curve of the charging pile when charging to 80% SOC at high temperature, according to the integration, the output energy of the charging pile is 43.50kWh, and the proportion of charging economy is 0.95.