CN114996639A - Low-cost mode cascade utilization multi-factor screening method for power battery - Google Patents

Low-cost mode cascade utilization multi-factor screening method for power battery Download PDF

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CN114996639A
CN114996639A CN202210723903.7A CN202210723903A CN114996639A CN 114996639 A CN114996639 A CN 114996639A CN 202210723903 A CN202210723903 A CN 202210723903A CN 114996639 A CN114996639 A CN 114996639A
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陈子龙
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Abstract

The invention relates to a low-cost mode cascade utilization multi-factor screening method for power batteries, which carries out comprehensive calculation and judgment through multi-factor influence, fully considers various factors influencing the technical state of a scrapped power battery, gives different weight coefficients to the various influencing factors after unified calculation domain conversion, distinguishes the batteries with different use conditions, can quickly divide the power batteries with close use conditions, environment temperatures and the like together, facilitates subsequent cascade utilization, reduces the screening cost of the scrapped power batteries and has wide market application prospect.

Description

Low-cost mode cascade utilization multi-factor screening method for power battery
The application has the following application numbers: 202110140111.2, filing date: 2021-02-02, the invention patent titled "electric vehicle power battery cascade utilization multi-parameter influence screening method".
Technical Field
The invention relates to the technical field of power battery recovery of electric vehicles, in particular to a low-cost mode multi-factor screening method for cascade utilization of power batteries.
Background
At present, the size of a power battery and the voltage of the power battery are unified and standardized in China, and the specification of the power battery used by each automobile manufacturer tends to be designed uniformly in the future, namely the size and the interface of the power battery between each manufacturer can be universal, only the type and the capacity of the battery are different, so that the recycling and large-scale cascade utilization of the power battery become a new development trend, and the number of scrapped power batteries of the same type can reach hundreds of thousands of groups.
The temporary method for recycling and managing the power storage batteries of the new energy automobile also specifically mentions that waste power storage batteries are classified, recombined and utilized, and the echelon utilization battery products are coded, so that great cost can be saved for cascade utilization, the cascade utilization is the best recycling mode of the power batteries from the aspects of environmental protection and recycling, and when the quantity of the power batteries is large and the power batteries are recycled to form a certain scale, considerable economic benefit can still be generated if policies are proper, and the method has great significance for environmental protection.
Through research, exploration and pilot demonstration of several years, the application field of cascade utilization of power batteries in China has been concentrated in other related fields such as power system energy storage, communication base station standby power supply, low-speed electric vehicles, small-sized distributed household energy storage, wind-solar hybrid streetlamps, mobile charging vehicles, electric forklifts and the like. At present, manufacturers for energy storage propose a group-string distributed concept, a power battery which is retired from a whole vehicle is used as a basic energy storage unit, the original state and consistency of the battery pack are guaranteed to be unchanged to the maximum extent, then a Process Control System (PCS) with medium and low power is matched, a basic energy storage unit is formed by adding a proper monitoring unit, and the basic energy storage unit and the PCS are connected in parallel to form an energy storage power system with unequal power. The consistency problem is considered at the beginning of the design of the power battery, and a battery management system is provided. The retired battery is not damaged and cannot be used, but the whole capacity is insufficient, so that the problem of consistency is not great when the whole battery is used.
However, the power battery retired from the whole vehicle is used as a basic energy storage unit, the biggest problem is that the retired power battery is not simply combined to be used, and the detection and screening link is the key of echelon utilization. Due to inconsistency of recycling power batteries, a large amount of detection needs to be carried out on the residual use value and the health state of the power batteries when the power batteries are used in a gradient manner, a comprehensive application software technology, a measurement and control technology, a processing process technology and the like are needed in a detection and screening link, cross-industry multidisciplinary technologies such as light, machine and electricity are involved, the cost and the detection equipment requirements are very high, the screening of scrapped power batteries is not favorably carried out rapidly in a large scale, and the existing testing technology for the power batteries is also mostly a test for new batteries, and a screening method specially developed for the scrapped power batteries is not provided.
In fact, the technical state of the scrapped power battery is not only influenced by the number of use cycles and the number of charging times, but also related to unreasonable use such as overcharge, overdischarge, short circuit and the like and the environmental temperature during working, and meanwhile, the discharge current of the battery also influences the service life of the battery; the service state and the service environment of the power battery can influence the technical state after the power battery is scrapped, and the existing detection method for the new battery can not consider the factors, so that the detection method for the new battery can not be directly used for screening the scrapped power battery.
In patent CN102755966A, a power battery cascade utilization sorting evaluation method only considers relevant parameters, but has no specific calculation method, cannot be directly used for sorting power batteries, and has no practical use value.
Disclosure of Invention
Based on the method, the power battery cascade utilization multi-factor screening method in the low-cost mode is high in detection speed, low in cost and high in accuracy.
In order to achieve the purpose, the invention provides the following technical scheme:
the power battery cascade utilization multi-factor screening method in the low-cost mode comprises the following steps of:
step a: during the normal use period of the electric automobile, a power battery management system BMS records first-layer screening data and second-layer screening data in real time;
the first layer of screening data comprises: the method comprises the following steps of (1) running total mileage VMT of the electric automobile, total cycle charging times CN and power battery failure times GZ;
the second layer screening data comprises: the average environmental temperature TV of the electric automobile in each hundred kilometers of travel and the total time TM that the discharge current of a power battery exceeds a certain threshold value in each hundred kilometers of travel are obtained;
step b: the first layer screening data was processed as follows:
if the total driving mileage VMT of the electric automobile is in a certain range [ VTM _1, VTM _2], the total cyclic charging frequency CN is in a certain range [ CN _1, CN _2], and the power battery fault frequency GZ is in a certain range [ GZ _1, GZ _2], entering a step c, and if not, entering a step h, wherein the power battery fault frequency comprises overcharge, overdischarge and short circuit frequency;
step c: performing a unified computational domain transform according to equations (1-1) to (1-3):
Figure BDA0003712647690000031
Figure BDA0003712647690000032
Figure BDA0003712647690000033
step d: calculating a first influence factor Hi according to the formula (1-4):
Figure BDA0003712647690000034
in the above formula, α, β and γ are each Δ 1 、Δ 2 、Δ 3 Respective weight coefficient, range taken as (0,1)
After Hi values of a plurality of automobile power batteries are calculated, dividing the Hi values into a first interval, a second interval and a third interval; the Hi value in the first interval is less than the Hi value in the second interval and less than the Hi value in the third interval; dividing the power batteries into a first interval, and entering the step e; f, dividing the power batteries into a second interval, and entering the step f; dividing the power battery into a third interval, and entering the step g;
step e: and calculating the second-layer screening data of the power battery divided into the first interval according to a formula (1-5) and a formula (1-6):
data set TV formed by a plurality of average ambient temperatures TV per hundred kilometers of travel 1 、TV 2 ……TV n Calculating the root mean square value of the group of data:
Figure BDA0003712647690000041
data set TM formed by a plurality of total time durations TM when discharge current of power battery exceeds a certain threshold value within one hundred kilometers of travel 1 、TM 2 ……TM n Calculating the root mean square value of the group of data:
Figure BDA0003712647690000042
Figure BDA0003712647690000043
in a certain range according to the formula (1-7)
Figure BDA0003712647690000044
Unified computational domain transformation;
Figure BDA0003712647690000045
in a certain range according to the formula (1-8)
Figure BDA0003712647690000046
Unified computational domain transformation;
Figure BDA0003712647690000047
Figure BDA0003712647690000048
the second influence factor Yi is then calculated according to equation (1-9):
Figure BDA0003712647690000049
in the above formula, λ and θ are respectively Δ 5 、Δ 4 The respective weight coefficient and the range are (0, 1);
after the Yi values of a plurality of automobiles are calculated, dividing the Yi values into at least three primary subintervals according to the size, and then connecting the power batteries in the same primary subinterval in parallel for cascade utilization;
step f: e, dividing the power battery into a second interval, dividing the power battery into different first-level subintervals according to the Yi value, then performing a 1C current constant-current discharge test on the fully-charged battery at the temperature of 20 +/-5 ℃, and calculating a standard discharge time value, namely the discharge current is equal to the rated current of the power battery;
dividing each primary subinterval into at least two secondary subintervals according to the discharge time rate, and connecting the power batteries in each secondary subinterval in parallel for cascade utilization;
step g: e, f, dividing the power battery in the third interval into different secondary subintervals according to the Yi value and the standard discharge time rate C/n, then performing a full-charge battery low-rate current constant-current discharge test, dividing each secondary subinterval into at least two tertiary subintervals according to the low-rate discharge time rate, and connecting the power batteries in each tertiary subinterval in parallel for cascade utilization;
step h: and marking the power battery of the electric automobile as not having the current step utilization requirement.
Preferably, when the total number of times CN of cyclic charging is counted, the number of times of one continuous charging is counted as the number of times of one continuous charging when the time length of one continuous charging exceeds 1h, and the count of the number of times of power battery faults includes a power battery overcharge fault, a power battery overdischarge fault and a power battery short circuit fault.
Preferably, α is 0.5 to 0.7, β is 0.25 to 0.45, γ is 0.15 to 0.3, and α + β + γ is 1; the lambda is 0.4-0.6, the theta is 0.4-0.6, and the lambda + theta is 1;
preferably, in the step g, in the fully-charged battery low-rate current constant current discharge test, the low-rate current is 0.1 to 0.2C.
Preferably, before the step a, at least 3 pre-screening regions are divided according to the ratio of the current battery capacity value of the scrapped power battery to the calibrated power battery capacity for pre-screening, and after pre-screening, the steps a to h are performed on different pre-screening regions.
Preferably, in the screening method, the first layer of screening data and the second layer of screening data recorded by the BMS in real time are sent to the controller through a communication line or a wireless signal sending manner, and the controller stores the first layer of screening data and the second layer of screening data in the storage device through the communication line or the wireless signal sending manner or uploads the first layer of screening data and the second layer of screening data to the cloud server through the internet; the controller is an AT89C52 singlechip or an STM32 singlechip or a Mitsubishi PLC industrial personal computer or a microprocessor with a CAN bus interface, the controller is in communication connection with the BMS through a CAN bus connection mode, and the storage device is a solid state disk or a U disk.
Compared with the prior art, the invention has the following beneficial effects:
the invention fully considers various factors influencing the technical state of the scrapped power battery, gives different weight coefficients to the various influencing factors after the unified calculation domain conversion, screens the batteries in different technical states, can quickly divide the power batteries with similar use conditions, environmental temperatures and the like together, is convenient for subsequent cascade utilization, adopts different subsequent testing steps for the batteries in different states, greatly reduces the testing links of the scrapped power batteries, reduces the screening cost of the scrapped power batteries, has wide market application prospect, quickly detects and screens the retired batteries of a plurality of similar vehicles, and has higher accuracy rate on the basis of saving the cost and ensures the smooth cascade utilization.
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FIG. 1 is a flow chart of a screening method decision;
fig. 2 is a schematic diagram of the controller connection.
Detailed Description
The technical solutions of the present invention will be described in detail and fully with reference to the accompanying drawings, and it should be understood that the described embodiments are only some embodiments, but not all embodiments, of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the orientations or positional relationships indicated as the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., appear based on the orientations or positional relationships shown in the drawings only for the convenience of describing the present invention and simplifying the description, but not for indicating or implying that the referred devices or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the invention.
Referring to fig. 1, a low cost mode power cell cascade utilizes a multi-factor screening method comprising the following steps performed in sequence:
the first embodiment is as follows:
the BMS of the conventional electric vehicle power battery management system can monitor relevant parameters of a power battery in real time, so that when the electric vehicle normally runs, relevant important parameters influencing the technical state of the power battery are collected in real time, and partial screening links of the scrapped power battery are advanced to the normal use stage before scrapping to collect information;
step a: during the normal use period of the electric automobile, a BMS (Power Battery management System) records first-layer screening data and second-layer screening data in real time;
the first layer screening data comprises: the method comprises the following steps of (1) running total mileage VMT of the electric automobile, total cycle charging times CN and power battery failure times GZ;
the second layer screening data comprises: the average environmental temperature TV of the electric automobile in each hundred kilometers of travel and the total time TM that the discharge current of a power battery exceeds a certain threshold value in each hundred kilometers of travel are obtained;
and when the total cyclic charging times CN are counted, the time length of single continuous charging exceeds 1h and is recorded as the one-time charging times, and the counting of the power battery fault times comprises a power battery overcharge fault, a power battery overdischarge fault and a power battery short circuit fault.
The first layer of screening data has direct influence on parameters such as the service life of the power battery, the current battery capacity and the self-discharge rate, and the second layer of screening data also has direct influence on parameters such as the internal resistance and the state of charge (SOC) of the power battery, so that a plurality of scrapped power batteries with close service conditions and service environments of the batteries can be selected according to the first layer of screening data and are put together for cascade utilization, the indexes such as the battery capacity, the residual service life and the self-discharge rate of the scrapped power batteries are close, the first layer of screening data is data which can be collected when an automobile normally runs, the scrapped power batteries can be directly screened, and a plurality of detection processes after scrapping are omitted; if the technical state of the scrapped power batteries is poor, the second-layer screening data is further required to be further screened, so that the scrapped power batteries with the poor technical state can be kept stable after being connected in parallel.
Step b: the first layer screening data was processed as follows:
if the total driving mileage VMT of the electric automobile is in a certain range [ VTM _1, VTM _2], the total cyclic charging frequency CN is in a certain range [ CN _1, CN _2], the power battery failure frequency and GZ is in a certain range [ GZ _1, GZ _2], entering the step c, otherwise, entering the step h, wherein the power battery failure frequency comprises overcharge, overdischarge and short circuit frequency;
step b is to perform a first directional screening according to the use condition of the scrapped power battery, for example, when the scrapped power battery is used as an energy storage device, the self-discharge rate index is important, the total number of times of the corresponding total cycle charging of the electric vehicle, the total discharge time should be appropriately short, and the requirement on the stability of the scrapped battery is high, then [ VTM _1, VTM _2] can be set as [5000km, 20000km ], [ CN _1, CN _2] as [500, 2000], [ GZ _1, GZ _2] as [0, 30 ]; for another example, if the index can be lowered when the scrapped power battery is used as a household backup power source, [ VTM _1, VTM _2] can be set to [10000km, 30000km ], [ CN _1, CN _2] can be set to [500, 2600], [ GZ _1, GZ _2] can be set to [0, 60 ].
Step c: performing a unified computational domain transform according to equations (1-1) to (1-3):
Figure BDA0003712647690000081
Figure BDA0003712647690000082
Figure BDA0003712647690000083
after the domain transformation is uniformly calculated, the three different parameters of the unit are changed into percentages, and the percentages can be used for subsequent comprehensive judgment.
Step d: calculating a first influence factor Hi according to the formula (1-4):
Figure BDA0003712647690000091
in the above formula, α, β and γ are each Δ 1 、Δ 2 、Δ 3 The respective weight coefficients and ranges are (0,1), alpha, beta and gamma can be valued according to experience, a certain number of scrapped power batteries are selected to be screened and then subjected to corresponding performance tests, the performance tests are adjusted according to test results, secondary fine adjustment can be performed according to the types of electric vehicles during adjustment, for example, the values of alpha, beta and gamma are different when the same power battery is used on cars, SUVs and MPVs, and the value ranges recommended by the technical scheme are as follows: alpha is 0.5-0.7, beta is 0.25-0.45, gamma is 0.15-0.3, and alpha + beta + gamma1; one recommended value that can be used for most household electric cars is that α is 0.55, β is 0.3, and γ is 0.15.
After the values Hi of the scrapped power batteries of the plurality of electric automobiles are calculated, dividing the Hi into a first interval, a second interval and a third interval; the Hi value in the first interval is less than the Hi value in the second interval and less than the Hi value in the third interval; the respective limit values of the three intervals can be preset, and can also be dynamically adjusted according to the quantity of a certain batch of scrapped power batteries and the distribution of Hi values of the certain batch of scrapped power batteries.
Dividing the power batteries into a first interval, and entering the step e; f, dividing the power batteries into a second interval, and entering the step f; dividing the power battery into a third interval, and entering the step g;
step e: the technical state of the power battery divided into the first interval is better, and the second-layer screening data can be directly calculated according to the formula (1-5) and the formula (1-6):
data set TV formed by multiple TV sets of average ambient temperature in each hundred kilometers of travel 1 、TV 2 ……TV n Calculating the root mean square value of the group of data:
Figure BDA0003712647690000092
data set TM formed by a plurality of total time durations TM when discharge current of power battery exceeds a certain threshold value within one hundred kilometers of travel 1 、TM 2 ……TM n Calculating the root mean square value of the group of data:
Figure BDA0003712647690000101
Figure BDA0003712647690000102
in a certain range according to the formula (1-7)
Figure BDA0003712647690000103
Unified computational domain transformation;
Figure BDA0003712647690000104
in a certain range according to the formula (1-8)
Figure BDA0003712647690000105
Unified computational domain transformation;
Figure BDA0003712647690000106
the numerical value can be calculated by selecting one or more scrapped power batteries through an experimental method and then pushed out, and the calculated scrapped power batteries can also be pushed out
Figure BDA0003712647690000107
As the minimum value of
Figure BDA0003712647690000108
A plurality of
Figure BDA0003712647690000109
As a maximum value of
Figure BDA00037126476900001010
Of a plurality of rejected power cells to be calculated
Figure BDA00037126476900001011
As the minimum value of
Figure BDA00037126476900001012
Will be provided with
Figure BDA00037126476900001013
As a maximum value of
Figure BDA00037126476900001014
Figure BDA00037126476900001015
Figure BDA00037126476900001016
The second influence factor Yi is then calculated according to equation (1-9):
Figure BDA00037126476900001017
in the above formula, λ and θ are respectively Δ 5 、Δ 4 The respective weight coefficient and the range are (0, 1); in the technical scheme, the recommended lambda is 0.4-0.6, theta is 0.4-0.6, and lambda + theta is 1; one of the recommended values for the household electric car is λ 0.4 and θ 0.6.
After the Yi values of a plurality of automobiles are calculated, dividing the Yi values into at least three primary subintervals according to the size, and then connecting the power batteries in the same primary subinterval in parallel for cascade utilization;
step f: the scrapped power batteries divided into the second interval are reduced compared with the scrapped power batteries in the first interval, the difference among the scrapped power batteries is increased, in order to improve the stability of parallel use, step e is firstly carried out, after different primary subintervals are drawn according to the Yi value, a full-charge battery 1C current constant-current discharge test is carried out at the temperature of 20 +/-5 ℃, and a standard discharge time rate value C/n is calculated, wherein in the standard discharge time rate, C is rated capacity, n is discharge current, and 1C discharge current is 1 multiplying power discharge, namely the discharge current is equal to the rated current of the power batteries;
and according to the discharge time rate value (C/n), the primary subinterval under each second interval is subdivided into at least two secondary subintervals, and the power batteries in the secondary subintervals under each second interval are connected in parallel for cascade utilization.
Step g: if the technical state of the scrapped power battery divided into the third interval is worse than that of the first interval and the second interval, the steps e and f are firstly carried out, the power battery in the third interval is divided into different secondary sub-intervals according to the Yi value and the standard discharge time rate (C/n), a full-charge battery low-rate current constant-current discharge test is also carried out, each secondary sub-interval is divided into at least two tertiary sub-intervals according to the low-rate discharge time rate, and the power battery in each tertiary sub-interval is connected in parallel for cascade utilization; the small multiplying current recommended by the technical scheme is 0.1-0.2C.
Step h: the controller (1) or the cloud server (3) marks the power battery of the electric automobile as not having the current step utilization requirement.
In the screening process, the data in the electric automobile BMS can be directly read in the steps a to e and calculated, the screening process of scrapped power batteries is advanced to a normal use link, the screening is quick, the scrapped power batteries with various parameters close to each other can be screened into a group, and the stability of the subsequent parallel use of a plurality of scrapped power batteries can be greatly improved.
When the technical state and the use environment of the scrapped power battery are severe, a corresponding standard discharge time rate test or a low-current discharge time rate test is added for further screening so as to ensure the stability of subsequent cascade utilization.
The scheme fully considers various factors influencing the technical state of the scrapped power battery, gives different weight coefficients to the various influencing factors after unified calculation domain conversion, distinguishes the batteries with different use conditions, can quickly divide the power batteries with similar use conditions, environment temperature and the like together, is convenient for subsequent cascade utilization, adopts different subsequent test steps for the batteries with different states, greatly reduces the test links of the scrapped power batteries, reduces the screening cost of the scrapped power batteries, has wide market application prospect, quickly detects and screens the retired batteries of a plurality of similar vehicles, has higher accuracy on the basis of saving the cost, ensures the smooth cascade utilization, and can greatly reduce the cost of the screening process under the scheme when the number of the scrapped power batteries is 10 ten thousand or more, has very wide market prospect.
Example two: when the use occasions of the vehicles corresponding to the scrapped power batteries are different, the scrapping standards of the power batteries are possibly inconsistent, for example, the household electric car has no mandatory scrapping age, and the power batteries are scrapped when the battery capacity of the power batteries carried on the household electric car is reduced to be below 80% of the calibrated battery capacity according to the power battery industry regulation, and at the moment, the battery capacity of most of the household electric car is basically maintained at 75% -80% after the power batteries are scrapped, so that pre-screening can be omitted;
however, for a service vehicle, such as a dedicated vehicle, after the vehicle runs for 600000km or the running age exceeds 8 years, the whole vehicle is forcibly scrapped, and at this time, the battery capacity of the power battery may not reach the scrapping standard or is relatively close to the scrapping standard, so before step a, at least 3 pre-screening sections may be further divided according to the ratio of the current battery capacity value of the scrapped power battery to the calibrated battery capacity to perform pre-screening, for example, 75% -80%, 80% -84%, and 84% -87%. After pre-screening, steps a to h are performed for different pre-screening zones.
In the screening method, first-layer screening data and second-layer screening data recorded by a BMS in real time are sent to a controller (1) through a communication line or a wireless signal sending mode, and the controller (1) stores the first-layer screening data and the second-layer screening data in a storage device (9) through the communication line or the wireless signal sending mode or uploads the first-layer screening data and the second-layer screening data to a cloud server (3) through the Internet; the controller (1) is an AT89C52 singlechip or an STM32 singlechip or a Mitsubishi PLC industrial personal computer or a microprocessor with a CAN bus interface, the controller (1) is in communication connection with the BMS through a CAN bus connection mode, and the storage device (9) is a solid state disk or a U disk.

Claims (3)

1. The multi-factor screening method for the cascade utilization of the power battery in the low-cost mode is characterized by comprising the following steps of: the screening method comprises the following steps which are carried out in sequence:
step a: during the normal use period of the electric automobile, a power battery management system BMS records first-layer screening data and second-layer screening data in real time;
the first layer screening data comprises: the method comprises the following steps of (1) running total mileage VMT, total cycle charging times CN and power battery fault times GZ of the electric automobile;
the second layer screening data comprises: the average environmental temperature TV of the electric automobile in each hundred kilometers of travel and the total time TM that the discharge current of a power battery exceeds a certain threshold value in each hundred kilometers of travel are obtained;
step b: the first layer screening data was processed as follows:
if the total driving mileage VMT of the electric automobile is in a certain range [ VTM _1, VTM _2], the total cyclic charging frequency CN is in a certain range [ CN _1, CN _2], the power battery fault frequency GZ is in a certain range [ GZ _1, GZ _2], entering the step c, otherwise, entering the step h, wherein the power battery fault frequency comprises overcharge, overdischarge and short circuit frequency;
step c: performing a unified computational domain transform according to equations (1-1) to (1-3):
Figure FDA0003712647680000011
Figure FDA0003712647680000012
Figure FDA0003712647680000013
step d: calculating a first influence factor Hi according to the formula (1-4):
Figure FDA0003712647680000014
in the above formula, α, β and γ are each Δ 1 、Δ 2 、Δ 3 The respective weight coefficients, alpha, beta, gamma ranges take (0, 1);
after Hi values of a plurality of automobile power batteries are calculated, dividing the Hi values into a first interval, a second interval and a third interval; the Hi value in the first interval is less than the Hi value in the second interval and less than the Hi value in the third interval; e, the power batteries divided into the first interval enter the step e; f, dividing the power batteries into a second interval, and entering the step f; dividing the power battery into a third interval, and entering the step g;
step e: and calculating the second-layer screening data of the power battery divided into the first interval according to a formula (1-5) and a formula (1-6):
data set TV formed by a plurality of average ambient temperatures TV per hundred kilometers of travel 1 、TV 2 ……TV n Calculating the root mean square value of the group of data:
Figure FDA0003712647680000021
data set TM formed by a plurality of total time durations TM when discharge current of power battery exceeds a certain threshold value within one hundred kilometers of travel 1 、TM 2 ……TM n Calculating the root mean square value of the group of data:
Figure FDA0003712647680000022
Figure FDA0003712647680000023
in a certain range according to the formula (1-7)
Figure FDA0003712647680000024
Uniformly calculating domain transformation;
Figure FDA0003712647680000025
in a certain range according to the formula (1-8)
Figure FDA0003712647680000026
Unified computational domain transformation;
Figure FDA0003712647680000027
Figure FDA0003712647680000028
the second influence factor Yi is then calculated according to equation (1-9):
Figure FDA0003712647680000029
in the above formula, λ and θ are respectively Δ 5 、Δ 4 The respective weight coefficients, lambda and theta, are in the range of (0, 1);
after the Yi values of a plurality of automobiles are calculated, dividing the Yi values into at least three primary subintervals according to the size, and then connecting the power batteries in the same primary subinterval in parallel for cascade utilization;
step f: e, dividing the power battery into a second interval, dividing the power battery into different first-level subintervals according to the Yi value, then performing a 1C current constant-current discharge test on the fully-charged battery at the temperature of 20 +/-5 ℃, and calculating a standard discharge time value, namely the discharge current is equal to the rated current of the power battery;
dividing each primary subinterval into at least two secondary subintervals according to the discharge time rate, and connecting the power batteries in each secondary subinterval in parallel for cascade utilization;
step g: e and f, dividing the power batteries divided into a third interval into different secondary subintervals according to the Yi value and the standard discharge time rate C/n, then performing a fully-charged battery low-rate current constant-current discharge test, dividing the secondary subintervals under each third interval into at least two three-level subintervals according to the low-rate discharge time rate, and connecting the power batteries in each three-level subintervals in parallel for cascade utilization;
step h: marking the power battery of the electric automobile as not having the current step utilization requirement;
the total circulating charging frequency CN counting method comprises the following steps: recording the time length of single continuous charging exceeding 1h as the time number of one charging, wherein the counting of the power battery fault times comprises the sum of the power battery overcharge fault times, the power battery overdischarge fault times and the power battery short circuit fault times; the alpha is 0.5-0.7, the beta is 0.25-0.45, the gamma is 0.15-0.3, and the alpha + beta + gamma is 1; the lambda is 0.4-0.6, the theta is 0.4-0.6, and the lambda + theta is 1;
when the scrapped power battery is used as an energy storage device, the [ VTM _1 and VTM _2] is set to be [5000km and 20000km ], [ CN _1 and CN _2] is set to be [500 and 2000], [ GZ _1 and GZ _2] is set to be [0 and 30 ]; when the scrapped power battery is used as a household standby power supply, the [ VTM _1 and VTM _2] is set to [10000km and 30000km ], [ CN _1 and CN _2] is set to [500 and 2600], [ GZ _1 and GZ _2] are set to [0 and 60 ].
2. The low cost mode power cell cascade utilization multi-factor screening method of claim 1, wherein: in the step g, in the full-charge battery low-rate current constant current discharge test, the low-rate current is 0.1C-0.2C.
3. The low cost mode power cell cascade utilization multi-factor screening method of claim 1, wherein: before the step a, at least 3 pre-screening areas are divided according to the ratio of the current battery capacity value of the scrapped power battery to the calibrated power battery capacity for pre-screening, and after pre-screening, the steps a to h are carried out on different pre-screening areas.
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