A circuit and method for testing battery capacity and internal resistance change

Abstract

The present invention provides a circuit and method for testing battery capacity and internal resistance changes, including a BMS detection device, wherein the BMS detection device includes a first current acquisition module, an output module, and a controller module, wherein the controller module is electrically connected to the first current acquisition module and a display module, and further includes at least two battery cells, wherein the battery cells are connected in parallel to form a series unit, wherein the output circuit of the series unit is a series unit main circuit, and there are multiple first current acquisition modules, each of which is used to collect current data of a corresponding battery cell. Through this circuit structure, the battery cell with a problem can be directly locked, which is convenient for the later maintenance and processing of the battery pack; the calculation is more accurate, and the internal resistance and capacity changes of the battery cell can be deduced by collecting the current data of each battery cell, and the calculation of a single data source is more accurate.

Description

Technical Field

[0001] The invention belongs to the field of battery circuits, and in particular relates to a circuit and method for testing battery capacity and internal resistance changes. Background Art

[0002] Existing battery packs are only equipped with current BMS detection devices on the main series circuit, which means that the existing technical solutions can only monitor the collected current of the main circuit, and the capacity calculated based on the current is only the capacity of the battery pack (according to the principle of the shortest board of the wooden barrel, the measured capacity is the capacity of the module with the smallest capacity). The capacity of the battery cell in the module is a blind spot for the entire BMS detection device. However, for the entire battery pack, the battery cell is the smallest component unit of the battery pack, and its performance is bound to affect the performance of the entire battery pack. The deterioration of the performance of individual single cells may even cause the entire battery pack to catch fire and explode.

[0003] In a parallel circuit, the voltage of each parallel unit is equal, and the current is inversely proportional to the internal resistance, so the change in internal resistance can be inferred by comparing the change in current. Internal resistance is an important indicator of battery performance degradation, so understanding the change in battery internal resistance is very important for understanding the health status of the battery. The existing technology is to perform an initial complete charge and discharge on a battery pack (a battery pack composed of battery cells), and the capacity value of the battery pack can be obtained by current integration. The capacity value obtained by a second complete charge and discharge is compared with the initial capacity value to obtain the capacity change of the battery pack.

[0004] If the current of a single battery can be monitored and recorded, the capacity of the single battery can be calculated. In addition, the change in internal resistance can be inferred. This is of great significance for understanding the current status of the battery, predicting the performance of the battery, and avoiding safety accidents caused by the deterioration of the battery. Summary of the invention

[0005] The present invention provides a circuit for testing battery capacity and internal resistance changes, which performs current detection on all battery cells in a battery pack, thereby monitoring the capacity change and internal resistance change of individual batteries, grasping the health status of the battery cells, and avoiding the deterioration of the performance of individual battery cells causing accidents in the entire battery pack.

[0006] The present invention provides a circuit for testing battery capacity and internal resistance changes, including a BMS detection device, wherein the BMS detection device includes a first current acquisition module, an output module, and a controller module, wherein the controller module is electrically connected to the first current acquisition module and a display module, and further includes at least two battery cells, wherein the battery cells are connected in parallel to form a series unit, wherein the output circuit of the series unit is a series unit main circuit, and there are a plurality of first current acquisition modules, each of which is used to collect current data of a corresponding battery cell.

[0007] Furthermore, it also includes a second current acquisition module, which is connected in series with the series unit to collect current data of the series unit, and the second current acquisition module is electrically connected to the controller module.

[0008] Furthermore, there are a plurality of series connection units, and the series connection units are connected in series with adjacent series connection units.

[0009] Furthermore, the first current acquisition module and the second current acquisition module are access-type acquisition modules or non-access-type acquisition modules.

[0010] More specifically, the non-accessible acquisition module is a Hall current detector, and the coil of the Hall current detector is sleeved on the circuit to be measured;

[0011] The access type acquisition module is a shunt and an amplifier, the current end of the shunt is connected in series with the battery monomer, the potential end of the shunt is electrically connected to the amplifier, and the amplifier is electrically connected to the controller module.

[0012] Furthermore, the BMS detection device also includes a voltage acquisition module and a temperature probe. The voltage acquisition module is electrically connected to the controller module and is used to collect voltage data of the series cells. The temperature probe is electrically connected to the controller module. There are multiple temperature probes. The output module is any one of a display screen, an LED light, and a buzzer.

[0013] The method for using the above circuit to test the change of battery internal resistance includes the following steps:

[0014] S1. Collect the current I of each battery cell at the initial moment k1 ,I k2 ……I km , and the current I of the main circuit of the series unit 总0 , calculate the first ratios K1, K2…K of the current of each battery cell and the current of the main circuit of the series unit at the initial moment nm , where K1 = I k1 / I 总0 、K2=I k2 / I 总0 …K nm =I km / I 总0 ;

[0015] S2, collecting the current of each battery cell and the main circuit of the series unit at the current moment, and calculating the second ratio K1', K2'...K of the current of each battery cell and the main circuit of the series unit at the current moment nm ', the calculation method is the same as step S1;

[0016] S3, calculating the internal resistance change rate of each battery cell by the first ratio and the second ratio, the internal resistance change rate of each battery cell θ1=(K1′-K1) / K1, θ2=(K2′-K2) / K2…θ nm =(K nm '-K nm ) / K nm ; If θ1, θ2…θ nm If any value is greater than the set threshold value X, the circuit will be powered off for maintenance.

[0017] Furthermore, in step S2, the current of each battery cell and the main circuit of the series unit at the current moment is collected in real time;

[0018] In step S3, the threshold value X is set to 0.2.

[0019] The above circuit is used for testing the method of battery capacity change, wherein at least one series unit is connected in series through a series unit main circuit to form a battery pack, and the following steps are included:

[0020] Q1. Complete the first complete charge and discharge process of the battery pack, collect the current data of the battery cell in real time, and calculate the capacity C0 of the battery cell by current integration;

[0021] Q2. Complete the Nth complete charge and discharge process for the battery pack, where N is a natural number greater than or equal to 2, and calculate the capacity C of the battery cell after the Nth complete charge and discharge process by current integration. N ;

[0022] Q3. Calculate the capacity decay rate of the battery cell W = C N / C0, if W is less than the set threshold value P, the battery cell is maintained.

[0023] Furthermore, in step Q3, the threshold value P is set to 0.85.

[0024] The advantages of the circuit and method for testing battery capacity and internal resistance change of the present invention are:

[0025] 1. Perform current detection on all battery cells in the battery pack, and then monitor the capacity change and internal resistance change of individual batteries, and timely warn of battery cells with problems, so as to avoid the failure of a battery cell or a series unit (battery module), which may cause the loss of function of the entire battery pack, and avoid the expansion and deterioration of local faults and cause safety accidents;

[0026] 2. The circuit structure can directly lock the battery cell with problems, which is convenient for the later maintenance and processing of the battery pack;

[0027] 3. The calculation is more accurate. By collecting the current data of each battery cell, the internal resistance and capacity changes of the battery cell can be calculated. The calculation of a single data source is more accurate.

[0028] 4. The calculation steps are simple and efficient. The internal resistance change of the battery cell is directly calculated. There is no need to calculate the internal resistance value and then calculate the internal resistance change based on the internal resistance value, which is beneficial to improving the operating efficiency of the controller module. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the connection between the first current acquisition module and the battery cell in Example 2;

[0030] Figure 2 This is a schematic diagram of the connection of a single series unit in Example 2;

[0031] Figure 3 This is a schematic diagram of the connection between multiple series units and a BMS detection device in Example 2;

[0032] Figure 4 Schematic diagram of the connection between multiple series units and the BMS detection device in Example 3. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are mostly within the scope of protection of the present invention.

[0034] Embodiment 1:

[0035] The present invention provides a circuit for testing battery capacity and internal resistance changes, including a BMS detection device, wherein the BMS detection device includes a first current acquisition module, an output module, and a controller module, wherein the controller module is electrically connected to the first current acquisition module and the display module, and further includes at least one battery cell, wherein the battery cells are connected in parallel to form a series unit, wherein the output line of the series unit is a series unit main circuit, wherein there are multiple first current acquisition modules, each of which is used to collect current data of a corresponding battery cell, wherein the series unit is used to power a load, wherein a plurality of battery cells are connected in parallel to obtain a larger capacity.

[0036] In this embodiment, the current data I of the battery cell is collected by the first current collection module. k1 ,I k2 ……I km, the current data of the series unit can be calculated by adding up the data of each battery cell in the same series unit to get I 总0 .

[0037] The first current acquisition module is an access-type acquisition module, which is a shunt and an amplifier. The current end of the shunt is connected in series with the battery cell, the potential end of the shunt is electrically connected to the amplifier, and the amplifier is electrically connected to the controller module. The current data collected by the shunt is amplified by the amplifier and input into the ADC input pin of the controller module. The current data is converted into a binary number through the comparator inside the controller module, and the controller module measures the current.

[0038] The output module is any one of a display screen, an LED light, and a buzzer.

[0039] In this embodiment, the output module is a display screen.

[0040] The BMS detection device further includes a voltage acquisition module, which is electrically connected to the controller module and is used to collect voltage data of the series-connected cells.

[0041] The BMS detection device also includes a temperature probe, which is electrically connected to the controller module.

[0042] There are multiple temperature probes, which are used to detect the temperature of each battery cell and determine whether the temperature of the battery cell changes. If the temperature rises sharply and continuously, it means that the battery cell has a fault and needs to be powered off for maintenance.

[0043] The method for using the above circuit to test the change of battery internal resistance includes the following steps:

[0044] S1. Collect the current I of each battery cell at the initial moment k1 ,I k2 ……I km , and the current I of the main circuit of the series unit 总0 , calculate the first ratios K1, K2…K of the current of each battery cell and the current of the main circuit of the series unit at the initial moment nm , where K1 = I k1 / I 总0 、K2=I k2 / I 总0 …K nm =I km / I 总0 ;

[0045] S2, collecting the current of each battery cell and the main circuit of the series unit at the current moment, and calculating the second ratio K1', K2'...K of the current of each battery cell and the main circuit of the series unit at the current moment nm ', the calculation method is the same as step S1;

[0046] S3, calculating the internal resistance change rate of each battery cell by the first ratio and the second ratio, the internal resistance change rate of each battery cell θ1=(K1′-K1) / K1, θ2=(K2′-K2) / K2…θ nm =(K nm '-K nm ) / K nm ; If θ1, θ2…θ nm If any value is greater than the set threshold value X, the circuit will be powered off for maintenance.

[0047] In this embodiment, the current of each battery cell and the main circuit of the series unit at the current moment is collected in real time in step S2; in step S3, the threshold value X is set to 0.2 and 0.3, when θ1, θ2…θ nm When any value in is greater than the set threshold value 0.2, the display screen will show a warning state. nm When any value is greater than the set threshold of 0.3, the power is cut off. This method is simple and efficient to test the internal resistance change of each battery cell. It can detect the internal resistance change of the battery cell in real time, which is of great significance for understanding the current status of the battery, predicting the performance of the battery, and avoiding safety accidents caused by the deterioration of the battery cell.

[0048] The above circuit is used for testing the method of battery capacity change, wherein at least one series unit is connected in series through a series unit main circuit to form a battery pack, and the following steps are included:

[0049] Q1. Complete the first complete charge and discharge process of the battery pack, collect the current data of the battery cell in real time, and calculate the capacity C0 of the battery cell by current integration;

[0050] Q2. Complete the Nth complete charge and discharge process for the battery pack, where N is a natural number greater than or equal to 2, and calculate the capacity C of the battery cell after the Nth complete charge and discharge process by current integration. N ;

[0051] Q3. Calculate the capacity decay rate of the battery cell W = C N / C0, if W is less than the set threshold value 0.8, the battery cell is maintained.

[0052] Embodiment 2:

[0053] like Figure 1-3As shown, the present invention is a circuit for testing battery capacity and internal resistance change, including a BMS detection device, the BMS detection device is connected to a power supply, the BMS detection device includes a first current acquisition module, an output module, and a controller module, the controller module is electrically connected to the first current acquisition module and the display module, and also includes at least one battery cell, that is, a battery cell Figure 2 , Figure 3 C 11 , C 12 ···C 1mm ; C 21 , C 22 ···C 2m ; C n1 , C n2 ···C nm The battery cells are connected in parallel to form a series unit, and the output circuit of the series unit is the series unit main circuit.

[0054] There are multiple first current acquisition modules, and the first current acquisition modules are Figure 2 , Figure 3 FL 11 , FL 12 ···FL 1m FL 21 , FL 22 ···FL 2m FL n1 , FL n2 ···FL nm Each first current acquisition module is used to collect current data I of a corresponding battery cell k1 ,I k2 ……I km .

[0055] It also includes a second current acquisition module, namely Figure 3 Medium FL 总 , through FL 总 Real-time collection of main circuit current data I 总0 The second current acquisition module is connected in series with the series unit to collect current data of the series unit. The second current acquisition module is electrically connected to the controller module. The controller module can directly collect current data of the series unit without accumulating and calculating the data of each battery cell in the series unit. The program execution in the controller module is more efficient and faster, wherein the BMS detection device is Figure 3 The BMS main control has a collection module inside, and the collection module includes a first current collection module and a second current collection module.

[0056] There are multiple series cells, and the series cells are connected in series with the adjacent series cells. In this embodiment, the number of battery cells and series cells is 10, that is, Figure 2 , Figure 3 In the example, m=10, n=10, the battery cells are connected in parallel to obtain their superimposed capacitance, and the series cells are connected in series to obtain a higher voltage to supply the power supply demand of the load. The first current acquisition module and the second current acquisition module are both access-type acquisition modules, and the access-type acquisition module is a shunt and an amplifier. The current end of the shunt is connected in series with the battery cell, the potential end of the shunt is electrically connected to the amplifier, and the amplifier is electrically connected to the controller module.

[0057] The output module is an LED lamp. If the internal resistance of the battery cell changes sharply, the controller module outputs a low level to light up the LED lamp, which is convenient for human-computer interaction and allows knowing the real-time status of the battery cell.

[0058] The BMS detection device further includes a voltage acquisition module, which is electrically connected to the controller module and is used to collect voltage data of the series-connected cells.

[0059] The BMS detection device also includes a temperature probe, which is electrically connected to the controller module.

[0060] There are multiple temperature probes, which are used to collect the temperature of each battery cell and a battery pack (a battery pack is composed of multiple series-connected cells), and not only detect whether the temperature of the battery cell changes, but also detect the temperature change of the environment in which the battery pack is located.

[0061] The method for using the above circuit to test the change of battery internal resistance includes the following steps:

[0062] S1. Collect the current I of each battery cell at the initial moment k1 ,I k2 ……I km , and the current I of the main circuit of the series unit 总0 , calculate the first ratios K1, K2…K of the current of each battery cell and the current of the main circuit of the series unit at the initial moment nm , where K1 = I k1 / I 总0 、K2=I k2 / I 总0 …K nm =I km / I 总0 ;

[0063] S2, collecting the current of each battery cell and the main circuit of the series unit at the current moment, and calculating the second ratio K1', K2'...K of the current of each battery cell and the main circuit of the series unit at the current moment nm ', the calculation method is the same as step S1;

[0064] S3, calculating the internal resistance change rate of each battery cell by the first ratio and the second ratio, the internal resistance change rate of each battery cell θ1=(K1′-K1) / K1, θ2=(K2′-K2) / K2…θ nm =(K nm '-K nm ) / K nm ; If θ1, θ2…θ nm If any value in is greater than the set threshold value X, the circuit is powered off for maintenance. Power off is completed through the power-off relay, which is integrated inside the BMS detection device. The control end of the power-off relay is electrically connected to the controller module, and the normally closed end of the power-off relay is connected to the main circuit. When power off maintenance is required, the controller module outputs a signal to close the power-off relay, and the power-off relay disconnects the main circuit.

[0065] In step S2, the current of each battery cell and the main circuit of the series unit is collected in real time;

[0066] In step S3, the threshold value X is set to 0.25. If θ1, θ2, ... nm If any value is greater than the set threshold value of 0.25, the controller module outputs a low level and lights up the LED to alarm.

[0067] The above circuit is used for testing the method of battery capacity change, wherein at least one series unit is connected in series through a series unit main circuit to form a battery pack, and the following steps are included:

[0068] Q1. Complete the first complete charge and discharge process of the battery pack, collect the current data of the battery cell in real time, and calculate the capacity C0 of the battery cell by current integration;

[0069] Q2. Complete the Nth complete charge and discharge process for the battery pack, where N is a natural number greater than or equal to 2, and calculate the capacity C of the battery cell after the Nth complete charge and discharge process by current integration. N ;

[0070] Q3. Calculate the capacity decay rate of the battery cell W = C N / C0, if W is less than the set threshold value P, the battery cell is maintained. In step Q3, the threshold value P is set to 0.85. When the capacity attenuation rate of the battery cell is less than the set threshold value 0.85, the controller module outputs a low level to light up the LED light to alarm.

[0071] Example 3

[0072] like Figure 4As shown, a circuit for testing battery capacity and internal resistance change includes a BMS detection device, the BMS detection device includes a first current acquisition module, an output module, and a controller module, the controller module is electrically connected to the first current acquisition module and the display module, and also includes at least one battery cell, the battery cells are connected in parallel to form a series unit, the output line of the series unit is the series unit main circuit,

[0073] There are multiple first current acquisition modules, and each first current acquisition module is used to acquire current data of a corresponding battery cell.

[0074] The second current acquisition module is also included, and the second current acquisition module is connected in series with the series unit to collect current data of the series unit, that is, the main circuit current I 总0 , the second current acquisition module is electrically connected to the controller module.

[0075] There are a plurality of series connection units, and each series connection unit is connected in series with its adjacent series connection units.

[0076] The first current acquisition module and the second current acquisition module are both non-access acquisition modules, and the non-access acquisition module is a Hall current detector. The coil of the Hall current detector is set on the measured circuit. In this embodiment, the first current acquisition module is Figure 4 Medium HCS 11 、HCS 12 ···HCS 1m ; HCS 21 、HCS 22 ···HCS 2m ; HCS n1 、HCS n2 ···HCS nm ; The second current acquisition module is Figure 4 Medium HCS 总 , where n=15, m=10.

[0077] The output module is a buzzer.

[0078] The BMS detection device further includes a voltage acquisition module, which is electrically connected to the controller module and is used to collect voltage data of the series-connected cells.

[0079] The BMS detection device also includes a temperature probe, which is electrically connected to the controller module.

[0080] There are multiple temperature probes, which are used to collect the temperature of each battery cell and a battery pack (a battery pack is composed of multiple series-connected cells), and detect not only whether the temperature of the battery cell changes, but also the temperature change of the environment where the battery pack is located.

[0081] The method for using the above circuit to test the change of battery internal resistance includes the following steps:

[0082] S1. Collect the current I of each battery cell at the initial moment k1 ,I k2 ……I km , and the current I of the main circuit of the series unit 总0 , calculate the first ratios K1, K2…K of the current of each battery cell and the current of the main circuit of the series unit at the initial moment nm , where K1 = I k1 / I 总0 、K2=I k2 / I 总0 …K nm =I km / I 总0 ;

[0083] S2, collecting the current of each battery cell and the main circuit of the series unit at the current moment, and calculating the second ratio K1', K2'...K of the current of each battery cell and the main circuit of the series unit at the current moment nm ', the calculation method is the same as step S1;

[0084] S3, calculating the internal resistance change rate of each battery cell by the first ratio and the second ratio, the internal resistance change rate of each battery cell θ1=(K1′-K1) / K1, θ2=(K2′-K2) / K2…θ nm =(K nm '-K nm ) / K nm ; If θ1, θ2…θ nm If any value is greater than the set threshold value X, the circuit will be powered off for maintenance.

[0085] Furthermore, in step S2, the current of each battery cell and the main circuit of the series unit is collected in real time; in step S3, the threshold value X is set to 0.3.

[0086] The above circuit is used for testing the method of battery capacity change, wherein at least one series unit is connected in series through a series unit main circuit to form a battery pack, and the following steps are included:

[0087] Q1. Complete the first complete charge and discharge process of the battery pack, collect the current data of the battery cell in real time, and calculate the capacity C0 of the battery cell by current integration;

[0088] Q2. Complete the Nth complete charge and discharge process for the battery pack, where N is a natural number greater than or equal to 2, and calculate the capacity C of the battery cell after the Nth complete charge and discharge process by current integration. N ;

[0089] Q3. Calculate the capacity decay rate of the battery cell W = C N / C0, if W is less than the set threshold value P, the battery cell is maintained. In step Q3, the threshold value P is set to 0.85.

Claims

1. A method for testing the change of battery internal resistance, using a circuit for testing the change of battery capacity and internal resistance, the circuit comprising a BMS detection device, the BMS detection device comprising a first current acquisition module, an output module, and a controller module, the controller module being electrically connected to the first current acquisition module and the display module, and further comprising at least two battery cells, the battery cells being connected in parallel to form a series cell, the output line of the series cell being a series cell main circuit, the first current acquisition module being multiple, each of the first current acquisition modules being used to collect current data of a corresponding battery cell, characterized in that: The method comprises the following steps: S1. Collect the current I of each battery cell at the initial moment k1 ,I k2 ……I km , and the current I of the main circuit of the series unit 总0 , calculate the first ratios K1, K2…K of the current of each battery cell and the current of the main circuit of the series unit at the initial moment nm , where K1 = I k1 / I 总0 、K2=I k2 / I 总0 …K nm =I km / I 总0 ; S2, collecting the current of each battery cell and the main circuit of the series unit at the current moment, and calculating the second ratio K1', K2'...K of the current of each battery cell and the main circuit of the series unit at the current moment nm ', the calculation method is the same as step S1; S3, calculating the internal resistance change rate of each battery cell by the first ratio and the second ratio, the internal resistance change rate of each battery cell θ1=(K1′-K1) / K1, θ2=(K2′-K2) / K2…θ nm =(K nm '-K nm ) / K nm ; If θ1, θ2…θ nm If any value is greater than the set threshold value X, the circuit will be powered off for maintenance.

2. The method for testing the change of internal resistance of a battery according to claim 1, characterized in that: The circuit further includes a second current acquisition module, which is connected in series with the series unit to collect current data of the series unit, and the second current acquisition module is electrically connected to the controller module.

3. The method for testing the change of internal resistance of a battery according to claim 1, characterized in that: There are a plurality of series connection units, and each series connection unit is connected in series with its adjacent series connection units.

4. The method for testing the change of battery internal resistance according to claim 3, characterized in that: The first current acquisition module and the second current acquisition module are access-type acquisition modules or non-access-type acquisition modules.

5. The method for testing the change of internal resistance of a battery according to claim 4, characterized in that: The non-accessible acquisition module is a Hall current detector, and the coil of the Hall current detector is sleeved on the circuit to be measured; The access type acquisition module is a shunt and an amplifier, the current end of the shunt is connected in series with the battery monomer, the potential end of the shunt is electrically connected to the amplifier, and the amplifier is electrically connected to the controller module.

6. The method for testing the change of internal resistance of a battery according to claim 5, characterized in that: The BMS detection device also includes a voltage acquisition module and a temperature probe. The voltage acquisition module is electrically connected to the controller module and is used to collect voltage data of the series units. The temperature probe is electrically connected to the controller module. There are multiple temperature probes. The output module is any one of a display screen, an LED light, and a buzzer.

7. The method for testing the change of internal resistance of a battery according to any one of claims 1 to 6, characterized in that: In step S2, the current of each battery cell and the main circuit of the series unit is collected in real time; In step S3, the threshold value X is set to 0.

2.

8. A method for testing battery capacity changes, using a circuit for testing battery capacity and internal resistance changes, the circuit comprising a BMS detection device, the BMS detection device comprising a first current acquisition module, an output module, and a controller module, the controller module being electrically connected to the first current acquisition module and the display module, and further comprising at least two battery cells, the battery cells being connected in parallel to form a series cell, the output circuit of the series cell being a series cell main circuit, the first current acquisition modules being multiple, each of the first current acquisition modules being used to collect current data of a corresponding battery cell, the circuit being connected in series with at least one series cell through the series cell main circuit to form a battery pack, characterized in that The following steps are involved: Q1. Complete the first complete charge and discharge process of the battery pack, collect the current data of the battery cell in real time, and calculate the capacity C0 of the battery cell by current integration; Q2. Complete the Nth complete charge and discharge process for the battery pack, where N is a natural number greater than or equal to 2, and calculate the capacity C of the battery cell after the Nth complete charge and discharge process by current integration. N ; Q3. Calculate the capacity decay rate of the battery cell W = C N / C0, if W is less than the set threshold value P, the battery cell is maintained.

9. The method for testing battery capacity change according to claim 8, characterized in that In step Q3, the threshold value P is set to 0.85.

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