A battery pack and its charging method

Abstract

The present invention provides a battery pack composed of battery cells (1), a charging module (2), a controller (3), a plurality of temperature sensors (4), voltage sensors (5), an electronic switch (6) and a resistor (7), which is used to ensure that the battery pack can be charged safely, stably, as fully as possible and quickly during the charging process. The present invention also provides a charging method applied to the above battery pack: when charging starts, the temperature value and the supply voltage value of each battery cell (1) are measured at time intervals Δt and compared with the corresponding maximum values to determine whether to end the charging; if the measured values do not meet the charging end condition, then compare the size of t and FΔt to collect data, and compare the measured data with its corresponding threshold value and perform corresponding operations to achieve safety and stability during the charging process of the battery pack. The structure of the present invention is relatively simple and has the advantages of safety, stability, being as fully charged as possible and fast charging at the same time.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and particularly to a battery pack and a charging method thereof. Background Art

[0002] Various batteries represented by lithium-ion batteries are widely used in the fields of transportation, energy storage, and digital electronic products. Since the voltage and energy of a single battery are relatively low, multiple batteries are usually connected in series and parallel to form a battery pack for use. During the service process of the battery pack, charging is often required, and it is desired that the charging process achieves the following three major objectives:

[0003] (1) Safe and stable: That is, during the charging process, the temperature of the battery pack cannot be too high, the voltage cannot exceed the cut-off voltage, and at the same time, the rising speeds of the temperature and voltage cannot be too fast;

[0004] (2) Fully charged: That is, as much charge as possible is charged within a safe and reasonable range. To this end, it is also necessary to maintain the consistency of each series unit to prevent the occurrence of the short-board effect;

[0005] (3) Fast: That is, the charging is as fast as possible on the premise of being safe, stable, and fully charged.

[0006] In the current well-known technologies, generally, temperature and voltage sensors are set and real-time monitoring is carried out to prevent the voltage and temperature from being too high during the charging process. Once related problems occur, charging is stopped or the charging current is reduced. These measures can solve the safety problems during the charging process, but cannot meet the requirements of being fully charged as much as possible and fast charging at the same time. Therefore, it is urgent to improve the existing technology and propose a battery pack charging technology that has the advantages of being safe, stable, fully charged as much as possible, and fast charging. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a battery pack with a relatively simple structure and having the advantages of being safe, stable, fully charged as much as possible, and fast charging, and provides a corresponding charging method.

[0008] According to one aspect of the present invention, there is provided a battery pack, including a plurality of battery units connected in series in sequence, a charging module for charging the battery units, a controller, and several temperature sensors; each battery unit is provided with a positive terminal, a negative terminal, a voltage sensor, an electronic switch, and a resistor. The voltage sensor is electrically connected to the positive terminal and the negative terminal respectively to measure the terminal voltage value of the battery unit where it is located. The positive terminal is electrically connected to the negative terminal through the electronic switch and the resistor in sequence; the temperature sensor is used to measure the temperature of a battery unit at a certain position; the controller is electrically connected to the charging module and all the temperature sensors, voltage sensors, and electronic switches respectively.

[0009] The above battery pack, wherein the battery cell is composed of 1 battery monomer or multiple battery monomers connected in parallel with each other.

[0010] The above battery pack, wherein the electronic switch is a normally open switch.

[0011] The above battery pack, wherein the resistance values of the resistors in all battery cells are equal.

[0012] The above battery pack, wherein the charging module is provided with a power taking port for obtaining electric energy from an external power supply, a power supply port for charging the battery cell, and a voltmeter for measuring the power supply voltage value of the power supply port.

[0013] The above battery pack, wherein the controller is used to collect the measurement data of the voltmeter, all temperature sensors and voltage sensors and control the operation of the charging module and the electronic switch.

[0014] The above battery pack, wherein the charging module can charge the battery cell with a constant current according to the instruction of the controller, and the magnitude of the charging current is adjustable.

[0015] According to another aspect of the present invention, there is provided a charging method applied to the above battery pack, obtaining in advance from the manufacturer the charging cut-off voltage value V c , the reference charging current value I0 and the maximum allowable charging temperature value T max ;

[0016] After starting charging, let the charging start time be t = 0, and continuously collect and store the terminal voltage value of each battery cell, the temperature value measured by each temperature sensor and the power supply voltage value E measured by the voltmeter at a fixed time interval Δt; for any sampling time, if the power supply voltage value E is greater than the charging cut-off voltage value V c or the temperature value measured by any temperature sensor is greater than the maximum allowable charging temperature value T max , then immediately end the charging, otherwise perform the following operations:

[0017] When t ≤ FΔt, charge the battery pack with a constant current at the reference charging current value I0, where F is a natural number;

[0018] When t > FΔt, at each sampling time t i , read the sampling data between t = t i - FΔt and t = t i to form a data set and statistically obtain the power supply voltage rise amplitude ΔE, the temperature rise amplitude ΔT and the unit voltage deviation index ΔU, where F is a natural number:

[0019] The power supply voltage rise amplitude ΔE is the difference between the maximum value and the minimum value of the power supply voltage value E in the data set;

[0020] The temperature rise ΔT is the difference between the average of the temperature values measured by all temperature sensors at time t = t i and the average of the temperature values measured by all temperature sensors at time t = t i - FΔt;

[0021] The unit voltage deviation index ΔU is obtained by, for each data time in the dataset, finding the maximum and minimum values among all battery cell terminal voltage values and calculating the difference between the two as the voltage deviation value at that time; taking the average of the voltage deviation values at all times in the dataset as the unit voltage deviation index ΔU;

[0022] Perform the following operations based on the above statistical results:

[0023] (i), If ΔE < ΔE c1 and ΔT ≤ ΔT c and ΔU ≤ ΔU c , then continue charging and increase the charging current by k on the original basis, where k is between 1% and 5%;

[0024] (ii), If ΔE c1 ≤ ΔE ≤ ΔE c2 and ΔT ≤ ΔT c and ΔU ≤ ΔU c , then continue charging and keep the charging current unchanged on the original basis;

[0025] (iii), If ΔU ≤ ΔU c , and either ΔE > ΔE c2 or ΔT > ΔT c is satisfied, then continue charging and decrease the charging current by k on the original basis, where k is between 1% and 5%;

[0026] (iv), If ΔU > ΔU c , then stop charging and enter the equalization mode;

[0027] The above ΔE c1 and ΔE c2 are the first threshold and the second threshold of the supply voltage rise amplitude respectively, ΔT c is the temperature rise amplitude threshold, and ΔU c is the unit voltage deviation index threshold;

[0028] After entering the equalization mode, continuously collect and store the terminal voltage values of each battery cell (1) at a fixed time interval Δt, and sequentially perform the following steps based on the collected data:

[0029] Step S1: Leave the battery pack idle for a period of time;

[0030] Step S2: Read the terminal voltage values of each battery cell at the end of the shelving period, and calculate their average value U m , and find out the battery cells with terminal voltage values higher than the average value;

[0031] Step S3: For each battery cell determined in Step S2 with a terminal voltage value higher than the average value U m , close the corresponding electronic switch respectively, and use the resistor to continuously discharge it until its terminal voltage value is less than the average value U m , and then disconnect the corresponding electronic switch;

[0032] Step S4: Shelve the battery pack for a period of time;

[0033] Step S5: End the equalization mode and restart the charging of the battery pack.

[0034] For the above battery pack charging method, the value of the fixed time interval Δt ranges from 1 millisecond to 1 second, the natural number F ranges from 10 to 10,000, and the shelving duration in Steps S1 and S5 ranges from 1 minute to 1 hour.

[0035] For the above battery pack charging method, the reference charging current value I0 is between 0.05 times and 2 times the current value corresponding to the battery pack charging at a 1C rate, the maximum allowable charging temperature value T max is between 45°C and 70°C, the temperature rise amplitude threshold ΔT c is between 2°C and 10°C, the cell voltage deviation index threshold ΔU c is between 5 millivolts and 100 millivolts, the first threshold ΔE of the supply voltage rise amplitude c1 is between 0.1% and 1% of the battery pack charging cut-off voltage value V c , the second threshold ΔE of the supply voltage rise amplitude c2 is between 1% and 2% of the battery pack charging cut-off voltage value V c , and the first threshold ΔE of the supply voltage rise amplitude c1 is less than the second threshold ΔE of the supply voltage rise amplitude c2 .

[0036] For the circuit connection structure of the battery pack of the present invention, in addition to the original normal circuit connection for power transmission, only an equalization circuit with a resistor is added to each battery cell, and relevant temperature and voltage sensors and a controller are set. The overall circuit structure is relatively simple. The main advantages of the present invention are to solve the following three major problems during the battery pack charging process simultaneously:

[0037] (1) Safe and stable: At any sampling moment, if the supply voltage value E is greater than the charging cut-off voltage value V cor the temperature value measured by any temperature sensor (4) is greater than the maximum allowable charging temperature value T max , the charging will be immediately terminated; if it is found through data statistics that the temperature and voltage rise rapidly during the charging process, the charging current will be gradually decreased appropriately on the original basis.

[0038] (2) Full charge: When the voltage deviation of each battery cell terminal is large during the charging process, the charging will be aborted, and the battery cell with a higher terminal voltage will be appropriately discharged to adjust the consistency between the battery cells, and then the charging will be restarted;

[0039] (3) Fast charge: If it is found through data statistics that the temperature and voltage rise slowly during the charging process, the charging current will be gradually increased appropriately on the original basis. Brief Description of the Drawings

[0040] Figure 1 is a schematic diagram of the composition of the battery pack in the embodiment of the present invention. In the figure, 1 is a battery cell, 2 is a charging module, 3 is a controller, 4 is a plurality of temperature sensors, 5 is a voltage sensor, 6 is an electronic switch, 7 is a resistor, 11 is a positive terminal, 12 is a negative terminal, 21 is a power-taking port, 22 is a power supply port, and 23 is a voltmeter.

[0041] Figure 2 is a flowchart of the battery pack charging method in the embodiment of the present invention. Detailed Embodiments

[0042] The following will further describe the present invention in conjunction with the appended Figure 1-2 drawings and embodiments.

[0043] A battery pack includes a plurality of battery cells 1 connected in series in sequence, a charging module 2 for charging the battery cells 1, a controller 3, and a plurality of temperature sensors 4; each battery cell (1) is provided with a positive terminal 11, a negative terminal 12, a voltage sensor 5, an electronic switch 6, and a resistor 7. The voltage sensor 5 is electrically connected to the positive terminal 11 and the negative terminal 12 respectively to measure the terminal voltage value of the battery cell 1 where it is located. The positive terminal is electrically connected to the negative terminal 12 through the electronic switch 6 and the resistor 7 in sequence; the temperature sensor 4 is used to measure the temperature of the battery cell 1 at a certain position; the controller 3 is electrically connected to the charging module 2 and all the temperature sensors 4, voltage sensors 5, and electronic switches 6 respectively.

[0044] For the above battery pack, the battery cell 1 is composed of 1 battery monomer or multiple battery monomers connected in parallel with each other.

[0045] For the above battery pack, the electronic switch 6 is a normally open switch.

[0046] For the above battery pack, the resistance values of the resistors 7 in all the battery cells 1 are equal.

[0047] For the above battery pack, the charging module 2 is provided with a power taking port 21 for obtaining electric energy from an external power supply, a power supply port 22 for charging the battery cells 1, and a voltmeter 23 for measuring the power supply voltage value of the power supply port 22.

[0048] For the above battery pack, the controller 3 is used to collect the measurement data of the voltmeter 23, all the temperature sensors 4 and the voltage sensors 5 and control the operation of the charging module 2 and the electronic switch 6.

[0049] For the above battery pack, the charging module 2 can charge the battery cells 1 with a constant current according to the instructions of the controller 3, and the magnitude of the charging current is adjustable.

[0050] A charging method applied to the above battery pack, obtaining in advance from the manufacturer the charging cut-off voltage value V c , the reference charging current value I0 and the maximum allowable charging temperature value T max ;

[0051] After starting the charging, let the charging start time be t = 0, and continuously collect and store the terminal voltage value of each battery cell 1, the temperature value measured by each temperature sensor 4, and the power supply voltage value E measured by the voltmeter 23 at fixed time intervals Δt; for any sampling time, if the power supply voltage value E is greater than the charging cut-off voltage value V c or the temperature value measured by any temperature sensor 4 is greater than the maximum allowable charging temperature value T max , then immediately end the charging, otherwise perform the following operations:

[0052] When t ≤ FΔt, charge the battery pack with a constant current at the reference charging current value I0, where F is a natural number;

[0053] When t > FΔt, at each sampling time t i , read the sampling data between t = t i -FΔt and t = t i to form a data set and statistically obtain the power supply voltage rise amplitude ΔE, the temperature rise amplitude ΔT, and the cell voltage deviation index ΔU, where F is a natural number:

[0054] The power supply voltage rise amplitude ΔE is the difference between the maximum and minimum values of the power supply voltage value E in the data set;

[0055] The temperature rise amplitude ΔT is the difference between the average value of the temperature values measured by all the temperature sensors 4 at t = t i and the average value of the temperature values measured by all the temperature sensors 4 at t = t i -FΔt;

[0056] The method for obtaining the cell voltage deviation index ΔU is as follows: for each data moment in the dataset, find the maximum and minimum values of the terminal voltage values of all battery cells at one end, and calculate the difference between the two as the voltage deviation value at this moment; take the average value of the voltage deviation values at all moments in the dataset as the cell voltage deviation index ΔU;

[0057] Perform the following operations according to the above statistical results:

[0058] (i), If ΔE < ΔE c1 and ΔT ≤ ΔT c and ΔU ≤ ΔU c , then continue to maintain charging and increase the charging current by k on the original basis, where k is between 1% and 5%;

[0059] (ii), If ΔE c1 ≤ ΔE ≤ ΔE c2 and ΔT ≤ ΔT c and ΔU ≤ ΔU c , then continue to maintain charging and keep the charging current unchanged on the original basis;

[0060] (iii), If ΔU ≤ ΔU c , and any one of the two conditions ΔE > ΔE c2 and ΔT > ΔT c is satisfied, then continue to maintain charging and reduce the charging current by k on the original basis, where k is between 1% and 5%;

[0061] (iv), If ΔU > ΔU c , then stop charging and enter the equalization mode;

[0062] The above ΔE c1 and ΔE c2 are the first threshold of the supply voltage rise amplitude and the second threshold of the supply voltage rise amplitude respectively, ΔT c is the temperature rise amplitude threshold, and ΔU c is the cell voltage deviation index threshold;

[0063] After entering the equalization mode, continuously collect and store the terminal voltage values of each battery cell (1) at a fixed time interval Δt, and sequentially perform the following steps in combination with the collected data:

[0064] Step S1: Leave the battery pack idle for a period of time;

[0065] Step S2: Read the terminal voltage values of each battery cell 1 at the end of the idle period, calculate their average value U m , and find the battery cells 1 with terminal voltage values higher than the average value;

[0066] Step S3: For each battery cell 1 whose terminal voltage value determined in Step S2 is higher than the average value U m respectively close the corresponding electronic switch 6, and continuously discharge it through the resistor 7 until its terminal voltage value is less than the average value U m then disconnect the corresponding electronic switch 6;

[0067] Step S4: Leave the battery pack for a period of time;

[0068] Step S5: End the equalization mode and restart the charging of the battery pack.

[0069] For the above battery pack charging method, the value of the fixed time interval Δt ranges from 1 millisecond to 1 second, the natural number F ranges from 10 to 10,000, and the leaving duration in Steps S1 and S5 ranges from 1 minute to 1 hour.

[0070] For the above battery pack charging method, the reference charging current value I0 is between 0.05 times and 2 times the current value corresponding to the battery pack charging at a 1C rate, the maximum allowable charging temperature value T max is between 45°C and 70°C, the temperature rise amplitude threshold ΔT c is between 2°C and 10°C, the cell voltage deviation index threshold ΔU c is between 5 millivolts and 100 millivolts, the first threshold ΔE of the supply voltage rise amplitude c1 is between 0.1% and 1% of the battery pack charging cut-off voltage value V c the second threshold ΔE of the supply voltage rise amplitude is between 1% and 2% of the battery pack charging cut-off voltage value V c2 and the first threshold ΔE of the supply voltage rise amplitude c is less than the second threshold ΔE of the supply voltage rise amplitude c1 c2 .

[0071] Embodiment

[0072] Please refer to Figures 1 to 2 to understand this embodiment.

[0073] A certain battery pack is composed of 15 lithium iron phosphate lithium-ion battery monomers connected in series. 1 battery monomer constitutes 1 battery cell, and each battery cell is respectively denoted as 1# to 15#. The rated capacity of this battery pack is 20Ah, the charging cut-off voltage value V c = 55V, the reference charging current value I0 = 20A, and the maximum allowable charging temperature value T max = 50°C.

[0074] ​In this embodiment, the time interval Δt = 1 second, the natural number F = 20, the shelving duration described in steps S1 and S5 is 10 minutes, the temperature rise amplitude threshold ΔT = 3 °C, and the unit voltage deviation index threshold ΔU c = 0.05 V, the first threshold ΔE of the supply voltage rise amplitude c1 = 0.2 V, the second threshold ΔE of the supply voltage rise amplitude c2 = 0.6 V.

[0075] One day, the battery pack is charged.

[0076] After starting the charging, let the charging start time be t = 0. Continuously collect and store the terminal voltage value of each battery cell (1), the temperature value measured by each temperature sensor 4, and the supply voltage value E measured by the voltmeter 23 at a fixed time interval Δt = 1 second.

[0077] When t ≤ FΔt, that is, t ≤ 20 s, the battery pack is charged at a constant current with a reference charging current value I0 = 20 A.

[0078] When t > FΔt, that is, t > 20 s, at each sampling time t i , read the sampling data between t = t i - 20 s and t = t i to form a data set and statistically obtain the supply voltage rise amplitude ΔE, the temperature rise amplitude ΔT, and the unit voltage deviation index ΔU.

[0079] For example, when the sampling time t i = 21 s, read the sampling data between t = t i - 20 s = 1 s and t = t i = 21 s to form a data set and statistically obtain the supply voltage rise amplitude ΔE = 0.18 V, the temperature rise amplitude ΔT = 2 °C, and the unit voltage deviation index ΔU = 0.03 V. At this time, ΔE < ΔE c1 and ΔT ≤ ΔT c and ΔU ≤ ΔU c , then continue to maintain the charging and increase the charging current by k = 5% to 21 A on the original basis. In this embodiment, k is taken as 5%.

[0080] When the sampling time t i = 22 s, read the sampling data between t = t i - 20 s = 2 s and t = t i = 22 s to form a data set and statistically obtain the supply voltage rise amplitude ΔE = 0.19 V, the temperature rise amplitude ΔT = 2.2 °C, and the unit voltage deviation index ΔU = 0.035 V. At this time, ΔE < ΔE c1 and ΔT ≤ ΔT c and ΔU ≤ ΔUc , continue to maintain charging and increase the charging current by k = 5% to 22.05 A on the original basis.

[0081] Sampling time t i = 23 s to t i = 1020 s, the statistical results at each sampling time all satisfy: ΔE c1 ≤ΔE≤ΔE c2 and ΔT≤ΔT c and ΔU≤ΔU c , continue to maintain charging and keep the charging current unchanged at the original 22.05 A.

[0082] Sampling time t i = 1021 s, read the sampling data from the time t = t i - 20 s = 1001 s to the time t = t i = 1021 s to form a data set and statistically obtain the power supply voltage rise amplitude ΔE = 0.72 V, the temperature rise amplitude ΔT = 3.5 °C, and the cell voltage deviation index ΔU = 0.04 V. At this time, ΔU≤ΔU c and ΔE>ΔE c2 , continue to maintain charging and reduce the charging current by k = 5% to 20.95 A on the original basis.

[0083] Sampling time t i = 1022 s to t i = 1080 s, the statistical results at each sampling time all satisfy: ΔE c1 ≤ΔE≤ΔE c2 and ΔT≤ΔT c and ΔU≤ΔU c , continue to maintain charging and keep the charging current unchanged at the original 20.95 A.

[0084] Sampling time t i = 1081 s, read the sampling data from the time t = t i - 20 s = 1061 s to the time t = t i = 1081 s to form a data set and statistically obtain the power supply voltage rise amplitude ΔE = 0.42 V, the temperature rise amplitude ΔT = 3.2 °C, and the cell voltage deviation index ΔU = 0.06 V. At this time, ΔU>ΔU c , abort charging and enter the balancing mode.

[0085] After entering the balancing mode, continuously collect and store the terminal voltage values of each battery cell (1) at a fixed time interval Δt = 1 s, and sequentially execute the following steps in combination with the collected data:

[0086] Step S1: Leave the battery pack idle for 10 minutes;

[0087] Step S2: Read the terminal voltage values of each battery cell (1) at the end of the shelving period, and calculate their average value U m = 3.25V, and identify the battery cells (1) with terminal voltage values higher than the average value as No. 1, No. 4, and No. 13;

[0088] Step S3: For each battery cell 1 determined in Step S2 with a terminal voltage value higher than the average value U m respectively close the corresponding electronic switch 6, and continuously discharge it through the resistor 7 until its terminal voltage value is less than the average value U m = 3.25V, and then disconnect the corresponding electronic switch 6;

[0089] Step S4: Shelve the battery pack for 10 minutes;

[0090] Step S5: End the equalization mode and restart the charging of the battery pack.

[0091] After restarting the charging, set the charging start time as t = 0, and continuously collect and store the terminal voltage values of each battery cell 1, the temperature values measured by each temperature sensor 4, and the supply voltage value E measured by the voltmeter 23 at a fixed time interval Δt = 1 second.

[0092] When t ≤ FΔt, that is, t ≤ 20s, charge the battery pack at a constant current with a reference charging current value I0 = 20A.

[0093] Sampling time t i = 21s to t i = 236s, the statistical results at each sampling time all satisfy: ΔE c1 ≤ ΔE ≤ ΔE c2 and ΔT ≤ ΔT c and ΔU ≤ ΔU c , then continue to maintain the charging and keep the charging current unchanged based on the original 20A.

[0094] Sampling time t i = 237s, the supply voltage value E = 55.2V, which is greater than the charging cut-off voltage value V c = 55V, so end the charging.

[0095] In this embodiment, the charging is started twice in total. The first time is the initial start of charging, and the second time is the restart of charging after completing the equalization mode. It should be noted that whether it is the initial start of charging or the restart of charging after completing the equalization mode, it is regarded as the start of charging of the battery pack. After each start of charging, the time is reset to zero and the same operation process is executed.

[0096] In the embodiment of the present invention, in addition to the original normal circuit connection for power transmission, only a balancing circuit with resistors is added to each battery unit, and relevant temperature and voltage sensors and a controller are provided. The overall circuit structure is relatively simple. This embodiment simultaneously solves the following three major problems during the charging process of the battery pack:

[0097] (1) Safety and stability: At any sampling moment, if the supply voltage value E is greater than the charging cut-off voltage value V c or the temperature value measured by any temperature sensor 4 is greater than the maximum allowable charging temperature value T max , the charging is immediately terminated; if it is found through data statistics that the temperature and voltage rise rapidly during the charging process, the charging current is appropriately gradually reduced on the original basis.

[0098] (2) Full charge: When the voltage deviation at the terminals of each battery unit is relatively large during the charging process, the charging is aborted, and the battery unit with a higher terminal voltage is appropriately discharged to adjust the consistency between each battery unit, and then the charging is restarted;

[0099] (3) Fast charging: If it is found through data statistics that the temperature and voltage rise slowly during the charging process, the charging current is appropriately gradually increased on the original basis.

Claims

1. A charging method for a battery pack, characterized in that, The battery pack includes a plurality of battery cells (1) connected in series in sequence, a charging module (2) for charging the battery cells (1), a controller (3), and several temperature sensors (4); each battery cell (1) is provided with a positive terminal (11), a negative terminal (12), a voltage sensor (5), an electronic switch (6), and a resistor (7). The voltage sensor (5) is electrically connected to the positive terminal (11) and the negative terminal (12) respectively to measure the terminal voltage value of the battery cell (1) where it is located. The positive terminal is electrically connected to the negative terminal (12) through the electronic switch (6) and the resistor (7) in sequence; the temperature sensor (4) is used to measure the temperature of the battery cell (1) at a certain position; the controller (3) is electrically connected to the charging module (2) and all the temperature sensors (4), voltage sensors (5), and electronic switches (6) respectively; The charging method is to obtain in advance from the manufacturer the charging cut-off voltage value V of the battery pack c , the reference charging current value I0, and the maximum allowable charging temperature value T max ; After starting charging, let the charging start time be t = 0. Continuously collect and store the terminal voltage value of each battery cell (1), the temperature value measured by each temperature sensor (4), and the supply voltage value E measured by the voltmeter (23) at fixed time intervals Δt. For any sampling moment, if the supply voltage value E is greater than the charging cut-off voltage value V c or the temperature value measured by any one of the temperature sensors (4) is greater than the maximum allowable charging temperature value T max , then immediately end the charging; otherwise, perform the following operations: When t ≤ FΔt, the battery pack is charged at a constant current with a reference charging current value I0, where F is a natural number; When t > FΔt, at each sampling moment t i , read the sampling data from the moment t = t i - FΔt to the moment t = t i to form a data set, and statistically obtain the power supply voltage rise amplitude ΔE, the temperature rise amplitude ΔT, and the cell voltage deviation index ΔU, where F is a natural number: The rising amplitude ΔE of the supply voltage is the difference between the maximum value and the minimum value of the supply voltage value E in the dataset; The temperature rise ΔT is the difference between the average of the temperature values measured by all the temperature sensors (4) at time t = t i and the average of the temperature values measured by all the temperature sensors (4) at time t = t i - FΔt; The acquisition method of the unit voltage deviation index ΔU is as follows: for each data moment in the dataset, find the maximum value and the minimum value among the terminal voltage values of all battery cells (1), and calculate the difference between the two as the voltage deviation value at this moment; take the average value of the voltage deviation values at all moments in the dataset as the unit voltage deviation index ΔU; Perform the following operations according to the above statistical results: (i), if ΔE < ΔE c1 and ΔT ≤ ΔT c and ΔU ≤ ΔU c , then continue to maintain charging and increase the charging current by k on the original basis, where k is between 1% and 5%; (ii), if ΔE c1 ≤ ΔE ≤ ΔE c2 and ΔT ≤ ΔT c and ΔU ≤ ΔU c , then continue charging and keep the charging current unchanged on the original basis; (iii), if ΔU ≤ ΔU c , and if either of the two conditions ΔE > ΔE c2 and ΔT > ΔT c is satisfied, continue charging and reduce the charging current by k on the original basis, where k ranges from 1% to 5%; (iv), if ΔU > ΔU c , then stop charging and enter the balancing mode; The above ΔE c1 and ΔE c2 are the first threshold value of the supply voltage rise amplitude and the second threshold value of the supply voltage rise amplitude respectively, and ΔT c is the threshold value of the temperature rise amplitude, and ΔU c is the threshold value of the cell voltage deviation index; After entering the equalization mode, continuously collect and store the terminal voltage values of each battery cell (1) at a fixed time interval Δt, and sequentially perform the following steps in combination with the collected data: Step S1: The battery pack is left idle for a period of time; Step S2: Read the terminal voltage values of each battery cell (1) at the end of the shelving period, calculate their average value U m , and find out the battery cells (1) with terminal voltage values higher than the average value; Step S3: For each battery cell (1) whose terminal voltage value determined in Step S2 is higher than the average value U m respectively close the corresponding electronic switch (6) thereof, and use the resistor (7) to continuously discharge it until its terminal voltage value is less than the average value U m then disconnect the corresponding electronic switch (6); Step S4: The battery pack is left idle for a period of time; Step S5: End the equalization mode and restart the charging of the battery pack.

2. The charging method of the battery pack according to claim 1, characterized in that, The battery cell (1) is composed of 1 battery monomer or multiple battery monomers connected in parallel with each other.

3. The charging method of the battery pack according to claim 1, characterized in that, The electronic switch (6) is a normally open switch.

4. The charging method of the battery pack according to claim 1, characterized in that The resistance values of the resistors (7) in all battery cells (1) are equal.

5. The charging method of the battery pack according to claim 1, characterized in that The charging module (2) is provided with a power taking port (21) for obtaining electric energy from an external power supply, a power supply port (22) for charging the battery cells (1), and a voltmeter (23) for measuring the supply voltage value of the power supply port (22).

6. The charging method of the battery pack according to claim 1, characterized in that, The controller (3) is used to collect the measurement data of the voltmeter (23), all temperature sensors (4), and voltage sensors (5) and control the operation of the charging module (2) and the electronic switch (6).

7. The charging method of the battery pack according to claim 1, characterized in that The charging module (2) can charge the battery cells (1) with a constant current according to the instruction of the controller (3), and the magnitude of the charging current is adjustable.

8. The charging method of the battery pack according to claim 1, characterized in that, The value of the fixed time interval Δt ranges from 1 millisecond to 1 second, the natural number F ranges from 10 to 10000, and the idle duration in steps S1 and S5 ranges from 1 minute to 1 hour.

9. The charging method of the battery pack according to claim 1, characterized in that, The reference charging current value I0 is between 0.05 times and 2 times the current value corresponding to the battery pack being charged at a 1C rate, and the maximum allowable charging temperature value T max is between 45°C and 70°C, and the temperature rise threshold ΔT c is between 2°C and 10°C, and the cell voltage deviation index threshold ΔU c is between 5 mV and 100 mV, and the first threshold ΔE for the supply voltage rise c1 is between 0.1% and 1% of the battery pack's charging cut-off voltage value V c , and the second threshold ΔE for the supply voltage rise c2 is between 1% and 2% of the battery pack's charging cut-off voltage value V c , and the first threshold ΔE for the supply voltage rise c1 is less than the second threshold ΔE for the supply voltage rise c2 .

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