Charging method and battery pack

Abstract

The present application provides a charging method and a battery pack. The charging method is applicable to charging a plurality of cells of a battery pack, and comprises the following steps: charging the cells of the battery pack with a charging voltage, and detecting a voltage difference ΔV between the cells. TDV , wherein the charging voltage is a rated charging voltage. TDV , obtain a new charging voltage value which is less than the rated charging voltage value, and charge the battery cell after reducing the charging voltage to the new charging voltage value.

Description

Technical Field

[0001] The present invention provides a charging method and a battery pack, and more particularly, relates to a charging method and a battery pack for adjusting charging conditions according to a voltage difference of a battery cell. Background Art

[0002] After being used or placed in a battery pack, the cells will have voltage differences when the battery pack is charged due to differences in characteristics, such as differences in the degree of aging or battery health. The greater the voltage difference between the cells, the more likely it is that the voltage of each cell will exceed the rated voltage during the charging process of the battery pack. The so-called rated voltage refers to the voltage within the range of use in the specification provided by the battery manufacturer. Excessive voltage of the cell can easily cause problems such as accelerated cell degradation and cell expansion caused by the generation of gas, and even raise safety concerns.

[0003] In the prior art, when a voltage difference occurs between battery cells, a voltage monitoring mechanism or a balancing mechanism is used to alleviate the voltage difference between the battery cells. However, the balancing mechanism cannot effectively suppress the voltage difference problem of the battery cells that have already become defective, and ultimately the voltage of the battery cells will still be too high.

[0004] Figure 1 A schematic diagram showing a battery system of the prior art. Figure 1 Schematic diagram of a battery system disclosed in Taiwan Patent Publication No. TW202114320, which discloses a structure and method for balancing the voltage difference between cells using a balancing mechanism. Figure 1 As shown, according to the technology, a battery module 12-1 includes a cell string group 123 and N balancing circuits 122-1, ..., 122-N-1, 122-N. The cell string group 123 has N cells B-1, ..., BN-1, BN connected in series, each of which is coupled to a module management circuit 121. In order to solve the problem of voltage imbalance, the battery system management unit 11 and the module management circuit 121 of the battery system 100 must perform voltage conversion, voltage collection and voltage monitoring for each cell (e.g., cell B-1, ..., BN-1, BN) in each battery module (e.g., battery modules 12-1, 12-2, ..., 12-M-1, 12-M), and then use the balancing circuit to charge or discharge each cell so as to perform an overall voltage balance control mechanism.

[0005] The overvoltage protection mechanism of the known technology can protect the battery from overvoltage during charging. However, if the battery is used continuously under the condition of voltage difference between the cells, the voltage difference between the cells will continue to expand, making the bad condition of the cells more serious, thus causing repeated overvoltage protection. As the number of overvoltage protection increases, the damage to the battery gradually increases, and eventually it will cause the cell expansion or safety problems of the battery pack. Summary of the invention

[0006] According to one embodiment of the present invention, a charging control method and a battery pack are provided. Another object is to use the voltage difference ΔV between the cells to control the charging voltage. TDV The charging voltage is dynamically adjusted so that the maximum voltage of the battery cell can be controlled to not exceed the rated charging voltage of each battery cell due to the decrease in the charging voltage.

[0007] According to an embodiment of the present invention, a charging method is provided, which is suitable for charging a plurality of cells of a battery pack, and includes the following steps: Setting the failure voltage difference ΔV PF The battery cell of the battery pack is charged with a rated charging voltage, and the voltage difference ΔV of the battery cell is detected. TDV According to the voltage difference ΔV of the battery cell TDV , obtain a first charging voltage value less than the rated charging voltage value, and charge the battery cell after reducing the rated charging voltage to the first charging voltage value. TDV , obtain a second charging voltage value less than the first charging voltage value, and charge the battery cell after reducing the first charging voltage value to the second charging voltage value. And, when the voltage difference ΔV TDV Meet the failure pressure difference ΔV PF When the charging voltage is reduced to a failure voltage difference protection charging voltage value.

[0008] In one embodiment, the voltage difference ΔV of the battery cell TDV The step of obtaining a first charging voltage value less than the rated charging voltage value comprises the following steps: obtaining a first threshold voltage and a first charging voltage value corresponding to the first threshold voltage from a memory of a battery management unit of the battery pack, wherein the first charging voltage value is less than the rated charging voltage value and greater than the battery failure protection charging voltage value. Determining the voltage difference ΔV of the battery cell TDV , whether the first threshold voltage is met. And, when the voltage difference ΔV TDV When the first threshold voltage is met, the rated charging voltage is reduced to the first charging voltage value.

[0009] In one embodiment, the voltage difference ΔV of the battery cell TDVThe step of obtaining a second charging voltage value less than the first charging voltage value comprises the following steps: obtaining a second threshold voltage and a second charging voltage value corresponding to the second threshold voltage from the memory of the battery management unit of the battery pack, wherein the second charging voltage value is less than the first charging voltage value and greater than the battery failure protection charging voltage value. Determining the voltage difference ΔV of the battery cell TDV , whether the second threshold voltage is met. And, when the voltage difference ΔV TDV When the second threshold voltage is met, the first charging voltage value is reduced to the second charging voltage value.

[0010] In one embodiment, the voltage difference ΔV of the battery cell TDV The step of obtaining a first charging voltage value less than the rated charging voltage value comprises the following steps: using a charging function Fcv and according to the voltage difference ΔV of the battery cell TDV , calculate the first charging voltage value.

[0011] In one embodiment, the charging function Fcv is the voltage difference ΔV of the battery cell. TDV function.

[0012] In one embodiment, the charging function Fcv is the voltage difference ΔV of the battery cell. TDV , the number of battery cell strings of the battery cell and the rated charging voltage value, and the values ​​obtained using the charging function Fcv are all less than the rated charging voltage value.

[0013] In one embodiment, the charging function Fcv is (the rated charging voltage value×the number of battery strings)-the voltage difference ΔV TDV ×(the number of battery cell strings - N), where N is a natural number greater than or equal to 1 and less than the number of battery cell strings.

[0014] In one embodiment, the battery pack does not include a plurality of balancing circuits respectively connected to the battery cells, and the charging method does not include a step of balancing the battery cells using the balancing circuits.

[0015] In one embodiment, the voltage difference ΔV of the battery cell is TDV , detection starts when any voltage of the battery cell is greater than a voltage difference starting detection value.

[0016] In one embodiment, the voltage difference ΔV of the battery cell is TDV It is the voltage difference between the cell with the maximum voltage and the cell with the minimum voltage.

[0017] According to an embodiment of the present invention, a battery pack is provided, which includes a plurality of battery cells, and the battery cells are charged using the charging method described in the above embodiments.

[0018] In summary, according to an embodiment of the present invention, a balancing circuit may not be provided in the battery pack, and a balancing mechanism may not be used during charging, but the voltage difference ΔV between the cells may be used to balance the battery pack. TDV To dynamically adjust the charging voltage so that the battery cell has a voltage difference ΔV TDV The battery is charged in the state of being charged, and the maximum voltage of the battery cell can be controlled to not exceed the rated charging voltage of each battery cell due to the drop in the charging voltage, thereby improving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a battery system according to prior art.

[0020] Figure 2 FIG. 1 is a schematic diagram of a battery pack according to an embodiment of the present invention.

[0021] Figure 3 FIG. 1 is a schematic diagram showing the maximum voltage difference of the battery cells and time of the battery pack according to the first embodiment of the present invention.

[0022] Figure 4 for Figure 3 Flow chart of a charging method according to an embodiment.

[0023] Figure 5 FIG. 1 is a schematic diagram showing the maximum voltage difference of the battery cells and time of the battery pack according to the second embodiment of the present invention.

[0024] Figure 6 for Figure 5 Flow chart of a charging method according to an embodiment.

[0025] Figure 7 This is the relationship diagram between the charging current and voltage of the battery.

[0026] Figure 8 It is a comparison diagram of the experiment according to the second embodiment of the present invention and the prior art.

[0027] Figure Number:

[0028] 100: Battery System

[0029] 11: Battery system management unit

[0030] 12-1~12-M: Battery module

[0031] 121: Module management circuit

[0032] 122-1~122-N:Balanced circuit

[0033] 123: Cell string group

[0034] 190: External power supply

[0035] 200: Battery Pack

[0036] 211: Battery Management Unit

[0037] 212: Memory

[0038] 220: Cell string group

[0039] 221-224: Battery Cell DETAILED DESCRIPTION

[0040] Figure 2 A schematic diagram showing a battery pack according to an embodiment of the present invention. Figure 2 As shown, according to one embodiment of the present invention, an external power source 190 charges a battery pack 200. The battery pack 200 includes a battery cell string group 220 and a battery management unit 211. The battery cell string group 220 includes a plurality of battery cells 221-224. The battery management unit 211 is electrically connected to the battery cell string group 220 and the battery cells 221-224 to measure the voltage of the battery cells 221-224. In one embodiment, the battery pack 200 adopts a method of adjusting the charging condition according to the voltage difference of the battery cells 221-224. Preferably, the battery pack 200 is a battery pack for a notebook computer.

[0041] According to an embodiment of the present invention, a charging method for charging a battery pack 200 is provided, which uses a charging mechanism to allow a battery management unit (BMU) 211 to measure the voltage of the battery cells 221-224 in each string of battery cell string groups 220, and through the measurement results of the battery cell voltages of each string, monitor in real time whether the voltage difference shows signs of gradually increasing, and then adjust the charging voltage to solve the above-mentioned overcharge voltage problem. When a voltage difference occurs between the battery cells 221-224 or even the voltage difference continues to expand, in the first embodiment, the charging voltage is reduced through several fixed battery cell voltage difference thresholds; or, in the second embodiment, the charging voltage is adjusted through real-time monitoring and calculation by the battery management unit 211. The reduced charging conditions can avoid the occurrence of over-voltage protection caused by excessive voltage of the battery cells 221-224. The following will be described in detail with respect to the embodiments of the present invention.

[0042] Figure 3 A schematic diagram showing the maximum voltage difference and time of the battery cells of the battery pack according to the first embodiment of the present invention. Figure 3 The vertical axis is voltage, and the horizontal axis is time. Cell 1 is the line of the maximum voltage among the multiple voltages of the battery cells 221-224. Cell 2 is the line of the minimum voltage among the multiple voltages of the battery cells 221-224. ΔV TDV is the voltage difference between Cell 1 and Cell 2, so Figure 3 In the embodiment, it is the maximum voltage difference between the voltages of two respective battery cells 221 - 224 . Figure 3 The voltage difference ΔV between the cells 221 - 224 in one embodiment is shown TDV After exceeding multiple voltage thresholds, the charging voltage is reduced.

[0043] In this embodiment, four cell voltage difference thresholds are used, and the threshold values ​​are, from small to large, a first threshold voltage ΔV1, a second threshold voltage ΔV2, a third threshold voltage ΔV3, and a failure voltage difference ΔV PF (PF: potential failure, or permanent failure). The present invention does not limit the value of the failure voltage difference. PF is usually a threshold value that prevents users from continuing to use the product. Its value can be appropriately set according to product specifications or user expectations. In addition, five charging voltages are set. The values ​​of the charging voltages are, from large to small, the rated charging voltage value Charging Voltage, the first charging voltage value Charging Voltage 1, the second charging voltage value Charging Voltage 2, the third charging voltage value Charging Voltage 3 and the failure voltage difference protection charging voltage value PF Charging Voltage. Preferably, the threshold voltage and the charging voltage are respectively stored in the memory 212 of the battery management unit 211, so that the battery management unit 211 can access them at an appropriate time. Please refer to Figure 3 According to an embodiment of the present invention, there is no step of increasing the value of the charging voltage during the charging process. Preferably, the charging voltage only decreases and does not increase during the entire charging process.

[0044] In one embodiment, the battery management unit 211 measures the voltage difference ΔV of the battery cells 221 - 224 TDV After reaching a certain threshold, the charging voltage corresponding to the threshold is read from the memory 212, and the corresponding charging voltage is used to charge the cells 221-224, thereby reducing the charging voltage of the external power supply 190 for charging the cells 221-224. Reducing the charging voltage can avoid the voltage difference V between the cells 221-224. TDV When the battery cell with the highest voltage is charged, an overvoltage condition occurs.

[0045] like Figure 3 More specifically, when the voltage difference ΔV between the cells 221 - 224 is TDV, when the voltage difference V between the cells 221 - 224 reaches the first threshold voltage ΔV1, the battery management unit 211 reduces the charging voltage of the cells 221 - 224 to the first charging voltage value ChargingVoltage 1. Similarly, when the voltage difference V between the cells 221 - 224 TDV , reaching the failure pressure difference ΔV PF When , the battery management unit 211 reduces the charging voltage of the battery cells 221 - 224 to the failure voltage difference protection charging voltage value PF Charging Voltage.

[0046] Figure 4 show Figure 3 Flow chart of a charging method of an embodiment. In one embodiment, a charging method is provided, which can charge a battery pack 200, and Figure 4 As shown, the charging method includes the following steps.

[0047] Step S02: Using a charging voltage to charge the cells 221-224, and the battery management unit 211 detects the voltage difference ΔV between the cells 221-224. TDV Preferably, the value of the charging voltage is a rated charging voltage value. In one embodiment, the voltage difference ΔV of the battery cells 221-224 is TDV , can be the voltage difference between any two of the cells 221-224. Preferably, the voltage difference ΔV TDV It can be the difference between the maximum voltage and the minimum voltage of the battery cells 221-224, that is, the voltage difference ΔV of the battery cells 221-224 TDV It may be the maximum voltage difference among the voltage differences between any two of the battery cells 221 - 224 .

[0048] Step S04: Determine the voltage difference ΔV of the cells 221 - 224 TDV , whether the first threshold voltage ΔV1 is met, preferably determining ΔV TDV ≥ΔV1, if yes, go to step S06, if no, go back to step S04 and execute again.

[0049] Step S06: The battery management unit 211 reduces the charging voltage to a first charging voltage value ChargingVoltage1. Preferably, the charging voltage is reduced from a rated charging voltage Charging Voltage to the first charging voltage value Charging Voltage 1.

[0050] Step S08: Determine the voltage difference ΔV between the cells 221 - 224 TDV , whether the second threshold voltage ΔV2 is met, preferably determining ΔV TDV ≥ΔV2, if yes, go to step S10, if no, go back to step S08 and execute again.

[0051] Step S10: the battery management unit 211 reduces the charging voltage to a second charging voltage value ChargingVoltage2.

[0052] Step S12: Determine the voltage difference ΔV between the cells 221 - 224 TDV , whether the third threshold voltage ΔV3 is met, preferably determining ΔV TDV ≥ΔV3, if yes, go to step S14, if no, go back to step S12 and execute again.

[0053] Step S14: the battery management unit 211 reduces the charging voltage to a third charging voltage value ChargingVoltage3.

[0054] Step S16: Determine the voltage difference ΔV between the cells 221 - 224 TDV , whether the failure pressure difference ΔV is satisfied PF , preferably determine ΔV TDV ≥ΔV PF If yes, go to step S18, if no, go back to step S16 and execute again.

[0055] Step S18: the battery management unit 211 reduces the charging voltage to a failure voltage protection charging voltage value PFCharging Voltage.

[0056] Figure 5 A schematic diagram showing the maximum voltage difference and time of the battery cells of the battery pack according to the second embodiment of the present invention. Figure 5 The vertical axis is voltage, and the horizontal axis is time. Cell 1 is the line of the maximum voltage among the multiple voltages of the battery cells 221-224. Cell 2 is the line of the minimum voltage among the multiple voltages of the battery cells 221-224. ΔV TDV is the voltage difference between Cell 1 and Cell 2, so Figure 3 In the embodiment, it is the maximum voltage difference between the voltages of two cells of the cells 221-224. Figure 5 In the embodiment, a charging function Fcv is used to calculate the charging voltage. Figure 3 In this embodiment, the memory 212 only needs to store an appropriate charging function Fcv, and does not need to store the threshold voltage and the charging voltage.

[0057] In the second embodiment of the present invention, the voltage difference ΔV between the cells 221 - 224 is measured. TDV The battery management unit 211 detects the condition of the battery according to the charging function Fcv stored in the memory 212 and the measured voltage difference ΔV TDV, calculate the appropriate new charging voltage value, and instantly update the charging voltage of the battery cells 221-224. In one embodiment, the charging function Fcv can be set based on the rated charging voltage value or the overcharge voltage protection value, and the charging function Fcv is obtained in a manner that does not exceed the rated charging voltage value or the overcharge protection voltage value. The battery management unit 211 uses the charging function Fcv and the measured voltage difference ΔV TDV After calculating the appropriate new charging voltage value, the charging voltage of the battery cells 221-224 is updated instantly and automatically.

[0058] In one embodiment, the charging function Fcv is the voltage difference ΔV of the cells 221-224. TDV , the number of battery cell strings of the battery cells 221 - 224 and the function Charging Voltage of the rated charging voltage, and the values ​​obtained using the charging function Fcv are all smaller than the function Charging Voltage of the rated charging voltage.

[0059] In one embodiment, the charging function Fcv is: new charging voltage value = (rated charging voltage value of a single cell × number of cell strings) - voltage difference ΔV TDV × (number of battery strings - N), where N is a natural number greater than or equal to 1 and less than the number of battery strings. Figure 2 The embodiments are examples, and N=1, N=2 or N=3 may also be used. Figure 5 According to an embodiment of the present invention, the charging function Fcv is a function that does not increase with time. More specifically, the charging function Fcv is a function that remains flat or decreases with time.

[0060] In one embodiment, a voltage difference Start CIMcompensation, which is a starting condition of voltage compensation, can also be stored in the memory 212. TDV When the voltage difference is greater than the starting condition Start CIM compensation, the battery management unit 211 starts to charge the battery according to the charging function Fcv and the voltage difference ΔV of the battery cells 221-224. TDV The new charging voltage value is calculated immediately, and the calculated new charging voltage value is used to charge the battery cells 221 - 224 .

[0061] Figure 6 for Figure 5 Flow chart of a charging method of an embodiment. In one embodiment, a charging method is provided, which can charge a battery pack 200, and Figure 6 As shown, the charging method includes the following steps.

[0062] Step S22: Charge the cells 221-224 with a charging voltage, and the battery management unit 211 detects the voltage difference ΔV between the cells 221-224. TDV . Regarding the voltage difference ΔV between cells 221-224 TDV For the type, please refer to the record of the aforementioned step S02.

[0063] Step S24: Determine the voltage difference ΔV TDV Whether the starting condition voltage difference ΔV is met S (Start CIM compensation), better determine ΔV TDV ≥ΔV S When the condition is met, go to step S26, and when the condition is not met, re-execute step S24.

[0064] Step S26: Based on the currently measured voltage difference ΔV TDV Preferably, the charging function Fcv stored in the memory 212 is read, and based on the charging function Fcv stored in the memory 212 and the measured voltage difference ΔV TDV , calculate the new charging voltage.

[0065] Step S28: the battery management unit 211 updates a new charging voltage.

[0066] Step S30: Determine the voltage difference ΔV of the cells 221 - 224 TDV , whether the failure pressure difference ΔV is satisfied PF , preferably determine ΔV TDV ≥ΔV PF If yes, go to step S32, if no, re-execute step S30.

[0067] Step S32: the battery management unit 211 reduces the charging voltage to the failure voltage protection charging voltage value PFCharging Voltage, that is, reduces the charging voltage to the PF Charging Voltage.

[0068] like Figure 5 and Figure 6 As shown, in one embodiment, the charging method may further include the following steps, preferably between step S28 and step S30. Step S40: Determine the voltage difference ΔV of the battery cells 221-224 TDV , whether the third threshold voltage ΔV3 is met, preferably determining ΔV TDV≥ΔV3, if yes, go to step S42, if no, re-execute step S40. In one embodiment, the third threshold voltage ΔV3 corresponds to the minimum charging voltage Min.Charging Voltage, which refers to the minimum charging voltage Min.Charging Voltage in a normal charging state.

[0069] Step S42: The battery management unit 211 reduces the charging voltage to the minimum charging voltage Min.ChargingVoltage. Then, the process proceeds to step S30.

[0070] According to the present invention, the voltage difference ΔV between the cells 221-224 is TDV The measurement is not limited to detection during charging or static state. In one embodiment, preferably, the voltage difference ΔV of the battery cells 221-224 TDV The measurement may be performed when the voltage of any of the cells 221 - 224 is greater than the voltage difference start detection value Delta V Start Detection in a charging cycle, so as to ensure the stability and effectiveness of the voltage difference. Figure 7 Displays the relationship between the charging current and voltage of the battery cell. For the curve of the cell voltage, Figure 7 The vertical axis is voltage, Figure 7 The horizontal axis is time. For the charging current ChargingCurrent line, Figure 7 The vertical axis is the current, Figure 7 The horizontal axis is time. Figure 7 As shown, in a charging cycle, when the voltage of the battery cell is greater than the voltage difference start detection value Delta V Start Detection, it begins to stabilize. At this time, detecting the voltage of the battery cells 221 - 224 can ensure the stability and effectiveness of the voltage difference.

[0071] For example, the charging voltage of the battery cell is 4450mV. When the battery cell is at a low voltage, the voltage consistency between the strings is poor. When the battery cell is charged to above 3700mV, the consistency will be more stable. Therefore, a more stable point above 3900mV can be used for detection. Therefore, when charging, when the voltage of any battery cell 221-224 in any string is higher than the voltage difference start detection value DeltaV StartDetection, that is, higher than 3900mV, the battery management unit 211 starts to measure the voltage difference V of the battery cells 221-224. TDV If the voltage difference V TDV When it is greater than the charging voltage update condition, the charging voltage is updated.

[0072] According to the aforementioned embodiments of the present invention, by timely or instantly adjusting or reducing the charging voltage, even if no balancing circuit or balancing mechanism is provided in the battery pack 200, the voltage of the battery cells 221-224 can still be effectively controlled to stop continuously increasing. Figure 8 It is a comparison diagram of the experiment according to the second embodiment of the present invention and the prior art. Figure 8 The vertical axis on the left is the voltage of the cells 221-224 (Cell Voltage (mV)), and the vertical axis on the right is the voltage of the battery pack (Pack Voltage (mV)). The horizontal axis is the voltage difference (Delta V (mV)), more specifically, the voltage difference between the Trad_Max_cell (mV) line and the Trad_Min cell (mV) line, the voltage difference between the New_Max cell (mV) line and the New_Min cell (mV) line, and the voltage difference between the Trad_PackV (mV) line and the New_PackV (mV) line. The Trad_Max_cell (mV) line represents the relationship between the maximum voltage and time of multiple cells when charged using a known method. The Trad_Min cell (mV) line represents the relationship between the minimum voltage and time of multiple cells when charged using a known method. The Trad_PackV (mV) line represents the relationship between the voltage and time of the battery pack when charged using a known method. The line of New_Max cell (mV) represents the relationship between the maximum voltage of the battery cells 221-224 and time when charged by the method of the second embodiment of the present invention. The line of New_Min cell (mV) represents the relationship between the minimum voltage of the battery cells 221-224 and time when charged by the method of the second embodiment of the present invention. The line of New_PackV (mV) represents the relationship between the voltage of the battery pack and time when charged by the method of the second embodiment of the present invention.

[0073] like Figure 8 As shown, the dotted line is a conventional fixed charging method. Under a fixed charging voltage, the battery cells 221-224 fail and a voltage difference between the battery cells 221-224 is generated. According to the conventional fixed charging method, the maximum voltage of the battery cells 221-224 will continue to increase, exceeding the rated charging voltage and causing safety concerns. The solid line is a charging method according to the second embodiment of the present invention. Through the voltage difference ΔV between the battery cells 221-224 TDV To dynamically adjust the charging voltage so that the cells 221-224 can have a voltage difference ΔV TDV The battery 221-224 is charged in the state of reducing the possibility of overvoltage. Figure 8As shown, when a voltage difference occurs between the battery cells 221 - 224 , the highest voltage of the battery cells 221 - 224 can be controlled to not exceed the rated charging voltage (eg, 4450 mV) due to the drop in charging voltage, thereby alleviating safety concerns.

[0074] In summary, according to an embodiment of the present invention, the battery pack 200 is not provided with a balancing circuit, nor does it use a balancing mechanism. Instead, the voltage difference ΔV between the cells 221 - 224 is used to balance the battery pack 200. TDV To dynamically adjust the charging voltage so that the cells 221-224 have a voltage difference ΔV TDV The maximum voltage of the cells 221-224 can be controlled to not exceed the rated charging voltage of each cell due to the drop in charging voltage, thereby alleviating safety concerns. Therefore, the problem of the maximum voltage of the cells 221-224 continuously rising and exceeding the rated charging voltage caused by charging at a fixed charging voltage can be avoided.

Claims

1. A charging method, suitable for charging a plurality of cells of a battery pack using a charging voltage, characterized in that: Include: The charging voltage is set to a rated charging voltage value, and the failure voltage difference ΔV is set PF ; The plurality of cells of the battery pack are charged using the rated charging voltage value, and a voltage difference ΔV of the plurality of cells is detected. TDV ; According to the voltage difference ΔV of the plurality of cells TDV , obtaining a first charging voltage value that is less than the rated charging voltage value, and charging the plurality of battery cells after reducing the rated charging voltage value to the first charging voltage value; According to the voltage difference ΔV of the plurality of cells TDV , obtaining a second charging voltage value that is less than the first charging voltage value, and charging the plurality of battery cells after reducing the first charging voltage value to the second charging voltage value; and When the voltage difference ΔV TDV Meet the failure pressure difference ΔV PF When the charging voltage is reduced to a failure voltage difference protection charging voltage value; Among them, the voltage difference ΔV of the multiple cells TDV , is one of the voltage differences between any two of the multiple battery cells.

2. The charging method according to claim 1, characterized in that: During the charging process, the value of the charging voltage is not increased.

3. The charging method according to claim 2, characterized in that: The voltage difference ΔV of the plurality of cells TDV , the step of obtaining a first charging voltage value less than the rated charging voltage value comprises: Obtaining a first threshold voltage and a first charging voltage value corresponding to the first threshold voltage from a memory of a battery management unit of the battery pack, wherein the first charging voltage value is less than the rated charging voltage value and greater than the battery failure protection charging voltage value; Determine the voltage difference ΔV of the multiple cells TDV , whether the first threshold voltage is met; When the voltage difference ΔV TDV When the first threshold voltage is met, the rated charging voltage is reduced to the first charging voltage value.

4. The charging method according to claim 3, characterized in that: The voltage difference ΔV of the plurality of cells TDV The step of obtaining a second charging voltage value which is less than the first charging voltage value comprises: Obtaining a second threshold voltage and a second charging voltage value corresponding to the second threshold voltage from the memory of the battery management unit of the battery pack, wherein the second charging voltage value is less than the first charging voltage value and greater than the battery failure protection charging voltage value; Determine the voltage difference ΔV of the multiple cells TDV , whether the second threshold voltage is met; When the voltage difference ΔV TDV When the second threshold voltage is met, the first charging voltage value is reduced to the second charging voltage value.

5. The charging method according to claim 1, characterized in that: The voltage difference ΔV of the plurality of cells TDV , the step of obtaining a first charging voltage value less than the rated charging voltage value comprises: Using a charging function Fcv and the voltage difference ΔV of the plurality of cells TDV , calculate the first charging voltage value.

6. The charging method according to claim 5, characterized in that: The charging function Fcv is a function that does not increase with time.

7. The charging method according to claim 5, characterized in that: The charging function Fcv is the voltage difference ΔV of the multiple cells. TDV function.

8. The charging method according to claim 5, characterized in that: The charging function Fcv is the voltage difference ΔV of the multiple cells. TDV , the number of battery cell strings of the plurality of battery cells and the rated charging voltage value, and The values ​​obtained by using the charging function Fcv are all smaller than the rated charging voltage value.

9. The charging method according to claim 8, characterized in that: The charging function Fcv is (the rated charging voltage value×the number of battery cell strings)-the voltage difference ΔV TDV ×(the number of battery cell strings-N), where N is a natural number greater than or equal to 1 and less than the number of battery cell strings.

10. The charging method according to any one of claims 1 to 9, characterized in that: The battery pack does not include a plurality of balancing circuits respectively connected to the plurality of cells, and The charging method does not include a step of balancing the multiple battery cells using the multiple balancing circuits.

11. The charging method according to any one of claims 1 to 9, characterized in that: The voltage difference ΔV of the plurality of cells TDV , detection starts when any voltage of the multiple battery cells is greater than a voltage difference starting detection value.

12. The charging method according to any one of claims 1 to 9, characterized in that: The voltage difference ΔV of the plurality of cells TDV It is the voltage difference between the cell with the maximum voltage and the cell with the minimum voltage.

13. A battery pack comprising a plurality of battery cells, wherein the plurality of battery cells are charged using the charging method according to any one of claims 1 to 12.

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