Power battery charging control method, system and vehicle

Abstract

The purpose of the present invention is to provide a power battery charging control method, system and vehicle, including real-time acquisition of the current power battery's maximum cell voltage U, minimum cell temperature T min and the maximum monomer temperature T max The system determines the vehicle's charging mode. If it's DC fast charging, it executes the fast charging strategy. If it's AC slow charging, it executes the slow charging strategy. This system takes into account the impact of temperature and charge rate on the cutoff voltage. By designing different cutoff voltages for the same charge at different temperatures and charge rates, it can avoid overcharging the power battery caused by high temperatures and low charge rates, thereby extending the power battery's service life.

Description

Technical Field

[0001] The present invention belongs to the field of new energy vehicle power battery charging control, and specifically relates to a power battery charging control method, system and vehicle. Background Art

[0002] Lithium batteries (hereinafter referred to as battery cells) are widely used as the mainstream power battery for electric vehicles due to their high energy density and power performance. Currently, lithium battery life degradation and safety failure remain the two most pressing concerns for users. The lifespan of a lithium battery is affected by two factors: charge and discharge cycles and storage. These two factors are mutually reinforcing and coupled in actual use. It is well known that lithium battery electrode materials at high states of charge (SOC) have poorer stability, and lithium battery life degradation is more severe when stored at high SOCs. The depth of discharge (DOD) of a lithium battery affects its charge and discharge cycle capability; an increase in DOD reduces the cycle life of the lithium battery. The upper limit of the SOC and the depth of discharge of a lithium battery are both determined by the battery's charging strategy, making the charging strategy closely related to the battery's lifespan.

[0003] The dynamic closed-circuit voltage of a battery cell is divided into static voltage and polarization voltage. The static voltage represents the true state of charge of the battery cell, while the polarization voltage is caused by internal polarization of the battery cell. At the same temperature, a smaller current can eliminate polarization of the battery cell, and the same current at a higher temperature has a better depolarization effect. Charging uses the dynamic closed-circuit voltage of the battery cell as a monitoring and control parameter, while the static voltage represents the true state of charge of the battery cell. A smaller charge rate (corresponding to a smaller charging current) results in less polarization of the battery cell during charging. If different charge rates use the same voltage as the charging cutoff condition, the polarization voltage of the battery cell will be smaller and the static voltage will be larger when charging at a low rate, while the polarization voltage of the battery cell will be larger and the static voltage will be smaller when charging at a high rate.

[0004] Among the many charging strategies, multi-stage constant current charging is the most widely used. The voltage-based multi-stage constant current charging strategy (VMCC) uses a preset voltage as the switching condition. After the battery cell reaches the preset voltage with constant current charging, it switches to the next stage of current charging, and this cycle repeats until the maximum charge cut-off voltage is reached. The higher the battery cell temperature and the lower the charge rate, the more lithium ions are charged into the negative electrode at the same charge cut-off voltage, meaning the polarization is reduced and the amount of charge can be charged.

[0005] The currently widely used charging strategy is: during fast charging, the preset charging voltage (i.e., stage charge cut-off voltage) for battery cells with the same SOC value at different temperatures is a constant value, usually the preset charging voltage corresponding to room temperature 25°C at that SOC. Using the preset charging voltage corresponding to 25°C as the stage charge cut-off voltage corresponding to all temperature points at that SOC will cause the amount of electricity charged at certain temperature points and certain charging rates to exceed the final allowable SOC upper limit, resulting in overcharging of the battery cells, and then overcharging of the power battery, affecting the life of the power battery. During slow charging, the smaller value of the stage charge rate during fast charging and the maximum charge rate (i.e., capacity) of the slow charging device is used as the stage charge rate, and the stage charge cut-off voltage is still based on the stage charge cut-off voltage during fast charging. When the actual charge rate is less than the stage charge rate during fast charging, charging at a lower charge rate will occur, the actual state of charge of the battery cells will be higher, and the battery cells will be overcharged.

[0006] CN114678610A discloses a method, device, and system for determining the safety margin of a battery charging strategy. The method dynamically adjusts the charging strategy based on determining whether a lithium-ion battery undergoes lithium deposition during charging. However, the method does not discuss the charging cutoff conditions for lithium-ion batteries, and lithium-ion batteries are at risk of overcharging. Summary of the Invention

[0007] The purpose of the present invention is to provide a charging control method, system and vehicle for a power battery to avoid overcharging of the power battery caused by high temperature and low rate charging process.

[0008] The power battery charging control method of the present invention includes:

[0009] Real-time acquisition of the current power battery's highest cell voltage U and lowest cell temperature T min and the maximum monomer temperature T max .

[0010] Determine the vehicle charging mode. If the vehicle charging mode is DC fast charging, execute the fast charging control strategy. If the vehicle charging mode is AC slow charging, execute the slow charging control strategy.

[0011] The fast charging control strategy includes:

[0012] S11, take U as the voltage to be looked up, T min As the table temperature, query the preset fast charge MAP table to obtain the stage charging rate C1 and the stage charging cut-off voltage U1; use U as the table voltage, T max As the table lookup temperature, the preset fast charge MAP table is queried to obtain the stage charge rate C2 and the stage charge cut-off voltage U2, and then S12 is executed.

[0013] S12: Determine whether C1 is less than C2. If so, execute S13; otherwise, execute S15.

[0014] S13, charging with C1 as the charging rate until U is equal to U1, and then executing S14.

[0015] S14, determine whether U is greater than or equal to Umax1, if yes, execute S17, otherwise return to execute S11. min As the table lookup temperature, a maximum charge cutoff voltage is obtained by looking up a preset maximum charge cutoff voltage table.

[0016] S15. Charge at a rate of C2 until U equals U2, and then execute S16.

[0017] S16, determine whether U is greater than or equal to Umax2, if yes, execute S17, otherwise return to execute S11. max As the table lookup temperature, a maximum charge cutoff voltage is obtained by looking up a preset maximum charge cutoff voltage table.

[0018] S17. Exit charging and then end.

[0019] Preferably, the preset fast charge MAP table is a table of correspondences between battery cell voltage, cell temperature, stage charge cut-off voltage, and stage charge rate obtained through calibration. The preset maximum charge cut-off voltage table is a table of correspondences between cell temperature and maximum charge cut-off voltage obtained through calibration.

[0020] Preferably, the slow charging control strategy includes:

[0021] S21, take U as the voltage to be looked up, T min As the table temperature, query the preset fast charge MAP table to obtain the stage charging rate C1 and the stage charging cut-off voltage U1; use U as the table voltage, T max As the table lookup temperature, query the preset fast charging MAP table to obtain the stage charging rate C2 and the stage charging cut-off voltage U2; determine the maximum charging rate Ct of the current slow charging device, and then execute S22.

[0022] S22: Determine whether Ct is less than C1 and Ct is less than C2 (ie, whether the minimum value among Ct, C1, and C2 is Ct). If so, execute S23; otherwise, execute S26.

[0023] S23, T maxUsing Ct as the lookup temperature and Ct as the lookup charge rate, the preset overcharge prevention MAP table is consulted to obtain the maximum allowable charging voltage Umaxt, and then S24 is executed. The preset overcharge prevention MAP table is a calibration-derived correspondence table of cell temperature, charge rate, and maximum allowable charging voltage.

[0024] S24: Charge at Ct as the charging rate, and then execute S25.

[0025] S25. Determine whether U is greater than or equal to Umaxt. If so, execute S211; otherwise, return to execute S24.

[0026] S26. Determine whether C1 is less than C2 (corresponding to whether the minimum value among Ct, C1, and C2 is C1). If so, execute S27; otherwise (corresponding to when the minimum value among Ct, C1, and C2 is C2), execute S29.

[0027] S27, charging with C1 as the charging rate until U is equal to U1, and then executing S28.

[0028] S28, determine whether U is greater than or equal to Umax1, if yes, execute S211, otherwise return to execute S21. min As the table lookup temperature, a maximum charge cutoff voltage is obtained by looking up a preset maximum charge cutoff voltage table.

[0029] S29, charging with C2 as the charging rate until U is equal to U2, and then executing S210.

[0030] S210, determine whether U is greater than or equal to Umax2, if yes, execute S211, otherwise return to execute S21. max As the table lookup temperature, a maximum charge cutoff voltage is obtained by looking up a preset maximum charge cutoff voltage table.

[0031] S211. Exit charging and then end.

[0032] At the same temperature, during slow charging, the smaller of the fast charging rate and the maximum charging rate of the slow charging device is used as the charging rate. If the smaller value is the fast charging rate, charging is performed according to the fast charging MAP table. If the smaller value is the maximum charging rate of the slow charging device, the maximum allowable charging voltage in the overcharge prevention MAP table is used as the charging cutoff voltage. This avoids overcharging during slow charging and helps extend the service life of the power battery. By querying the overcharge prevention MAP table to find the maximum allowable charging voltage, the consistency of slow charging is ensured.

[0033] Preferably, the calibration step of the preset fast charge MAP table includes:

[0034] The first step is to select n different cell temperatures and m different SOC values, and conduct three-electrode tests on the battery cells at these n cell temperatures and m SOC values to obtain n*m maximum charge rates corresponding to the battery cells at these n cell temperatures and m SOC values. The three-electrode test is widely used as a conventional electrochemical test method. In lithium batteries, if the negative electrode potential to lithium is less than 0mV, the charge rate is considered to exceed the maximum charge capacity (i.e., the maximum charge rate) of the lithium battery at this temperature and SOC value. Therefore, the three-electrode test at different temperatures can determine the maximum charge rate of the battery cells corresponding to different SOC values at different temperatures.

[0035] The second step is to determine n*m charging rates corresponding to m SOC values at n cell temperatures of the battery cell, without exceeding the maximum charging rate of the battery cell, according to the requirements of achieving the charging time and the smoothness of the charging curve.

[0036] The third step is to conduct rated capacity tests on the battery cells at n cell temperatures to obtain n rated capacities of the battery cells corresponding to the n cell temperatures.

[0037] Step 4: Use the formula: C ij = C i *SOC j , calculate the charge capacity C corresponding to the jth SOC value at the i-th cell temperature ij Among them, C i Indicates the rated capacity corresponding to the temperature of the i-th cell, SOC j represents the j-th SOC value, i takes all integers from 1 to n, and j takes all integers from 1 to m.

[0038] Step 5: At the temperature of the i-th monomer, CX ik Charge and read the charging capacity as C ik The battery cell voltage U ik Among them, CX ik represents the stage charge rate corresponding to the kth SOC value at the i-th cell temperature, C ik represents the charge capacity corresponding to the kth SOC value at the i-th cell temperature, where k is any integer from 2 to m.

[0039] Step 6: U ik As the temperature of the i-th cell, the stage charge rate CX ik Correspondingly, the battery cell voltage is U i(k-1) with U ik The stage charging cut-off voltage between , thus forming a fast charge MAP table. i(k-1)Indicates the temperature of the i-th monomer with CX i(k-1) Charge the battery to a capacity of C i(k-1) Battery cell voltage at the time; CX i(k-1) represents the stage charge rate corresponding to the k-1th SOC value at the i-th cell temperature, C i(k-1) represents the charge capacity corresponding to the k-1th SOC value at the i-th cell temperature.

[0040] Preferably, the calibration step of the preset anti-overcharge MAP table includes:

[0041] The first step is to select r charging rates at the i-th cell temperature, and the r charging rates are all smaller than the m charging rates at the i-th cell temperature in the fast charging MAP table.

[0042] Step 2: Control the battery cell to charge to a capacity of H at the i-th cell temperature according to the fast charge MAP table. i Among them, H i = C i *SOC thr , SOC thr Indicates the preset SOC threshold.

[0043] Step 3: At the i-th cell temperature, charge the battery cell obtained after step 2 to C at the w-th charging rate among the r charging rates. i , read the charge to C i Battery cell voltage U' iw ; Wherein, w takes all integers from 1 to r.

[0044] Step 4: U' iw The overcharge prevention MAP table is formed as the maximum charge allowable voltage corresponding to the i-th cell temperature and the w-th charge rate.

[0045] Preferably, the preset SOC threshold range is 75% to 85%, which is a better range that does not affect the total charging time and does not cause overcharging.

[0046] Preferably, the preset SOC threshold is 80%, which is the optimal value that does not affect the total charging time and does not cause overcharging.

[0047] Preferably, the method for determining the maximum charging rate Ct of the current slow charging device includes:

[0048] Get the total voltage Ut of the current power battery in real time.

[0049] Use the formula: It=P / Ut to calculate the maximum output current It of the slow charging device; where P represents the maximum power that the slow charging device can output.

[0050] Use the formula: Ct=It / C 25℃ , calculate the maximum charging rate Ct of the current slow charging device; where C 25℃ Indicates the rated capacity of the battery cell at 25°C.

[0051] During the actual charging process, the maximum charging power that the slow charging device can output remains constant, while the total voltage of the power battery continues to increase as the charging process progresses, and Ct will continue to decrease, and eventually usually becomes less than the smaller value of C1 and C2.

[0052] The power battery charging control system of the present invention includes a controller, and the controller is programmed to execute the above-mentioned charging control method.

[0053] The vehicle of the present invention includes the above-mentioned charging control system.

[0054] The present invention has the following effects:

[0055] (1) The influence of temperature and charging rate on the cut-off voltage is taken into consideration. By designing different temperatures and different charging rates, charging the same amount of electricity corresponding to different stage charging cut-off voltages, the problem of power battery overcharging caused by high temperature and low rate charging process is avoided, which is beneficial to extending the service life of the power battery.

[0056] (2) In actual use, the stage charging rate and stage charging cut-off voltage are found by querying the preset fast charging MAP table, and the maximum charging cut-off voltage is found by querying the preset maximum charging cut-off voltage table, which ensures the SOC consistency of the battery cell at the end of charging and prevents overcharging of the power battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a flow chart of the charging control of the power battery in this embodiment.

[0058] Figure 2 This is a flow chart of the fast charging control strategy in this embodiment.

[0059] Figure 3 This is a flow chart of the slow charging control strategy in this embodiment.

[0060] Figure 4 This is a flow chart of the calibration of the fast charge MAP table in this embodiment.

[0061] Figure 5 This is a calibration flow chart of the anti-overcharge MAP table in this embodiment. DETAILED DESCRIPTION

[0062] like Figures 1 to 5 As shown, the power battery charging control method in this embodiment includes:

[0063] Step 1: Obtain the total voltage Ut, the highest cell voltage U, and the lowest cell temperature T of the current power battery in real time min and the maximum monomer temperature T max , then proceed to step 2. For example, the voltage of all cells in the power battery is monitored through the low-voltage wiring harness, and the highest cell voltage U is obtained during the charging process. The temperature of all cells in the power battery is monitored through the thermistor, and the lowest cell temperature T is obtained. min and the maximum monomer temperature T max .

[0064] Step 2: Determine whether the vehicle is in DC fast charging mode. If so, proceed to step 3; otherwise, proceed to step 4. When the vehicle is plugged in and charging, signal detection is used to determine whether the vehicle is in DC fast charging or AC slow charging. For details, refer to GB / T 20234.

[0065] Step 3: Execute the fast charge control strategy and then end.

[0066] like Figure 2 As shown in Figure 1, the fast charging control strategy includes:

[0067] S11, use U as the table voltage, T min As the table temperature, query the preset fast charge MAP table to obtain the stage charging rate C1 and the stage charging cut-off voltage U1; use U as the table voltage, T max As the table lookup temperature, the preset fast charge MAP table is queried to obtain the stage charge rate C2 and the stage charge cut-off voltage U2, and then S12 is executed.

[0068] The preset fast charge MAP table is a correspondence table of battery cell voltage, cell temperature, stage charge cut-off voltage, and stage charge rate obtained through calibration.

[0069] like Figure 4 As shown, the calibration steps of the fast charge MAP table include:

[0070] The first step is to select n different cell temperatures and m different SOC values, perform three-electrode tests on the battery cell at n cell temperatures and m SOC values, and obtain n*m maximum charge rates corresponding to the battery cell at the n cell temperatures and m SOC values.

[0071] The second step is to determine n*m charge rates corresponding to m SOC values at n cell temperatures of the battery cell, without exceeding the maximum charge rate of the battery cell, according to the requirements of achieving the charging time and the smoothness of the charging curve (this belongs to the existing technology).

[0072] The third step is to conduct rated capacity tests on the battery cells at n cell temperatures (tested according to GB / T 31486) to obtain n rated capacities of the battery cells corresponding to the n cell temperatures.

[0073] Step 4: Use the formula: C ij = C i *SOC j , calculate the charge capacity C corresponding to the jth SOC value at the i-th cell temperature ij Among them, C i Indicates the rated capacity corresponding to the temperature of the i-th cell, SOC j represents the j-th SOC value, i takes all integers from 1 to n, and j takes all integers from 1 to m.

[0074] Step 5: At the temperature of the i-th monomer, CX ik Charge and read the charging capacity as C ik The battery cell voltage U ik Among them, CX ik represents the stage charge rate corresponding to the kth SOC value at the i-th cell temperature, C ik represents the charge capacity corresponding to the kth SOC value at the i-th cell temperature, where k is any integer from 2 to m.

[0075] Step 6: U ik As the temperature of the i-th cell, the stage charge rate CX ik Correspondingly, the battery cell voltage is U i(k-1) with U ik The stage charging cut-off voltage between , thus forming a fast charge MAP table; Among them, U i(k-1) Indicates the temperature of the i-th monomer with CX i(k-1) Charge the battery to a capacity of C i(k-1) Battery cell voltage at the time; CX i(k-1) represents the stage charge rate corresponding to the k-1th SOC value at the i-th cell temperature, C i(k-1) represents the charge capacity corresponding to the k-1th SOC value at the i-th cell temperature.

[0076] Taking 25°C as an example, assuming the rated capacity of a battery cell at 25°C is 100Ah and a SOC value of 10% corresponds to a capacity of 10Ah, charging is performed at 25°C using the staged charge rate determined above (assuming it is 1.6). The battery cell voltage at 10Ah is read (assuming it is 3.691V). 3.691V is used as the staged charge cutoff voltage corresponding to a cell temperature of 25°C, a staged charge rate of 1.6, and a cell voltage between 3.338V and 3.691V. 3.338V is also used as the staged charge cutoff voltage corresponding to a cell temperature of 25°C, a charge rate of 0.05, and a cell voltage between 0V and 3.338V.

[0077] At the same charging rate, the higher the temperature, the smaller the corresponding charging cut-off voltage.

[0078] S12: Determine whether C1 is less than C2. If so, execute S13; otherwise, execute S15.

[0079] S13, charging with C1 as the charging rate until U is equal to U1, and then executing S14.

[0080] S14, determine whether U is greater than or equal to Umax1, if yes, execute S17, otherwise return to execute S11. min The maximum charge cut-off voltage is obtained by querying a preset maximum charge cut-off voltage table as the lookup temperature. The preset maximum charge cut-off voltage table is a correspondence table between cell temperature and maximum charge cut-off voltage obtained by calibration, and the calibration method belongs to the prior art.

[0081] S15. Charge at a rate of C2 until U equals U2, and then execute S16.

[0082] S16, determine whether U is greater than or equal to Umax2, if yes, execute S17, otherwise return to execute S11. max As the table lookup temperature, a maximum charge cutoff voltage is obtained by looking up a preset maximum charge cutoff voltage table.

[0083] S17. Exit charging and then end.

[0084] Step 4: Determine whether the vehicle charging mode is AC slow charging. If so, proceed to step 5, otherwise end.

[0085] Step 5: Execute the slow charging control strategy and then end.

[0086] like Figure 3 As shown, the slow charging control strategy includes:

[0087] S21, take U as the voltage to be looked up, Tmin As the table temperature, query the preset fast charge MAP table to obtain the stage charging rate C1 and the stage charging cut-off voltage U1; use U as the table voltage, T max As the table lookup temperature, query the preset fast charging MAP table to obtain the stage charging rate C2 and the stage charging cut-off voltage U2; determine the maximum charging rate Ct of the current slow charging device, and then execute S22.

[0088] Methods for determining the maximum charge rate Ct of the current slow charging device include:

[0089] Use the formula: It = P / Ut to calculate the maximum output current It of the slow-charging device. P represents the maximum power that the slow-charging device can output.

[0090] Use the formula: Ct=It / C 25℃ , calculate the maximum charging rate Ct of the current slow charging device. 25℃ Indicates the rated capacity of the battery cell at 25°C.

[0091] S22: Determine whether Ct is less than C1 and Ct is less than C2 (ie, whether the minimum value among Ct, C1, and C2 is Ct). If so, execute S23; otherwise, execute S26.

[0092] S23, T max As the table lookup temperature, Ct as the table lookup charge rate, query the preset overcharge prevention MAP table, obtain the maximum charging allowable voltage Umaxt, and then execute S24.

[0093] The preset anti-overcharge MAP table is a correspondence table of cell temperature, charge rate and maximum allowable charging voltage obtained through calibration.

[0094] like Figure 5 As shown, the calibration steps of the anti-overcharge MAP table include:

[0095] The first step is to select r charging rates at the i-th cell temperature, and the r charging rates are all smaller than the m charging rates at the i-th cell temperature in the fast charge MAP table.

[0096] Step 2: Control the battery cell to charge to a capacity of H at the i-th cell temperature according to the fast charge MAP table. i Among them, H i = C i *SOC thr , SOC thr Indicates the preset SOC threshold. In this embodiment, SOC thr =80%.

[0097] Step 3: At the i-th cell temperature, charge the battery cell obtained after step 2 to C at the w-th charging rate among the r charging rates. i , read the charge to C i Battery cell voltage U' iw ; Wherein, w takes all integers from 1 to r.

[0098] Step 4: U' iw The overcharge prevention MAP table is formed as the maximum charge allowable voltage corresponding to the i-th cell temperature and the w-th charge rate.

[0099] Taking -10℃ as an example, the rated capacity C of the battery cell at -10℃ is obtained according to GB / T31486 test. -10℃ , assuming C -10℃ For example, the battery is 80Ah. When the SOC value is charged to 80% according to the fast charge MAP table (that is, after charging 64Ah), it is charged to 80Ah at a charging rate among r charging rates (assuming it is 0.05). The battery cell voltage when charged to 80Ah is read and the battery cell voltage is used as the maximum charging allowable voltage corresponding to the cell temperature of -10℃ and the charging rate of 0.05.

[0100] S24: Charge at Ct as the charging rate, and then execute S25.

[0101] S25. Determine whether U is greater than or equal to Umaxt. If so, execute S211; otherwise, return to execute S24.

[0102] S26. Determine whether C1 is less than C2 (corresponding to whether the minimum value among Ct, C1, and C2 is C1). If so, execute S27; otherwise (corresponding to when the minimum value among Ct, C1, and C2 is C2), execute S29.

[0103] S27, charging with C1 as the charging rate until U is equal to U1, and then executing S28.

[0104] S28, determine whether U is greater than or equal to Umax1, if yes, execute S211, otherwise return to execute S21. min As the table lookup temperature, a maximum charge cutoff voltage is obtained by looking up a preset maximum charge cutoff voltage table.

[0105] S29, charging with C2 as the charging rate until U is equal to U2, and then executing S210.

[0106] S210, determine whether U is greater than or equal to Umax2, if yes, execute S211, otherwise return to execute S21. maxAs the table lookup temperature, a maximum charge cutoff voltage is obtained by looking up a preset maximum charge cutoff voltage table.

[0107] S211. Exit charging and then end.

[0108] The power battery charging control system in this embodiment includes a controller programmed to execute the power battery charging control method described above.

[0109] This embodiment also provides a vehicle, which includes the above-mentioned power battery charging control system.

Claims

1. A power battery charging control method, characterized in that: include: Real-time acquisition of the current power battery's highest cell voltage U and lowest cell temperature T min and the maximum monomer temperature T max ; Determine the vehicle charging mode. If the vehicle charging mode is DC fast charging, the fast charging control strategy is executed. If the vehicle charging mode is AC slow charging, the slow charging control strategy is executed. The fast charging control strategy includes: S11, use U as the table voltage, T min As the table temperature, query the preset fast charge MAP table to obtain the stage charging rate C1 and the stage charging cut-off voltage U1; use U as the table voltage, T max As the table lookup temperature, query the preset fast charge MAP table to obtain the stage charge rate C2 and the stage charge cut-off voltage U2, and then execute S12; S12: Determine whether C1 is less than C2. If so, execute S13; otherwise, execute S15. S13, charging with C1 as the charging rate until U equals U1, and then executing S14; S14, determine whether U is greater than or equal to Umax1, if yes, execute S17, otherwise return to execute S11; wherein Umax1 is T min As the table lookup temperature, the maximum charge cut-off voltage is obtained by looking up the preset maximum charge cut-off voltage table; S15, charging at C2 as the charging rate until U equals U2, and then executing S16; S16, determine whether U is greater than or equal to Umax2, if yes, execute S17, otherwise return to execute S11; wherein Umax2 is T max As the table lookup temperature, the maximum charge cut-off voltage is obtained by looking up the preset maximum charge cut-off voltage table; S17. Exit charging and then end.

2. The power battery charging control method according to claim 1, characterized in that: The preset fast charge MAP table is a correspondence table of battery cell voltage, cell temperature, stage charge cut-off voltage, and stage charge rate obtained through calibration; The preset maximum charge cut-off voltage table is a correspondence table between cell temperature and maximum charge cut-off voltage obtained through calibration.

3. The power battery charging control method according to claim 2, characterized in that: The slow charging control strategy includes: S21, take U as the voltage to be looked up, T min As the table temperature, query the preset fast charge MAP table to obtain the stage charging rate C1 and the stage charging cut-off voltage U1; use U as the table voltage, T max As the table lookup temperature, query the preset fast charging MAP table to obtain the stage charging rate C2 and the stage charging cut-off voltage U2; determine the maximum charging rate Ct of the current slow charging device, and then execute S22; S22: Determine whether Ct is less than C1 and Ct is less than C2. If yes, execute S23; otherwise, execute S26. S23, T max Using Ct as the table lookup temperature and Ct as the table lookup charge rate, the preset overcharge prevention MAP table is queried to obtain the maximum allowable charging voltage Umaxt, and then S24 is executed; wherein the preset overcharge prevention MAP table is a correspondence table of cell temperature, charge rate, and maximum allowable charging voltage obtained through calibration; S24, charging at Ct as the charging rate, and then executing S25; S25. Determine whether U is greater than or equal to Umaxt. If so, execute S211; otherwise, return to execute S24. S26: Determine whether C1 is less than C2. If so, execute S27; otherwise, execute S29. S27, charging with C1 as the charging rate until U equals U1, and then executing S28; S28, determine whether U is greater than or equal to Umax1, if so, execute S211, otherwise return to execute S21; wherein Umax1 is T min As the table lookup temperature, the maximum charge cut-off voltage is obtained by looking up the preset maximum charge cut-off voltage table; S29, charging at C2 as the charging rate until U equals U2, and then executing S210; S210, determine whether U is greater than or equal to Umax2, if yes, execute S211, otherwise return to execute S21; wherein Umax2 is T max As the table lookup temperature, the maximum charge cut-off voltage is obtained by looking up the preset maximum charge cut-off voltage table; S211. Exit charging and then end.

4. The power battery charging control method according to claim 3, characterized in that: The calibration steps of the preset fast charge MAP table include: The first step is to select n different cell temperatures and m different SOC values, perform a three-electrode test on the battery cell at n cell temperatures and m SOC values, and obtain n*m maximum charge rates corresponding to the battery cell at the n cell temperatures and m SOC values; Step 2: Under the premise of not exceeding the maximum charge rate of the battery cell, determine n*m charge rates corresponding to m SOC values of the battery cell at n cell temperatures according to the requirements of achieving the charging time and the smoothness of the charging curve; Step 3: Perform rated capacity tests on the battery cells at n cell temperatures to obtain n rated capacities of the battery cells corresponding to the n cell temperatures. Step 4: Use the formula: C ij = C i *SOC j , calculate the charge capacity C corresponding to the jth SOC value at the i-th cell temperature ij Among them, C i Indicates the rated capacity corresponding to the temperature of the i-th cell, SOC j represents the j-th SOC value, i is any integer from 1 to n, and j is any integer from 1 to m; Step 5: At the temperature of the i-th monomer, CX ik Charge and read the charging capacity as C ik Battery cell voltage U ik Among them, CX ik represents the stage charge rate corresponding to the kth SOC value at the i-th cell temperature, where k is any integer from 2 to m; Step 6: U ik As the temperature of the i-th cell, the stage charge rate CX ik Correspondingly, the battery cell voltage is U i(k-1) with U ik The stage charging cut-off voltage between , thus forming a fast charge MAP table; Among them, U i(k-1) Indicates the temperature of the i-th monomer with CX i(k-1) Charge the battery to a capacity of C i(k-1) The battery cell voltage at .

5. The power battery charging control method according to claim 4, characterized in that: The calibration steps of the preset anti-overcharge MAP table include: The first step is to select r charging rates at the i-th cell temperature, which are all smaller than the m charging rates at the i-th cell temperature in the fast charge MAP table; Step 2: Control the battery cell to charge to a capacity of H at the i-th cell temperature according to the fast charge MAP table. i Among them, H i = C i *SOC thr , SOC thr Indicates the preset SOC threshold; Step 3: At the i-th cell temperature, charge the battery cell obtained after step 2 to C at the w-th charging rate among the r charging rates. i , read the charge to C i The battery cell voltage U' iw ;Wherein, w takes all integers from 1 to r; Step 4: U' iw The overcharge prevention MAP table is formed as the maximum charge allowable voltage corresponding to the i-th cell temperature and the w-th charge rate.

6. The power battery charging control method according to claim 5, characterized in that: The preset SOC threshold ranges from 75% to 85%.

7. The power battery charging control method according to claim 5, characterized in that: The preset SOC threshold is 80%.

8. The power battery charging control method according to any one of claims 1 to 7, characterized in that: Methods for determining the maximum charge rate Ct of the current slow charging device include: Get the total voltage Ut of the current power battery in real time; Use the formula: It=P / Ut to calculate the maximum output current It of the slow charging device; where P represents the maximum power that the slow charging device can output; Use the formula: Ct=It / C 25℃ , calculate the maximum charging rate Ct of the current slow charging device; where C 25℃ Indicates the rated capacity of the battery cell at 25°C.

9. A power battery charging control system, comprising a controller, characterized in that: The controller is programmed to execute the charging control method according to any one of claims 1 to 8.

10. A vehicle, characterized in that: Comprising the charging control system as claimed in claim 9.

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