Power battery system, electric vehicle, and power battery system control method

Abstract

The present invention discloses a power battery system, an electric vehicle and a power battery system control method. In the power battery system, a controller is connected to a control end of an electronic switch in a switching module. When not charged and no power-on instruction is received, if the absolute value of the voltage difference between at least two batteries is greater than or equal to a preset threshold, the controller generates a pulse signal to control the electronic switch in the switching module to be turned on to connect at least two batteries. The at least two batteries form a loop through the electronic switch, and the battery with a higher voltage among the at least two batteries discharges the battery with a lower voltage through the loop, so that when not charged and not powered on, especially after charging of multiple batteries in series is completed, the duty cycle of the electronic switch can be used to control the loop current size, and active battery voltage balancing is achieved with the maximum current allowed, which not only avoids excessive damage to the battery and switches such as relays in the switching module due to excessive loop current, but also quickly balances the battery voltage with the maximum current, thereby increasing the speed of parallel discharge of the batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of power batteries, and in particular to a power battery system, an electric vehicle, and a power battery system control method. Background Art

[0002] At present, dual-branch is a widely used electrical architecture in the battery systems used in electric vehicles. At the same time, a high-voltage charging platform (about 550V~930V) has been launched to charge the power batteries of electric vehicles at extremely high speed. That is, the dual-branch battery system is connected in series during overcharging and in parallel during discharge.

[0003] In a system including multiple batteries, in order to be compatible with low-voltage charging platforms (110V~450V) and high-voltage charging platforms, multiple batteries are usually connected in parallel to the charging port when charging the low-voltage charging platform, and multiple batteries are connected in series to the charging port when charging the high-voltage charging platform, such as Figure 1 (a) When charging on the high-voltage charging platform, the battery Batt1 and the battery Batt2 are connected in series to the charging ports DC+ and DC-. At the same time, in order to take into account the power demand of the load when charging on the high-voltage platform, power is taken from the series line between the battery Batt1 and the battery Batt2 to supply power to the load ports HV+ and HV-, resulting in the charging current of the battery Batt2 being less than the charging current of the battery Batt1. After charging, the voltage of the battery Batt1 is higher than the voltage of the battery Batt2, that is, there is a voltage difference after the battery Batt1 and the battery Batt2 are charged in series (charging on the high-voltage platform).

[0004] like Figure 1 As shown in (b), when the battery Batt1 and the battery Batt2 need to be connected in parallel to power the load port HV+, if the voltage of the battery Batt1 is greater than the voltage of the battery Batt2, a loop is formed between the battery Batt1 and the battery Batt2, and the battery Batt1 will supplement the battery Batt2 to form a loop current, such as Figure 1 The dotted line in (b) is the direction of the loop current. The loop current is large and uncontrollable, which can easily cause excessive current flowing through the switch on the line, causing adhesion damage to the switch and reducing the reliability of the entire system. If the loop current is small, it will extend the time for the voltage of battery Batt1 and battery Batt2 to reach equilibrium, reducing the speed of parallel discharge of battery Batt1 and battery Batt2. Summary of the invention

[0005] The present invention provides a power battery system, an electric vehicle and a power battery system control method to solve the problem that there is a voltage difference between batteries, the current of the loop formed by parallel power supply is uncontrollable, resulting in excessive current causing adhesion damage to the switch, or too small current causing a reduction in parallel discharge speed.

[0006] In a first aspect, the present invention provides a power battery system, comprising: at least two batteries, a switching module, a charging port, a load port and a controller, wherein the battery is connected to the charging port and the load port through the switching module, the switching module is connected to the controller, the switching module comprises a balancing unit provided with an electronic switch, the controller is connected to a control end of the electronic switch, and the controller is used to:

[0007] When not charging and not receiving a power-on instruction, determining an absolute value of a voltage difference between the at least two batteries;

[0008] Determining whether the absolute value of the voltage difference is greater than or equal to a preset threshold;

[0009] If so, a pulse signal is generated to control the electronic switch in the switching module to turn on to connect the at least two batteries, the at least two batteries form a loop through the electronic switch, and the battery with a higher voltage among the at least two batteries discharges to the battery with a lower voltage through the loop.

[0010] In a second aspect, the present invention further provides an electric vehicle, comprising the power battery system described in the first aspect.

[0011] In a third aspect, the present invention further provides a power battery system control method, which is applied to the power battery system according to the first aspect, wherein the power battery system comprises at least two batteries, a switching module, a charging port, a load port and a controller, wherein the battery is connected to the charging port and the load port through the switching module, the switching module is connected to the controller, the switching module comprises a balancing unit provided with an electronic switch, and the controller is connected to the control end of the electronic switch, wherein the power battery system control method comprises:

[0012] When not charging and not receiving a power-on instruction, determining an absolute value of a voltage difference between the at least two batteries;

[0013] Determining whether the absolute value of the voltage difference is greater than or equal to a preset threshold;

[0014] If so, a pulse signal is generated to control the electronic switch in the switching module to turn on to connect the at least two batteries, the at least two batteries form a loop through the electronic switch, and the battery with a higher voltage among the at least two batteries discharges to the battery with a lower voltage through the loop.

[0015] In the power battery system of the present embodiment, the switching module includes a balancing unit provided with an electronic switch. The controller can determine the absolute value of the voltage difference between at least two batteries when they are not charged and have not received a power-on instruction. When the absolute value of the voltage difference is greater than or equal to a preset threshold, a pulse signal is generated to control the electronic switch in the switching module to conduct to connect the at least two batteries. The at least two batteries form a loop through the electronic switch, so that the battery with a higher voltage among the at least two batteries discharges to the battery with a lower voltage through the loop, so that when the power battery system is not charged and not powered on, the loop is formed by controlling the electronic switch to conduct to connect multiple batteries with a voltage difference. The battery voltage is actively balanced, especially when multiple batteries are charged in series and the load port is powered on at the same time, and the absolute value of the battery voltage difference is large after charging is completed, the loop current of the formed loop can be controlled by the duty cycle of the electronic switch, and the active battery voltage is balanced with the maximum current allowed without excessive current. It can avoid excessive loop current from damaging the battery and switches such as relays in the switching module, and can quickly balance the battery voltage with the maximum current, so that the voltages of multiple batteries are balanced. When multiple batteries need to be connected in parallel to power the load port, the speed of parallel powering of the batteries can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention is further described in detail below based on the accompanying drawings and embodiments.

[0017] Figure 1 A schematic diagram of the loop current formed by parallel discharge when the voltages of batteries are unequal;

[0018] Figure 2 A schematic diagram of the structure of a power battery system provided by one embodiment of the present invention;

[0019] Figure 3 A schematic structural diagram of a power battery system provided by another embodiment of the present invention;

[0020] Figure 4 A schematic structural diagram of a power battery system provided by another embodiment of the present invention;

[0021] Figure 5 Schematic diagram of the circuit structure of a loop formed by N batteries in an embodiment of the present invention;

[0022] Figure 6 A schematic diagram of the circuit structure of a loop formed by two batteries in an embodiment of the present invention;

[0023] Figure 7 This is a schematic diagram of the circuit structure when N batteries are connected in parallel and discharged in an embodiment of the present invention;

[0024] Figure 8This is a schematic diagram of a circuit structure with a pre-charging function when n batteries are connected in parallel and discharged in an embodiment of the present invention;

[0025] Fig. 9 This is a schematic diagram of a circuit structure in which two batteries are connected in parallel and discharged with a pre-charging function in an embodiment of the present invention;

[0026] Fig.10 This is a schematic diagram of a circuit structure for charging n batteries in series in an embodiment of the present invention;

[0027] Fig.11 A schematic diagram of a circuit structure in which n batteries are charged in series and supply power to a load port in an embodiment of the present invention;

[0028] Fig.12 This is a schematic diagram of a circuit structure in which a unidirectional diode is provided according to an embodiment of the present invention;

[0029] Fig.13 A schematic diagram of a circuit structure for parallel discharge when a unidirectional diode is provided after series charging;

[0030] Fig.14 Schematic diagram of a circuit structure including two batteries in an embodiment of the present invention;

[0031] Fig.15 A flow chart of a power battery system control method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0033] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, unless otherwise clearly specified and limited, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0034] Figure 2FIG. 1 is a schematic diagram of the structure of a power battery system according to an embodiment of the present invention. The power battery system according to the present embodiment can be used in transportation tools such as electric vehicles and ships, and can also be used in other equipment that uses electric energy as the main energy source, such as Figure 2 As shown, the power battery system includes at least two batteries 10, a switching module 30, a charging port (DC+, DC-), a load port (HV+, HV-) and a controller 40. The battery 10 is connected to the charging port (DC+, DC-) and the load port (HV+, HV-) through the switching module 30. The switching module 30 is connected to the controller 40. The switching module 30 includes a balancing unit 301 provided with an electronic switch, and the controller 40 is connected to the control end of the electronic switch.

[0035] Among them, the battery can be a rechargeable battery such as a lithium battery, a lead-acid battery, etc., the number of batteries can be n, n is a positive integer greater than or equal to 2, the balancing unit 301 can be a circuit that adjusts the current through an electronic switch, and the electronic switch can be a semiconductor switch tube. Exemplarily, the electronic switch can be one of a triode, a MOS tube and an IGBT. In addition to the balancing unit 301, the switching module 30 can also include other switching devices, such as switching devices such as relays for switching battery charging and discharging.

[0036] In this embodiment, the controller 40 is used to determine the absolute value of the voltage difference between at least two batteries 10 when not charging and not receiving a power-on command, and judge whether the absolute value of the voltage difference is greater than or equal to a preset threshold value. If so, a pulse signal is generated to control the electronic switch in the switching module 30 to turn on to connect at least two batteries 10. At least two batteries 10 form a loop through the electronic switch, and the battery with a higher voltage among the at least two batteries 10 discharges to the battery with a lower voltage through the loop.

[0037] Taking the electronic switch as IGBT as an example, when not charged and no power-on instruction is received, the controller 40 can obtain the voltage of each battery 10 through the voltage detection module or communicate with the BMS of the battery, and calculate the absolute value of the voltage difference between each battery 10. If the absolute value of the voltage difference is greater than or equal to the preset threshold, if the voltage of multiple batteries 10 is not processed in any way, the high-voltage battery will discharge the low-voltage battery when supplying power to the load port (HV+, HV-) in parallel. In this embodiment, when not charged and not discharged, the controller 40 generates a pulse signal to control the IGBT to turn on. By adjusting the duty cycle of the IGBT, the size of the loop current in the loop when the high-voltage battery discharges the low-voltage battery can be controlled, so that the loop current is controllable, and the high-voltage battery can discharge the low-voltage battery quickly with the maximum current allowed, which not only avoids excessive damage to the battery and switches such as relays in the switching module 30 due to excessive loop current, but also can quickly and actively balance the battery voltage with the maximum current, thereby increasing the speed of parallel discharge of the batteries when multiple batteries need to be discharged in parallel later.

[0038] like Figure 3 As shown, in one embodiment, the switching module 30 also includes a driver 302, and the controller 40 is connected to the control end of the electronic switch through the driver 302, wherein the driver 302 can be a circuit or a component for controlling the electronic switch, and the controller 40 is used to generate a pulse signal and output it to the driver 302, and the driver 302 is used to adjust the driving voltage of the control end of the electronic switch according to the pulse signal. By way of example, taking the electronic switch as an IGBT as an example, after receiving the pulse signal of the controller 40, the driver 302 can directly amplify the pulse signal and then control the IGBT to be turned on or off. By setting the driver 302, the pulse signal of the controller 40 can be processed to reduce the signal energy of the pulse signal output by the controller 40, so that the controller 40 has lower power consumption, and the stability of the driving voltage of the electronic switch can be improved by the driver 302.

[0039] like Figure 4 As shown, in one embodiment, the switching module 30 also includes a detection module 303, which is connected to the controller 40. The detection module 303 is used to collect loop parameters of the loop and output them to the controller 40. The controller 40 is used to adjust the duty cycle of the pulse signal according to the loop parameters to adjust the loop current in the loop.

[0040] Exemplarily, the detection module 303 includes at least one of a current sampling module and a temperature detection module, the current sampling module is used to collect the loop current in the loop, the temperature detection module is used to collect the temperature of the electronic switch, and the controller 40 is used to adjust the duty cycle of the pulse signal according to at least one of the loop current and the temperature.

[0041] In one embodiment, the controller 40 can determine whether the loop current is equal to the current threshold. When the loop current is equal to the current threshold, the duty cycle of the pulse signal can be kept unchanged. When the loop current is less than the current threshold, the duty cycle of the pulse signal is increased to increase the loop current in the loop to be equal to the current threshold. When the loop current is greater than the current threshold, the duty cycle of the pulse signal is reduced to reduce the loop current in the loop to be equal to the current threshold. The current threshold can be determined based on the performance of the components in the switching module 30. For example, the current threshold can be the minimum value of the maximum current that each component can withstand, so that the high-voltage battery can discharge the low-voltage battery with the maximum current, thereby increasing the speed at which the voltages of multiple batteries with voltage differences in the power battery system reach equilibrium, that is, increasing the speed at which the power battery system is powered on in parallel to the load port.

[0042] In one embodiment, the electronic switch is a semiconductor switch. When the electronic switch is turned on and off at high frequency and current flows through it, a large amount of heat is generated, which increases the temperature of the electronic switch. In order to prevent the electronic switch from being damaged by excessive temperature, the controller 40 can determine whether the temperature is equal to the temperature threshold. When the temperature is equal to the temperature threshold, the duty cycle of the pulse signal is kept unchanged. When the temperature is greater than the temperature threshold, the duty cycle of the pulse signal is reduced to reduce the loop current in the loop, so that the temperature of the electronic switch is reduced until the temperature is equal to the temperature threshold. When the temperature is less than the temperature threshold, the duty cycle of the pulse signal can be increased to increase the loop current in the loop until the temperature is equal to the temperature threshold. The temperature threshold can be determined according to the performance of the electronic switch. For example, the temperature threshold can be the maximum operating temperature specified in the specification of the electronic switch. Under the premise of ensuring that the electronic switch operates within a safe temperature range, the high-voltage battery can discharge the low-voltage battery with a larger current, thereby increasing the speed at which the voltages of multiple batteries with voltage differences in the power battery system reach equilibrium, that is, increasing the speed at which the load port of the power battery system is powered on in parallel.

[0043] In one embodiment, the controller 40 can control the electronic switch according to the loop current and temperature at the same time. Specifically, the controller can determine whether the temperature is equal to the temperature threshold, keep the duty cycle of the pulse signal unchanged when the temperature is equal to the temperature threshold, reduce the duty cycle of the pulse signal when the temperature is greater than the temperature threshold to reduce the loop current in the loop, reduce the temperature to the temperature threshold, determine whether the loop current is equal to the current threshold when the temperature is less than the temperature threshold, keep the duty cycle of the pulse signal unchanged when the loop current is equal to the current threshold, increase the duty cycle of the pulse signal when the loop current is less than the current threshold to increase the loop current in the loop, and return to the step of determining whether the temperature is equal to the temperature threshold, reduce the duty cycle of the pulse signal when the loop current is greater than the current threshold to reduce the loop current in the loop, and return to the step of determining whether the temperature is equal to the temperature threshold. The loop current can be maximized while ensuring the safe operation of the electronic switch, which not only ensures the safe operation of the electronic switch, but also improves the efficiency of battery voltage balancing.

[0044] like Figure 5 FIG. 1 is a schematic diagram of a circuit structure of a loop formed by n batteries in an embodiment of the present invention. Figure 5 As shown, the battery 10 includes n-1 first batteries 101 and one second battery 102, the switching module 30 includes second switches (S2_1, S2_2, ..., S2_n-1) and third switches (S3_1, S3_2, ..., S3_n-1) equal in number to the number of the first batteries 101, the negative terminal of each first battery 101 is connected to the negative terminal of the second battery 102 through a second switch, and the positive terminal of each first battery 101 is connected in series with the electronic switch IGBT in the balancing unit 301 through a third switch, and then connected to the positive terminal of the second battery 102, as shown in FIG. Figure 5 As shown, n is a positive integer greater than or equal to 2. When n is equal to 2, the number of batteries in the power battery system is 2, that is, Figure 6 The circuit structure diagram of the loop formed by two batteries is shown in FIG. 1 . When n is greater than 2, as shown in FIG. Figure 5As shown, n-1 first batteries include batteries 10_1 to batteries 10_n-1, wherein the battery 10_1 is connected to the negative terminal of the second battery 102 through the second switch S2_1, and the battery 10_1 is connected to the positive terminal of the second battery 102 in series with the electronic switch IGBT in the balancing unit 301 through the third switch S3_1, and the battery 10_2 is connected to the negative terminal of the second battery 102 through the second switch S2_2, and the battery 10_2 is connected to the positive terminal of the second battery 102 in series with the electronic switch IGBT in the balancing unit 301 through the third switch S3_2, and so on, multiple batteries are connected in parallel, wherein a current sampling resistor R2 is arranged after each second switch (S2_1, S2_2, ..., S2_n-1) for sampling the loop current, and a thermistor RT1 can be arranged on the electronic switch of the balancing unit 301 to detect the temperature of the electronic switch IGBT.

[0045] like Figure 5 As shown, when the controller 40 determines that the absolute value of the voltage difference between the battery 10_1 to the battery 10_n-1 and the second battery 102 is greater than or equal to the preset threshold, the second switch (S2_1, S2_2, ..., S2_n-1) and the third switch (S3_1, S3_2, ..., S3_n-1) can be controlled to be closed, and the battery 10_1 to the battery 10_n-1 and the second battery 102 form a loop, and n batteries are connected in parallel. When the voltages of the batteries 10_1 to the battery 10_n-1 are all higher than the voltage of the second battery 102, the batteries 10_1 to the battery 10_n-1 discharge the second battery 102 through the formed loop. When the battery 10_1 to the battery 10_n-1 are connected to the second battery 102, the battery 10_1 to the battery 10_n-1 discharges the second battery 102 through the formed loop. When the voltages of the batteries in batteries 10_1 to 10_n-1 are all lower than the voltage of the second battery 102, the second battery 102 discharges the batteries in batteries 10_1 to 10_n-1 through the formed loop. In addition, when the voltages of the batteries in batteries 10_1 to 10_n are not equal and the absolute value of the voltage difference is greater than or equal to a preset threshold, the batteries with high voltage in batteries 10_1 to 10_n-1 discharge the batteries with low voltage, that is, after n batteries are connected in parallel, the high voltage battery discharges the low voltage battery through the loop formed, and the loop current and the temperature of the electronic switch are collected during the discharge process, and the loop current is controlled by the aforementioned adjustment method of the duty cycle of the electronic switch.

[0046] like Figure 6 The schematic diagram is shown as a schematic diagram of two power batteries. If the first battery 101 and the second battery 102 are connected by Figure 1After the series charging method shown in (a) is completed, the voltage of the first battery 101 is greater than the voltage of the second battery 102. The controller 40 can control the second switch S2 and the third switch S3 to close after the series charging is completed, and control the electronic switch IGBT to be turned on to form a loop, so that the first battery 101 discharges the second battery 102 through the loop. Of course, if the voltage of the second battery 102 is greater than the voltage of the first battery 101, the second battery 102 can discharge the first battery 101 through the loop.

[0047] like Figure 7 As shown, in Figure 5 On the basis of the circuit structure of the loop formed by the n batteries shown, the switching module 30 also includes a fourth switch S4, a sixth switch S6 and an eighth switch S8, the eighth switch S8 is connected in parallel at both ends of the balancing unit 301, and the common node of the balancing unit 301 and the third switch S3 (S3_1, S3_2, ..., S3_n-1) is connected to the positive terminal HV+ of the load port through the sixth switch S6, and the common node of the second battery 102 and the second switch (S2_1, S2_2, ..., S2_n-1) is connected to the negative terminal HV- of the load port through the fourth switch S4.

[0048] like Figure 7 As shown, when the controller 40 is not charged (including parallel and series charging) and has not received a power-on instruction, if the absolute value of the voltage difference between the battery 10_1 to the battery 10_n-1 and the second battery 102 is greater than or equal to the preset threshold, the controller 40 first controls the second switch (S2_1, S2_2, ..., S2_n-1) and the third switch (S3_1, S3_2, ..., S3_n-1) to be closed, and controls the electronic switch IGBT to be turned on, and n batteries are connected in parallel to form a loop, and the battery with a higher voltage among the n batteries discharges to the battery with a lower voltage. For example, the battery with a higher voltage than the second battery 102 among the batteries 10_1 to the battery 10_n-1 discharges to the second battery 102 until the voltage difference is less than the preset threshold, and then the electronic switch IGBT is controlled to be turned off, thereby achieving active balancing of the battery voltages. If the voltages of n batteries have been actively balanced through the electronic switch IGBT after charging is completed, when the controller 40 receives a power-on command, the controller 40 can control the second switch (S2_1, S2_2, ..., S2_n-1), the third switch (S3_1, S3_2, ..., S3_n-1), the fourth switch S4, the sixth switch S6 and the eighth switch S8 to close, so that the n batteries are connected in parallel to power on the load ports (HV+, HV-).

[0049] In a preferred embodiment, Figure 8 As shown, in Figure 7On the basis of the circuit structure shown, the switching module 30 also includes a pre-charging resistor R1 and a seventh switch S7. The pre-charging resistor R1 and the seventh switch S7 are connected in series and then connected in parallel at both ends of the sixth switch S6. The controller 40 is used to control the second switch S2_1 to S2_n-1, the third switch S3_1 to S3_n-1, the fourth switch S4, the eighth switch S8 and the seventh switch S7 to be closed when receiving the power-on instruction, if the absolute value of the voltage difference between the battery 10_1 to the battery 10_n-1 and the second battery 102 is less than the preset threshold, so that the battery 10_1 to the battery 10_n-1 and the second battery 102 are connected in parallel to pre-power on the load port (HV+, HV-). After the voltage of the load port (HV+, HV-) meets the preset voltage, the sixth switch S6 is controlled to be closed and the seventh switch S7 is controlled to be opened. The pre-charging resistor R1 can reduce the current of pre-powering on the load port, so as to avoid directly closing the sixth switch S6. The power-on current is too large to damage each switch in the switching module 30.

[0050] Fig. 9 This is a schematic diagram of the circuit structure when there are two batteries. Fig. 9 In the power battery system shown in FIG. 1 , the battery voltage is actively balanced when not charging (including parallel and series charging) and no power-on command is received, and the control process of each switch when powering on is the same as that of FIG. Figure 7 and Figure 8 Similar, please refer to Figure 7 and Figure 8 The control of each switch during the power-on process will not be described in detail here.

[0051] like Fig.10 FIG. 1 is a schematic diagram of a circuit structure in which n batteries are charged in series in a power battery system according to an embodiment of the present invention. Specifically, Fig.10 As shown, the number of batteries 10 is n, and the switching module 30 includes a first switch S1, a fourth switch S4, and a fifth switch S5. The first to nth batteries are sequentially connected in series, and the positive terminal of the first battery in the series-connected batteries is connected to the positive terminal DC+ of the charging port through the fifth switch S5, and the negative terminal of the nth battery in the series-connected batteries is connected to the negative terminal DC- of the charging port through the fourth switch S4, wherein the negative terminal of the n-1th battery is connected to the positive terminal of the nth battery through the first switch S1, and n is a positive integer greater than or equal to 2. Fig.10 As shown, when the controller 40 detects that the charging port (DC+, DC-) is connected to the charging device, it determines the charging mode of the charging device. When the charging mode is high-voltage fast charging, it controls the first switch S1, the fourth switch S4 and the fifth switch S5 to be closed, so that n batteries are connected in series to the charging port (DC+, DC-) to achieve high-voltage fast charging.

[0052] like Fig.11FIG. 1 is a schematic diagram of a circuit structure in which n batteries are charged in series and supply power to a load port in a power battery system according to an embodiment of the present invention. Specifically, Fig.11 As shown, in Fig.10 Based on the circuit structure shown in FIG. 1 , the positive terminal of the nth battery is also connected to the positive terminal HV+ of the load port, and the negative terminal HV- of the load port is connected to the negative terminal of the nth battery through the fourth switch S4. Fig.11 As shown, the 1st to nth batteries are connected in series to the charging port (DC+, DC-), and the positive terminal of the nth battery is connected to the positive terminal HV+ of the load port. During the charging process, after the n-1th battery, the charging current is divided into two paths (such as Fig.11 One way flows into the load port HV+, and the other way flows into the nth battery for charging, thereby realizing power supply to the load port at the same time during series charging.

[0053] like Fig.11 As shown, the 1st to nth batteries are connected in series to the charging port (DC+, DC-), the charging current of the nth battery is less than the charging current of the 1st to n-1th batteries, and after charging, the voltage of the nth battery is less than the voltage of the 1st to n-1th batteries. When n batteries are required to be connected in parallel to supply power to the load port, the voltage of the 1st to n-1th batteries is greater than the voltage of the nth battery, and a loop can be formed through the above (such as Figure 5 , Figure 7 , Figure 8 The control process of forming a loop balances the voltages of n batteries, and after the voltages are balanced, the n batteries are connected in parallel to supply power to the load port.

[0054] like Fig.12 As shown, in Fig.11On the basis of the circuit structure shown in the figure, the balancing unit 301 also includes a unidirectional diode D1, and the nth battery is connected to the positive terminal HV+ of the load port through the unidirectional diode D1, wherein the anode of the unidirectional diode D1 is connected to the positive terminal of the nth battery. By setting the unidirectional diode D1, a certain voltage difference can be formed between the 1st to n-1th batteries and the nth battery after the charging is completed, and the loop cannot be formed for balancing or the balancing time is too short due to damage of the electronic switch, resulting in failure to effectively balance and reduce the voltage difference. When the power-on instruction is received, it must be connected in parallel In the case of discharging the load, the unidirectional diode D1 is used to conduct unidirectionally, so that when the 1st to n-1th batteries are connected in parallel to the load port with the nth battery, the 1st to n-1th batteries are prevented from discharging the nth battery due to excessive voltage. The load port is first powered by the 1st to n-1th batteries. When the voltage of the 1st to n-1th batteries and the voltage of the nth battery meet the conduction threshold of the unidirectional diode D1, the unidirectional diode D1 is turned on, and the 1st to n-1th batteries and the nth battery jointly power the load port.

[0055] Specifically, Fig.13 As shown, the switching module 30 also includes a sixth switch S6 and n-1 second switches S2 (S2_1, S2_2, ..., S2_n-1) and a third switch S3 (S3_1, S3_2, ..., S3_n-1), the negative terminal of each battery from the first battery to the n-1th battery is connected to the negative terminal of the nth battery through a second switch S2, the positive terminal of each battery from the first battery to the n-1th battery is connected to the cathode of the unidirectional diode D1 through a third switch S3, and the cathode of the unidirectional diode D1 is connected to the positive terminal HV+ of the load port through the sixth switch S6. The controller 40 is also used to control the second switch S2 (S2_1, S2_2, ..., S2_n-1), the third switch S3 (S3_1, S3_2, ..., S3_n-1), the fourth switch S4 and the sixth switch S6 to close when receiving a power-on instruction, so that the power supply is turned on through Fig.12In the manner shown, when the voltage of the first battery to the n-1th battery is higher than the voltage of the nth battery after series charging, the first battery to the n-1th battery will first discharge to the load port during parallel discharge, and due to the effect of the unidirectional diode D1, the first battery to the n-1th battery will not discharge to the nth battery. When the voltage of the first battery to the n-1th battery and the nth battery meets the conduction threshold of the unidirectional diode D1, the unidirectional diode D1 is turned on, and the n batteries are discharged to the load port in parallel. When the series charging is completed and the electronic switch cannot be balanced (such as the electronic switch is damaged), or the balancing time is too short, resulting in the failure to effectively balance and reduce the voltage difference and receiving the power-on instruction to discharge in parallel to the load, it can be avoided that when the first to the n-1th battery is connected in parallel with the nth battery to the load port, the first to the n-1th battery discharges to the nth battery due to excessive voltage and excessive current to damage the circuit.

[0056] like Fig.14 As shown, in one embodiment, the battery in the power battery system includes a first battery 101 and a second battery 102, the switching module 30 includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, a seventh switch S7, an eighth switch S8 and a pre-charging resistor, the positive terminal of the first battery 101 is connected to the positive terminal of the charging port through the fifth switch S5, the negative terminal of the first battery 101 is connected to the positive terminal of the second battery 102 through the first switch S1, the negative terminal of the second battery 102 is connected to the negative terminal of the charging port and the negative terminal of the load port through the fourth switch S4, and the positive terminal of the first battery 101 is connected to the negative terminal of the charging port and the negative terminal of the load port through the third switch S4 in sequence. S3 and the sixth switch S6 are connected to the positive terminal of the load port, the pre-charging resistor R1 is connected in series with the seventh switch S7 and then connected in parallel to the two ends of the sixth switch S6, the eighth switch S8 is connected in parallel with the electronic switch in the balancing unit 301, the common node of the third switch S3 and the sixth switch S6 is connected to the positive terminal of the second battery 102 through the eighth switch S8 and the electronic switch after being connected in parallel, the negative terminal of the first battery 101 is also connected to the negative terminal of the second battery 102 through the second switch S2, and the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8 and the control end of the electronic switch are all connected to the controller 40.

[0057] The following combination Fig.14 The working principle of the power battery system of the embodiment of the present invention is further described, and the specific process is as follows:

[0058] (I) Series charging and simultaneous power supply

[0059] When the charging mode of the charging device connected to the charging port (DC+, DC-) is super fast charging, the controller 40 controls switches S1, S4, and S5 to close, and the first battery 101 and the second battery 102 are connected in series to the charging port (DC+, DC-) to achieve super fast charging.

[0060] When the load port HV+ needs to be powered during the series charging process, the switches S6 and S8 are controlled to be closed, so that the second battery 102 can power the load ports HV+ and HV- through the switches S8 and S6 during the series charging. Alternatively, when the diode is set to connect the collector and emitter of the switching tube IGBT, the control S6 is closed, so that the second battery 102 can power the load ports HV+ and HV- through the diode and the switch S6 during the series charging.

[0061] (2) Parallel charging

[0062] When the charging mode of the charging device connected to the charging port (DC+, DC-) is normal fast charging, the controller 40 controls switches S2, S3, S4, S5, and S8 to close, and the first battery 101 and the second battery 102 are connected in parallel to the charging port (DC+, DC-) for charging.

[0063] (III) Active voltage balancing

[0064] When not charging (including parallel and series charging) and no power-on command is received, the controller 40 can communicate with the BMS of the first battery 101 and the second battery 102, obtain the voltage of the first battery 101 and the second battery 102 and calculate the absolute value of the voltage difference. If the absolute value of the voltage difference is greater than a preset threshold, the controller 40 controls the switches S2 and S3 to close and controls the electronic switch IGBT to turn on, so that the first battery 101 and the second battery 102 form a loop. If the voltage of the first battery 101 is greater than the voltage of the second battery 102, the first battery 101 discharges the second battery 102. If the voltage of the first battery 101 is less than the voltage of the second battery 102, the controller 40 detects the loop current through the resistor R2 and the thermistor current through the thermistor current. The resistor RT1 detects the temperature of the electronic switch IGBT, and controls the duty cycle of the electronic switch IGBT according to at least one of the temperature and the loop current to adjust the size of the loop current until the absolute value of the voltage difference between the first battery 101 and the second battery 102 is less than the preset threshold value, and then controls the electronic switch IGBT to be disconnected, and controls the switches S2 and S3 to be disconnected, so that active balancing can be performed when there is a certain voltage difference between the batteries when they are not charged and discharged. For example, it may be a voltage difference caused by inconsistent battery aging performance, or when there is a battery voltage difference after charging is completed due to high-voltage series charging and simultaneous discharge to the load port, active voltage balancing can be achieved by controlling the electronic switch IGBT.

[0065] (IV) Power on the load port

[0066] When the controller 40 receives a power-on instruction for the load port (HV+, HV-), it first determines whether the absolute value of the voltage difference between the first battery 101 and the second battery 102 is greater than or equal to a preset threshold value. If not, the control switches S2, S3, S4, S7, and S8 are closed to pre-power on the load port (HV+, HV-). When the voltage of the load port (HV+, HV-) reaches the preset voltage, the control switch S6 is closed and the control switch S7 is opened to officially power on the load port (HV+, HV-).

[0067] If the voltage difference is greater than or equal to the preset threshold, the control switches S2, S3, S4, and S7 are closed, the voltage of the first battery 101 is higher than that of the second battery 102, and the first battery 101 pre-powers on the load port (HV+, HV-). When the voltage of the load port (HV+, HV-) reaches the preset voltage, the control switch S6 is closed and the control switch S7 is disconnected, and the load port (HV+, HV-) is officially powered on. The unidirectional conduction characteristic of the unidirectional diode D1 can prevent the first battery 101 from discharging the second battery 102. When the voltage difference between the first battery 101 and the second battery 102 meets the conduction threshold of the unidirectional diode D1, the switch S8 is closed, so that the first battery 101 and the second battery 102 are connected in parallel to discharge the load port (HV+, HV-).

[0068] It should be noted that although Fig.14 The invention only includes the first battery 101 and the second battery 102, but in practical applications, more than two batteries may be included, such as Figure 5 , Figure 7 , Figure 8 When there are more than two batteries, the control method of each switch can refer to Fig.14 The process of connecting the two batteries will not be described in detail here.

[0069] An embodiment of the present invention also provides an electric vehicle, which includes a power battery system provided by any of the aforementioned embodiments, wherein a load port in the power battery system is connected to an input terminal of a load of the electric vehicle so that the battery provides high voltage to the electric vehicle, and a charging port in the power battery system is arranged on the vehicle body to connect an external charging device.

[0070] Fig.15 A flow chart of a power battery system control method provided by an embodiment of the present invention, such as Fig.15 As shown, the power battery system control method includes:

[0071] S101 : when not charging and not receiving a power-on instruction, determining an absolute value of a voltage difference between at least two batteries.

[0072] like Figure 2 As shown, the power battery system includes at least two batteries 10, a switching module 30, a charging port (DC+, DCC-), a load port (HV+, HV-) and a controller 40. The battery 10 is connected to the charging port (DC+, DC-) and the load port (HV+, HV-) through the switching module 30. The switching module 30 is connected to the controller 40. The switching module 30 includes a balancing unit 301 provided with an electronic switch, and the controller 40 is connected to the control end of the electronic switch.

[0073] When not charging and no power-on command is received, the controller 40 may obtain the voltage of each battery 10 through a voltage detection module or communicate with the BMS of the battery, and calculate the absolute value of the voltage difference of each battery 10 .

[0074] S102: Determine whether the absolute value of the voltage difference is greater than or equal to a preset threshold.

[0075] Specifically, the absolute value of the voltage difference may be compared with a preset threshold. If the absolute value of the voltage difference is greater than or equal to the preset threshold, S103 may be executed. If not, it indicates that the voltages of the batteries 10 are relatively balanced and no voltage balancing operation is required.

[0076] S103, generating a pulse signal to control the electronic switch in the switching module to be turned on to connect at least two batteries, the at least two batteries form a loop through the electronic switch, and the battery with a higher voltage among the at least two batteries discharges to the battery with a lower voltage through the loop.

[0077] In one embodiment, Figure 4 As shown, the switching module 30 also includes a detection module 303, which is connected to the controller 40. The detection module 303 is used to collect loop parameters of the loop and output them to the controller 40. The controller 40 is used to adjust the duty cycle of the pulse signal according to the loop parameters to adjust the loop current in the loop.

[0078] Exemplarily, the detection module 303 includes at least one of a current sampling module and a temperature detection module, the current sampling module is used to collect the loop current in the loop, the temperature detection module is used to collect the temperature of the electronic switch, and the controller 40 is used to adjust the duty cycle of the pulse signal according to at least one of the loop current and the temperature.

[0079] like Figure 5As shown, the battery 10 includes n-1 first batteries 101 and one second battery 102, the switching module 30 includes second switches (S2_1, S2_2, ..., S2_n-1) and third switches (S3_1, S3_2, ..., S3_n-1) equal in number to the number of the first batteries 101, the negative terminal of each first battery 101 is connected to the negative terminal of the second battery 102 through a second switch, and the positive terminal of each first battery 101 is connected in series with the electronic switch IGBT in the balancing unit 301 through a third switch, and then connected to the positive terminal of the second battery 102, as shown in FIG. Figure 5 As shown, n is a positive integer greater than or equal to 2, and the n first batteries include batteries 10_1 to batteries 10_n-1, wherein the battery 10_1 is connected to the negative terminal of the second battery 102 through the second switch S2_1, and the battery 10_1 is connected to the positive terminal of the second battery 102 in series with the electronic switch IGBT in the balancing unit 301 through the third switch S3_1, and the battery 10_2 is connected to the negative terminal of the second battery 102 through the second switch S2_2, and the battery 10_2 is connected to the positive terminal of the second battery 102 in series with the electronic switch IGBT in the balancing unit 301 through the third switch S3_2, and the battery 10_2 is connected to the positive terminal of the second battery 102, and so on, multiple batteries are connected in parallel, wherein a current sampling resistor R2 is arranged after each second switch (S2_1, S2_2, ..., S2_n-1) for sampling the loop current, and a thermistor RT1 can be arranged on the electronic switch of the balancing unit 301 to detect the temperature of the electronic switch IGBT.

[0080] like Figure 5 As shown, when the controller 40 determines that the voltage difference between the battery 10_1 to the battery 10_n-1 and the second battery 102 is greater than or equal to the preset threshold, the second switch (S2_1, S2_2, ..., S2_n-1) and the third switch (S3_1, S3_2, ..., S3_n-1) can be controlled to be closed, and the battery 10_1 to the battery 10_n and the second battery 102 form a loop, and the battery 10_1 to the battery 10_n-1 with a voltage higher than the second battery 102 discharges the second battery 102 through the loop, or the second battery 102 discharges the battery 10_1 to the battery 10_n-1 with a lower voltage through the loop, or the high-voltage battery 101 to the battery 10_n-1 discharges the low-voltage battery, and the loop current and the temperature of the electronic switch are collected during the discharge process.

[0081] In one embodiment, in one embodiment, the controller 40 can determine whether the loop current is equal to the current threshold. When the loop current is equal to the current threshold, the duty cycle of the pulse signal can be kept unchanged. When the loop current is less than the current threshold, the duty cycle of the pulse signal is increased to increase the loop current in the loop to be equal to the current threshold. When the loop current is greater than the current threshold, the duty cycle of the pulse signal is reduced to reduce the loop current in the loop to be equal to the current threshold. The current threshold can be determined based on the performance of the components in the switching module 30. For example, the current threshold can be the minimum value of the maximum current that each component can withstand, so that the high-voltage battery can discharge the low-voltage battery with the maximum current, thereby increasing the speed at which the voltages of multiple batteries with voltage differences in the power battery system reach equilibrium, that is, increasing the speed at which the power battery system is powered on in parallel to the load port.

[0082] In one embodiment, the electronic switch is a semiconductor switch. When the electronic switch is turned on and off at high frequency and current flows through it, a large amount of heat is generated, which increases the temperature of the electronic switch. In order to prevent the electronic switch from being damaged by excessive temperature, the controller 40 can determine whether the temperature is equal to the temperature threshold. When the temperature is equal to the temperature threshold, the duty cycle of the pulse signal is kept unchanged. When the temperature is greater than the temperature threshold, the duty cycle of the pulse signal is reduced to reduce the loop current in the loop, so that the temperature of the electronic switch is reduced until the temperature is equal to the temperature threshold. When the temperature is less than the temperature threshold, the duty cycle of the pulse signal can be increased to increase the loop current in the loop until the temperature is equal to the temperature threshold. The temperature threshold can be determined according to the performance of the electronic switch. For example, the temperature threshold can be the maximum operating temperature specified in the specification of the electronic switch. Under the premise of ensuring that the electronic switch operates within a safe temperature range, the high-voltage battery can discharge the low-voltage battery with a larger current, thereby increasing the speed at which the voltages of multiple batteries with voltage differences in the power battery system reach equilibrium, that is, increasing the speed at which the load port of the power battery system is powered on in parallel.

[0083] In one embodiment, the controller 40 can control the electronic switch according to the loop current and temperature at the same time. Specifically, the controller can determine whether the temperature is equal to the temperature threshold, keep the duty cycle of the pulse signal unchanged when the temperature is equal to the temperature threshold, reduce the duty cycle of the pulse signal when the temperature is greater than the temperature threshold to reduce the loop current in the loop, reduce the temperature to the temperature threshold, determine whether the loop current is equal to the current threshold when the temperature is less than the temperature threshold, keep the duty cycle of the pulse signal unchanged when the loop current is equal to the current threshold, increase the duty cycle of the pulse signal when the loop current is less than the current threshold to increase the loop current in the loop, and return to the step of determining whether the temperature is equal to the temperature threshold, reduce the duty cycle of the pulse signal when the loop current is greater than the current threshold to reduce the loop current in the loop, and return to the step of determining whether the temperature is equal to the temperature threshold. The loop current can be maximized while ensuring the safe operation of the electronic switch, which not only ensures the safe operation of the electronic switch, but also improves the efficiency of battery voltage balancing.

[0084] It should be noted that, for the method embodiment, since it is basically similar to the power battery system embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the power battery system embodiment.

[0085] The power battery system control method provided by the embodiment of the present invention is applied to the power battery system control system provided by the embodiment of the present invention, so that the power battery system control method has corresponding beneficial effects.

[0086] In the description of this specification, the description with reference to the terms "an embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0087] In addition, it should be understood that although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0088] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the scope of protection of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods will fall within the scope of protection of the present invention.

Claims

1. A power battery system, characterized in that: include: At least two batteries (10), a switching module (30), a charging port, a load port and a controller (40), wherein the battery is connected to the charging port and the load port via the switching module (30), the switching module (30) is connected to the controller (40), the switching module (30) comprises a balancing unit (301) provided with an electronic switch, the controller (40) is connected to a control end of the electronic switch, and the controller (40) is used to: When not charging and not receiving a power-on instruction, determining an absolute value of a voltage difference between the at least two batteries; Determining whether the absolute value of the voltage difference is greater than or equal to a preset threshold; If so, a pulse signal is generated to control the electronic switch in the switching module (30) to be turned on to connect the at least two batteries, the at least two batteries form a loop through the electronic switch, and the battery with a higher voltage among the at least two batteries discharges to the battery with a lower voltage through the loop.

2. The power battery system according to claim 1, characterized in that: The switching module (30) further comprises a driver (302), the controller (40) is connected to the control end of the electronic switch via the driver (302), and the controller (40) is used to: A pulse signal is generated and output to the driver (302), and the driver (302) is used to adjust the driving voltage of the control end of the electronic switch according to the pulse signal.

3. The power battery system according to claim 1, characterized in that: The switching module (30) further comprises a detection module (303), wherein the detection module (303) is connected to the controller (40), and the detection module (303) is used to collect loop parameters of the loop and output them to the controller (40), and the controller (40) is used to: The duty cycle of the pulse signal is adjusted according to the loop parameter to adjust the loop current in the loop.

4. The power battery system according to claim 3, characterized in that: The detection module (303) comprises at least one of a current sampling module and a temperature detection module, the current sampling module is used to collect the loop current in the loop, the temperature detection module is used to collect the temperature of the electronic switch, and the controller (40) is used to: The duty cycle of the pulse signal is adjusted according to at least one of the loop current and the temperature.

5. The power battery system according to claim 4, characterized in that: The detection module (303) comprises a current sampling module, the current sampling module is used to collect the loop current in the loop, and the controller (40) is specifically used to: Determining whether the loop current is equal to a current threshold; When the loop current is equal to the current threshold, maintaining the duty cycle of the pulse signal unchanged; When the loop current is less than the current threshold, increasing the duty cycle of the pulse signal to increase the loop current in the loop to be equal to the current threshold; When the loop current is greater than the current threshold, the duty cycle of the pulse signal is reduced to reduce the loop current in the loop to be equal to the current threshold.

6. The power battery system according to claim 4, characterized in that: The detection module (303) comprises a temperature detection module, and the temperature detection module is used to collect the temperature of the electronic switch. The controller (40) is specifically used to: Determining whether the temperature is equal to a temperature threshold; When the temperature is equal to the temperature threshold, maintaining the duty cycle of the pulse signal unchanged; When the temperature is greater than the temperature threshold, reducing the duty cycle of the pulse signal to reduce the loop current in the loop and reduce the temperature to the temperature threshold; When the temperature is less than the temperature threshold, the duty cycle of the pulse signal is increased to increase the loop current in the loop and to increase the temperature to the temperature threshold.

7. The power battery system according to claim 4, characterized in that: The detection module (303) comprises a current sampling module and a temperature detection module, wherein the current sampling module is used to collect the loop current in the loop, and the temperature detection module is used to collect the temperature of the electronic switch. The controller (40) is specifically used to: Determining whether the temperature is equal to a temperature threshold; When the temperature is equal to the temperature threshold, maintaining the duty cycle of the pulse signal unchanged; When the temperature is greater than the temperature threshold, reducing the duty cycle of the pulse signal to reduce the loop current in the loop and reduce the temperature to the temperature threshold; When the temperature is less than the temperature threshold, determining whether the loop current is equal to a current threshold; When the loop current is equal to the current threshold, maintaining the duty cycle of the pulse signal unchanged; When the loop current is less than the current threshold, increasing the duty cycle of the pulse signal to increase the loop current in the loop, and returning to the step of determining whether the temperature is equal to the temperature threshold; When the loop current is greater than the current threshold, the duty cycle of the pulse signal is reduced to reduce the loop current in the loop, and the process returns to the step of determining whether the temperature is equal to the temperature threshold.

8. The power battery system according to claim 1, characterized in that: The battery comprises at least one first battery (101) and one second battery (102); the switching module (30) comprises a number of second switches (S2) and third switches (S3) equal to the number of the first batteries (101); the negative terminal of each first battery (101) is connected to the negative terminal of the second battery (102) via one of the second switches (S2); the positive terminal of each first battery (101) is connected to the positive terminal of the second battery (102) via one of the third switches (S3) and the electronic switch in the balancing unit (301) in series.

9. The power battery system according to claim 8, characterized in that: The controller (40) is used to: If the voltage difference is greater than or equal to a preset threshold, the second switch (S2) and the third switch (S3) connected to the first battery (101) are controlled to be closed.

10. The power battery system according to claim 8, characterized in that: The switching module (30) further comprises a fourth switch (S4), a sixth switch (S6) and an eighth switch (S8); the eighth switch (S8) is connected in parallel to both ends of the balancing unit (301); a common node between the balancing unit (301) and the third switch (S3) is connected to the positive terminal of the load port via the sixth switch (S6); and a common node between the second battery (102) and the second switch (S2) is connected to the negative terminal of the load port via the fourth switch (S4).

11. The power battery system according to claim 10, characterized in that: The switching module (30) further comprises a pre-charging resistor (R1) and a seventh switch (S7); the pre-charging resistor (R1) and the seventh switch (S7) are connected in series and then connected in parallel at both ends of the sixth switch (S6).

12. The power battery system according to claim 10, characterized in that: The controller (40) is also used for: If the absolute value of the voltage difference is greater than or equal to a preset threshold, upon receiving a power-on instruction, controlling the second switch (S2) and the third switch (S3) connected to the first battery (101) to be closed; Determining whether the absolute value of the voltage difference is less than a preset threshold; If so, the second switch (S2), the third switch (S3), the fourth switch (S4), the sixth switch (S6) and the eighth switch (S8) are controlled to be closed.

13. The power battery system according to claim 1, characterized in that: The number of the batteries (10) is n, and the switching module (30) comprises a first switch (S1), a fourth switch (S4) and a fifth switch (S5). The first to nth batteries (10) are sequentially connected in series, and the positive terminal of the first battery in the series-connected batteries (10) is connected to the positive terminal of the charging port through the fifth switch (S5), and the negative terminal of the nth battery in the series-connected batteries (10) is connected to the negative terminal of the charging port through the fourth switch (S4), wherein the negative terminal of the n-1th battery is connected to the positive terminal of the nth battery through the first switch (S1), and n is a positive integer greater than or equal to 2.

14. The power battery system according to claim 13, characterized in that: The balancing unit (301) further comprises a unidirectional diode, the positive terminal of the nth battery is connected to the positive terminal of the load port via the unidirectional diode, the negative terminal of the nth battery is connected to the negative terminal of the load port via the fourth switch (S4), wherein the anode of the unidirectional diode is connected to the positive terminal of the nth battery.

15. The power battery system according to claim 14, characterized in that: The switching module (30) further comprises a sixth switch (S6) and n-1 second switches (S2) and third switches (S3), the negative terminal of each battery from the first battery to the n-1th battery is connected to the negative terminal of the nth battery via one of the second switches (S2), the positive terminal of each battery from the first battery to the n-1th battery is connected to the cathode of the unidirectional diode via one of the third switches (S3), the cathode of the unidirectional diode is connected to the positive terminal of the load port via the sixth switch (S6), and the controller (40) is further used for: When a power-on instruction is received, the second switch (S2), the third switch (S3), the fourth switch (S4) and the sixth switch (S6) are controlled to be closed.

16. The power battery system according to claim 1, characterized in that: The battery comprises a first battery (101) and a second battery (102); the switching module (30) comprises a first switch (S1), a second switch (S2), a third switch (S3), a fourth switch (S4), a fifth switch (S5), a sixth switch (S6), a seventh switch (S7), an eighth switch (S8) and a pre-charging resistor; the positive terminal of the first battery (101) is connected to the positive terminal of the charging port through the fifth switch (S5); the negative terminal of the first battery (101) is connected to the positive terminal of the second battery (102) through the first switch (S1); the negative terminal of the second battery (102) is connected to the negative terminal of the charging port and the negative terminal of the load port through the fourth switch (S4); the positive terminal of the first battery (101) is connected to the positive terminal of the charging port and the negative terminal of the load port through the third switch (S3) and the sixth switch (S6) in sequence; ) is connected to the positive terminal of the load port, the pre-charging resistor (R1) is connected in series with the seventh switch (S7) and then connected in parallel to the two ends of the sixth switch (S6), the eighth switch (S8) is connected in parallel to the electronic switch in the balancing unit (301), the common node of the third switch (S3) and the sixth switch (S6) is connected to the positive terminal of the second battery (102) through the eighth switch (S8) and the electronic switch after being connected in parallel, the negative terminal of the first battery (101) is also connected to the negative terminal of the second battery (102) through the second switch (S2), and the first switch (S1), the second switch (S2), the third switch (S3), the fourth switch (S4), the fifth switch (S5), the sixth switch (S6), the seventh switch (S7), the eighth switch (S8) and the control end of the electronic switch are all connected to the controller (40).

17. An electric vehicle, characterized in that: A power battery system comprising any one of claims 1-16.

18. A power battery system control method, characterized in that: A power battery system according to any one of claims 1 to 16, the power battery system comprising at least two batteries (10), a switching module (30), a charging port, a load port and a controller (40), the battery being connected to the charging port and the load port via the switching module (30), the switching module (30) being connected to the controller (40), the switching module (30) comprising a balancing unit (301) provided with an electronic switch, the controller (40) being connected to a control end of the electronic switch, the power battery system control method comprising: When not charging and not receiving a power-on instruction, determining an absolute value of a voltage difference between the at least two batteries; Determining whether the absolute value of the voltage difference is greater than or equal to a preset threshold; If so, a pulse signal is generated to control the electronic switch in the switching module (30) to be turned on to connect the at least two batteries, the at least two batteries form a loop through the electronic switch, and the battery with a higher voltage among the at least two batteries discharges to the battery with a lower voltage through the loop.

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