Battery heating method, system, and vehicle

Abstract

The present disclosure relates to a battery heating method, system and vehicle, which comprises the following steps: when it is determined to start battery heating, the specified switch is controlled to be closed, and the target current amplitude and target frequency range of the heating current required for battery heating are obtained; in each frequency adjustment period, the current target heating current frequency is determined in an incremental and / or decremental manner, wherein the target heating current frequency belongs to the target frequency range; and the motor controller is controlled according to the target current amplitude and the target heating current frequency, so that the first battery pack and the second battery pack are alternately charged and discharged, thereby achieving the heating of the power battery. Since the frequency of the alternating current used for battery heating can be increased and / or decreased within the target frequency range, the superposition of the same frequency magnetic field intensity can be effectively reduced, and the external radiation magnetic field intensity during the battery heating process can be reduced.

Description

Technical Field

[0001] This disclosure relates to the field of battery heating technology, specifically to a battery heating method, system, and vehicle. Background Technology

[0002] With the development of new energy vehicle technology, users' demands for the experience of new energy vehicles are also increasing. As is well known, vehicle power batteries are typically lithium-ion batteries, which are highly sensitive to low temperatures. At low temperatures, the internal resistance of lithium-ion batteries increases sharply, significantly limiting their discharge capacity and charge / discharge performance. This can easily lead to insufficient power performance and a significantly shortened driving range in low-temperature environments. Furthermore, power batteries are almost impossible to charge below -20°C; forcibly charging them can easily cause internal short circuits, creating safety hazards. Therefore, it is necessary to heat the power battery to raise its temperature, thereby minimizing the impact of cold conditions on the performance of electric vehicles.

[0003] However, current battery heating methods typically only consider battery heating efficiency, neglecting the problem that the battery heating process can cause excessive external radiated magnetic field strength. Summary of the Invention

[0004] The purpose of this disclosure is to provide a battery heating method, system, and vehicle.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a battery heating method applied to a designated controller in a battery heating system. The battery heating system includes a power battery, a motor controller, a motor, a designated switch, and the designated controller. The power battery is formed by connecting a first battery pack and a second battery pack in series. The motor controller includes a multi-phase bridge arm, and the motor includes multi-phase windings. The midpoint of each phase bridge arm is connected to the first end of a phase winding. The second ends of each phase winding in the multi-phase windings are connected together and then connected to the first end of the designated switch. The second end of the designated switch is connected between the first battery pack and the second battery pack. The first busbar of the multi-phase bridge arm is connected to the positive terminal of the first battery pack, and the second busbar of the multi-phase bridge arm is connected to the negative terminal of the second battery pack. The method includes:

[0006] If it is determined that battery heating should be started, the designated switch is controlled to close, and the target current amplitude and target frequency range of the heating current required for battery heating are obtained;

[0007] Within each frequency adjustment cycle, the current target heating current frequency is determined in an incremental and / or decremental manner, wherein the target heating current frequency belongs to the target frequency range;

[0008] The motor controller is controlled according to the target current amplitude and the target heating current frequency to make the first battery pack and the second battery pack alternately charge and discharge, thereby heating the power battery.

[0009] Optionally, obtaining the target current amplitude and target frequency range of the heating current required for battery heating includes:

[0010] Obtain the first maximum charge / discharge current of the first battery pack and the second maximum charge / discharge current of the second battery pack within a preset historical time period.

[0011] Obtain the current ambient temperature, and at the current ambient temperature, the first impedance of the first battery pack and the second impedance of the second battery pack;

[0012] The target frequency range is determined based on the current ambient temperature, the first impedance, and the second impedance.

[0013] The target current amplitude is determined based on the first maximum charge / discharge current and the second maximum charge / discharge current.

[0014] Optionally, determining the target frequency range based on the current ambient temperature, the first impedance, and the second impedance includes:

[0015] The first current frequency corresponding to the fastest temperature rise rate of the first battery pack is determined based on the current ambient temperature and the first impedance.

[0016] The second current frequency corresponding to the fastest temperature rise rate of the second battery pack is determined based on the current ambient temperature and the second impedance.

[0017] The heating current frequency at which the power battery currently heats up the fastest is determined based on the first current frequency and the second current frequency.

[0018] The target frequency range is determined based on the heating current frequency at which the power battery currently heats up the fastest.

[0019] Optionally, determining the heating current frequency that determines the fastest heating rate of the power battery based on the first current frequency and the second current frequency includes:

[0020] The larger of the first current frequency and the second current frequency is taken as the heating current frequency with the fastest current heating rate of the power battery.

[0021] Optionally, determining the target frequency range based on the heating current frequency at the current fastest heating rate of the power battery includes:

[0022] Obtain the number of phases containing windings in the motor;

[0023] The target frequency range is obtained by taking half of the heating current frequency as the lower limit of the target frequency range and the product of the number of phases and the lower limit as the upper limit of the target frequency range.

[0024] Optionally, determining the target current amplitude based on the first maximum charge / discharge current and the second maximum charge / discharge current includes:

[0025] The smaller of the first maximum charge / discharge current and the second maximum charge / discharge current is taken as the target current amplitude.

[0026] Optionally, determining the current target heating current frequency in an incremental and / or decremental manner within each frequency adjustment cycle includes:

[0027] Within each frequency adjustment cycle, the target heating current frequency is determined by first increasing the starting frequency with the lower limit of the target frequency range and incrementing by the first increment value; then, the target heating current frequency is determined by decreasing the starting frequency with the upper limit of the target frequency range and decrementing by the second increment value; or

[0028] Within each frequency adjustment cycle, the target heating current frequency is determined by first decreasing the starting frequency with the upper limit of the target frequency range and then decreasing it with a second step value. The target heating current frequency is then determined by increasing the starting frequency with the lower limit of the target frequency range and then increasing it with a first step value.

[0029] Optionally, determining to activate battery heating includes:

[0030] If it is determined that the vehicle is in a non-faulty state, in response to determining that the vehicle is in a parked state, the first temperature of the first battery pack and the second temperature of the second battery pack are obtained.

[0031] If the first temperature and / or the second temperature is greater than a preset temperature threshold, battery heating is activated.

[0032] A second aspect of this disclosure provides a battery heating system, including a power battery, a motor controller, a motor, a designated switch, and a designated controller. The power battery is formed by connecting a first battery pack and a second battery pack in series. The motor controller includes a multi-phase bridge arm, and the motor includes multi-phase windings. The midpoint of each phase bridge arm is connected to the first end of a phase winding. The second ends of each phase winding in the multi-phase winding are connected together and then connected to the first end of the designated switch. The second end of the designated switch is connected between the first battery pack and the second battery pack. The first busbar of the multi-phase bridge arm is connected to the positive terminal of the first battery pack, and the second busbar of the multi-phase bridge arm is connected to the negative terminal of the second battery pack.

[0033] The designated controller is used to implement the battery heating method described in the first aspect above.

[0034] A third aspect of this disclosure provides a vehicle that includes the battery heating system described in the second aspect above.

[0035] The above technical solution enables the closing of a designated switch when battery heating is initiated, and the target current amplitude and target frequency range of the heating current required for battery heating are obtained. Within each frequency adjustment cycle, the current target heating current frequency is determined by increasing and / or decreasing. This target heating current frequency falls within the target frequency range. The motor controller is then controlled based on the target current amplitude and target heating current frequency to heat the power battery. Because the frequency of the AC power used for battery heating can increase and / or decrease within this target frequency range, the superposition of magnetic field strengths at the same frequency can be effectively reduced, thus effectively lowering the magnetic field strength radiated externally during the battery heating process.

[0036] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0038] Figure 1 This is a block diagram illustrating a battery heating system according to an exemplary embodiment of the present disclosure;

[0039] Figure 2 This is a schematic diagram of a battery heating circuit shown in an exemplary embodiment of the present disclosure;

[0040] Figure 3 This is a flowchart illustrating a battery heating method according to an exemplary embodiment of the present disclosure;

[0041] Figure 4 It is based on Figure 3 The illustrated embodiment shows a flowchart of a battery heating method;

[0042] Figure 5 This is a schematic diagram illustrating a method for determining the frequency of a target heating current, as shown in an exemplary embodiment of this disclosure.

[0043] Figure 6 This is a schematic diagram illustrating a method for determining the frequency of a target heating current, as shown in another exemplary embodiment of this disclosure;

[0044] Figure 7 This is a schematic diagram illustrating the external electromagnetic radiation intensity at N points, as shown in an exemplary embodiment of this disclosure;

[0045] Figure 8 It is based on Figure 4 The illustrated embodiment shows a flowchart of a battery heating method. Detailed Implementation

[0046] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0047] Before detailing the specific embodiments of this disclosure, the application scenarios of this disclosure are first explained below. This disclosure can be applied to battery heating scenarios, such as heating power batteries in vehicles and heating batteries in electronic devices in low-temperature environments. Here, we take the heating process of power batteries in vehicles as an example. Currently, commonly used power battery heating methods include external heating and internal heating. External heating uses a PTC (Positive Temperature Coefficient) heater or a heating wire heater to heat the coolant in the battery cooling circuit at low temperatures, thereby heating the battery cells to a predetermined temperature. Internal heating utilizes motor inductance and motor controller bridge arms to achieve self-heating. By adjusting the amplitude and frequency of the self-heating AC current, the heat generated in the self-heating process can be efficiently adjusted. Compared with external heating, it has a higher heating speed and more uniform heating, and it does not require external heating hardware, simplifying the topology and reducing costs. Therefore, internal heating is more widely studied. However, current internal heating methods often suffer from the problem of excessive external radiated magnetic field strength during the heating process.

[0048] To achieve the above objectives, this disclosure provides a battery heating method, system, and vehicle. The battery heating method can increase and / or decrease the frequency of the alternating current used for battery heating within the target frequency range, thereby effectively reducing the superposition of magnetic field strength at the same frequency and thus effectively reducing the magnetic field strength radiated to the outside during the battery heating process.

[0049] The technical solution of this disclosure will be described in detail below with reference to specific embodiments.

[0050] Figure 1 This is a block diagram illustrating an exemplary embodiment of a battery heating system, such as... Figure 1 As shown, the battery heating system includes a power battery 101, a motor controller 102, a motor 103, a designated switch 104, and a designated controller 105. The power battery 101 is formed by connecting a first battery pack 1011 and a second battery pack 1012 in series. The motor controller 102 includes a multi-phase bridge arm, and the motor 103 includes a multi-phase winding. The midpoint of each phase bridge arm is connected to the first end of a phase winding. The second end of each phase winding in the multi-phase winding is connected to the first end of the designated switch 104. The second end of switch 104 is connected between the first battery pack 1011 and the second battery pack 1012 (i.e., the second end of the designated switch 104 is connected to the midpoint of the first battery pack 1011 and the second battery pack 1012). The first bus terminal of the multiphase bridge arm is connected to the positive terminal of the first battery pack 1011, and the second bus terminal of the multiphase bridge arm is connected to the negative terminal of the second battery pack 1012. That is, the first bus terminal and the second bus terminal of the multiphase bridge arm are respectively connected to the positive terminal and the negative terminal of the power battery 101.

[0051] The designated switch 104 can be a contactor, a relay, or other automatic control switch. The designated controller 105 can be a vehicle controller or another control unit in the vehicle besides the vehicle controller. The motor controller 102 can be a reversible PWM rectifier. The number of bridge arms in the motor controller 102 is the same as the number of phases in the windings of the motor 103. The motor 103 can be a three-phase, five-phase, six-phase, or nine-phase permanent magnet synchronous motor, or a three-phase or higher asynchronous motor. Each phase winding can include n coil branches. The n coil branches of each phase winding are connected to form a phase endpoint. One coil branch of each phase winding is also connected to one coil branch of another phase winding to form n connection points. Figure 2 As shown, Figure 2This is a schematic diagram of a battery heating circuit according to an exemplary embodiment of the present disclosure. The motor controller 102 includes three bridge arms, and the motor 103 is a three-phase motor, including four sets of three-phase windings. The first set of windings includes coil branches A1, B1, and C1; the second set of windings includes coil branches A2, B2, and C2; the third set of windings includes coil branches A3, B3, and C3; and the fourth set of windings includes coil branches A4, B4, and C4. Each of the four coil branches (A1, A2, A3, and A4) of the A-phase winding is also connected to one coil branch of the other phase winding to form connection points a1, a2, a3, and a4. The designated controller 105 can obtain the current required by each phase of the motor by adjusting the PWM duty cycle of each phase bridge arm in the motor controller 102. It should be noted that controlling the current intensity in each phase winding of the motor by adjusting the duty cycle is a relatively mature technical solution in the prior art, and since the focus of this disclosure is not on this, this disclosure does not limit it.

[0052] Figure 3 This is a flowchart illustrating a battery heating method according to an exemplary embodiment of this disclosure; as shown below. Figure 3 As shown, this battery heating method can be achieved by... Figure 1 The designated controller 105 in the battery heating system shown executes, such as Figure 3 As shown, the battery heating method may include:

[0053] Step 301: If it is determined that battery heating will be started, control the designated switch to close, and obtain the target current amplitude and target frequency range of the heating current required for battery heating.

[0054] In this step, the implementation method for determining the start of battery heating may be as follows: when it is determined that the vehicle is in a non-faulty state, in response to determining that the vehicle is in a parked state, a first temperature of the first battery pack and a second temperature of the second battery pack are obtained; when the first temperature and / or the second temperature are greater than a preset temperature threshold, it is determined that battery heating is started.

[0055] It should be noted that temperature sensors can be installed in the first and second battery packs to obtain the first and second temperatures. The above-described method for determining that the vehicle is in a non-faulty state can be as follows: if it is determined that the CAN communication is normal, the temperatures of the power battery, motor windings, and electronic control power switching devices are normal, and no hardware faults are detected in the vehicle control unit, battery system, or electronic control system, then the vehicle is determined to be in a non-faulty state.

[0056] Furthermore, the implementation method for obtaining the target current amplitude and target frequency range of the heating current required for battery heating in this step can be as follows: Figure 4 ( Figure 4 It is based on Figure 3 The flowchart shown in the embodiment illustrates a battery heating method, which includes:

[0057] S1, obtain the first maximum charge / discharge current of the first battery pack and the second maximum charge / discharge current of the second battery pack within a preset historical time period.

[0058] The battery management system can store the charging and discharging data of the first and second battery packs within a specified time period. This charging and discharging data typically includes information such as charging and discharging current, voltage status, and remaining power.

[0059] It should be noted that this step can obtain the first maximum charge / discharge current by obtaining the maximum charge / discharge current of the first battery pack within the preset historical time period from the battery management system; and obtain the maximum charge / discharge current of the second battery pack within the preset historical time period to obtain the second maximum charge / discharge current.

[0060] S2, obtain the current ambient temperature, and at the current ambient temperature, the first impedance of the first battery pack and the second impedance of the second battery pack.

[0061] The current ambient temperature can be obtained by an ambient temperature sensor. The first impedance and the second impedance can be pre-calibrated after experimental testing, or the impedance values ​​of the battery pack provided by the battery manufacturer at different temperatures can be obtained to determine the first impedance of the first battery pack and the second impedance of the second battery pack at the current ambient temperature.

[0062] S3, determine the target frequency range based on the current ambient temperature, the first impedance, and the second impedance.

[0063] In this step, a first current frequency corresponding to the fastest temperature rise rate of the first battery pack can be determined based on the current ambient temperature and the first impedance; a second current frequency corresponding to the fastest temperature rise rate of the second battery pack can be determined based on the current ambient temperature and the second impedance; a heating current frequency for the fastest temperature rise rate of the power battery can be determined based on the first current frequency and the second current frequency; and a target frequency range can be determined based on the heating current frequency for the fastest temperature rise rate of the power battery.

[0064] S4, determine the target current amplitude based on the first maximum charge / discharge current and the second maximum charge / discharge current.

[0065] In this step, the smaller of the first maximum charge / discharge current and the second maximum charge / discharge current can be used as the target current amplitude.

[0066] Thus, by using the schemes shown in S1 to S4 above, the target current amplitude and target frequency range of the heating current required for battery heating can be obtained quickly and effectively.

[0067] Step 302: In each frequency adjustment cycle, determine the current target heating current frequency in an increasing and / or decreasing manner, wherein the target heating current frequency belongs to the target frequency range.

[0068] In this step, the current target heating current frequency can be determined by incrementing and decrementing within each frequency adjustment cycle.

[0069] For example, such as Figure 5 As shown, Figure 5 This is a schematic diagram illustrating an exemplary embodiment of the present disclosure of a method for determining a target heating current frequency. Within each frequency adjustment cycle T, the target heating current frequency is first determined by incrementing the starting frequency (e.g., f1) with the lower limit of the target frequency range and incrementing by the first step value X. Then, the target heating current frequency is determined by decrementing the starting frequency (e.g., 3f1) with the upper limit of the target frequency range and decrementing by the second step value Y. Wherein, X ≠ Y, and both X and Y are positive integers greater than 1. Alternatively, as shown... Figure 6 As shown, Figure 6 This is a schematic diagram illustrating a method for determining a target heating current frequency according to another exemplary embodiment of the present disclosure; within each frequency adjustment cycle T, the target heating current frequency is first determined by decreasing the starting frequency (e.g., 3f1) with the upper limit of the target frequency range and decreasing it with the second step value Y; then, the target heating current frequency is determined by increasing the starting frequency (e.g., f1) with the lower limit of the target frequency range and increasing it with the first step value X, wherein X ≠ Y, and X and Y are both positive integers greater than 1.

[0070] It should be noted that, in passing Figure 5 After adjusting the frequency of the heating current during the battery heating process using the method shown, the Figure 2 The intensity of the external radiated magnetic field at point N is Figure 7 As shown, Figure 7 This is a schematic diagram illustrating the external electromagnetic radiation intensity at N points, as shown in an exemplary embodiment of this disclosure. It is evident that after determining the current target heating current frequency in an incremental and decremental manner, Figure 2 The intensity of external electromagnetic radiation at point N was significantly below the standard line, thus achieving the effect of reducing external electromagnetic radiation.

[0071] Alternatively, in this step, the current target heating current frequency can be determined by increasing or decreasing within each frequency adjustment cycle. For example, within each frequency adjustment cycle T, the target heating current frequency is determined by increasing the lower limit of the target frequency range as the starting frequency and increasing the first step value X, until the current cycle ends, or the target heating current frequency is greater than the upper limit of the target frequency range. Then, the target heating current frequency is determined by increasing the lower limit of the target frequency range as the starting frequency and increasing the first step value X.

[0072] Step 303: Control the motor controller according to the target current amplitude and the target heating current frequency to make the first battery pack and the second battery pack alternately charge and discharge, thereby heating the power battery.

[0073] In this step, the PWM duty cycle of the switching transistor in each phase bridge arm can be determined based on the target current amplitude and the target heating current frequency. Then, the upper and lower bridge switching transistors in each phase bridge arm can be turned on by controlling the PWM duty cycle, so that the first battery pack and the second battery pack can be charged and discharged alternately to heat the power battery.

[0074] The above technical solutions can effectively reduce the superposition of magnetic field strength at the same frequency by increasing and / or decreasing the frequency of the AC power used for battery heating within the target frequency range, thereby effectively reducing the magnetic field strength radiated by the battery during the heating process.

[0075] Figure 8 It is based on Figure 4 The illustrated embodiment shows a flowchart of a battery heating method; as shown Figure 8 As shown, Figure 4 The implementation method described in S3 for determining the target frequency range based on the current ambient temperature, the first impedance, and the second impedance may include:

[0076] S31, determine the first current frequency corresponding to the fastest temperature rise rate of the first battery pack based on the current ambient temperature and the first impedance.

[0077] Specifically, the current frequencies corresponding to the fastest heating rates under different ambient temperatures and impedances can be pre-stored in a preset data format, such as a list, text, or database. In this step, the corresponding current frequency can be retrieved from the pre-stored data using the current ambient temperature and the first impedance to obtain the first current frequency.

[0078] S32, determine the second current frequency corresponding to the fastest temperature rise rate of the second battery pack based on the current ambient temperature and the second impedance.

[0079] In this step, the corresponding current frequency can be found from a pre-stored data list using the current ambient temperature and the second impedance to obtain the second current frequency.

[0080] S33, determine the heating current frequency of the power battery with the fastest current heating rate based on the first current frequency and the second current frequency.

[0081] In this step, the larger of the first current frequency and the second current frequency can be used as the heating current frequency with the fastest current heating rate of the power battery.

[0082] S34, determine the target frequency range based on the heating current frequency of the current fastest heating rate of the power battery.

[0083] In this step, the number of phases containing windings in the motor can be obtained; half of the heating current frequency is taken as the lower limit of the target frequency range, and the product of the number of phases and the lower limit is taken as the upper limit of the target frequency range, so as to obtain the target frequency range.

[0084] For example, if the heating current frequency obtained in step S33 above is f Tvmax That is, the heating current frequency with the fastest current heating rate is f. Tvmax If the motor has three phases including windings, i.e., the motor is a three-phase motor, then the lower limit f1 of the target frequency range is 1 / 2f Tvmax The upper limit of the target frequency range is 3f1; if the motor has six phases including windings, i.e., the motor is a six-phase motor, then the lower limit of the target frequency range, f1, is 1 / 2f. Tvmax The upper limit of the target frequency range is 6f1.

[0085] Thus, through the above S31 to S34, the target frequency range of the battery heating current can be effectively determined, so that the frequency of the AC power used for battery heating increases and / or decreases within the target frequency range. Therefore, the superposition of magnetic field strength at the same frequency can be effectively reduced, thereby effectively reducing the magnetic field strength radiated by the battery during the heating process.

[0086] Another exemplary embodiment of this disclosure provides a vehicle, the vehicle comprising the above... Figure 1 The aforementioned battery heating system.

[0087] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0088] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0089] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A battery heating method, characterized in that, A designated controller is applied to a battery heating system, the battery heating system including a power battery, a motor controller, a motor, a designated switch, and the designated controller. The power battery is formed by connecting a first battery pack and a second battery pack in series. The motor controller includes a multi-phase bridge arm, the motor includes multi-phase windings, the midpoint of each phase bridge arm is connected to the first end of a phase winding, the second ends of each phase winding in the multi-phase windings are connected together and then connected to the first end of the designated switch, the second end of the designated switch is connected between the first battery pack and the second battery pack, the first bus terminal of the multi-phase bridge arm is connected to the positive terminal of the first battery pack, and the second bus terminal of the multi-phase bridge arm is connected to the negative terminal of the second battery pack; the method includes: If it is determined that battery heating should be started, the designated switch is controlled to close, and the target current amplitude and target frequency range of the heating current required for battery heating are obtained; Within each frequency adjustment cycle, the current target heating current frequency is determined in an incremental and / or decremental manner, wherein the target heating current frequency belongs to the target frequency range; The motor controller is controlled according to the target current amplitude and the target heating current frequency to make the first battery pack and the second battery pack alternately charge and discharge, thereby heating the power battery; The target current amplitude and target frequency range for obtaining the heating current required for battery heating include: Obtain the first maximum charge / discharge current of the first battery pack and the second maximum charge / discharge current of the second battery pack within a preset historical time period. Obtain the current ambient temperature, and at the current ambient temperature, the first impedance of the first battery pack and the second impedance of the second battery pack; The target frequency range is determined based on the current ambient temperature, the first impedance, and the second impedance. The target current amplitude is determined based on the first maximum charge / discharge current and the second maximum charge / discharge current; Determining the target frequency range based on the current ambient temperature, the first impedance, and the second impedance includes: The first current frequency corresponding to the fastest temperature rise rate of the first battery pack is determined based on the current ambient temperature and the first impedance. The second current frequency corresponding to the fastest temperature rise rate of the second battery pack is determined based on the current ambient temperature and the second impedance. The heating current frequency at which the power battery currently heats up the fastest is determined based on the first current frequency and the second current frequency. The target frequency range is determined based on the heating current frequency at the current fastest heating rate of the power battery. Determining the target frequency range based on the heating current frequency of the current fastest heating rate of the power battery includes: Obtain the number of phases containing windings in the motor; The target frequency range is obtained by taking half of the heating current frequency as the lower limit of the target frequency range and the product of the number of phases and the lower limit as the upper limit of the target frequency range.

2. The battery heating method according to claim 1, characterized in that, The step of determining the heating current frequency that provides the fastest current heating rate of the power battery based on the first current frequency and the second current frequency includes: The larger of the first current frequency and the second current frequency is taken as the heating current frequency with the fastest current heating rate of the power battery.

3. The battery heating method according to claim 1, characterized in that, Determining the target current amplitude based on the first maximum charge / discharge current and the second maximum charge / discharge current includes: The smaller of the first maximum charge / discharge current and the second maximum charge / discharge current is taken as the target current amplitude.

4. The battery heating method according to claim 1, characterized in that, Determining the current target heating current frequency in an incremental and / or decremental manner within each frequency adjustment cycle includes: Within each frequency adjustment cycle, the target heating current frequency is determined by first increasing the starting frequency with the lower limit of the target frequency range and incrementing by the first increment value; then, the target heating current frequency is determined by decreasing the starting frequency with the upper limit of the target frequency range and decrementing by the second increment value; or Within each frequency adjustment cycle, the target heating current frequency is determined by first decreasing the starting frequency with the upper limit of the target frequency range and then decreasing it with a second step value. The target heating current frequency is then determined by increasing the starting frequency with the lower limit of the target frequency range and then increasing it with a first step value.

5. The battery heating method according to any one of claims 1-4, characterized in that, To activate battery heating, the steps include: If it is determined that the vehicle is in a non-faulty state, in response to determining that the vehicle is in a parked state, the first temperature of the first battery pack and the second temperature of the second battery pack are obtained. If the first temperature and / or the second temperature is greater than a preset temperature threshold, battery heating is activated.

6. A battery heating system, characterized in that, The system includes a power battery, a motor controller, a motor, a designated switch, and a designated controller. The power battery is formed by connecting a first battery pack and a second battery pack in series. The motor controller includes a multi-phase bridge arm, and the motor includes multi-phase windings. The midpoint of each phase bridge arm is connected to the first end of a phase winding. The second ends of each phase winding in the multi-phase winding are connected together and then connected to the first end of the designated switch. The second end of the designated switch is connected to the midpoint of the first battery pack and the second battery pack. The first busbar of the multi-phase bridge arm is connected to the positive terminal of the first battery pack, and the second busbar of the multi-phase bridge arm is connected to the negative terminal of the second battery pack. The designated controller is used to implement the battery heating method according to any one of claims 1-5.

7. A vehicle, characterized in that, The vehicle includes the battery heating system as described in claim 6.

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