Battery heating method, battery system and energy storage system

Abstract

The embodiments of the present application disclose a battery heating method, a battery system, and an energy storage system. The battery heating method includes: when the temperature of the battery is lower than a first temperature, obtaining an optimal pulse heating frequency calculated based on the impedance characteristics of the battery; allocating the optimal pulse heating frequency to a first frequency and a second frequency, the sum of the first frequency and the second frequency being equal to the optimal pulse heating frequency; controlling the battery to perform alternating charge and discharge to perform pulse heating on the battery, the battery being charged at the first frequency when charging, and the battery being discharged at the second frequency when discharging. In the embodiments provided in the present application, using the optimal pulse heating frequency to alternately charge and discharge the battery can make the battery generate heat faster, and can improve the heating efficiency of the battery.

Description

Technical Field

[0001] The present application relates to the electrical field, and in particular to a battery heating method, a battery system and an energy storage system. Background Art

[0002] Lithium-ion batteries have the advantages of less pollution, long life, high energy density, and good power performance. However, lithium-ion batteries have poor performance at low temperatures. At low temperatures, the kinetic conditions of the positive and negative electrodes of the battery deteriorate, the viscosity of the electrolyte increases, and the conductivity of the battery decreases, making it difficult for lithium-ion batteries to discharge at low temperatures. When charging a battery at low temperatures, the battery may cause lithium deposition at the negative electrode, which will not only cause the battery's available capacity and output power to decay rapidly, but may also cause a short circuit inside the battery.

[0003] In order to enable the battery to discharge normally in a low temperature environment, the prior art discloses that the battery can be heated by controlling the charging and discharging of the battery, which can solve the problem of the battery having difficulty discharging in a low temperature environment. However, its heating efficiency is relatively low, which will result in a longer time to start the battery and discharge it normally. Summary of the invention

[0004] The embodiments of the present application provide a battery heating method, a battery system, and an energy storage system, which can improve the heating efficiency of the battery.

[0005] In a first aspect, the present application provides a battery heating method, which includes: when the temperature of the battery is lower than a first temperature, obtaining an optimal pulse heating frequency calculated based on the impedance characteristics of the battery; allocating the optimal pulse heating frequency into a first frequency and a second frequency, the sum of the first frequency and the second frequency being equal to the optimal pulse heating frequency; controlling the battery to perform alternate charge and discharge to perform pulse heating on the battery, the battery being charged at the first frequency during charging, and the battery being discharged at the second frequency during discharging.

[0006] The optimal pulse heating frequency is calculated based on the impedance characteristics of the battery. After obtaining the internal resistance of the battery, the Nyquist diagram of the impedance characteristics in the battery can be determined. According to the Nyquist diagram, it can be determined that the battery has an optimal frequency in the charging and discharging frequency band, which maximizes the impedance of the battery. When the current pulse intensity remains unchanged, the battery is alternately charged and discharged using the optimal pulse heating frequency, which can make the battery generate heat faster and improve the heating efficiency of the battery. When the battery is alternately charged and discharged using the optimal pulse heating frequency, the optimal pulse heating frequency is allocated to a first frequency and a second frequency, so that the battery is charged at the first frequency and discharged at the second frequency.

[0007] In combination with the first aspect, in a possible implementation, before obtaining the optimal pulse heating frequency calculated based on the impedance characteristics of the battery, the battery heating method further includes: obtaining the internal resistance of the battery when the battery is operating within a preset temperature range, wherein the battery operating within the preset temperature range includes charging the battery within the preset temperature range and discharging the battery within the preset temperature range; the first temperature is less than or equal to the minimum temperature within the preset temperature range; determining the impedance characteristics of the battery based on the internal resistance of the battery; and calculating the optimal pulse heating frequency based on the impedance characteristics of the battery. By obtaining the internal resistance of the battery when the battery was most recently operating within the preset temperature range, the internal resistance of the battery obtained is closer to the true value, and the calculated optimal pulse heating frequency is more accurate.

[0008] In combination with the first aspect, in a possible implementation, the obtaining of the internal resistance of the battery when the battery is operating within a preset temperature range includes: collecting a set of voltage values ​​and a set of current values ​​when the battery is operating within the preset temperature range for a preset time; and calculating the internal resistance of the battery based on the set of voltage values ​​and the set of current values. In order to more accurately obtain the internal resistance of the battery, the set of voltage values ​​and the set of current values ​​when the battery is operating within the preset temperature range for a preset time are collected. Based on the set of voltage values ​​and the set of current values, the internal resistance of the battery is accurately obtained through an identification algorithm, thereby avoiding large errors caused by collecting too little data of voltage values ​​and current values ​​when obtaining the internal resistance of the battery.

[0009] In combination with the first aspect, in a possible implementation, before obtaining the optimal pulse heating frequency calculated based on the impedance characteristics of the battery, the battery heating method further includes: collecting a voltage value set and a current value set within a preset time when the battery is running within a preset temperature range; sending the voltage value set and the current value set to a cloud battery management unit, the cloud battery management unit calculates the internal resistance of the battery according to the voltage value set and the current value set, determines the impedance characteristics of the battery based on the internal resistance of the battery, and calculates the optimal pulse heating frequency based on the impedance characteristics of the battery; receiving and storing the optimal pulse heating frequency sent by the cloud battery management unit. In order to more accurately obtain the internal resistance of the battery, by collecting the voltage value set and the current value set within a preset time when the battery is running within the preset temperature range, based on the voltage value set and the current value set, the internal resistance of the battery is accurately obtained through an identification algorithm, so as to avoid too little data of the voltage value and the current value when obtaining the internal resistance of the battery, resulting in a large error. Among them, by obtaining the internal resistance of the battery through the cloud battery management unit, the internal resistance state of the battery can be remotely known.

[0010] In combination with the first aspect, in a possible implementation, the battery heating method further includes: when the battery is heated to a temperature above a second temperature, adjusting a first current value of the battery during charging and a second current value of the battery during discharging according to the real-time temperature of the battery. The second temperature is greater than the first temperature. By adjusting the first current value and the second current value, it is possible to avoid the battery heating up too quickly when the battery is alternately charged and discharged, thereby damaging the performance and service life of the battery.

[0011] In combination with the first aspect, in a possible implementation, adjusting the first current value of the battery when charging and adjusting the second current value of the battery when discharging according to the real-time temperature of the battery includes: determining the temperature range in which the real-time temperature of the battery is located; and adjusting the first current value of the battery when charging and the second current value when discharging according to the temperature range in which the real-time temperature of the battery is located. By adjusting the first current value and the second current value when the battery is alternately charged and discharged according to the temperature range, the temperature rise rhythm of the battery can be better controlled to avoid excessive increase in the battery temperature, which affects the battery's performance and service life.

[0012] In combination with the first aspect, in a possible implementation, the method further includes: when the battery is heated to a temperature above a third temperature, controlling the battery to stop alternate charging and discharging, the third temperature being greater than the second temperature. Controlling the battery to stop alternate charging and discharging according to the temperature change of the battery can protect the battery, and avoid the situation where the controller continues to control the battery to perform alternate charging and discharging when the temperature of the battery is high enough (the temperature reaches the third temperature), causing the real-time temperature of the battery to continue to rise.

[0013] In a second aspect, the present application provides a battery system, the battery system comprising: a local battery management unit, a controller and a battery; when the temperature of the battery is lower than a first temperature, the local battery management unit is used to allocate an optimal pulse heating frequency to a first frequency and a second frequency, the sum of the first frequency and the second frequency being equal to the optimal pulse heating frequency; the optimal pulse heating frequency is calculated based on the impedance characteristics of the battery. The controller is used to control the battery to alternately charge and discharge so as to perform pulse heating on the battery, the battery is charged at the first frequency when charging, and the battery is discharged at the second frequency when discharging.

[0014] In combination with the second aspect, in a possible implementation, the battery system also includes a first switch and a second switch; the controller is used to control the first switch to be alternately closed and opened at a first frequency, so that the battery is alternately connected and disconnected from the power supply at the first frequency, so as to control the battery to be charged at the first frequency, wherein when the first switch is closed, the battery is connected to the power supply, and when the first switch is disconnected, the battery is disconnected from the power supply; the controller is also used to control the second switch to be alternately closed and opened at a second frequency, so that the battery is alternately connected and disconnected from the load at the second frequency, so as to control the battery to be discharged at the second frequency, wherein when the second switch is closed, the battery is connected to the load, and when the second switch is disconnected, the battery is disconnected from the load.

[0015] In combination with the second aspect, in one possible implementation, the optimal pulse heating frequency is calculated based on the internal resistance of the battery when the battery was previously operating within a preset temperature range; the operation of the battery within the preset temperature range includes charging the battery within the preset temperature range and discharging the battery within the preset temperature range, and the first temperature is less than or equal to the minimum temperature within the preset temperature range.

[0016] In combination with the second aspect, in a possible implementation, the battery system also includes a first sensor and a second sensor; the first sensor is used to collect a set of voltage values ​​within a preset time when the battery is operating within a preset temperature range; the second sensor is used to collect a set of current values ​​within a preset time when the battery is operating within a preset temperature range; the local battery management unit is used to send the received voltage value set and current value set to the cloud battery management unit, and receive the optimal pulse heating frequency transmitted by the cloud battery management unit; wherein the cloud battery management unit calculates the internal resistance of the battery based on the voltage value set and the current value set, and obtains the optimal pulse heating frequency based on the internal resistance of the battery.

[0017] In combination with the second aspect, in a possible implementation, when the battery is heated to above a second temperature, the local battery management unit is used to adjust a first current value of the battery during charging and a second current value of the battery during discharging according to the real-time temperature of the battery.

[0018] In combination with the second aspect, in a possible implementation, the local battery management unit is used to determine the temperature range in which the real-time temperature of the battery is located; the local battery management unit is also used to determine the first current value during charging and the second current value during discharging when the battery is alternately charged and discharged based on the temperature range in which the real-time temperature of the battery is located.

[0019] In combination with the second aspect, in a possible implementation, when the battery is heated to above a third temperature, the local battery management unit is used to control the battery to stop alternately charging and discharging, and the third temperature is greater than the second temperature.

[0020] In a third aspect, an embodiment of the present application provides an energy storage system, which includes an inverter and a battery system as described above, wherein the output end of the inverter is connected to the battery system, and the input end of the inverter is connected to a load. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 An architecture diagram of a power supply system provided in one embodiment of the present application;

[0023] Figure 2 A schematic diagram of the structure of a battery system provided in one embodiment of the present application;

[0024] Figure 3 A schematic diagram of a battery heating method according to an embodiment of the present application;

[0025] Figure 4 Nyquist plot of the battery impedance characteristics;

[0026] Figure 5 A schematic diagram of the structure of another battery system provided for this application;

[0027] Figure 6 A schematic diagram of a process for calculating an optimal pulse heating frequency and storing the optimal pulse heating frequency in a local battery management unit;

[0028] Figure 7 This is a schematic diagram of the process of starting a battery at low temperature in one embodiment of the present application. DETAILED DESCRIPTION

[0029] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0030] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products or devices.

[0031] The serial numbers assigned to the components in this article, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning.

[0032] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0033] When the battery is charged at low temperatures, lithium deposition may occur at the negative electrode, which will not only cause the battery's available capacity and output power to decay rapidly, but may also cause a short circuit inside the battery.

[0034] Currently, the battery is heated by controlling the charging and discharging of the battery, but the heating efficiency is relatively low, which results in a relatively long time for starting the battery to discharge normally.

[0035] See also Figure 1 , Figure 1 This is an architecture diagram of a power supply system provided in one embodiment of the present application. The power supply system includes a battery system 100, a power supply source 200 and a load 300. The functions of the above devices are introduced below.

[0036] The power supply 200 may be a mains power supply, and the power supply 200 is used to provide power to the battery system 100 , wherein the mains power supply is industrial frequency alternating current.

[0037] The load 300 may be a power-consuming device. For example, the load 300 may be an engine, a base station, or the like.

[0038] The battery system 100 can receive and store electric energy provided by the power supply source 200 . The battery system 100 can generate heat using the electric energy provided by the power supply source 200 . The battery system 100 can also use the stored electric energy to power the load 300 .

[0039] An embodiment of the present application provides an energy storage system, which may include an inverter 400 and a battery system 100 .

[0040] The inverter 400 may be used to convert direct current into alternating current. For example, the inverter 400 may convert direct current in the battery system 100 into alternating current, and transmit the alternating current to an alternating current motor.

[0041] The energy storage system can be applied to the power supply system. Specifically, the power supply source 200 can be used to charge the energy storage system. The electric energy in the energy storage system can be transmitted to the load 300 through the inverter 400 to provide electric energy for the load 300.

[0042] In the embodiments provided in the present application, the energy storage system can power electric vehicles, the energy storage system can also power base stations, and the energy storage system can power various power-consuming devices, and the embodiments of the present application will not be described one by one.

[0043] See also Figure 2 , Figure 2 This is a schematic diagram of the structure of a battery system 100 provided in one embodiment of the present application, and the battery system 100 may include a local battery management unit 130, a controller 110, a battery 120, a first sensor 150, a second sensor 160, a temperature sensor 170, a first switch 180, and a second switch 190. The various units in the battery system 100 are introduced below.

[0044] The battery 120 can be used to store electrical energy. The battery 120 can also discharge. The battery 120 can provide the stored electrical energy to the load 300. The battery may include materials such as molybdenum and titanium. When the battery 120 is in the process of alternating charge and discharge, the pulse current flows through the materials such as molybdenum and titanium, which will generate Joule heat.

[0045] The first sensor 150 may be a voltage sensor, which may be used to collect a set of voltage values ​​of the battery 120 during operation.

[0046] The second sensor 160 may be a current sensor, which may be used to collect a set of current values ​​of the battery 120 during operation.

[0047] The temperature sensor 170 may be used to collect the temperature of the battery 120 .

[0048] The local battery management unit 130 can be used to monitor the battery voltage, battery current, battery cluster insulation status, battery SOC, battery module and single cell status (voltage, current, temperature, SOC, etc.), safely manage the battery cluster charging and discharging process, alarm and emergency protection processing for possible faults, and safely and optimally control the operation of the battery 120 to ensure the safe, reliable and stable operation of the battery 120. The local battery management unit 130 can receive the voltage value set collected by the first sensor 150, and can also receive the current value set collected by the second sensor 160. In some embodiments, the local battery management unit 130 can calculate the optimal pulse heating frequency based on the received voltage value set and current value set, and use the optimal pulse heating frequency to control the battery 120 to perform alternating charging and discharging, so that the heating efficiency of the battery 120 is higher.

[0049] The battery system 100 can be connected to the cloud battery management unit 140 for communication. The cloud battery management unit 140 can calculate the internal resistance of the battery 120 based on the voltage value set and current value set of the battery 120 during normal operation (charging or discharging within a preset temperature range). The cloud battery management unit 140 can also calculate the optimal pulse heating frequency for heating the battery 120 by alternately charging and discharging the battery 120 based on the impedance characteristics of the battery. It should be noted that the cloud battery management unit 140 can obtain the voltage value set and current value set of the battery 120 during normal operation (charging or discharging within a preset temperature range) from the local battery management unit 130. When calculating the optimal pulse heating frequency of the battery 120, the cloud battery management unit 140 calculates the optimal pulse heating frequency based on the Nyquist diagram of the battery impedance, wherein the operation of the battery 120 includes the battery 120 receiving charging and the battery 120 discharging.

[0050] The first switch 180 is used to control the electrical connection between the battery 120 and the power supply 200, so as to connect or disconnect the battery 120 and the power supply 200. When the first switch 180 is closed, the battery 120 is connected to the power supply 200, and the power supply 200 provides electrical energy to the battery 120 to charge the battery 120. When the first switch 180 is opened, the battery 120 is disconnected from the power supply 200.

[0051] The second switch 190 is used to control the electrical connection between the battery 120 and the load 300, so as to connect or disconnect the battery 120 and the load 300. When the second switch 190 is closed, the battery 120 is connected to the load 300, and the battery 120 supplies power to the load 300. When the second switch 190 is opened, the battery 120 is disconnected from the load 300.

[0052] The controller 110 is used to control the battery system 100 to perform alternate charging and discharging. Specifically, the controller 110 can control the first switch 180 to be closed and opened, and the controller 110 can also control the second switch 190 to be closed and opened.

[0053] See also Figure 3 , Figure 3 The flowchart of a battery heating method provided in an embodiment of the present application is shown below. The method can be implemented based on the battery system 100. The method includes but is not limited to the following steps:

[0054] S101, when the temperature of the battery is lower than a first temperature, the local battery management unit obtains an optimal pulse heating frequency calculated based on the impedance characteristics of the battery.

[0055] In the embodiment provided in the present application, when the battery 120 is started to charge or discharge the battery 120, the temperature of the battery 120 can be detected by the temperature sensor 170. If the temperature of the battery 120 is lower than the first temperature, the local battery management unit 130 obtains a pre-stored optimal pulse heating frequency, which is calculated based on the impedance characteristics of the battery 120.

[0056] The first temperature may be a preset temperature. When the temperature of the battery 120 is lower than the first temperature, the battery 120 may not be charged or discharged normally. The embodiment of the present application heats the battery 120 so as to start the battery 120 normally.

[0057] Generally speaking, the temperature at which the battery 120 can be normally charged and discharged is 3-5°C. The first temperature can be set to 0°C or 3°C. The present application does not impose any specific limitation on the value of the first temperature setting.

[0058] In the embodiment provided in the present application, the optimal pulse heating frequency is the frequency of alternately charging and discharging the battery 120. The impedance characteristics of the battery 120 are related to the frequency of alternately charging and discharging the battery 120. Figure 4 , Figure 4 It is the Nyquist diagram of the impedance characteristics of the battery 120. In the Nyquist diagram, the x-axis is the real component of the internal resistance of the battery 120, and the y-axis is the imaginary component of the internal resistance of the battery 120. The Nyquist diagram has multiple frequency bands in the x-axis direction, namely, the Ohm effect frequency band, the conditional effect frequency band, the charge transfer effect frequency band and the diffusion effect frequency band. In the charge transfer effect frequency band (the battery 120 is charged and discharged), there is an optimal frequency that can maximize the real impedance of the battery 120.

[0059] In the embodiment of the present application, when the battery 120 is alternately charged and discharged by the optimal pulse heating frequency, the calculation formula of the heat generation power P is as follows:

[0060] P=R*I 2

[0061] When the current pulse intensity remains unchanged, the battery 120 is alternately charged and discharged using the optimal pulse heating frequency, so that the heat generation power P of the battery 120 can be maximized.

[0062] S102: The local battery management unit allocates the optimal pulse heating frequency to a first frequency and a second frequency, wherein the sum of the first frequency and the second frequency is equal to the optimal pulse heating frequency.

[0063] In the embodiment provided in the present application, the first allocated frequency is used to charge the battery 120 , and the second allocated frequency is used to discharge the battery 120 .

[0064] In an embodiment of the present application, if the optimal pulse heating frequency is f, the first frequency is f1, and the second frequency is f2, then f=f1+f2.

[0065] In the embodiment provided in the present application, when the battery 120 is alternately charged and discharged, the battery 120 may be charged at a first frequency first and then discharged at a second frequency. The battery 120 may also be discharged at a second frequency first and then charged at a first frequency.

[0066] Exemplarily, when the power stored in battery 120 is too low to support the battery 120 to discharge at the second frequency first, the battery 120 can be charged at the first frequency first, and then discharged at the second frequency, so that the battery 120 can be smoothly charged and discharged alternately at the first frequency and the second frequency.

[0067] When the battery 120 is in a fully charged state, the battery 120 may be discharged at the second frequency first, and then discharged at the first frequency, so that the battery 120 may be smoothly alternately charged and discharged at the first frequency and the second frequency.

[0068] In the embodiments provided in the present application, the first frequency and the second frequency may be equal or different.

[0069] S103, the controller controls the battery to perform alternate charge and discharge so as to perform pulse heating on the battery, wherein the battery is charged at the first frequency when being charged and is discharged at the second frequency when being discharged.

[0070] In the embodiment provided in the present application, the controller 110 is communicatively connected to the local battery management unit 130. After the local battery management unit 130 allocates the optimal pulse heating frequency as the first frequency and the second frequency, the controller 110 can obtain the first frequency and the second frequency from the local battery management unit 130.

[0071] Correspondingly, after the local battery management unit 130 allocates the optimal pulse heating frequency to the first frequency and the second frequency, the local battery management unit 130 may send the first frequency and the second frequency to the controller 110 .

[0072] In the embodiment provided in the present application, when the controller 110 controls the battery 120 to alternately charge and discharge, the controller 110 controls the first switch 180 to be repeatedly closed and opened at a first frequency, so that the power supply 200 charges the battery 120 at the first frequency.

[0073] The controller 110 controls the second switch 190 to be repeatedly closed and opened at a second frequency, so that the battery 120 discharges the load 300 at the second frequency.

[0074] When the controller 110 controls the first switch 180 to be closed, the controller 110 controls the second switch 190 to be opened; when the controller 110 controls the first switch 180 to be opened, the controller 110 controls the second switch 190 to be closed.

[0075] In the embodiment provided in the present application, the local battery management unit 130 obtains the optimal pulse heating frequency calculated according to the impedance characteristics of the battery 120, and allocates the optimal pulse heating frequency to the first frequency and the second frequency, and controls the battery 120 to alternately charge and discharge at the first frequency and the second frequency through the controller 110, so as to achieve heating of the battery 120 while improving the heating efficiency of the battery 120. When the battery 120 is charging, the controller 110 controls the battery 120 to charge at the first frequency. When the battery 120 is discharging, the controller 110 controls the battery 120 to discharge at the second frequency.

[0076] In the first possible implementation, see Figure 5 , Figure 5A structural schematic diagram of another battery system 100 provided in the present application, when it is necessary to calculate the optimal pulse heating frequency, the local battery management unit 130 obtains the internal resistance of the battery 120 when it is previously operating within a preset temperature range, and the local battery management unit 130 determines the Nyquist diagram of the impedance characteristics of the battery 120 based on the internal resistance of the battery 120, and according to the Nyquist diagram, it can be determined that the battery 120 has an optimal pulse heating frequency in the charge transfer effect frequency band (the battery 120 is charging and discharging), and when the battery is alternately charged and discharged by the optimal pulse heating frequency, the impedance of the battery 120 can be maximized, and when the current pulse intensity remains unchanged, the battery 120 can generate heat faster, which can improve the heating efficiency of the battery 120.

[0077] It should be noted that if the moment when the cloud battery management unit 140 calculates the optimal pulse heating frequency is called the first moment, then the "before" in the internal resistance of the battery 120 previously operated within the preset temperature range obtained by the local battery management unit 130 may refer to before the first moment. The battery internal resistance obtained by the local battery management unit 130 may be the internal resistance of the battery once, twice or multiple times before the first moment when it is operated within the preset temperature range. The battery internal resistance obtained by the local battery management unit 130 may also be the internal resistance of the battery when it is operated within the preset temperature range in one time period, two time periods or multiple time periods before the first moment. Exemplarily, if the local battery management unit 130 obtains the optimal pulse heating frequency at the first moment, the optimal pulse heating frequency is calculated based on the impedance characteristics of the internal resistance when the battery 120 is operating within the preset temperature range in the first time period, and the first time period is before the first moment. The first time period may be the time period when the battery was last operating within the preset temperature range before the first moment. The first time period may be the time period when the battery 120 was last operating within the preset temperature range before the first moment. Since the battery ages with the increase of usage time, obtaining the internal resistance of the battery 120 when it last operated within the preset temperature range before the first moment can improve the accuracy of the optimal pulse heating frequency, thereby improving the efficiency of battery heating.

[0078] If the moment when the local battery management unit 130 obtains the optimal pulse heating frequency is used as the start-up moment of the current battery low-temperature heating, then the "before" in the internal resistance of the battery 120 previously operated within the preset temperature range obtained by the local battery management unit 130 may refer to before the start-up moment. The battery internal resistance obtained by the local battery management unit 130 may be the internal resistance of the battery when it is operated within the preset temperature range once, twice or multiple times before the start-up moment. The battery internal resistance obtained by the local battery management unit 130 may also be the internal resistance of the battery when it is operated within the preset temperature range for one time period, two time periods or multiple time periods before the start-up moment. Exemplarily, if the local battery management unit 130 obtains the optimal pulse heating frequency at the start-up moment, the optimal pulse heating frequency is calculated based on the impedance characteristics of the internal resistance when the battery 120 is operated within the preset temperature range in the second time period, and the second time period is before the start-up moment. The first time period may be the same as or different from the second time period. The second time period may be the time period when the battery 120 was most recently operated within the preset temperature range before the start-up moment. As the battery ages with increasing usage time, obtaining the internal resistance of the battery 120 when it last operated within a preset temperature range before the startup moment can improve the accuracy of the optimal pulse heating frequency, thereby improving the efficiency of battery heating.

[0079] In the embodiment provided in the present application, the battery 120 operating within a preset temperature includes the battery 120 being charged within a preset temperature range (normal charging) and the battery 120 being discharged within a preset temperature range (normal discharging).

[0080] Wherein, the first temperature is less than or equal to the minimum temperature in the preset temperature range. For example, when the temperature of the battery 120 is 3-5°C, the battery 120 can charge and discharge normally, the preset temperature range can be set to 3-5°C, and the first temperature can be set to 3°C, 2°C, 1°C, 0°C, -1°C. This application does not limit the specific value of the first temperature.

[0081] The internal resistance of the battery 120 is not constant. The battery 120 has a certain lifespan. As the battery 120 is used for a longer time, the internal resistance of the battery 120 will also change without considering the influence of temperature, air pressure and other factors. In order to obtain the internal resistance of the battery 120 more accurately, the local battery management unit 130 can obtain the internal resistance of the battery 120 most recently within a preset temperature range (normal operation), and determine the optimal pulse heating frequency based on the impedance characteristics of the internal resistance. The local battery management unit 130 can store the optimal pulse heating frequency. When the battery 120 is started under low temperature conditions, the local battery management unit 130 calls the optimal pulse heating frequency and allocates the optimal pulse heating frequency to a first frequency and a second frequency. The controller 110 controls the battery 120 to alternately charge and discharge, so as to achieve efficient heating of the battery 120.

[0082] In an embodiment of the present application, when the local battery management unit 130 obtains the internal resistance of the battery 120 within a preset temperature range (normal operation), in order to reduce the error of the collected internal resistance and make the collected internal resistance closer to the actual internal resistance of the battery 120, a set of voltage values ​​of the battery 120 within a preset time when it was previously operating within a preset temperature range is collected through the first sensor 150, and a set of current values ​​of the battery 120 within a preset time when it was previously operating within the preset temperature range is collected through the second sensor 160. The local battery management unit 130 obtains the voltage value set collected by the first sensor 150 and the current value set collected by the second sensor 160. Based on the voltage value set and the current value set, the local battery management unit 130 calculates the internal resistance of the battery 120 through an identification algorithm.

[0083] The voltage value set and the current value set are corresponding, wherein the elements in the voltage value set correspond one to one with the elements in the current value set. Exemplarily, if the battery 120 is normally charged and discharged within the preset temperature range for the last time, the first sensor 150 collects the voltage value set within the time period [A, B], and the second sensor 160 also collects the current value set within the time period [A, B].

[0084] When the local battery management unit 130 calculates the internal resistance of the battery 120 through the identification algorithm based on the voltage value set and the current value set, if the voltage value set C within the time period [A, B] collected by the first sensor 150 is [V1, V2, V3, ..., V n ], the current value set D collected by the second sensor 160 in the time period [A, B] is [I1, I2, I3, ..., I n ], where V1 and I1 correspond to the same acquisition time, V2 and I2 correspond to the same acquisition time, V3 and I3 correspond to the same acquisition time, and so on. n and I nCorresponding to the same collection time, the local battery management unit 130 calculates the internal resistance of the battery according to the one-to-one corresponding elements in the voltage value set and the current value set.

[0085] When the battery 120 in a low temperature environment is started, the temperature of the battery 120 is collected by the temperature sensor 170, and the temperature sensor 170 sends the temperature to the controller 110. The controller 110 determines whether the temperature of the battery 120 is less than the first temperature. If the temperature of the battery 120 is less than the first temperature, the controller 110 sends a heating signal to the local battery management unit 130, and the local battery management unit 130 calls the optimal pulse heating frequency stored therein, and allocates the optimal pulse heating frequency to the first frequency and the second frequency. The local battery management unit 130 sends the first frequency and the second frequency to the controller 110, and the controller 110 controls the battery 120 to charge and discharge alternately according to the first frequency and the second frequency, so as to heat the battery 120. When the controller 110 controls the battery 120 to charge and discharge alternately according to the first frequency and the second frequency, the controller 110 controls the first switch 180 to close and open at the first frequency, so that the battery 120 is charged at the first frequency. The controller 110 controls the second switch 190 to close and open at the second frequency, so that the battery 120 is discharged at the second frequency.

[0086] The optimal pulse heating frequency is calculated by the local battery management unit 130 according to the impedance characteristics of the internal resistance of the battery 120 during normal operation (within a preset temperature range).

[0087] In the second possible implementation, see Figure 6 , Figure 6 The schematic diagram of the process for calculating the optimal pulse heating frequency and storing the optimal pulse heating frequency in the local battery management unit is as follows:

[0088] S201: The local battery management unit obtains a voltage value set and a current value set from a first sensor and a second sensor.

[0089] S202, the cloud battery management unit obtains a voltage value set and a current value set from the local battery management unit.

[0090] S203, the cloud-based battery management unit identifies the internal resistance of the battery according to the voltage value set and the current value set, and calculates the optimal pulse heating frequency according to the impedance characteristics of the battery internal resistance.

[0091] S204, the cloud battery management unit sends the optimal pulse heating frequency to the local battery management unit.

[0092] Specifically, when calculating the optimal pulse heating frequency, the cloud-based battery management unit 140 obtains the internal resistance of the battery 120 when it was previously operating within a preset temperature range. The cloud-based battery management unit 140 determines the Nyquist diagram of the impedance characteristics of the battery based on the internal resistance of the battery. According to the Nyquist diagram, the optimal pulse heating frequency of the battery 120 can be determined. In the Nyquist diagram, the battery 120 has an optimal frequency in the charging and discharging frequency band, which maximizes the impedance of the battery 120. When the current pulse intensity remains unchanged, the battery 120 is alternately charged and discharged using the optimal pulse heating frequency, which can make the battery 120 generate heat faster and improve the heating efficiency of the battery 120.

[0093] After determining the optimal pulse heating frequency, the cloud battery management unit 140 sends the optimal pulse heating frequency to the local battery management unit 130, and the local battery management unit 130 stores the optimal pulse heating frequency. When the battery 120 is started under low temperature conditions, the local battery management unit 130 calls the optimal pulse heating frequency and allocates the optimal pulse heating frequency to the first frequency and the second frequency, and controls the battery 120 to alternately charge and discharge through the controller 110, so as to achieve efficient heating of the battery 120.

[0094] When the cloud battery management unit 140 obtains the internal resistance of the battery 120 when the battery 120 previously operated within the preset temperature range, the first sensor 150 collects the voltage value set of the battery 120 operating within the preset temperature range within the preset time, and the second sensor 160 collects the current value set of the battery 120 operating within the preset temperature range within the preset time, the local battery management unit 130 obtains the voltage value set and the current value set from the first sensor 150 and the second sensor 160, and the cloud battery management unit 140 obtains the voltage value set and the current value set from the local battery management unit 130. Based on the voltage value set and the current value set, the cloud battery management unit 140 calculates the internal resistance of the battery 120 through an identification algorithm.

[0095] When starting the battery 120 in a low-temperature environment, unlike the first possible implementation method, the optimal pulse heating frequency is calculated by the cloud-based battery management unit 140 based on the impedance characteristics of the battery 120 during normal operation (within a preset temperature range), and the cloud-based battery management unit 140 sends the calculated optimal pulse heating frequency to the local battery management unit 130, which stores the optimal pulse heating frequency.

[0096] In this implementation, the cloud battery management unit 140 may correspond to multiple batteries 120, and the cloud battery management unit 140 may obtain the internal resistance of multiple batteries 120, and then monitor the use of each battery 120. The battery 120 has a certain lifespan. As the battery 120 is used for a longer time, the internal resistance of the battery 120 will also change without considering the influence of temperature, air pressure and other factors. The cloud battery management unit 140 may estimate the remaining service life of each battery 120 according to the change law of the internal resistance of the battery 120. For example, when the battery 120 is used to provide electric energy for an electric vehicle, the cloud battery management unit 140 may estimate the remaining service life of each battery 120 according to the real-time internal resistance of each battery 120. When the remaining service life of a battery 120 is less than the preset time, or the mileage corresponding to the remaining service life of the battery 120 is less than the preset mileage, the cloud battery management unit 140 sends a prompt to the owner corresponding to the battery 120, and the prompt may be used to remind the owner to replace the battery 120.

[0097] In an embodiment of the present application, as the temperature in the battery 120 gradually increases, when the battery 120 is heated to above the second temperature, the controller 110 adjusts the first current value of the battery 120 during charging and adjusts the second current value of the battery 120 during discharging according to the real-time temperature of the battery 120.

[0098] In the embodiments provided in the present application, the second temperature is greater than the first temperature. For example, when the first temperature is set to 0°C, the second temperature can be set to 3°C, 2°C, 1°C, etc. The present application does not impose any specific restrictions on the specific value of the second temperature.

[0099] In the embodiment provided in the present application, the real-time temperature of the battery 120 is detected by the temperature sensor 170. In order to prevent the temperature of the battery 120 from rising too quickly and exceeding the maximum value in the preset temperature range of the battery 120 when the battery 120 is alternately charged and discharged, when the real-time temperature of the battery 120 reaches the second temperature, the present application regulates the first current value and the second current value of the battery 120 during the alternate charging and discharging through the controller 110. In the process of alternate charging and discharging of the battery 120, the first current value is the current value of the battery 120 during charging, and the second current value is the current value of the battery 120 during discharging.

[0100] In the embodiment provided in the present application, when the real-time temperature of the battery 120 reaches the second temperature, the controller 110 regulates the first current value and the second current value according to the real-time temperature of the battery 120. Specifically, as the temperature of the battery 120 increases, the controller 110 gradually reduces the first current value and the second current value.

[0101] Exemplarily, when the real-time temperature of the battery 120 reaches the second temperature, the controller 110 controls the magnitude of the first current value to decrease by 0.1A for every 0.5°C increase in the temperature of the battery 120, and the controller 110 controls the magnitude of the second current value to decrease by 0.1A, until the magnitudes of the first current value and the second current value decrease to 0. In the embodiment provided in the present application, the magnitudes of the first current value and the second current value may be equal or unequal. When the real-time temperature of the battery 120 reaches the second temperature, when the controller 110 regulates the first current value and the second current value according to the real-time temperature of the battery 120, the magnitudes of the first current value and the second current value controlled by the controller 110 may be equal or unequal, and when the controller 110 controls the first current value to decrease to 0, the second current value also decreases to 0.

[0102] In the embodiment provided in the present application, when the controller 110 regulates the first current value and the second current value according to the real-time temperature of the battery 120, the real-time temperature of the battery 120 is first collected by the temperature sensor 170, and the controller 110 determines whether the real-time temperature of the battery 120 is greater than or equal to the second temperature. When the real-time temperature of the battery 120 is greater than or equal to the second temperature, the controller 110 further determines the temperature range in which the real-time temperature of the battery 120 is located, and the controller 110 then regulates the first current value of the battery 120 during charging and the second current value of the battery 120 during discharging according to the temperature range in which the real-time temperature of the battery 120 is located.

[0103] Exemplarily, if the second temperature is 0°C, the temperature above the second temperature can be divided into multiple temperature intervals. Specifically, the temperature interval can be [0, 0.5), [0.5, 1), [1, 1.5), [1.5, 2), [2, 2.5), [2.5, 3), [3, 3.5) ..., each temperature interval can correspond to the reduction amplitude of the first current value and the reduction amplitude of the second current value. Exemplarily, when the temperature interval is [0, 0.5), the corresponding reduction amplitude of the first current value is a1, and the reduction amplitude of the second current value is b1. When the temperature interval is [0.5, 1), the corresponding reduction amplitude of the first current value is a2, and the reduction amplitude of the second current value is b2. When the temperature interval is [1, 1.5), the corresponding reduction amplitude of the first current value is a3, and the reduction amplitude of the second current value is b3. When the temperature interval is [1.5, 2), the corresponding reduction amplitude of the first current value is a4, and the reduction amplitude of the second current value is b4. When the temperature range is [2, 2.5), the corresponding first current value is reduced by a5, and the second current value is reduced by b5. When the temperature range is [2.5, 3), the corresponding first current value is reduced by a6, and the second current value is reduced by b6. When the temperature range is [3, 3.5), the corresponding first current value is reduced by a7, and the second current value is reduced by b7.

[0104] If the temperature of the battery 120 is lower than the second temperature, the first current value is a, and the second current value is b. As the temperature of the battery 120 gradually increases, when the temperature of the battery 120 is in the temperature interval [0, 0.5), the controller 110 controls the first current value to decrease by a1, and the controller 110 controls the second current value to decrease by b1. That is, when the real-time temperature of the battery 120 is in the temperature interval [0, 0.5), the first current value is a-a1, and the second current value is b-b1. When the temperature of the battery 120 is in the temperature interval [0.5, 1), the controller 110 controls the first current value to decrease by a2, and the controller 110 controls the second current value to decrease by b2. That is, when the real-time temperature of the battery 120 is in the temperature interval [0.5, 1), the first current value is a-a2, and the second current value is b-b2. By analogy, when the real-time temperature of the battery 120 is in other temperature intervals, the controller 110 can determine the first current value and the second current value according to the temperature interval in which the real-time temperature of the battery 120 is located.

[0105] In the embodiment provided in the present application, the controller 110 regulates the first current value and the second current value of the battery 120 during alternating charge and discharge according to the temperature range of the battery 120, so as to better control the heating rhythm of the battery 120 and avoid excessive increase in the temperature of the battery 120, which may affect the performance and service life of the battery 120.

[0106] It should be noted that regulating the battery 120 to alternately charge and discharge so as to achieve the first current value and the second current value means that the first current value and the second current value are increased or decreased on the original basis.

[0107] In the embodiment provided in the present application, the controller 110 controls the battery 120 to perform alternate charge and discharge to achieve heating of the battery 120. When the real-time temperature of the battery 120 rises to the third temperature, the controller 110 controls the battery 120 to stop alternate charge and discharge, thereby preventing the temperature of the battery 120 from being too high and affecting the performance and service life of the battery 120.

[0108] Specifically, the temperature sensor 170 collects the temperature of the battery 120 in real time, and the controller 110 determines the temperature collected by the temperature sensor 170. When the temperature is greater than a third temperature, the controller 110 controls the battery 120 to stop alternately charging and discharging.

[0109] In the embodiment provided in the present application, the third temperature is greater than the second temperature, the third temperature may be within a preset temperature range, and the third temperature may also be set to be greater than a maximum value within the preset temperature range.

[0110] Exemplarily, if the preset temperature range is 3°C-5°C, the third temperature may be set to 5°C, or the third temperature may be set to be greater than 5°C.

[0111] In the embodiment provided in the present application, when the temperature of the battery 120 is greater than the third temperature, the controller 110 controls the battery 120 to stop alternately charging and discharging, which can protect the battery 120 and prevent the temperature of the battery 120 from being too high (greater than the third temperature). The controller 110 also controls the battery 120 to perform alternate charging and discharging, so that the real-time temperature of the battery 120 continues to rise.

[0112] See the figure, Figure 7It is a flow chart of the battery 120 when starting at low temperature in the embodiment of the present application. In the embodiment provided by the present application, when the battery 120 is started at low temperature, the real-time temperature of the battery 120 is collected by the temperature sensor 170, and the temperature sensor 170 transmits the collected real-time temperature to the controller 110. The controller 110 determines whether the real-time temperature of the battery is less than the first temperature. If it is less than the first temperature, the controller 110 obtains the first frequency and the second frequency for controlling the alternating charge and discharge of the battery 120 from the local battery management unit 130; the local battery management unit 130 allocates the pre-stored optimal pulse heating frequency as the first frequency and the second frequency, and sends the first frequency and the second frequency to the controller 110. The controller 110 controls the first switch 180 and the second switch 190 according to the first frequency and the second frequency, so that the battery 120 is alternately charged and discharged. When the temperature of the battery 120 rises to the second temperature, the controller 110 adjusts the first current value and the second current value of the battery 120 during the alternating charge and discharge according to the real-time temperature of the battery 120 to avoid the temperature of the battery 120 rising too fast. When the temperature of the battery 120 reaches the third temperature, the controller 110 controls the first switch 180 and the second switch 190 to stop the battery 120 from alternately charging and discharging, so as to prevent the temperature of the battery 120 from being too high.

[0113] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A battery heating method, characterized in that: include: Acquiring the internal resistance of the battery when it operates within a preset temperature range, wherein the battery operating within the preset temperature range includes charging the battery within the preset temperature range and discharging the battery within the preset temperature range; Determining a Nyquist plot of the impedance characteristics of the battery based on the internal resistance of the battery when operating within a preset temperature range; Determining, according to the Nyquist diagram, that the battery has an optimal pulse heating frequency in the charge and discharge frequency band, wherein the optimal pulse frequency maximizes the internal resistance of the battery; Allocating the optimal pulse heating frequency into a first frequency and a second frequency, wherein the sum of the first frequency and the second frequency is equal to the optimal pulse heating frequency; When the temperature of the battery is lower than a first temperature, the battery is controlled to be alternately charged and discharged to perform pulse heating on the battery, the battery is charged at the first frequency when charging, and the battery is discharged at the second frequency when discharging, and the first temperature is less than or equal to the minimum temperature within the preset temperature range.

2. The battery heating method according to claim 1, characterized in that: The obtaining of the internal resistance of the battery when the battery is operating within a preset temperature range includes: Collecting a set of voltage values ​​and a set of current values ​​of the battery when it operates within the preset temperature range for a preset time; The internal resistance of the battery is calculated based on the voltage value set and the current value set.

3. The battery heating method according to claim 1, characterized in that: The battery heating method further includes: Collecting a set of voltage values ​​and a set of current values ​​of the battery when the battery is running within a preset temperature range for a preset time; Sending the voltage value set and the current value set to a cloud-based battery management unit, wherein the cloud-based battery management unit calculates the internal resistance of the battery according to the voltage value set and the current value set, determines the impedance characteristics of the battery based on the internal resistance of the battery, and calculates the optimal pulse heating frequency based on the impedance characteristics of the battery; Receive and store the optimal pulse heating frequency sent by the cloud battery management unit.

4. The battery heating method according to any one of claims 1 to 3, characterized in that: The battery heating method further includes: When the battery is heated to a temperature above a second temperature, a first current value of the battery during charging is adjusted according to the real-time temperature of the battery, and a second current value of the battery during discharging is adjusted.

5. The battery heating method according to claim 4, characterized in that: The adjusting, according to the real-time temperature of the battery, a first current value of the battery during charging, and adjusting a second current value of the battery during discharging, comprises: Determine a temperature range in which the real-time temperature of the battery lies; According to the temperature range of the real-time temperature of the battery, a first current value of the battery during charging and a second current value of the battery during discharging are regulated.

6. The battery heating method according to claim 5, characterized in that: The battery heating method further includes: When the battery is heated to a temperature above a third temperature, the battery is controlled to stop alternately charging and discharging.

7. A battery system, characterized in that: The battery system comprises: a local battery management unit, a controller and a battery; When the temperature of the battery is lower than a first temperature, the local battery management unit is used to obtain the internal resistance of the battery when it operates within a preset temperature range, wherein the operation of the battery within the preset temperature range includes charging the battery within the preset temperature range and discharging the battery within the preset temperature range; determining a Nyquist diagram of the impedance characteristic of the battery according to the internal resistance of the battery when it operates within the preset temperature range, wherein the first temperature is less than or equal to the minimum temperature within the preset temperature range; determining, according to the Nyquist diagram, that there is an optimal pulse heating frequency in the charging and discharging frequency band of the battery, wherein the optimal pulse frequency maximizes the internal resistance of the battery; allocating the optimal pulse heating frequency into a first frequency and a second frequency, wherein the sum of the first frequency and the second frequency is equal to the optimal pulse heating frequency; The controller is used to control the battery to perform alternate charging and discharging so as to perform pulse heating on the battery. The battery is charged at the first frequency during charging and discharged at the second frequency during discharging.

8. The battery system according to claim 7, characterized in that: The battery system also includes a first switch and a second switch; The controller is used to control the first switch to be alternately closed and opened at a first frequency, so that the battery is alternately connected and disconnected from the power supply at the first frequency, so as to control the battery to be charged at the first frequency, wherein when the first switch is closed, the battery is connected to the power supply, and when the first switch is opened, the battery is disconnected from the power supply; The controller is also used to control the second switch to be alternately closed and opened at a second frequency, so that the battery is alternately connected and disconnected from the load at the second frequency, thereby controlling the battery to discharge at the second frequency, wherein when the second switch is closed, the battery is connected to the load, and when the second switch is opened, the battery is disconnected from the load.

9. The battery system according to claim 7, characterized in that: The battery system also includes a first sensor and a second sensor; The first sensor is used to collect a set of voltage values ​​of the battery when it is running within a preset temperature range for a preset time; The second sensor is used to collect a set of current values ​​of the battery when it is running within a preset temperature range for a preset time; The local battery management unit is used to send the received voltage value set and current value set to the cloud battery management unit, and receive the optimal pulse heating frequency transmitted by the cloud battery management unit; wherein the cloud battery management unit calculates the internal resistance of the battery based on the voltage value set and the current value set, and obtains the optimal pulse heating frequency based on the internal resistance of the battery.

10. The battery system according to any one of claims 7 to 9, characterized in that: When the battery is heated to a temperature above a second temperature, the local battery management unit is used to adjust a first current value of the battery during charging and a second current value of the battery during discharging according to the real-time temperature of the battery.

11. The battery system according to claim 10, characterized in that: The local battery management unit is used to determine the temperature interval in which the real-time temperature of the battery is located; The local battery management unit is also used to determine, according to the temperature range in which the real-time temperature of the battery is located, a first current value during charging and a second current value during discharging when the battery is alternately charged and discharged.

12. The battery system according to claim 11, characterized in that: When the battery is heated to a temperature above a third temperature, the local battery management unit is used to control the battery to stop alternately charging and discharging.

13. An energy storage system, characterized in that: The energy storage system comprises an inverter and a battery system according to any one of claims 7 to 12, wherein the output end of the inverter is connected to the battery system, and the input end of the inverter is connected to a load.

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