A method and device for low-temperature uniform preheating of a battery without external power supply

Abstract

The application provides a battery low-temperature uniform preheating method and device without external power supply, the method comprises two heating forms of mutual pulse heating and self-discharge pulse, different heating modes are selected according to different open-circuit voltages and temperature conditions through monitoring the voltage and temperature of the battery, so that the temperature of two batteries uniformly rises to not less than a preset temperature on the basis of minimizing the capacity loss of the battery, the cost is reduced, and the device is easy to be miniaturized. The application is especially suitable for efficient, safe and rapid starting when the battery temperature is not uniform, the controller and multiple sensors are arranged, the voltage and temperature conditions of the battery are monitored and controlled, the heating mode and the charging and discharging process of the battery are reasonably distributed, so that the heating strategy of the application can operate more stably, the reliability is improved, and the cost is saved.

Description

Technical Field

[0001] This invention belongs to the field of batteries, and more specifically, relates to a method and apparatus for uniformly preheating batteries at low temperatures without the need for an external power source. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density, long cycle life, low self-discharge rate, and no memory effect. However, their performance degrades significantly at low temperatures. In cold environments, the capacity and charge / discharge performance of lithium-ion batteries decrease drastically, and the formation of lithium dendrites can cause internal short circuits, leading to irreversible damage. The unsatisfactory low-temperature performance of lithium-ion batteries hinders their widespread adoption in northern China, where temperatures frequently drop below 0°C. Therefore, achieving rapid, uniform, safe, and damage-free battery heating at low temperatures has become a hot topic in thermal management research. Currently, there are two main methods for low-temperature preheating of lithium-ion batteries: external heating, which uses an external heat source to provide energy for preheating based on the principles of heat conduction and convection; and internal heating, which utilizes the heat generated by the battery's internal resistance during charging and discharging to achieve self-heating. Compared to external heating, internal heating does not require an additional heat transfer medium, has higher and more uniform heating efficiency, and offers better heating performance.

[0003] Chinese patent document CN109904540A discloses a low-temperature alternating excitation preheating method for lithium iron phosphate (LFP) power batteries. It includes a temperature sensor, a controller, a bidirectional DC / DC converter, and a supercapacitor. Under low-temperature conditions, the LFP power battery discharges to the supercapacitor through the bidirectional DC / DC converter. After absorbing electrical energy, the supercapacitor recharges the LFP power battery through the bidirectional DC / DC converter. However, this proposed method requires the addition of a supercapacitor and the calculation of the optimal charge / discharge frequency for battery preheating, increasing system complexity and energy consumption.

[0004] Chinese patent document CN115064797A discloses a method and system for low-temperature battery startup without external power supply. It includes a charging / discharging inductor and a power conversion device, which alternately controls the discharge of one battery and charges the other through the power conversion device, achieving mutual pulse heating between the two batteries to raise their temperatures to a level not lower than a preset temperature. However, this method has the following main problems: 1) When both batteries have high charge levels, the charging process can lead to excessively high battery voltage, affecting battery life and safety; 2) When the two batteries have uneven temperatures, the battery with the higher temperature will continue to preheat, not only wasting energy but also potentially causing overheating and safety issues. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method and apparatus for uniform preheating of batteries at low temperatures without the need for an external power source, which aims to solve the problems of low heating efficiency, energy waste and safety hazards of existing low-temperature battery heating technologies.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for uniformly preheating a battery at low temperature without the need for an external power source, the method being applied to two batteries; the method includes the following steps:

[0007] Determine the temperature and open-circuit voltage of the two batteries;

[0008] When the temperatures of both batteries are below the preset temperature and their open-circuit voltages are not both above the preset voltage value, the first battery is controlled to discharge through its discharge circuit and boost converter to provide input voltage to the boost converter. The boost converter then boosts the input voltage and outputs the corresponding voltage to charge the second battery. When the voltage of either battery exceeds the corresponding preset voltage range, the second battery is controlled to discharge through its discharge circuit and boost converter to provide input voltage to the boost converter. The boost converter then boosts the input voltage and outputs the corresponding voltage to charge the first battery. When the voltage of either battery exceeds the corresponding preset voltage range, the above process is repeated to switch the charging and discharging order of the two batteries. The two batteries are mutually pulsed heated by pulsed current discharge until the temperature of one battery is not lower than the preset temperature or the open-circuit voltages of both batteries are higher than the preset voltage value.

[0009] When the temperature of both batteries is lower than the preset temperature and the open circuit voltage is higher than the preset voltage value, the two batteries are controlled to discharge to the corresponding discharge circuit at a preset frequency to perform self-discharge heating until the temperature of the corresponding battery is not lower than the preset temperature.

[0010] When the temperature of one battery is lower than the preset temperature and the temperature of the other battery is not lower than the preset temperature, the battery with the lower temperature is controlled to discharge its discharge circuit at a preset frequency to perform self-discharge heating until its temperature is not lower than the preset temperature.

[0011] Optionally, the boost power conversion device includes a boost DC / DC converter.

[0012] Optionally, when the two batteries are of different models and have different preset voltage values, if the temperature of one of the batteries is lower than the preset temperature, the battery with the lower temperature discharges its discharge circuit at a preset frequency to perform self-discharge heating until its temperature is not lower than the preset temperature.

[0013] Secondly, the present invention provides a battery low-temperature preheating device that does not require an external power source. The device is applied to two batteries and includes: a first charging circuit, a second charging circuit, a first discharging circuit, a second discharging circuit, a first single-pole triple-throw switch, a second single-pole triple-throw switch, a third single-pole triple-throw switch, a fourth single-pole triple-throw switch, and a boost-type power conversion device.

[0014] The positive terminal of the first battery is connected to one end of the first charging circuit, one end of the first discharging circuit, and the first stationary terminal of the first single-pole three-throw switch, respectively.

[0015] The other end of the first charging circuit is connected to the first stationary terminal of the third single-pole three-throw switch.

[0016] The negative terminal of the first battery is connected to the other end of the first discharge circuit, the first stationary terminal of the second single-pole triple-throw switch, and the first stationary terminal of the fourth single-pole triple-throw switch, respectively.

[0017] The positive terminal of the second battery is connected to one end of the second charging circuit, one end of the second discharging circuit, and the second stationary terminal of the first single-pole three-throw switch, respectively.

[0018] The other end of the second charging circuit is connected to the second stationary terminal of the third single-pole triple-throw switch;

[0019] The negative terminal of the second battery is connected to the other end of the second discharge circuit, the second stationary terminal of the fourth single-pole triple-throw switch, and the second stationary terminal of the second single-pole triple-throw switch, respectively.

[0020] The input side of the boost-type power converter is connected to the moving terminals of the first single-pole triple-throw switch and the second single-pole triple-throw switch, respectively, and the output side is connected to the moving terminals of the third single-pole triple-throw switch and the fourth single-pole triple-throw switch, respectively.

[0021] When the first battery discharges to the first discharge circuit and the boost power conversion device, and the boost power conversion device charges the second battery, the moving ends of the first single-pole triple-throw switch and the second single-pole triple-throw switch are both connected to the first fixed end, and the moving ends of the third single-pole triple-throw switch and the fourth single-pole triple-throw switch are both connected to the second fixed end. The first discharge circuit is turned on, and the second discharge circuit is turned off.

[0022] When the second battery discharges to the second discharge circuit and the boost power conversion device, and the boost power conversion device charges the first battery, the moving ends of the first single-pole triple-throw switch and the second single-pole triple-throw switch are both connected to the second fixed end, and the moving ends of the third single-pole triple-throw switch and the fourth single-pole triple-throw switch are both connected to the first fixed end. The first discharge circuit is disconnected, and the second discharge circuit is turned on.

[0023] When the first battery does not discharge to the boost power converter, or when the second battery does not discharge to the boost power converter, the moving terminals of the first single-pole triple-throw switch, the second single-pole triple-throw switch, the third single-pole triple-throw switch, and the fourth single-pole triple-throw switch are all connected to the third stationary terminal.

[0024] Optionally, when the moving ends of the first single-pole triple-throw switch, the second single-pole triple-throw switch, the third single-pole triple-throw switch, and the fourth single-pole triple-throw switch are all connected to the third stationary end, if the first discharge circuit or the second discharge circuit is turned on, it will be turned on at a preset frequency so that the corresponding battery can be self-heated at a preset frequency.

[0025] Optionally, the first charging circuit includes a first charging inductor;

[0026] The second charging circuit includes a second charging inductor;

[0027] The first discharge circuit includes a first switching transistor and a first discharge inductor;

[0028] The second discharge circuit includes a second switching transistor and a second discharge inductor.

[0029] Optionally, when the two batteries are of different models and have different preset voltage values, if the temperature of one of the batteries is lower than the preset temperature, the battery with the lower temperature discharges its discharge circuit at a preset frequency to perform self-discharge heating until its temperature is not lower than the preset temperature.

[0030] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0031] This invention provides a method and apparatus for uniformly preheating batteries at low temperatures without the need for an external power source. Taking into account factors such as different battery capacities and temperature uniformity, it provides a strategy for uniformly preheating batteries at low temperatures without the need for an external power source. The strategy includes two heating methods: mutual pulse heating and self-discharge pulse heating. By monitoring the battery voltage and temperature, different heating modes are selected according to different open-circuit voltages and temperatures. This ensures that the battery capacity loss is minimized and the efficiency is maximized, while achieving a uniform temperature rise of the two batteries to a level not lower than the preset temperature. This reduces costs and makes the equipment easier to miniaturize.

[0032] This invention provides a method and apparatus for uniformly preheating batteries at low temperatures without the need for an external power source. It ensures that both batteries reach their target temperature while minimizing their own energy consumption, stopping the preheating process immediately. A problem with existing strategies is that if one battery is hotter than the other, both batteries will heat simultaneously, causing the hotter battery to rise further, which not only wastes energy but also poses a safety hazard. Another problem with existing measurement methods is that if both batteries are fully charged, the old charging method can lead to excessively high battery voltages, potentially damaging the batteries. This invention ensures that both batteries reach their target temperature precisely, effectively utilizing energy and maintaining a relatively safe heating process, achieving uniform preheating at low temperatures. This invention is particularly suitable for efficient, safe, and rapid start-up when battery temperatures are uneven. By using a controller and multiple sensors to monitor and control battery voltage and temperature, it rationally allocates the battery heating mode and charging / discharging process, making the heating strategy more stable, improving reliability, and saving costs. Attached Figure Description

[0033] Figure 1 This is a flowchart of a battery low-temperature uniform preheating strategy that does not require an external power source, provided by an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of a battery low-temperature uniform preheating strategy that does not require an external power source, provided by an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of the workflow of a battery low-temperature uniform preheating strategy that does not require an external power source, provided by an embodiment of the present invention.

[0036] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is a first lithium-ion battery, 2 is a second lithium-ion battery, 3 is a first charging inductor, 4 is a first MOSFET device, 5 is a DC / DC converter, 6 is a second MOSFET device, 7 is a second charging inductor, 8 is a second discharging inductor, 9 is a first discharging inductor, 10 is a first single-pole three-throw switch, 11 is a third single-pole three-throw switch, 12 is a second single-pole three-throw switch, 13 is a fourth single-pole three-throw switch, 14 is a first temperature sensor, 15 is a second temperature sensor, 16 is a first voltage monitoring device, 17 is a second voltage monitoring device, and 18 is a controller. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0040] This invention provides a low-temperature uniform preheating strategy for batteries without the need for an external power source. The strategy includes two heating methods: mutual pulse heating and self-discharge pulse heating. By monitoring the battery voltage and temperature, different heating modes are selected based on different open-circuit voltages and temperatures. This ensures that the temperature of both batteries rises uniformly to a preset temperature while minimizing battery capacity loss, reducing costs and facilitating device miniaturization. This invention is particularly suitable for efficient, safe, and rapid start-up when battery temperatures are uneven. By setting up a controller and multiple sensors to monitor and control battery voltage and temperature, the heating mode and charging / discharging process of the batteries are rationally allocated, enabling the heating strategy of this invention to operate more stably, improving reliability, and saving costs.

[0041] Figure 1 This is a flowchart of a battery low-temperature uniform preheating strategy that does not require an external power source, provided by an embodiment of the present invention; as shown. Figure 1 As shown, it includes the following steps:

[0042] S1, determine the temperature of the two batteries;

[0043] S2, determine whether the temperature of both batteries is lower than the set temperature. If yes, proceed to S4; otherwise, proceed to S3.

[0044] S3, determine if the temperature of one of the two batteries is lower than the minimum limit temperature. If yes, proceed to S5; otherwise, stop the preheating operation.

[0045] S4. Determine whether the open-circuit voltage of both batteries exceeds a certain set value. If yes, execute S5; otherwise, execute S7.

[0046] S5: Activate self-discharge pulse heating mode: Only control the first battery and / or the second battery, which are below the lowest preset temperature, to discharge through the corresponding discharge inductor pulse at a certain frequency. At this time, the boost power conversion device does not work.

[0047] S6, determine whether the temperature of both batteries is lower than the set temperature. If yes, execute S5; otherwise, execute S3.

[0048] S7 activates the bidirectional pulse heating mode: mainly divided into S8-S13:

[0049] S8, control the first battery to discharge through the discharge inductor and simultaneously discharge to the boost power conversion device to provide input voltage to the power conversion device. The boost power conversion device boosts the input voltage and outputs a corresponding voltage to charge the second battery.

[0050] S9, determine whether the temperature of both batteries is lower than the minimum set temperature value. If yes, proceed to S10; otherwise, proceed to S3.

[0051] S10, determine whether the voltage of the two batteries is within the range of the lowest and highest set voltages. If yes, continue to S8; otherwise, execute S11.

[0052] S11, control the second battery to discharge through the discharge inductor and simultaneously discharge to the boost power conversion device to provide input voltage to the power conversion device. The boost power conversion device boosts the input voltage and outputs a corresponding voltage to charge the first battery.

[0053] S12, determine whether the temperature of both batteries is lower than the minimum set temperature. If yes, execute S13; otherwise, execute S3.

[0054] S13, determine whether the voltage of the two batteries is within the range of the lowest and highest set voltages. If yes, continue to S11; otherwise, execute S8.

[0055] It should be noted that the low-temperature heating method for batteries provided by this invention is applicable to batteries whose charge and discharge performance deteriorates at low temperatures, such as lithium-ion batteries. Some parts of this invention are illustrated using lithium-ion batteries as an example only. Those skilled in the art will understand that the method of this invention is obviously not limited to specific battery materials or types, and this invention will not further elaborate on these aspects.

[0056] In this system, when the open-circuit voltages of both batteries are not higher than a certain value and their temperatures are both below the minimum preset temperature, the purpose of discharging one battery is to achieve self-heating through pulsed current discharge, while the purpose of charging the other battery is to quickly reduce its polarization and increase its voltage to within the normal operating voltage range by applying a reverse current. When the voltage of the discharging battery decreases to near the minimum operating voltage, its discharge stops. The charged battery is then controlled to perform pulsed current discharge self-heating, and this cycle repeats to achieve alternating pulsed heating of the two batteries. When the open-circuit voltages of both batteries are higher than a certain value before preheating, the batteries have less polarization at low temperatures and do not require charging current. They only need to rest (stop discharging) for a few milliseconds to achieve reverse polarization. Therefore, only self-discharge pulses are needed for both batteries. At this time, the boost power conversion device does not work, reducing energy loss. Furthermore, if the open-circuit voltage of a battery is higher than a certain value, charging the battery at this time may cause it to explode, posing a safety hazard. When only one battery is below the preset temperature, it only needs to undergo a self-discharge pulse. The other battery, which is above the preset temperature, does not need to be operated. If it were to undergo alternating charging and discharging, it would cause unnecessary energy consumption of the battery at the preset temperature, resulting in energy waste. Therefore, the boost power conversion device does not work at this time, reducing energy loss.

[0057] Specifically, setting a preset voltage range ensures the battery operates normally without overusing it. The preset voltage range falls within the battery's normal operating voltage range, meaning: the battery has a maximum and a minimum cutoff voltage; the minimum voltage within the preset range is not less than the minimum cutoff voltage, and the maximum voltage within the preset range is not greater than the maximum cutoff voltage. The battery will only operate normally when its voltage falls between the minimum and maximum cutoff voltages.

[0058] In an optional example, the boost power converter receives the discharge voltage of one battery at its input and charges another battery at its output.

[0059] The output terminal of the boost-type power converter outputs a preset fixed voltage;

[0060] The preset fixed voltage is set according to the rated voltage of the battery;

[0061] The activation and deactivation of the boost-type power conversion device are determined by the heating strategy.

[0062] In one optional example, the boost power conversion device includes a boost DC / DC converter.

[0063] In an optional example, the first battery is the one with the relatively higher open-circuit voltage of the two batteries; if the open-circuit voltages of the two batteries are equal, then the first battery is either of the two batteries.

[0064] The present invention provides a low-temperature uniform preheating strategy for batteries that does not require an external power source, comprising a lithium-ion battery module, a discharge current control module, and a charging current control module.

[0065] The lithium-ion battery module includes a lithium-ion battery body for generating charging and discharging current to generate heat; the lithium-ion battery module and the discharge current control module form a first circuit, enabling the lithium-ion battery body to achieve high-current discharge; the lithium-ion battery module and the charging current control module form a second circuit, enabling the lithium-ion battery body to generate charging current.

[0066] This invention provides a low-temperature uniform preheating strategy for batteries that requires no external power supply. The strategy includes two preheating methods: mutual pulse heating and self-discharge pulse heating. By monitoring the battery voltage and temperature, different heating modes are selected based on different open-circuit voltages and temperatures. This ensures that the temperature of both batteries rises uniformly to a preset temperature while minimizing battery capacity loss, reducing costs and facilitating device miniaturization. This invention also utilizes a controller and multiple sensors to monitor and control the battery voltage and temperature, rationally allocating the battery heating mode and charging / discharging process. This results in a more stable heating strategy, improved reliability, and cost savings.

[0067] The lithium-ion battery module includes a first lithium-ion battery and a second lithium-ion battery. The two lithium-ion batteries select different preheating modes according to different open-circuit voltages and temperatures to perform discharge or charging operations.

[0068] In some embodiments, the lithium-ion battery module further includes a single-pole triple-throw switch. The moving terminals of the first single-pole triple-throw switch are the positive terminal of the first lithium-ion battery, the positive terminal of the second lithium-ion battery, and a neutral terminal, respectively. The moving terminals of the third single-pole triple-throw switch are the negative terminal of the first lithium-ion battery, the negative terminal of the second lithium-ion battery, and a neutral terminal, respectively. The moving terminals of the second single-pole triple-throw switch are the first charging inductor, the second charging inductor, and a neutral terminal, respectively. The moving terminals of the fourth single-pole triple-throw switch are the negative terminal of the first lithium-ion battery, the negative terminal of the second lithium-ion battery, and a neutral terminal, respectively.

[0069] In some embodiments, the discharge current control module includes a MOSFET device and a discharge inductor device. Specifically, a first MOSFET device is connected to the first lithium-ion battery via a first discharge inductor device; and a second MOSFET device is connected to the second lithium-ion battery via a second discharge inductor device.

[0070] In some embodiments, the charging current control module includes a power conversion device. The power conversion device has its inlet connected to the stationary terminals of a first single-pole three-throw switch and a third single-pole three-throw switch, respectively, and its outlet connected to the stationary terminals of a second single-pole three-throw switch and a fourth single-pole three-throw switch, respectively. The power conversion device includes a DC / DC (direct-to-direct-current) converter.

[0071] In some embodiments, the charging current control module further includes a charging inductor. A first charging inductor is disposed between the positive terminal of the first lithium-ion battery and the first moving point of the second single-pole triple-throw switch, and a second charging inductor is disposed between the positive terminal of the second lithium-ion battery and the second moving point of the second single-pole triple-throw switch.

[0072] In this invention, the lithium-ion battery low-temperature rapid start-up system may further include a control module, which includes a controller. The control terminal of the controller is electrically connected to the voltage sensing device, temperature sensing device, MOSFET device and single-pole triple-throw switch to control the closed state of the switch, thereby controlling the discharge and charging states of the two batteries.

[0073] In some embodiments, the control module may further include a first voltage monitoring device and a second voltage monitoring device. The first voltage monitoring device is disposed on the first lithium-ion battery and electrically connected to the input terminal of the controller, and the second voltage monitoring device is disposed on the second lithium-ion battery and electrically connected to the input terminal of the controller. The first voltage monitoring device monitors the voltage of lithium-ion battery 1, and the second voltage monitoring device monitors the voltage of lithium-ion battery 2, and both are fed back to the controller. The controller executes different preheating methods according to the voltage conditions and controls the opening and closing of the switch and MOSFET device to control the charging / discharging state of the two batteries.

[0074] In some embodiments, the control module may further include a first temperature sensor and a second temperature sensor. The first temperature sensor is disposed on the first lithium-ion battery and electrically connected to the input terminal of the controller, and the second temperature sensor is disposed on the second lithium-ion battery and electrically connected to the input terminal of the controller. The first temperature sensor monitors the surface temperature of the lithium-ion battery 1, and the second temperature sensor monitors the surface temperature of the lithium-ion battery 2, and both are fed back to the controller. The controller controls the execution of different preheating methods according to the battery temperature, controls the opening and closing of the switch and MOSFET device, and controls the start and stop of the low-temperature fast start system and the charging / discharging state of the two batteries.

[0075] The above technical solution will be described in detail below with reference to specific embodiments.

[0076] In this embodiment, the lithium-ion battery low-temperature rapid start-up system is described below. Figure 2 The system includes a first lithium-ion battery 1, a second lithium-ion battery 2, a first charging inductor 3, a first MOSFET device 4, a DC / DC converter 5, a second MOSFET device 6, a second charging inductor 7, a second discharging inductor 8, a first discharging inductor 9, a first single-pole triple-throw switch 10, a third single-pole triple-throw switch 11, a second single-pole triple-throw switch 12, a fourth single-pole triple-throw switch 13, a first temperature sensor 14, a second temperature sensor 15, a first voltage monitoring device 16, a second voltage monitoring device 17, and a controller 18.

[0077] The first temperature sensor is used to obtain the temperature of the first lithium-ion battery;

[0078] The second temperature sensor is used to obtain the temperature of the second lithium-ion battery;

[0079] The first voltage monitoring device is used to acquire the voltage of the first lithium-ion battery;

[0080] The second voltage monitoring device is used to acquire the voltage of the second lithium-ion battery;

[0081] The boost-type power conversion device is connected to a first lithium-ion battery and a second lithium-ion battery;

[0082] The controller is connected to a first temperature sensor, a second temperature sensor, a first voltage monitoring device, and a second voltage monitoring device.

[0083] When the temperatures of both batteries are below a preset temperature and their open-circuit voltages are not both above a certain value, the controller executes a bidirectional pulse heating mode. This involves controlling the first lithium-ion battery to discharge through a discharge inductor and simultaneously discharging into a boost converter to provide input voltage. The boost converter then boosts the input voltage and outputs a corresponding voltage to charge the second lithium-ion battery. When the voltage of either battery exceeds the corresponding preset voltage range, the controller controls the second lithium-ion battery to discharge through a discharge inductor and simultaneously discharge into the boost converter to provide input voltage. The boost converter then boosts the input voltage and outputs a corresponding voltage to charge the first lithium-ion battery. When the voltage of either battery exceeds the corresponding preset voltage range, the controller repeats the above process to switch the charging and discharging order of the two batteries until the temperature of one battery is not lower than the preset temperature or the open-circuit voltages of both batteries are above a certain value.

[0084] When the temperature of both batteries is lower than the preset temperature and the open circuit voltage is higher than a certain value, the controller executes the self-discharge heating mode, that is, only controls the first lithium-ion battery and the second lithium-ion battery to discharge through the corresponding discharge inductor pulse at a certain frequency. At this time, the boost power conversion device does not work.

[0085] When only one battery is below the preset temperature during the low-temperature preheating process, only the first or second lithium-ion battery below the minimum preset temperature is controlled to discharge through the corresponding discharge inductor pulse at a certain frequency. At this time, the boost power conversion device does not work.

[0086] In an optional example, the system further includes: a first charging circuit, a second charging circuit, a first discharging circuit, a second discharging circuit, a first single-pole three-throw switch, a second single-pole three-throw switch, a third single-pole three-throw switch, and a fourth single-pole three-throw switch;

[0087] The positive terminal of the first lithium-ion battery is connected to one end of the first charging circuit, one end of the first discharging circuit, and the first stationary terminal of the first single-pole three-throw switch, respectively.

[0088] The other end of the first charging circuit is connected to the first stationary terminal of the third single-pole three-throw switch.

[0089] The negative terminal of the first lithium-ion battery is connected to the other end of the first discharge circuit, the first stationary terminal of the second single-pole triple-throw switch, and the first stationary terminal of the fourth single-pole triple-throw switch, respectively.

[0090] The positive terminal of the second lithium-ion battery is connected to one end of the second charging circuit, one end of the second discharging circuit, and the second stationary terminal of the first single-pole three-throw switch.

[0091] The other end of the second charging circuit is connected to the second stationary terminal of the third single-pole triple-throw switch;

[0092] The negative terminal of the second lithium-ion battery is connected to the other end of the second discharge circuit, the second stationary terminal of the fourth single-pole triple-throw switch, and the second stationary terminal of the second single-pole triple-throw switch, respectively.

[0093] The first discharge circuit includes a first discharge inductor; the second discharge circuit includes a second discharge inductor.

[0094] The input side of the boost-type power converter is connected to the moving terminals of the first single-pole triple-throw switch and the second single-pole triple-throw switch, respectively, and the output side is connected to the moving terminals of the third single-pole triple-throw switch and the fourth single-pole triple-throw switch, respectively.

[0095] When the first lithium-ion battery is discharging and the second lithium-ion battery is charging, the moving ends of the first and second single-pole triple-throw switches are both connected to the first stationary end, and the moving ends of the third and fourth single-pole triple-throw switches are both connected to the second stationary end. The first discharge circuit is turned on and the second discharge circuit is turned off.

[0096] When the second lithium-ion battery discharges and the first lithium-ion battery is charged, the moving ends of the first and second single-pole triple-throw switches are both connected to the second stationary end, and the moving ends of the third and fourth single-pole triple-throw switches are both connected to the first stationary end. The first discharge circuit is disconnected and the second discharge circuit is turned on.

[0097] When the first lithium-ion battery discharges and the second lithium-ion battery discharges, the moving ends of the first single-pole triple-throw switch, the second single-pole triple-throw switch, the third single-pole triple-throw switch and the fourth single-pole triple-throw switch are all connected to the third non-moving end, and the first discharge circuit and the second discharge circuit are both turned on.

[0098] In an optional example, the first charging circuit includes a first charging inductor;

[0099] The second charging circuit includes a second charging inductor;

[0100] The first discharge circuit also includes a first switching transistor;

[0101] The second discharge circuit also includes a second switching transistor.

[0102] In an optional example, the first and second switching transistors are MOSFETs.

[0103] In an optional example, the boost power converter receives the discharge voltage of one battery at its input and charges another battery at its output.

[0104] The output terminal of the boost-type power converter outputs a preset fixed voltage;

[0105] The preset fixed voltage is set according to the rated voltage of the battery;

[0106] The activation and deactivation of the boost-type power conversion device are determined by the heating strategy.

[0107] In one optional example, the first lithium-ion battery is the one with the relatively higher open-circuit voltage of the two batteries; if the open-circuit voltages of the two batteries are equal, then the first lithium-ion battery is either one of the two batteries.

[0108] like Figure 3 The heating strategy of the circuit is as follows:

[0109] Step 1: Use the first temperature sensor 14 and the second temperature sensor 15 to collect the surface temperatures of the first lithium-ion battery 1 and the second lithium-ion battery 2 respectively, and determine whether the surface temperatures of the two lithium-ion batteries are both lower than the set temperature value Tmin; if yes, proceed to step 3; if no, proceed to step 2.

[0110] Step 2: Determine if the surface temperature of either of the two lithium-ion batteries is lower than Tmin. If yes, proceed to step 4; otherwise, stop the preheating operation.

[0111] Step 3: Use the first voltage monitoring device 16 and the second voltage monitoring device 17 to monitor the open-circuit voltage of the first lithium-ion battery 1 and the second lithium-ion battery 2 respectively, and determine whether the open-circuit voltage of the two batteries exceeds the set value U1. If yes, proceed to step 4; otherwise, proceed to step 6.

[0112] Step 4: Activate the self-discharge pulse heating mode: Set the moving ends of the single-pole three-throw switch 10, 11, 12, and 13 to position c. The MOSFETs corresponding to the batteries whose temperatures are lower than the set temperature Tmin (MOSFET4 for battery 1 and MOSFET6 for battery 2) will close once every Δt time, while the other MOSFETs will open to perform the self-discharge pulse heating operation.

[0113] Step 5: Use the first temperature sensor 14 and the second temperature sensor 15 to collect the surface temperatures of the first lithium-ion battery 1 and the second lithium-ion battery 2 respectively, and determine whether the surface temperatures of the two lithium-ion batteries are both lower than the set temperature value Tmin; if yes, proceed to step 4; if no, proceed to step 2.

[0114] Step Six: Activate the bidirectional pulse heating mode: mainly divided into S1-S6:

[0115] S1, the moving ends of the first single-pole triple-throw switch 10 and the second single-pole triple-throw switch 12 are adjusted to position a, the moving ends of the third single-pole triple-throw switch 11 and the fourth single-pole triple-throw switch 13 are adjusted to position b, the first MOSFET device 4 is closed, and the second MOSFET device 6 is open;

[0116] S2, the surface temperatures of the first lithium-ion battery 1 and the second lithium-ion battery 2 are collected by the first temperature sensor 14 and the second temperature sensor 15 respectively, and it is determined whether the surface temperatures of the two lithium-ion batteries are both lower than the set temperature value Tmin; if yes, proceed to S3, otherwise proceed to step two.

[0117] S3, the first voltage monitoring device 16 and the second voltage monitoring device 17 are used to collect the voltages at the two ends of the first lithium-ion battery 1 and the second lithium-ion battery 2 respectively, and it is determined whether the voltages of the two lithium-ion batteries are within the range of the lowest set voltage and the highest set voltage. If yes, continue to S1; if no, execute S4.

[0118] S4, the moving ends of the first single-pole triple-throw switch 10 and the second single-pole triple-throw switch 12 are adjusted to position b, the moving ends of the third single-pole triple-throw switch 11 and the fourth single-pole triple-throw switch 13 are adjusted to position a, the first MOSFET device 4 is disconnected, and the second MOSFET device 6 is closed;

[0119] S5, the surface temperatures of the first lithium-ion battery 1 and the second lithium-ion battery 2 are collected by the first temperature sensor 14 and the second temperature sensor 15 respectively, and it is determined whether the surface temperatures of the two lithium-ion batteries are both lower than the set temperature value Tmin; if yes, proceed to S6, otherwise proceed to step two.

[0120] S6, the first voltage monitoring device 16 and the second voltage monitoring device 17 are used to collect the voltages at both ends of the first lithium-ion battery 1 and the second lithium-ion battery 2 respectively, and it is determined whether the voltages of the two lithium-ion batteries are within the range of the lowest set voltage and the highest set voltage. If yes, continue to S4; if no, execute S1.

[0121] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for uniformly preheating a battery at low temperature without the need for an external power source, the method being applied to two batteries; characterized in that, The method includes the following steps: Determine the temperature and open-circuit voltage of the two batteries; When the temperatures of both batteries are below the preset temperature and their open-circuit voltages are not both above the preset voltage value, a bidirectional pulse heating mode is executed. The bidirectional pulse heating mode includes: controlling the first battery to discharge through its discharge circuit and boost converter to provide input voltage to the boost converter; the boost converter then boosts the input voltage and outputs a corresponding voltage to charge the second battery; when the voltage of either battery exceeds the corresponding preset voltage range, controlling the second battery to discharge through its discharge circuit and boost converter to provide input voltage to the boost converter; the boost converter then boosts the input voltage and outputs a corresponding voltage to charge the first battery; when the voltage of either battery exceeds the corresponding preset voltage range, repeating the above process to switch the charging and discharging order of the two batteries, and using pulse current discharge between the two batteries to achieve mutual pulse heating between them, until the temperature of one battery is not below the preset temperature or the open-circuit voltage of both batteries is above the preset voltage value. When the temperatures of both batteries are below the preset temperature and their open-circuit voltages are both above the preset voltage, or when the temperature of one battery is below the preset temperature and the temperature of the other battery is not below the preset temperature, the self-discharge pulse heating mode is executed; the self-discharge pulse heating mode includes: When the temperature of both batteries is lower than the preset temperature and the open circuit voltage is higher than the preset voltage value, the two batteries are controlled to discharge to the corresponding discharge circuit at a preset frequency and the boost power conversion device is not working, so as to perform self-discharge heating until the temperature of the corresponding battery is not lower than the preset temperature. When the temperature of one battery is lower than the preset temperature and the temperature of the other battery is not lower than the preset temperature, the battery with the lower temperature is controlled to discharge at a preset frequency to its discharge circuit, and the boost power conversion device does not work, so as to perform self-discharge heating until its temperature is not lower than the preset temperature.

2. The method according to claim 1, characterized in that, The boost-type power conversion device includes a boost-type DC / DC converter.

3. The method according to claim 1, characterized in that, When the two batteries are of different models, their preset voltage values ​​are different. In this case, when the temperature of one of the batteries is lower than the preset temperature, the battery with the lower temperature discharges its discharge circuit at a preset frequency to perform self-discharge heating until its temperature is not lower than the preset temperature.

4. A battery low-temperature preheating device that requires no external power supply, characterized in that, The device is applied to two batteries and includes: a first charging circuit, a second charging circuit, a first discharging circuit, a second discharging circuit, a first single-pole triple-throw switch, a second single-pole triple-throw switch, a third single-pole triple-throw switch, a fourth single-pole triple-throw switch, a boost-type power conversion device, and a controller; the controller applies the battery low-temperature uniform preheating method without external power supply as described in claim 1. The positive terminal of the first battery is connected to one end of the first charging circuit, one end of the first discharging circuit, and the first stationary terminal of the first single-pole three-throw switch, respectively. The other end of the first charging circuit is connected to the first stationary terminal of the third single-pole three-throw switch. The negative terminal of the first battery is connected to the other end of the first discharge circuit, the first stationary terminal of the second single-pole triple-throw switch, and the first stationary terminal of the fourth single-pole triple-throw switch, respectively. The positive terminal of the second battery is connected to one end of the second charging circuit, one end of the second discharging circuit, and the second stationary terminal of the first single-pole three-throw switch, respectively. The other end of the second charging circuit is connected to the second stationary terminal of the third single-pole triple-throw switch; The negative terminal of the second battery is connected to the other end of the second discharge circuit, the second stationary terminal of the fourth single-pole triple-throw switch, and the second stationary terminal of the second single-pole triple-throw switch, respectively. The input side of the boost-type power converter is connected to the moving terminals of the first single-pole triple-throw switch and the second single-pole triple-throw switch, respectively, and the output side is connected to the moving terminals of the third single-pole triple-throw switch and the fourth single-pole triple-throw switch, respectively. When the first battery discharges to the first discharge circuit and the boost power conversion device, and the boost power conversion device charges the second battery, the moving ends of the first single-pole triple-throw switch and the second single-pole triple-throw switch are both connected to the first fixed end, and the moving ends of the third single-pole triple-throw switch and the fourth single-pole triple-throw switch are both connected to the second fixed end. The first discharge circuit is turned on, and the second discharge circuit is turned off. When the second battery discharges to the second discharge circuit and the boost power conversion device, and the boost power conversion device charges the first battery, the moving ends of the first single-pole triple-throw switch and the second single-pole triple-throw switch are both connected to the second fixed end, and the moving ends of the third single-pole triple-throw switch and the fourth single-pole triple-throw switch are both connected to the first fixed end. The first discharge circuit is disconnected, and the second discharge circuit is turned on. When the first battery does not discharge to the boost power converter, or when the second battery does not discharge to the boost power converter, the moving terminals of the first single-pole triple-throw switch, the second single-pole triple-throw switch, the third single-pole triple-throw switch, and the fourth single-pole triple-throw switch are all connected to the third stationary terminal. When the moving ends of the first, second, third, and fourth single-pole three-throw switches are all connected to the third stationary end, if the first or second discharge circuit is turned on, it will be turned on at a preset frequency so that the corresponding battery can be self-heated at a preset frequency.

5. The apparatus according to claim 4, characterized in that, The first charging circuit includes a first charging inductor; The second charging circuit includes a second charging inductor; The first discharge circuit includes a first switching transistor and a first discharge inductor; The second discharge circuit includes a second switching transistor and a second discharge inductor.

6. The apparatus according to claim 4, characterized in that, When the two batteries are of different models, their preset voltage values ​​are different. In this case, when the temperature of one of the batteries is lower than the preset temperature, the battery with the lower temperature discharges its discharge circuit at a preset frequency to perform self-discharge heating until its temperature is not lower than the preset temperature.

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