A control method for low-temperature heating of a battery system

Abstract

The application relates to a control method for low-temperature heating of a battery system, and belongs to the technical field of battery heating. The control method solves the problem that the battery system is not heated in time and completely in the prior art, and the reliability and effectiveness of the battery system are low. The control method comprises the following steps: powering on the battery system, detecting the minimum temperature of the battery system by a BMS; if the minimum temperature is less than a first temperature threshold, detecting whether the battery system is connected to commercial power by the BMS; if the battery system is connected to commercial power, the battery system enters a commercial power heating mode; otherwise, the battery system enters a battery self-heating mode; and when the minimum temperature is greater than or equal to a second temperature threshold, the heating process of the battery system is completed. The control method provided by the application enables the battery to be heated in time and completely, improves the reliability of the battery system heating, and guarantees the safe use of the battery system.

Description

Technical Field

[0001] This invention relates to the field of battery heating technology, and in particular to a control method for low-temperature heating of a battery system. Background Technology

[0002] With the increasing severity of global energy shortages and environmental pollution, lithium batteries have been widely used due to their high voltage, high energy density, good cycle performance, low self-discharge, no memory effect, and environmental friendliness. However, lithium batteries have poor low-temperature performance. Under low-temperature conditions, the activity of the positive and negative electrode materials deteriorates, and the charge and discharge capacity of the electrolyte also weakens, only allowing for small-current charging or even no charging at all. The discharge capacity decreases, and the internal resistance of the battery increases during low-temperature discharge, resulting in a decrease in the discharge capacity and thus affecting the battery's cycle life.

[0003] Generally, charging a battery is not permitted when the battery temperature is below 0°C. Therefore, to address the issue of low-temperature charging of lithium batteries, a dedicated heating system is designed for thermal management. Typically, during the low-temperature charging phase, the battery heating circuit is activated first, using a PTC heating plate or heating film to raise the overall temperature of the battery system until it reaches the charging threshold to initiate charging. However, if heating is not timely or thorough, it can lead to a sharp reduction in battery life or excessively long low-temperature charging times resulting in low efficiency, significantly impacting product performance and affecting the charging and discharging performance of the battery system.

[0004] Therefore, it is urgent to reasonably control the low-temperature heating of the battery system to ensure the timeliness and thoroughness of heating, improve battery charging efficiency, enhance the reliability and effectiveness of the battery system, and ensure the safe and reasonable use of the battery box. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a control method for low-temperature heating of a battery system, in order to solve the problem that the existing battery system is not heated in a timely and thorough manner, resulting in low reliability and effectiveness of the battery system.

[0006] On one hand, embodiments of the present invention provide a method for controlling low-temperature heating of a battery system, characterized by comprising the following steps:

[0007] When the battery system is powered on, the BMS detects the lowest temperature of the battery system.

[0008] If the lowest temperature is less than the first temperature threshold, the BMS will detect whether the battery system is connected to the mains power.

[0009] If the battery system is connected to AC power, the battery system will enter AC power heating mode; otherwise, it will enter battery self-heating mode.

[0010] The heating process of the battery system is complete when the lowest temperature is greater than or equal to the second temperature threshold.

[0011] Furthermore, the battery system includes several parallel battery boxes and a control box. The BMS continuously monitors the minimum temperature of the battery system based on preset conditions, including the following steps:

[0012] Each battery box's slave board BMS detects the temperature of each cell in the battery module and transmits it to the corresponding battery box's secondary master control BMS.

[0013] The secondary main control BMS compares the temperature of each cell to obtain the lowest temperature of the corresponding battery box, and transmits it to the primary main control BMS of the control box.

[0014] The primary control BMS compares the lowest temperature of each battery box to obtain the lowest temperature of the battery system.

[0015] Furthermore, the mains heating mode of the battery system is specifically as follows:

[0016] After the battery system enters the AC heating mode, the BMS checks whether the charging relay in the control box is closed.

[0017] If the charging relay is closed, the lowest temperature is compared with the fourth temperature threshold.

[0018] When the minimum temperature is less than the fourth temperature threshold, the main positive relay of the battery box is disconnected, the heating relay of the battery box is closed, and a heating request is sent to the charging equipment to heat the battery system.

[0019] When the lowest temperature is greater than or equal to the fourth temperature threshold and less than the first temperature threshold, the main positive relay of the battery box and the heating relay of the battery box are closed, and a heating request is sent to the charging equipment to heat the battery system.

[0020] When the minimum temperature is greater than or equal to the second temperature threshold, the main positive relay of the battery box is closed, the heating relay of the battery box is opened, and a charging request is sent to the charging equipment to charge the battery system, thus completing the heating process of the battery system.

[0021] Furthermore, the mains heating mode of the battery system also includes, if the charging relay of the BMS detection control box is not closed, comparing the lowest temperature with the fourth temperature threshold after closing the charging relay of the control box.

[0022] Furthermore, the heating request includes a request for a heating current, and the heating current I... h for:

[0023] I h =I1×n;

[0024] Where I1 represents the heating current value of a single battery box, and n represents the number of battery boxes to be heated; the charging request includes a requested charging current, and the charging current I c for:

[0025] I c =I²×n.

[0026] Where I2 represents the charging current value of a single battery pack.

[0027] Furthermore, the mains heating mode of the battery system also includes:

[0028] When the battery system is heated to a minimum temperature greater than or equal to the first temperature threshold and less than the second temperature threshold, the main positive relay and the heating relay of the battery box are closed, and a heating and charging request is sent to the charging equipment to heat and charge the battery system.

[0029] Furthermore, the heating and charging request includes a request for a heating and charging current, and the heating and charging current I... hc for:

[0030] I hc = (I1+I2)×n.

[0031] Furthermore, the battery system's self-heating mode specifically includes:

[0032] After the battery system enters the battery self-heating mode, the lowest temperature is compared with the third temperature threshold.

[0033] If the minimum temperature is less than the third temperature threshold and the duration is greater than or equal to the time threshold, then the main positive relay of the battery box is disconnected, the heating relay of the battery box is closed, and the battery system is heated.

[0034] When the lowest temperature is greater than or equal to the third temperature threshold and less than the first temperature threshold, the main positive relay and the heating relay of the battery box are closed to heat the battery system.

[0035] When the minimum temperature value is greater than or equal to the second temperature threshold, the main positive relay of the battery box is closed, the heating relay of the battery box is opened, and the heating process of the battery system is completed.

[0036] Furthermore, the control method further includes:

[0037] When the BMS continuously detects the lowest temperature of the battery system based on preset conditions, it also records the lowest temperature of each battery box.

[0038] During the battery self-heating and mains power heating processes, the lowest temperature of each battery box is compared with the second temperature threshold.

[0039] When the lowest temperature of the battery box is greater than or equal to the second temperature threshold, the main positive relay of the battery box is closed, the heating relay of the battery box is opened, and the heating process of the battery box is completed.

[0040] Furthermore, the control method also includes, after the battery system is powered on, before the BMS detects the minimum temperature of the battery system, the BMS performs a self-test to check for faults. If the self-test finds no faults, the minimum temperature is detected; otherwise, the BMS continues to perform a self-test.

[0041] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0042] This invention provides a control method for low-temperature heating of a battery system. By detecting the minimum temperature of the battery system through a BMS (Battery Management System), and based on the minimum temperature and whether mains power is available, it provides both mains power heating mode and battery self-heating mode for the battery system. This makes battery heating more timely and thorough, improves the reliability of battery system heating, and ensures the safe use of the battery system. Furthermore, when the battery system heats to a suitable temperature, it controls the battery system to simultaneously heat and charge, improving charging efficiency and enhancing the effectiveness and safety of the battery system design.

[0043] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0044] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0045] Figure 1 This is a flowchart of the control method for low-temperature heating of the battery system in an embodiment of the present invention;

[0046] Figure 2 This is a block diagram of the battery system in an embodiment of the present invention;

[0047] Figure 3 This is a detailed flowchart of the control method for low-temperature heating of the battery system in an embodiment of the present invention. Detailed Implementation

[0048] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0049] A specific embodiment of the present invention discloses a method for controlling low-temperature heating of a battery system, the process of which is as follows: Figure 1 As shown, the detailed flowchart is as follows: Figure 3 As shown, it includes the following steps:

[0050] S1. The battery system is powered on, and the BMS detects the lowest temperature of the battery system.

[0051] In implementation, the battery system includes several parallel battery boxes and a control box. The BMS continuously monitors the minimum temperature of the battery system based on preset conditions, including the following steps:

[0052] Each battery box's slave board BMS detects the temperature of each cell in the battery module and transmits the data to the corresponding battery box's secondary master control BMS.

[0053] The secondary main control BMS compares the temperature of each cell to obtain the lowest temperature of the corresponding battery box, and transmits it to the primary main control BMS in the control box.

[0054] The primary control BMS compares the lowest temperature of each battery box to obtain the lowest temperature of the battery system.

[0055] Specifically, after the battery system is powered on, the BMS continuously monitors the minimum temperature of the battery system based on preset conditions. In other words, the BMS continuously monitors the temperature of the battery system. The preset conditions of the BMS can be the time interval of the monitoring, such as an interval of 1 second or 1 minute.

[0056] Understandably, detecting the lowest temperature of the battery system in this way allows for more timely and thorough heating during subsequent heating processes, ensuring that each battery box is heated to the appropriate temperature.

[0057] Specifically, the battery system block diagram is as follows: Figure 2 As shown, the control box contains a primary control BMS (Battery Management System), charging relays, discharging relays, diode relays, a display and control board, charging fuses, and discharging fuses. The charging equipment can be installed either inside or outside the control box, depending on specific requirements, and is connected to mains power.

[0058] Each battery box contains a secondary master control BMS, a slave BMS, a heating relay, a display and control board, a heating fuse, a main positive relay, a pre-charge resistor, a pre-charge relay, and a battery module. The battery module is equipped with a heating element.

[0059] S2. If the lowest temperature is less than the first temperature threshold, the BMS will detect whether the battery system is connected to the mains power.

[0060] Specifically, the connection of the battery system to mains power is determined by checking whether the plug of the charging device is connected to the charging connector of the battery box.

[0061] S3. If the battery system is connected to AC power, the battery system will enter AC power heating mode; otherwise, it will enter battery self-heating mode.

[0062] In practice, the mains heating mode of the battery system is specifically as follows:

[0063] After the battery system enters the AC heating mode, the BMS checks whether the charging relay in the control box is closed.

[0064] If the charging relay is closed, the lowest temperature is compared with the fourth temperature threshold. Understandably, closing the charging relay in the control box allows the charging equipment to power the heating elements on the battery modules inside the battery box, and also to charge the battery system.

[0065] When the minimum temperature is below the fourth temperature threshold, the main positive relay of the battery box is disconnected, the heating relay of the battery box is closed, and a heating request is sent to the charging equipment to heat the battery system. Understandably, the battery cells are in an unsafe operating state during this process. Disconnecting the main positive relay prevents the battery system from charging and discharging, protecting the cells from damage. Only the heating relay of the battery box is closed during this process to heat the battery box.

[0066] When the lowest temperature is greater than or equal to the fourth temperature threshold but less than the first temperature threshold, the main positive relay and the heating relay of the battery box are closed, and a heating request is sent to the charging equipment to heat the battery system. It is understood that the cell temperature within this temperature range meets the safety requirements for discharge; therefore, the main positive relay of the battery box is closed to allow the battery system to discharge and supply power to the load, but the battery system is not charging at this time; the heating relay of the battery box is closed to maintain heating.

[0067] When the minimum temperature is greater than or equal to the second temperature threshold, the main positive relay of the battery box closes, the heating relay of the battery box opens, and a charging request is sent to the charging equipment to charge the battery system, completing the heating process of the battery system. It can be understood that the battery box temperature at this point meets the safe charging and discharging temperature of the battery cells. Therefore, the main positive relay of the battery box closes to allow the battery system to charge and discharge, and the heating relay of the battery box closes to stop the heating of the battery system.

[0068] Preferably, the mains heating mode of the battery system further includes comparing the lowest temperature with a fourth temperature threshold after closing the charging relay of the control box if the charging relay of the BMS detection control box is not closed.

[0069] Specifically, the heating request includes a request for a heating current, and the heating current I...h for:

[0070] I h =I1×n;

[0071] Where I1 represents the heating current value of a single battery box, and n represents the number of battery boxes to be heated; the charging request includes a requested charging current, and the charging current I c for:

[0072] I c =I²×n.

[0073] Where I2 represents the charging current value of a single battery pack.

[0074] Preferably, the mains heating mode of the battery system further includes:

[0075] When the battery system is heated to a minimum temperature greater than or equal to the first temperature threshold and less than the second temperature threshold, the main positive relay and the heating relay of the battery box are closed, and a heating and charging request is sent to the charging equipment to heat and charge the battery system.

[0076] Specifically, the heating and charging request includes a request for a heating and charging current, and the heating and charging current I... hc for:

[0077] I hc = (I1+I2)×n.

[0078] Understandably, when the battery system is heated to a temperature at which the cells can be safely used, the battery system simultaneously heats and charges to improve charging efficiency and enhance the effectiveness and safety of the battery system design.

[0079] In practice, the battery system's self-heating mode is specifically as follows:

[0080] After the battery system enters the battery self-heating mode, the lowest temperature is compared with the third temperature threshold.

[0081] If the minimum temperature is lower than the third temperature threshold and the duration is greater than or equal to the time threshold, the main positive relay of the battery box is disconnected, and the heating relay of the battery box is closed to heat the battery system. It is understandable that when the minimum temperature of the battery system is lower than the third temperature threshold, the battery cells are in an unsafe discharge state. Disconnecting the main positive relay prevents the battery system from discharging and damaging it; only the heating relay is closed to heat the battery system. Furthermore, the probability of errors occurring when the minimum temperature is lower than the third temperature threshold during battery self-heating is relatively high, and this has a significant impact on the battery system. Therefore, confirming that the minimum temperature is indeed below the third temperature threshold by ensuring the minimum temperature is lower than the third temperature threshold for a duration greater than or equal to the time threshold prevents inaccurate temperature readings due to temperature detection errors. The time threshold can be determined based on the actual situation.

[0082] When the lowest temperature is greater than or equal to the third temperature threshold and less than the first temperature threshold, the main positive relay and the heating relay of the battery box are closed to heat the battery system. Understandably, when the lowest temperature is greater than or equal to the third temperature threshold and less than the first temperature threshold, the battery cells are in a safe discharge state. The main positive relay of the battery box is closed to supply power to the load, and the heating relay of the battery box is closed to maintain heating of the battery system.

[0083] When the minimum temperature value is greater than or equal to the second temperature threshold, the main positive relay of the battery box closes, and the heating relay of the battery box opens, completing the heating process of the battery system. Understandably, when the minimum temperature value is greater than or equal to the second temperature threshold, the cells in the battery system are in a safe charging and discharging state, and the battery system can be charged and discharged subsequently. Simultaneously, the heating relay of the battery box opens, stopping heating.

[0084] S4. When the minimum temperature is greater than or equal to the second temperature threshold, the heating process of the battery system is complete. Understandably, once the battery system temperature meets the safe charging and discharging temperature of the cells, the heating process is complete, and the battery system can proceed with routine operations such as charging.

[0085] In practice, the control method further includes, after the battery system is powered on, before the BMS detects the minimum temperature of the battery system, the BMS performs a self-test to check for faults. If the self-test finds no faults, the minimum temperature is detected; otherwise, the BMS continues to perform a self-test.

[0086] Preferably, the first temperature threshold is 0℃, the second temperature threshold is 5℃, the third temperature threshold is -20℃, the fourth temperature threshold is -40℃, and the time threshold is 6 minutes.

[0087] Preferably, the control method in this embodiment further includes establishing a communication connection between the charging device and the BMS through a handshake message transmitted between the BMS and the BMS after the BMS has no faults during self-test and before the BMS detects the minimum temperature of the battery system. Specifically:

[0088] After the BMS self-test is successful, the charging equipment controller periodically sends a charging equipment handshake message (CHM) to the BMS.

[0089] After receiving the CHM message, the BMS will periodically send a BMS handshake message (BHM) to the charging equipment controller. The communication network between the charging equipment controller and the BMS generally uses the CAN 2.0B communication protocol.

[0090] If the handshake message between the BMS and the charging equipment controller is received normally and correctly, the handshake between the BMS and the charging equipment is successful, and a communication connection is established. The communication network between the charging equipment controller and the BMS typically uses the CAN 2.0B communication protocol.

[0091] It should be noted that after the communication connection is established, the BMS and the charging equipment will continue to send and receive messages periodically to monitor whether the communication of the battery system remains normal throughout the entire heating and charging process. If any abnormality occurs, the BMS will be notified in a timely manner.

[0092] More preferably, the control method in this embodiment further includes the following steps:

[0093] When the BMS continuously detects the lowest temperature of the battery system based on preset conditions, it also records the lowest temperature of each battery box.

[0094] During the battery self-heating and mains power heating processes, the lowest temperature of each battery box is compared with the second temperature threshold.

[0095] When the lowest temperature of the battery box is greater than or equal to the second temperature threshold, the main positive relay of the battery box is closed, the heating relay of the battery box is opened, and the heating process of the battery box is completed.

[0096] Understandably, by comparing the lowest temperature of each battery box during the heating process, and turning off the heating relay of that battery box once the lowest temperature meets the condition, it is possible to prevent any battery box in a parallel circuit from being heated for too long, which could damage the battery. At the same time, it can also save energy and avoid energy waste.

[0097] Compared with existing technologies, the present invention provides a control method for low-temperature heating of a battery system. By detecting the lowest temperature of the battery system through a BMS, and based on the lowest temperature of the battery system and whether it is powered by mains, the method provides a mains heating mode and a battery self-heating mode for the battery system. This makes the battery heating more timely and thorough, improves the reliability of the battery system heating, and ensures the safe use of the battery system. In addition, when the battery system is heated to a suitable temperature, the method controls the battery system to heat and charge simultaneously, improving charging efficiency and enhancing the effectiveness and safety of the battery system design.

[0098] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0099] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling low-temperature heating in a battery system, characterized in that, Includes the following steps: When the battery system is powered on, the BMS detects the lowest temperature of the battery system. The BMS continuously detects the lowest temperature of the battery system based on preset conditions, where the preset conditions are the detection time intervals. If the lowest temperature is less than the first temperature threshold, the BMS will detect whether the battery system is connected to the mains power. If the battery system is connected to AC power, the battery system will enter AC power heating mode; otherwise, it will enter battery self-heating mode. When the lowest temperature is greater than or equal to the second temperature threshold, the heating process of the battery system is complete. The mains power heating mode of the battery system is specifically as follows: After the battery system enters the AC heating mode, the BMS checks whether the charging relay in the control box is closed. If the charging relay is closed, the lowest temperature is compared with the fourth temperature threshold. When the minimum temperature is less than the fourth temperature threshold, the main positive relay of the battery box is disconnected, the heating relay of the battery box is closed, and a heating request is sent to the charging equipment to heat the battery system. When the lowest temperature is greater than or equal to the fourth temperature threshold and less than the first temperature threshold, the main positive relay of the battery box and the heating relay of the battery box are closed, and a heating request is sent to the charging equipment to heat the battery system. When the battery system is heated to a minimum temperature greater than or equal to the first temperature threshold and less than the second temperature threshold, the main positive relay and the heating relay of the battery box are closed, and a heating and charging request is sent to the charging equipment to heat and charge the battery system. When the minimum temperature is greater than or equal to the second temperature threshold, the main positive relay of the battery box is closed, the heating relay of the battery box is opened, and a charging request is sent to the charging equipment to charge the battery system, thus completing the heating process of the battery system.

2. The control method for low-temperature heating of a battery system according to claim 1, characterized in that, The battery system includes several battery boxes connected in parallel and a control box. The BMS continuously monitors the minimum temperature of the battery system based on preset conditions, including the following steps: Each battery box's slave board BMS detects the temperature of each cell in the battery module and transmits the data to the corresponding battery box's secondary master control BMS. The secondary main control BMS compares the temperature of each cell to obtain the lowest temperature of the corresponding battery box, and transmits it to the primary main control BMS of the control box. The primary control BMS compares the lowest temperature of each battery box to obtain the lowest temperature of the battery system.

3. The control method for low-temperature heating of a battery system according to claim 1, characterized in that, The mains heating mode of the battery system also includes comparing the lowest temperature with the fourth temperature threshold after closing the charging relay of the control box if the charging relay of the BMS detection control box is not closed.

4. The control method for low-temperature heating of a battery system according to claim 1, characterized in that, The heating request includes a request for heating current, and the heating current... for: ； in, This indicates the heating current value of a single battery compartment. Indicates the number of battery boxes to be heated; The charging request includes a requested charging current, and the charging current... for: ； in, This indicates the charging current value of a single battery pack. This indicates the number of battery boxes to be heated.

5. The control method for low-temperature heating of a battery system according to claim 1, characterized in that, The heating and charging request includes a request for a heating and charging current, and the heating and charging current... for: ； In the formula, This indicates the heating current value of a single battery compartment. This indicates the charging current value of a single battery pack. This indicates the number of battery boxes to be heated.

6. The control method for low-temperature heating of a battery system according to claim 1, characterized in that, The battery system's self-heating mode is specifically as follows: After the battery system enters the battery self-heating mode, the lowest temperature is compared with the third temperature threshold. If the minimum temperature is less than the third temperature threshold and the duration is greater than or equal to the time threshold, then the main positive relay of the battery box is disconnected and the heating relay of the battery box is closed to heat the battery system. When the lowest temperature is greater than or equal to the third temperature threshold and less than the first temperature threshold, the main positive relay and the heating relay of the battery box are closed to heat the battery system. When the minimum temperature value is greater than or equal to the second temperature threshold, the main positive relay of the battery box is closed, the heating relay of the battery box is opened, and the heating process of the battery system is completed.

7. The control method for low-temperature heating of a battery system according to claim 1, characterized in that, The control method further includes: When the BMS continuously detects the lowest temperature of the battery system based on preset conditions, it also records the lowest temperature of each battery box. During the battery self-heating and mains power heating processes, the lowest temperature of each battery box is compared with the second temperature threshold. When the lowest temperature of the battery box is greater than or equal to the second temperature threshold, the main positive relay of the battery box is closed, the heating relay of the battery box is opened, and the heating process of the battery box is completed.

8. The method for controlling low-temperature heating of a battery system according to claim 1, characterized in that, The control method further includes, after the battery system is powered on, before the BMS detects the minimum temperature of the battery system, the BMS performs a self-check to check for faults. If the self-check finds no faults, the minimum temperature is detected; otherwise, the BMS continues to perform a self-check.

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