Battery system and voltage equalization method thereof

Abstract

This invention relates to the field of battery management and equalization control technology, specifically to a battery system and its voltage equalization method, comprising: providing a main battery pack and multiple slave battery packs; providing a voltage equalization circuit for parallel connection of the main battery pack and multiple slave battery packs; when a slave battery pack requests access to the voltage equalization circuit, the voltage equalization circuit performs a first-level voltage equalization on the main battery pack and the slave battery packs; after the slave battery packs are connected to the voltage equalization circuit, the voltage equalization circuit performs a second-level voltage equalization on the multiple slave battery packs. This application achieves hierarchical voltage equalization between the main battery pack and slave battery packs, and among the multiple slave battery packs, prioritizing voltage equalization between the main battery pack and slave battery packs, effectively suppressing the risk of large instantaneous circulating currents caused by large voltage differences between the main battery pack and slave battery packs, thereby reducing the risk of damage to circuit components and the main battery pack, and thus improving the reliability of the battery system.

Description

Technical Field

[0001] This invention relates to the field of battery management and equalization control technology, and in particular to a battery system and its voltage equalization method. Background Technology

[0002] Currently, high-voltage, high-capacity battery packs have become core components supporting the reliable operation of residential and commercial energy storage systems. To meet the differentiated voltage and capacity requirements of various application scenarios, a modular design approach is often adopted in practical engineering, combining multiple battery packs into a complete system through series or parallel connections. A typical architecture is a "master battery pack + slave battery pack" structure. In this structure, the master battery pack usually has a built-in Battery Management System (BMS) responsible for managing unit communication and issuing unified equalization control commands; the slave battery pack is equipped with a slave BMS, which executes the master control commands and feeds back its own status information. This master-slave topology effectively simplifies system wiring and improves scalability and maintenance convenience. However, due to inherent differences in manufacturing, initial capacity, internal resistance, and self-discharge rate among battery packs, coupled with differences in temperature fields, charge / discharge conditions, and aging rates during operation, voltage imbalance between battery packs is inevitable. When the voltage difference between battery packs widens, the usable capacity of the entire system in a series connection is limited by the battery pack with the lowest voltage, resulting in a significant decrease in energy utilization. In a parallel connection, circulating currents between packs may occur, exacerbating local overheating and lifespan degradation. Therefore, how to implement efficient and accurate voltage balancing for battery systems with master-slave structures has become a key technical challenge to ensure system safety and economy.

[0003] Existing technologies lack structures or methods for graded voltage balancing between the main battery pack and slave battery packs. When the main battery pack has a low charge (low voltage) and the slave battery packs have a high charge (high voltage), direct parallel connection will generate instantaneous circulating currents several times the rated current, which may damage relays, fuses, or battery cells. In addition, when there is a large voltage difference between multiple slave battery packs, the high-voltage pack charges the low-voltage pack, which also forms an uncontrollable large current, which can easily damage circuit components as well as the main and slave battery packs. Currently, the safety and reliability of battery systems using the "main battery pack + slave battery pack" structure still need to be improved. Summary of the Invention

[0004] The purpose of this invention is to provide a battery system and its voltage balancing method to address the issue that the safety and reliability of existing battery systems using a "main battery pack + slave battery pack" structure still need to be improved.

[0005] The technical solution of the present invention is: a voltage equalization method for a battery system, comprising: providing a main battery pack and a plurality of slave battery packs; providing a voltage equalization circuit, wherein the voltage equalization circuit is used to connect the main battery pack and the plurality of slave battery packs in parallel; when a slave battery pack requests to connect to the voltage equalization circuit, the voltage equalization circuit performs a first-level voltage equalization on the main battery pack and the slave battery packs; after the slave battery packs are connected to the voltage equalization circuit, the voltage equalization circuit performs a second-level voltage equalization on the plurality of slave battery packs.

[0006] Preferably, the step of the voltage equalization circuit performing the first-level voltage equalization between the main battery pack and the slave battery pack includes: when a slave battery pack requests access to the voltage equalization circuit, acquiring the first voltage of the main battery pack, the voltage of the already connected slave battery pack, and the voltage of the slave battery pack requesting access; calculating the first difference between the first voltage of the main battery pack and the maximum voltage of the multiple slave battery packs; the voltage equalization circuit has a first threshold, comparing the first difference with the first threshold, if the first difference is greater than the first threshold, prohibiting the requested slave battery pack from accessing, and charging the main battery pack; during the charging process of the main battery pack, monitoring the second voltage of the main battery pack in real time, and simultaneously calculating the second difference between the second voltage of the main battery pack and the maximum voltage of the multiple slave battery packs; the voltage equalization circuit has a first recovery threshold, comparing the second difference with the first recovery threshold, if the second difference is less than the recovery threshold, stopping the charging of the main battery pack, connecting the requested slave battery pack, and completing the voltage equalization between the main battery pack and the slave battery pack.

[0007] Preferably, the step of the voltage equalization circuit performing a second-level voltage equalization on the plurality of slave battery packs includes: acquiring the voltage of each slave battery pack; calculating a third difference between the maximum and minimum voltages of the plurality of slave battery packs; the voltage equalization circuit having a second threshold, comparing the third difference with the second threshold, if the third difference is greater than the second threshold, the remaining slave battery packs charge the slave battery pack with the minimum voltage; real-time monitoring of the voltages of the maximum and minimum voltages of the remaining slave battery packs, and synchronously calculating a fourth difference between the voltages of the maximum and minimum voltages of the remaining slave battery packs; the voltage equalization circuit having a second recovery threshold, comparing the fourth difference with the second recovery threshold, if the fourth difference is less than the second recovery threshold, stopping the remaining slave battery packs from charging the battery pack with the minimum voltage, thus completing the voltage equalization among the plurality of slave battery packs.

[0008] Preferably, in the step of providing a main battery pack and a plurality of slave battery packs, the battery capacity of the main battery pack is greater than the battery capacity of the slave battery packs.

[0009] Preferably, in the step of the voltage equalization circuit performing a first-level voltage equalization on the main battery pack and the slave battery pack, the first recovery threshold is less than the first threshold; in the step of the voltage equalization circuit performing a second-level voltage equalization on the plurality of slave battery packs, the second recovery threshold is less than the second threshold.

[0010] Preferably, in the remaining steps of charging from the battery pack to the minimum voltage from the battery pack, the charging current has an upper limit.

[0011] Preferably, when the voltage equalization circuit performs the first-level voltage equalization on the main battery pack and the slave battery pack, if a new slave battery pack requests to connect to the voltage equalization circuit, the charging process of the main battery pack is not interrupted. The voltage of the already connected slave battery pack and the voltage of the requested slave battery pack are re-acquired, and the maximum voltage of multiple slave battery packs is updated. Before the main battery pack completes the charging process, the new slave battery pack is not connected to the voltage equalization circuit.

[0012] Preferably, the step of the voltage equalization circuit performing a second-level voltage equalization on the plurality of battery packs further includes: the remaining battery packs charging the minimum voltage battery pack for a standard time; when the charging time of the remaining battery packs to the minimum voltage battery pack exceeds the standard time, and the fourth difference is still not less than the second recovery threshold, the voltage equalization circuit issues an alarm.

[0013] This application also discloses a battery system, comprising: a battery pack group, including: a main battery pack and a plurality of slave battery packs; a voltage equalization circuit for connecting the main battery pack and the plurality of slave battery packs in parallel; and a battery management system electrically connected to the voltage equalization circuit, wherein the battery management system is used to perform the steps of the voltage equalization method as described in any one of claims 1 to 8.

[0014] Compared with the prior art, the advantages of the present invention are: (1) The voltage equalization method of the battery system disclosed in this application realizes the hierarchical voltage equalization between the main battery pack and the slave battery pack, as well as among multiple slave battery packs. It prioritizes the voltage equalization of the main battery pack and the slave battery pack, effectively suppressing the risk of large instantaneous circulating current caused by a large voltage difference between the main battery pack and the slave battery pack. This helps to reduce the risk of damage to circuit components and the main battery pack, and thus helps to improve the reliability of the battery system.

[0015] (2) In the voltage equalization method of the battery system disclosed in this application, when the first difference is greater than the first threshold, the connection of the battery pack to the voltage equalization circuit is prohibited. After the main battery pack has finished charging, the connection of the battery pack to the voltage equalization circuit is allowed. Thus, while completing the voltage equalization between the main battery pack and the battery pack, dynamic control of the connection of the battery pack to the voltage equalization circuit is realized, so that the battery system can adjust the connection and disconnection of the battery pack in real time according to the real-time status of each battery pack, and adjust the charging and discharging current of the circuit system in real time, which is beneficial to improving the working performance and reliability of the battery system. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a flowchart of a voltage equalization method for a battery system according to the present invention; Figure 2 This is a flowchart of the first-stage voltage equalization method in a battery system voltage equalization method according to the present invention; Figure 3 This is a flowchart of the second-stage voltage equalization method in a battery system voltage equalization method according to the present invention; Figure 4 This is a block diagram of the voltage equalization circuit in a voltage equalization method for a battery system according to the present invention. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to specific embodiments: To facilitate understanding, the application scenario of this application is first explained. For battery systems employing a "main battery pack + slave battery pack" structure, existing technologies lack a structure or method for graded voltage balancing between the main and slave battery packs. When the main battery pack has a low charge (low voltage) and the smaller battery packs have a high charge (high voltage), direct parallel connection will generate instantaneous circulating currents several times the rated current, potentially damaging relays, fuses, or battery cells. Furthermore, when there are large voltage differences between multiple smaller battery packs, the high-voltage pack charges the low-voltage pack, also creating uncontrollable large currents that can easily damage circuit components and both the main and slave battery packs. Currently, the safety and reliability of battery systems using a "main battery pack + slave battery pack" structure still need improvement. Therefore, this application provides a battery system and its voltage balancing method.

[0018] like Figure 1 As shown, Figure 1 This is a flowchart of a voltage equalization method for a battery system according to the present invention.

[0019] S1 provides a main battery pack and multiple slave battery packs.

[0020] The main battery pack is used to provide the primary driving energy for the battery system.

[0021] As an example, the main battery pack uses lithium iron phosphate (LFP) batteries, which have a low degradation rate, resulting in a longer lifespan for the main battery pack. Furthermore, LFP batteries can achieve a thermal peak value exceeding 350 degrees Celsius, maintaining stable discharge performance even at high temperatures, thus improving the versatility and reliability of the main battery pack. In addition, LFP batteries possess excellent high-current discharge characteristics, meeting the instantaneous high-power demands of the main battery pack during startup or under high load conditions, thereby enhancing the overall performance of the battery system. In other embodiments, the main battery pack may also use lithium batteries.

[0022] In some embodiments, in the step of providing a main battery pack and multiple slave battery packs, the battery capacity of the main battery pack is greater than that of the slave battery packs. The battery system adopts an asymmetric capacity design with multiple batteries. The main battery pack serves as the primary power supply element of the battery system, enabling the battery management system to employ a hierarchical scheduling strategy of "main supply + auxiliary supplementation." That is, under low load conditions, the battery system can be powered solely by the main battery pack, which helps reduce the frequency of slave battery pack start-ups and shutdowns and suppresses the conversion losses caused by frequent start-ups and shutdowns of slave battery packs. When the main battery pack enters a low-charge state, is depleted, or requires a large instantaneous current, the slave battery packs are then connected to the power supply circuit, which helps improve the energy utilization rate and overall energy efficiency of the battery system. In addition, concentrating a larger capacity in the main battery pack facilitates the lightweight and miniaturized design of the slave battery packs, reduces the difficulty of carrying and plugging / unplugging the slave battery packs, optimizes the weight distribution of the battery system, and improves the spatial rationality and portability of the battery system.

[0023] The battery pack is used to provide auxiliary power to the battery system and extend the driving range when needed.

[0024] As an example, the secondary battery pack is detachably connected to the main battery pack, allowing it to be removed from the main battery pack when auxiliary power and extended range are not required, thus saving space in the battery system. In other embodiments, the secondary battery pack can also be wired to the main battery pack, with a switch on the wire that can be controlled to turn on and off, corresponding to controlling the connection and disconnection between the secondary and main battery packs.

[0025] As an example, the secondary battery pack uses the same type of battery as the main battery pack, namely lithium iron phosphate batteries. In other embodiments, the secondary battery pack may also use lithium batteries.

[0026] In some embodiments, the battery capacities of the multiple slave battery packs are equal. When multiple slave battery packs are connected in parallel to the battery system, the equal battery capacities of the multiple slave battery packs, based on the parallel characteristics of the circuit, facilitate the uniform distribution of current in the branch where each slave battery pack is located. This effectively suppresses the problem of overload heating or accelerated aging of the slave battery packs caused by current imbalance in the branch where each slave battery pack is located, which is beneficial to improving the safety and reliability of the battery system. In addition, the equal battery capacities of the multiple slave battery packs ensure that the parallel topology and the corresponding battery management system hardware specifications are the same, which helps to simplify the design difficulty of the battery system and the difficulty of mass production.

[0027] In some embodiments, each slave battery pack has an independent charge / discharge switch on its independent parallel branch. The charge / discharge switch controls the connection or disconnection of the independent parallel branch containing a single slave battery pack, thereby controlling the connection or isolation of a single slave battery pack from the main battery pack. Having a one-to-one corresponding charge / discharge switch for each slave battery pack improves the sensitivity of control over the connection or isolation status of the slave battery packs.

[0028] S2. Provides a voltage balancing circuit for parallel connection of the main battery pack and multiple slave battery packs.

[0029] like Figure 4 As shown, Figure 4 This is a block diagram of the voltage equalization circuit in a voltage equalization method for a battery system according to the present invention.

[0030] In the voltage balancing circuit, the main battery pack and multiple slave battery packs are connected in parallel, which allows for an increase in the total battery capacity and total energy of the battery system by increasing the number of slave battery packs without changing the operating voltage of the battery system. When the main battery pack or any slave battery pack fails, is damaged, or is depleted, the slave battery packs on the remaining parallel branches in the voltage balancing circuit can independently provide emergency power, improving the reliability of the battery system. In addition, it also helps to reduce the operational difficulty of connecting or isolating slave battery packs according to actual needs.

[0031] In some embodiments, the battery system further includes a battery management system (BMS), which monitors the operating status parameters of the main battery pack and slave battery packs in real time and performs charge and discharge protection and thermal management control, thereby improving the operational safety and efficiency of the battery system.

[0032] S3. When the battery pack requests access to the voltage balancing circuit, the voltage balancing circuit performs the first stage of voltage balancing on the main battery pack and the slave battery pack.

[0033] The voltage equalization method for battery systems disclosed in this application achieves hierarchical voltage equalization between the main battery pack and slave battery packs, as well as among multiple slave battery packs. It prioritizes voltage equalization between the main battery pack and slave battery packs, effectively suppressing the risk of large instantaneous circulating currents caused by large voltage differences between the main battery pack and slave battery packs. This helps reduce the risk of damage to circuit components and the main battery pack, thereby improving the reliability of the battery system.

[0034] refer to Figure 2 , Figure 2 This is a flowchart of the first-stage voltage equalization method in a battery system voltage equalization method according to the present invention. In some embodiments, the step of the voltage equalization circuit performing the first-stage voltage equalization on the main battery pack and the slave battery pack includes: S31. When a battery pack requests access to the voltage balancing circuit, the first voltage of the main battery pack, the voltage of the already connected slave battery pack, and the voltage of the slave battery pack requesting access are collected.

[0035] When a new slave battery pack requests to connect to the voltage balancing circuit, the voltage of the main battery pack is collected. This facilitates subsequent determination of whether the main battery pack's state of charge (SOC) needs charging based on the voltage difference. Simultaneously, the voltage of the slave battery pack already connected to the voltage balancing circuit is collected, reducing the risk of excessive instantaneous current surges caused by excessive voltage differences between the slave and main battery packs during connection. This avoids damage to circuit components, as well as the main and slave battery packs, thereby improving the reliability of the battery system.

[0036] S32. Calculate the first voltage of the main battery pack and the first difference between the maximum voltages of the multiple slave battery packs.

[0037] The first difference is used to reflect the maximum voltage difference between the main battery pack and the slave battery pack.

[0038] Specifically, after collecting the voltage of the connected slave battery pack and the voltage of the slave battery pack that is requested to be connected, the voltage value of the slave battery pack with the maximum voltage is collected and subtracted from the first voltage of the main battery pack to obtain a first difference.

[0039] S33. The voltage equalization circuit has a first threshold. It compares the first difference with the first threshold. If the first difference is greater than the first threshold, it prohibits the access of the requested slave battery pack and charges the main battery pack.

[0040] The first threshold is used to calibrate the maximum allowable voltage difference between the main battery pack and the slave battery pack in the battery system.

[0041] If the voltage difference between the main battery pack and the slave battery pack exceeds a first threshold, meaning the voltage difference exceeds the allowable range of the battery system, it is likely to generate a large instantaneous current surge when the slave battery pack is connected or the battery system is running, increasing the risk of damage to circuit components, the main battery pack, and the slave battery pack. When the first difference is greater than the first threshold, it indicates that the state of charge of the main battery pack is too low, i.e., the remaining charge is too low, and the connection of the slave battery pack and its charging of the main battery pack are prohibited.

[0042] When the first difference is greater than the first threshold, access to the voltage balancing circuit from the battery pack is prohibited. After the main battery pack has finished charging, access to the voltage balancing circuit from the battery pack is allowed. This achieves voltage balancing between the main battery pack and the battery packs while dynamically controlling access to the voltage balancing circuit from the battery packs. This allows the battery system to adjust the access and shutdown of the battery packs in real time according to their real-time status, and to regulate the charging and discharging current of the circuit system in real time, which is beneficial to improving the performance and reliability of the battery system.

[0043] It should be noted that the battery system controls the inverter or DC-DC converter through the battery management system to charge the main battery pack. As an example, the battery system uses the battery management system to control the DC-DC converter to charge the main battery pack.

[0044] It should also be noted that when the battery system charges the main battery pack, the energy required for the charging process is provided by the secondary battery packs already connected to the battery system and external power sources.

[0045] S34. During the charging process of the main battery pack, the second voltage of the main battery pack is monitored in real time, and the second difference between the second voltage of the main battery pack and the maximum voltage of multiple slave battery packs is calculated simultaneously.

[0046] The second difference is used to reflect the maximum voltage difference between the main battery pack and the slave battery pack during charging.

[0047] Real-time monitoring of the main battery pack voltage during charging facilitates the acquisition of changes in the voltage difference between the main and slave battery packs, enabling timely adjustment of the main battery pack's charging parameters based on the second difference value.

[0048] Specifically, after acquiring the second voltage of the main battery pack, the voltage value of the slave battery pack with the maximum voltage is subtracted from the second voltage of the main battery pack to obtain the second difference.

[0049] S35. The voltage balancing circuit has a first recovery threshold. It compares a second difference with the first recovery threshold. If the second difference is less than the recovery threshold, it stops charging the main battery pack and connects the requested slave battery pack to complete the voltage balancing between the main battery pack and the slave battery pack.

[0050] The first recovery threshold is used to calibrate the maximum allowable voltage difference between the main battery pack and the slave battery pack in the battery system when the main battery pack is charging.

[0051] When the voltage difference between the main battery pack and the slave battery pack during charging is less than the first recovery threshold, it means that the voltage difference between the main battery pack and the slave battery pack is within the allowable voltage difference range of the battery system. The charging process of the main battery pack is stopped and the slave battery pack to be connected is allowed to be connected to the battery system. This greatly reduces the risk of a large instantaneous current surge when the slave battery pack is connected, which is beneficial to improving the reliability of the battery system.

[0052] In some embodiments, during the step of the voltage equalization circuit performing a first-level voltage equalization on the main battery pack and the slave battery pack, the first recovery threshold is less than the first threshold. This provides a buffer area between the on and off states of the main battery pack charging process, preventing high-frequency oscillations during command determination caused by the first threshold and the first recovery threshold being equal. This ensures that the battery system's state switching for the main battery pack charging process is unidirectional, which helps improve the stability and reliability of the battery system operation.

[0053] It should be noted that when the voltage balancing circuit performs the first-stage voltage balancing of the main battery pack and slave battery packs, if a new slave battery pack requests to connect to the voltage balancing circuit, the charging process of the main battery pack is not interrupted. The voltages of the already connected slave battery packs and the requested slave battery packs are re-acquired, and the maximum voltages of multiple slave battery packs are updated. The new slave battery pack will not connect to the voltage balancing circuit until the main battery pack completes its charging process. When the main battery pack's capacity is low, priority is given to ensuring the completion of the main battery pack's charging process, effectively suppressing the problem of the main battery pack's capacity being too low or the charging process being interrupted, and improving the safety of the main battery pack's charging process.

[0054] S4. After the battery pack is connected to the voltage equalization circuit, the voltage equalization circuit performs a second-level voltage equalization on the multiple battery packs.

[0055] After the battery pack is connected to the battery system, the voltage of multiple battery packs is monitored in real time and a second-level voltage equalization is performed. The voltage difference between the battery packs is monitored and equalized at the moment a new battery pack is connected and during the subsequent operation of the battery system. This effectively suppresses the risk of uncontrollable current surges caused by large voltage differences between multiple battery packs, avoids damage to circuit components and battery packs in the battery system, and improves the reliability of the battery system.

[0056] refer to Figure 3 , Figure 3 This is a flowchart of the second-stage voltage equalization method in a battery system voltage equalization method according to the present invention. In some embodiments, the step of the voltage equalization circuit performing second-stage voltage equalization on multiple battery packs includes: S41. Collect the voltage of each battery pack.

[0057] When a new slave battery pack is connected to the voltage balancing circuit, the voltage of multiple slave battery packs is collected, and the state of charge of each slave battery pack is monitored to facilitate the selection of the slave battery pack with the highest voltage and the slave battery pack with the lowest voltage.

[0058] S42. Calculate the third difference between the maximum and minimum voltages from multiple battery packs.

[0059] The third difference is used to reflect the maximum voltage difference between multiple slave battery packs connected to the battery system.

[0060] Specifically, after collecting the voltages of multiple battery packs, the voltage of the battery pack with the highest voltage is selected and subtracted from the voltage of the battery pack with the lowest voltage to obtain a third difference.

[0061] S43. The voltage equalization circuit has a second threshold. It compares the third difference with the second threshold. If the third difference is greater than the second threshold, the remaining voltage is charged from the battery pack to the minimum voltage.

[0062] The second threshold is used to calibrate the maximum allowable voltage difference between individual battery packs in the battery system.

[0063] If the voltage difference between the maximum and minimum voltage slave battery packs exceeds the second threshold, it means that the voltage difference between the maximum and minimum voltage slave battery packs exceeds the allowable range of the battery system. This can easily generate large, uncontrollable current surges during battery system operation, increasing the risk of damage to circuit components, the main battery pack, and the slave battery packs. When the third difference is greater than the second threshold, it indicates that the minimum voltage slave battery pack has a low state of charge, meaning its remaining charge is too low. The other slave battery packs connected to the battery system then charge the minimum voltage slave battery pack.

[0064] It should be noted that when the other slave battery packs connected to the battery system are charging the slave battery pack with the lowest voltage, other functions of the battery system continue to operate. This ensures that the operation of the battery system is not interrupted while the voltage of multiple slave battery packs is balanced, thereby improving the operating efficiency of the battery system.

[0065] In some embodiments, the charging current during the remaining steps of charging from the battery pack to the minimum voltage from the battery pack has an upper limit.

[0066] The charging current when charging the minimum voltage battery pack from the main battery pack should not be too large. This is to avoid the minimum voltage battery pack being subjected to excessive current surges in a short period of time during the charging process, effectively reducing the risk of local overheating during the charging process, which could trigger the battery system's overcharge protection or thermal runaway, and improving the safety and reliability of the battery system. Setting an upper limit on the charging current helps to limit the charging current of the minimum voltage battery pack within a safe threshold, suppressing the problem of increased internal resistance and permanent capacity loss caused by the structural degradation of the battery pack's internal materials, and extending the battery pack's service life.

[0067] As an example, the upper limit of the charging current when the battery pack is charged from the minimum voltage is 10 amps.

[0068] S44. Monitor the maximum and minimum voltages of the remaining battery packs in real time, and simultaneously calculate the fourth difference between the maximum and minimum voltages of the remaining battery packs.

[0069] The fourth difference is used to reflect the maximum voltage difference between the slave battery pack with the lowest voltage and the other slave battery packs during charging.

[0070] The voltage of the slave battery pack is monitored in real time during the charging process, which facilitates the collection of voltage difference changes between the other slave battery packs and the minimum voltage slave battery pack, and allows for timely adjustment of the charging parameters of the minimum voltage slave battery pack based on the fourth difference value.

[0071] S45. The voltage equalization circuit has a second recovery threshold. It compares the fourth difference with the second recovery threshold. If the fourth difference is less than the second recovery threshold, it stops the remaining battery packs from charging the battery pack with the lowest voltage, thus completing the voltage equalization between multiple battery packs.

[0072] The second recovery threshold is used to calibrate the maximum allowable voltage difference between multiple slave battery packs in the battery system when the slave battery pack with the minimum voltage is charging.

[0073] If the voltage difference between the minimum voltage battery pack and the maximum voltage difference between the remaining slave battery packs is less than the second recovery threshold, it means that the voltage difference between the minimum voltage battery pack and the remaining slave battery packs is within the allowable voltage difference range of the battery system. Stopping the charging process of the minimum voltage battery pack greatly reduces the risk of large uncontrollable current surges between the slave battery packs during battery system operation, which is beneficial to improving the reliability of the battery system.

[0074] In some embodiments, during the second-level voltage equalization step of the voltage equalization circuit for multiple slave battery packs, the second recovery threshold is less than the second threshold. This provides a buffer region for the on and off states of the minimum voltage slave battery pack charging process, preventing high-frequency oscillations during command determination caused by the second threshold and the second recovery threshold being equal. This ensures that the battery system's state switching for the minimum voltage slave battery pack charging process is unidirectional, which helps improve the stability and reliability of the battery system operation.

[0075] In some embodiments, the step of the voltage equalization circuit performing a second-level voltage equalization on multiple battery packs further includes: the remaining battery packs charging the minimum voltage battery pack for a standard time; when the charging time of the remaining battery packs to the minimum voltage battery pack exceeds the standard time, and the fourth difference is still not less than the second recovery threshold, the voltage equalization circuit issues an alarm.

[0076] When the charging time from the remaining battery packs to the minimum voltage battery pack exceeds the standard time, i.e., the charging time of the minimum voltage battery pack is too long, it increases the risk that the rated battery capacity of the multiple battery packs in the battery system may differ. This can easily lead to different currents in the parallel branches of the multiple battery packs in the battery system, increasing the risk of damage to the battery system circuit components. Alternatively, there may be a risk of open circuit in the circuit where the remaining battery packs charge the minimum voltage battery pack. An alarm will be issued to notify the staff to investigate in a timely manner and improve the reliability of the battery system.

[0077] This application also discloses a battery system, comprising: a battery pack group, including: a main battery pack and a plurality of slave battery packs; a voltage equalization circuit for connecting the main battery pack and the plurality of slave battery packs in parallel; and a battery management system electrically connected to the voltage equalization circuit, wherein the battery management system is used to perform the steps of the voltage equalization method as described in any one of claims 1 to 8.

[0078] The battery system disclosed in this application executes the steps of the voltage equalization method as described in any one of claims 1 to 8 through the battery management system, thereby achieving hierarchical voltage equalization between the main battery pack and the slave battery packs, as well as among multiple slave battery packs. Prioritizing voltage equalization between the main battery pack and the slave battery packs effectively suppresses the risk of large instantaneous circulating currents caused by large voltage differences between the main battery pack and the slave battery packs, thereby reducing the risk of damage to circuit components and the main battery pack, and thus improving the reliability of the battery system.

[0079] The description of the main battery pack, slave battery pack, and voltage equalization circuit in this embodiment is similar to that in the previous embodiment. Please refer to the relevant content in the previous embodiment, and it will not be repeated here.

[0080] The battery management system is used to perform the steps of the voltage equalization method as described in any one of claims 1 to 8.

[0081] The battery system controls the inverter or DC-DC converter through the battery management system to charge the main battery pack. As an example, the battery system controls the DC-DC converter through the battery management system to charge the main battery pack.

[0082] Specifically, the battery management system includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the voltage equalization method as described in any one of claims 1 to 8.

[0083] The above embodiments are merely illustrative of the technical concept and features of the present invention, intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and thus all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

Claims

1. A method of voltage equalization of a battery system, characterized by, include: Provides a main battery pack and multiple slave battery packs; A voltage equalization circuit is provided, which is used to connect the main battery pack and the plurality of slave battery packs in parallel. When a request is made from the battery pack to access the voltage equalization circuit, the voltage equalization circuit performs a first-stage voltage equalization on the main battery pack and the slave battery pack. After the battery packs are connected to the voltage equalization circuit, the voltage equalization circuit performs a second-level voltage equalization on the plurality of battery packs.

2. The voltage equalization method for a battery system according to claim 1, characterized in that: The voltage equalization circuit performs the first-stage voltage equalization of the main battery pack and the slave battery pack, including the following steps: When a battery pack requests access to the voltage equalization circuit, the first voltage of the main battery pack, the voltage of the already connected slave battery pack, and the voltage of the slave battery pack requesting access are collected. Calculate the first voltage of the main battery pack and the first difference between the maximum voltages of the multiple slave battery packs; The voltage equalization circuit has a first threshold. It compares the first difference with the first threshold. If the first difference is greater than the first threshold, it prohibits the requesting access of the slave battery pack and charges the main battery pack. During the charging process of the main battery pack, the second voltage of the main battery pack is monitored in real time, and the second difference between the second voltage of the main battery pack and the maximum voltage of multiple slave battery packs is calculated simultaneously. The voltage equalization circuit has a first recovery threshold. It compares the second difference with the first recovery threshold. If the second difference is less than the recovery threshold, it stops charging the main battery pack and connects the requested slave battery pack, thus completing the voltage equalization between the main battery pack and the slave battery pack.

3. The voltage equalization method for a battery system according to claim 1, characterized in that: The voltage equalization circuit performs a second-stage voltage equalization on the plurality of battery packs, including the following steps: Collect the voltage of each battery pack; Calculate a third difference between the maximum and minimum voltages from multiple battery packs; The voltage equalization circuit has a second threshold. The third difference is compared with the second threshold. If the third difference is greater than the second threshold, the remaining voltage is charged from the battery pack to the minimum voltage. The voltage of the maximum and minimum voltage slave battery packs in the remaining slave battery packs is monitored in real time, and a fourth difference between the voltage of the maximum and minimum voltage slave battery packs in the remaining slave battery packs is calculated synchronously; the voltage equalization circuit has a second recovery threshold, and the fourth difference is compared with the second recovery threshold. If the fourth difference is less than the second recovery threshold, the charging of the remaining slave battery packs to the minimum voltage slave battery pack is stopped, thus completing the voltage equalization among the multiple slave battery packs.

4. The voltage equalization method for a battery system according to claim 1, characterized in that: In the step of providing a main battery pack and multiple slave battery packs, the battery capacity of the main battery pack is greater than the battery capacity of the slave battery packs.

5. A voltage equalization method for a battery system according to claim 2 or 3, characterized in that: In the step of the voltage equalization circuit performing the first-level voltage equalization of the main battery pack and the slave battery pack, the first recovery threshold is less than the first threshold. In the step of the voltage equalization circuit performing a second-level voltage equalization on the plurality of battery packs, the second recovery threshold is less than the second threshold.

6. The voltage equalization method for a battery system according to claim 3, characterized in that: In the remaining steps of charging from the battery pack to the minimum voltage from the battery pack, the charging current has an upper limit.

7. The method of claim 2, wherein: When the voltage equalization circuit performs the first-stage voltage equalization on the main battery pack and the slave battery pack, if a new slave battery pack requests to connect to the voltage equalization circuit, the charging process of the main battery pack is not interrupted. The voltage of the already connected slave battery pack and the voltage of the requested slave battery pack are re-acquired, and the maximum voltage of multiple slave battery packs is updated. Before the main battery pack completes the charging process, the new slave battery pack is not connected to the voltage equalization circuit.

8. The method of claim 3, wherein: The step of the voltage equalization circuit performing the second-level voltage equalization on the multiple battery packs further includes: the remaining battery packs charging the minimum voltage battery pack for a standard time; when the charging time of the remaining battery packs to the minimum voltage battery pack exceeds the standard time, and the fourth difference is still not less than the second recovery threshold, the voltage equalization circuit issues an alarm.

9. A battery system characterized by, include: The battery pack assembly includes: a main battery pack and multiple slave battery packs; A voltage balancing circuit is used to connect the main battery pack and the plurality of slave battery packs in parallel. A battery management system electrically connected to the voltage equalization circuit, the battery management system being used to perform the steps of the voltage equalization method as described in any one of claims 1 to 8.

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