A battery management system and power battery system with active balancing function

Abstract

A battery management system and a power battery system with active balancing function are disclosed. The battery management system includes an active balancing circuit, an analog front-end, and a microcontroller. The analog front-end collects data from N battery cells and sends it to the microcontroller. The active balancing circuit includes N balancing chips, the same number as the battery cells. Each balancing chip is connected to one battery cell. When the microcontroller detects a voltage difference between adjacent cells, the active balancing circuit, under the control of the microcontroller, transfers energy from the higher-energy cell to the lower-energy cell, thereby achieving battery balancing. This invention is an active balancing system where battery energy is transferred rather than dissipated, resulting in significantly higher efficiency than passive balancing, reduced heat generation, and improved overall system energy efficiency.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to a battery management system and a power battery system with active balancing function. Background Technology

[0002] With the rapid development of new energy vehicles, energy storage power stations, and other fields, the application of lithium-ion battery packs (PACKs) is becoming increasingly widespread. The Battery Management System (BMS), as the "brain" of the PACK, directly determines the safety, lifespan, and energy utilization rate of the battery pack. In practical applications, unavoidable inconsistencies exist between individual battery cells, mainly in voltage, internal resistance, and capacity. This inconsistency leads to a decrease in the charge and discharge capacity of the battery pack, reducing usable energy, and in severe cases, even causing localized overcharging and over-discharging, resulting in safety accidents such as thermal runaway. Therefore, how to efficiently manage battery consistency and provide accurate early warnings before thermal runaway occurs is a key technical challenge that urgently needs to be solved in the current BMS technology field.

[0003] Patent publication number CN118040815A discloses a passive balancing circuit and a battery management system. This battery management system dissipates usable electrical energy directly as heat through resistors, reducing the overall energy utilization rate of the battery pack. This is especially true for large-capacity battery packs, where the accumulated wasted energy is considerable. Due to limitations in the power and heat dissipation capacity of the resistors, the balancing current is usually small (typically in the 100mA range). For large-capacity battery packs or those with significant consistency differences, the balancing effect is slow and may not even be able to effectively compensate for the differences caused by self-discharge. Moreover, high-current balancing generates a large amount of heat, exacerbating the internal temperature rise of the battery pack and potentially affecting battery life and safety. Therefore, additional heat dissipation design is required.

[0004] Patent application number 201711004084.6 discloses a passive equalization control device and method for power batteries. The battery management system requires the MCU to generate an independent PWM signal for each equalization channel, resulting in large software overhead and hardware resource consumption. The PWM switching action will introduce high-frequency noise, which may interfere with the precise sampling accuracy of the voltage by the AFE. Moreover, it is a non-linear adjustment, and the average current is related to the MOSFET on-resistance, temperature, etc., making precise control difficult. Summary of the Invention

[0005] To address the aforementioned technical problems in the existing technology, this utility model provides a battery management system and a power battery system with active balancing function. The battery management system adopts integrated management, has high reliability, and realizes non-dissipative and active energy transfer between batteries, thereby improving balancing efficiency and energy utilization.

[0006] To achieve the above objectives, this utility model provides a battery management system with active balancing function for actively balancing a battery. The battery consists of N cells connected in series. The battery management system includes an active balancing circuit, an analog front-end, and a microcontroller. The analog front-end collects data from the N cells and sends it to the microcontroller. The active balancing circuit includes N balancing chips, the same number as the number of cells. Each balancing chip is connected to one cell. When the microcontroller detects a voltage difference between adjacent cells, the active balancing circuit, under the control of the microcontroller, transfers energy from the higher-energy cell to the lower-energy cell to achieve battery balancing. Here, N is an integer greater than 1.

[0007] As a further preferred embodiment of this utility model, the active equalization circuit, analog front end, and microcontroller are integrated on a PCB board.

[0008] As a further preferred embodiment of this utility model, the model number of the analog front end is BQ7692000.

[0009] As a further preferred embodiment of this utility model, the analog front end includes a multiplexer, a sampling circuit, and a sampling resistor. The multiplexer is used to measure the voltage of each cell, the sampling resistor is used to read the temperature of the battery, and the sampling resistor is used to transmit the battery current signal to the microcontroller.

[0010] As a further preferred embodiment of this utility model, the equalization chip is model ETA3000D2I.

[0011] As a further preferred embodiment of this utility model, there are four battery cells, namely a first battery cell, a second battery cell, a third battery cell, and a fourth battery cell; and there are four equalization chips, namely a first equalization chip, a second equalization chip, a third equalization chip, and a fourth equalization chip.

[0012] As a further preferred embodiment of this utility model, the pin ISET of the first equalization chip is connected to the negative terminal of the battery through a filter circuit, and the pin SW of the first equalization chip is connected to the positive terminal of the first cell and one end of the third capacitor through a first inductor, with the other end of the third capacitor grounded; the pin ISET of the second equalization chip is connected to the positive terminal of the first cell through a filter circuit, and the pin SW of the second equalization chip is connected to the positive terminal of the second cell and one end of the sixth capacitor through a second inductor, with the other end of the sixth capacitor grounded; the pin ISET of the third equalization chip is connected to the positive terminal of the second cell through a filter circuit, and the pin SW of the third equalization chip is connected to the positive terminal of the third cell and one end of the ninth capacitor through a third inductor, with the other end of the ninth capacitor grounded; the pin ISET of the fourth equalization chip is connected to the positive terminal of the third cell through a filter circuit, and the pin SW of the fourth equalization chip is connected to the positive terminal of the fourth cell and one end of the twelfth capacitor through a fourth inductor, with the other end of the twelfth capacitor grounded; the pin BATP of the fourth cell is connected to the positive terminal of the battery.

[0013] As a further preferred embodiment of this utility model, the filter circuit is composed of resistors and capacitors arranged in parallel.

[0014] As a further preferred embodiment of this utility model, the data information includes voltage, current, and temperature.

[0015] This utility model also provides a power battery system, including a battery, a load, an electronic switch, and a battery management system with active balancing function as described above. The electronic switch is connected to the charging and discharging circuit between the battery and the load, so that when the battery management system detects a safety alarm, it disconnects the electronic switch to cut off the charging and discharging circuit.

[0016] The battery management system and power battery system with active balancing function of this utility model can achieve the following beneficial effects by adopting the above technical solution:

[0017] 1. High-efficiency active balancing: The battery energy of this invention is transferred rather than dissipated, which is far more efficient than passive balancing, reduces heat generation, and improves the overall energy efficiency of the system.

[0018] 2. Bidirectional lossless balancing: The battery energy of this invention can be freely transferred bidirectionally between any two cells, offering great flexibility. Whether charging, discharging, or in a static state, as long as an inconsistency is detected, the active balancing circuit can be activated to perform balancing.

[0019] 3. Reduced heat generation and simplified thermal management: Since energy is transferred rather than dissipated, the heat generated by the active balancing circuit itself is much less than that of the passive balancing circuit (especially during high-current balancing).

[0020] 4. Preventing extreme deviations: In the early stages of battery use, inconsistencies may be small, but these differences gradually increase over time. The active balancing mechanism of this invention can continuously suppress the expansion of such deviations, thereby preventing any single cell from entering a dangerous overcharge or over-discharge state, thus improving battery lifespan. Attached Figure Description

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1 This is a structural block diagram of an embodiment of the battery management system with active balancing function provided by this utility model. In the figure, the cylinders are battery cells, and there are 4 of them.

[0023] Figure 2 This is a schematic diagram of an embodiment of the active equalization circuit provided in this utility model.

[0024] The purpose, features, and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Terms such as "upper," "lower," "left," "right," "middle," and "one" used in the preferred embodiments are merely for clarity of description and are not intended to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of implementation of the present invention.

[0026] The working principle of a traditional passive equalization circuit is as follows:

[0027] When the acquisition chip detects a voltage difference in the battery, it controls the corresponding transistor, such as Q8, to conduct. The current forms a loop through transistors BC1-Q8-BR15 / BR23-BC0. The current flows through the resistor and generates heat, and the energy is dissipated in the form of heat. This equalization method can only be used for small current equalization and has low efficiency. If a larger current is used for equalization, a large amount of heat will be generated, which will aggravate the temperature rise inside the battery pack and may affect the battery's life and safety. Therefore, additional heat dissipation design is required.

[0028] like Figure 1 , Figure 2As shown, this utility model provides a battery management system with active balancing function. The battery consists of N cells connected in series. The battery management system includes an active balancing circuit, an analog front-end, and a microcontroller. The analog front-end collects data from the N cells and sends it to the microcontroller. The active balancing circuit includes N balancing chips, the same number as the number of cells. Each balancing chip is connected to one cell. When the microcontroller detects a voltage difference between adjacent cells, the active balancing circuit, under the control of the microcontroller, transfers energy from the higher-energy cell to the lower-energy cell to achieve battery balancing. Here, N is an integer greater than 1. The battery is a lithium-ion battery or a lithium polymer battery, and the data includes voltage, current, and temperature.

[0029] To make the battery management system compact and occupy a small size, the active balancing circuit, analog front end, and microcontroller are preferably integrated on a PCB board.

[0030] In specific implementation, the analog front-end (also known as AFE) is model BQ7692000. This analog front-end includes a multiplexer, a sampling circuit, and a sampling resistor. The multiplexer measures the voltage of each cell, the sampling resistor reads the battery temperature, and the sampling resistor transmits the battery current signal to the microcontroller (MCU). Specifically, the AFE sends the collected voltage and temperature data to the MCU via an SPI interface. Simultaneously, the hardware comparator inside the AFE (integrated within the BQ7692000) continuously compares the voltage and temperature values ​​with preset safety thresholds. If any parameter exceeds the limit (e.g., overvoltage 0V, overtemperature OT), the AFE immediately (without MCU intervention) shuts down its driving (connected in series with the charging / discharging circuit electronic switch) protection FET (discharging FET or charging FET), disconnecting the circuit and achieving hardware-level protection with fast response and good performance.

[0031] Specifically, the equalization chip is model ETA3000D2I.

[0032] like Figure 2 As shown, there are four battery cells: a first battery cell, a second battery cell, a third battery cell, and a fourth battery cell; and four equalization chips: a first equalization chip, a second equalization chip, a third equalization chip, and a fourth equalization chip. Of course, in specific implementations, the number of battery cells and equalization chips can be other values, and this is not limited here.

[0033] The first equalization chip's pin ISET is connected to the negative terminal of the battery through a filter circuit. The first equalization chip's pin SW is connected to the positive terminal of the first battery cell and one end of the third capacitor through a first inductor, with the other end of the third capacitor grounded. The second equalization chip's pin ISET is connected to the positive terminal of the first battery cell through a filter circuit. The second equalization chip's pin SW is connected to the positive terminal of the second battery cell and one end of the sixth capacitor through a second inductor, with the other end of the sixth capacitor grounded. The third equalization chip's pin ISET is connected to the positive terminal of the second battery cell through a filter circuit. The third equalization chip's pin SW is connected to the positive terminal of the third battery cell and one end of the ninth capacitor through a third inductor, with the other end of the ninth capacitor grounded. The fourth equalization chip's pin ISET is connected to the positive terminal of the third battery cell through a filter circuit. The fourth equalization chip's pin SW is connected to the positive terminal of the fourth battery cell and one end of the twelfth capacitor through a fourth inductor, with the other end of the twelfth capacitor grounded. The fourth battery cell's pin BATP is connected to the positive terminal of the battery. Specifically, the filter circuit consists of resistors and capacitors arranged in parallel.

[0034] The following section primarily uses the first equalization chip (the working principle of other equalization chips is similar) as an example to illustrate its active equalization principle for battery cells:

[0035] The MCU reads the voltage of each battery cell to determine if the voltage difference between adjacent cells meets the equalization requirements. When two adjacent cells meet the equalization start-up conditions, the MCU controls the EN pin of the first equalization chip (also known as ETA3000D2I). At this time, the equalization circuit starts to work. For example, when the positive voltage B2 of the second battery cell is higher than the positive voltage B1 of the first battery cell, the upper MOSFET integrated inside the ETA3000D2I is turned on. The current path is B2-upper MOSFET-first inductor L1-B1. The first inductor L1 stores energy, and after a certain period of time, the internal upper MOSFET... When the circuit is disconnected, the lower MOSFET inside the first equalization chip is turned on, and the current path is L1-B1-GND-lower MOSFET-L1. By repeatedly opening and closing the upper and lower MOSFETs inside the first equalization chip, the energy of the higher voltage cell is transferred to the lower energy cell. Since the inductor is a non-energy-consuming device, the heat generation of the circuit is greatly reduced. At the same time, the equalization current can be programmed through the resistor R1 on the ISET pin of the ETA3000D2I chip. The equalization current can be adjusted according to the application requirements to maximize the equalization efficiency. Thus, voltage balance is achieved, ensuring the consistency of cell voltage.

[0036] This utility model also provides a power battery system, including a battery, a load, an electronic switch K, and a battery management system with active balancing function as described in any of the above embodiments. The electronic switch is connected to the charging and discharging circuit between the battery and the load so that when the battery management system detects a safety alarm (e.g., an overcurrent or short circuit), it disconnects the electronic switch to cut off the charging and discharging circuit.

[0037] Although specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. A battery management system with active balancing function, used for active balancing management of a battery, the battery being composed of N cells in series, characterized in that, The system includes an active balancing circuit, an analog front-end, and a microcontroller. The analog front-end collects data from N battery cells and sends it to the microcontroller. The active balancing circuit contains N balancing chips, the same number as the battery cells. Each balancing chip is connected to one of the battery cells. When the microcontroller detects a voltage difference between adjacent battery cells, the active balancing circuit, under the control of the microcontroller, transfers energy from the higher-energy battery cell to the lower-energy battery cell to achieve battery balancing. Here, N is an integer greater than 1.

2. The battery management system with active balancing function according to claim 1, characterized in that: The active equalization circuit, analog front-end, and microcontroller are integrated on a PCB board.

3. The battery management system with active balancing function according to claim 1, characterized in that: The model of the analog front end is BQ7692000.

4. The battery management system with active balancing function according to claim 3, characterized in that: The analog front end includes a multiplexer, a sampling circuit, and a sampling resistor. The multiplexer is used to measure the voltage of each cell, the sampling resistor is used to read the battery temperature, and the sampling resistor is used to transmit the battery current signal to the microcontroller.

5. The battery management system with active balancing function according to claim 1, wherein: The equalizer chip is model ETA3000D2I.

6. The battery management system with active equalization function according to claim 5, characterized in that: The battery cells consist of four components: a first battery cell, a second battery cell, a third battery cell, and a fourth battery cell. The equalization chips consist of four components: a first equalization chip, a second equalization chip, a third equalization chip, and a fourth equalization chip.

7. The battery management system with active balancing function according to claim 6, characterized in that: The first equalization chip's pin ISET is connected to the negative terminal of the battery through a filter circuit. The first equalization chip's pin SW is connected to the positive terminal of the first battery cell and one end of the third capacitor through a first inductor, with the other end of the third capacitor grounded. The second equalization chip's pin ISET is connected to the positive terminal of the first battery cell through a filter circuit. The second equalization chip's pin SW is connected to the positive terminal of the second battery cell and one end of the sixth capacitor through a second inductor, with the other end of the sixth capacitor grounded. The third equalization chip's pin ISET is connected to the positive terminal of the second battery cell through a filter circuit. The third equalization chip's pin SW is connected to the positive terminal of the third battery cell and one end of the ninth capacitor through a third inductor, with the other end of the ninth capacitor grounded. The fourth equalization chip's pin ISET is connected to the positive terminal of the third battery cell through a filter circuit. The fourth equalization chip's pin SW is connected to the positive terminal of the fourth battery cell and one end of the twelfth capacitor through a fourth inductor, with the other end of the twelfth capacitor grounded. The fourth battery cell's pin BATP is connected to the positive terminal of the battery.

8. The battery management system with active equalization function according to claim 7, characterized in that: The filter circuit consists of resistors and capacitors arranged in parallel.

9. The battery management system with active balancing function according to any one of claims 1 to 8, characterized in that: The data includes voltage, current, and temperature.

10. A power battery system, characterized in that: The device includes a battery, a load, an electronic switch, and a battery management system with active balancing function as described in any one of claims 1 to 9, wherein the electronic switch is connected to the charging and discharging circuit between the battery and the load, and disconnects the electronic switch to cut off the charging and discharging circuit when the battery management system detects a safety alarm.

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