A cell balancing system

Abstract

This utility model discloses a cell balancing system, including a balancing module and a balancing control module. The balancing module includes multiple independently configured isolated power supply units and power supply units that supply power to each isolated power supply unit. Each cell in the cell pack is equipped with an isolated power supply unit, and each isolated power supply unit is connected to a balancing control module. The balancing control module sends independent balancing control signals to each isolated power supply unit. Under the control of the balancing control module, each isolated power supply unit starts or stops charging its corresponding cell, thereby achieving capacity balancing among the cells in the cell pack. The cell pack includes multiple cells connected in series, and the cell pack forms a loop with a bidirectional inverter to achieve charging and discharging operations with the power grid through the bidirectional inverter. The cells are lithium iron phosphate batteries. This utility model can achieve efficient balancing of the cells in the cell pack, with no limit on the number of cells to be balanced, low cost, and is suitable for widespread application.

Description

Technical Field

[0001] This utility model relates to a cell balancing system, belonging to the field of cell capacity balancing technology. Background Technology

[0002] Currently, large-scale energy storage systems have increasingly higher energy storage capacity requirements. These systems consist of several cell clusters, which in turn contain several cell packs (also known as battery modules). Each cell pack contains several cells connected in series (also known as individual cells). In other words, an energy storage system is composed of a large number of individual cells. Individual cells typically use lithium-ion batteries. During use, the actual usable capacity of a cell pack decreases over time, exhibiting significant dispersion. It also exhibits the following characteristics: the actual effective capacity of the cell pack is often less than the actual capacity of its individual cells; the rate of capacity decay within the cell pack is often greater than that of individual cells; the greater the dispersion of individual cells within the cell pack, i.e., the worse the consistency, the worse the charge / discharge capability of the cell pack; if a single cell exhibits inconsistency, it becomes a factor limiting the overall charge / discharge performance. In other words, if a single cell reaches the charge / discharge cutoff voltage, the entire cell pack must stop charging / discharging, otherwise it may lead to cell failure or even a fire. As can be seen from the above, balancing the capacity of each individual cell in the battery pack can give the battery pack good consistency, which can greatly increase its actual usable effective capacity and significantly extend its service life.

[0003] Currently, there are two main methods for battery cell equalization: passive equalization and active equalization. Passive equalization uses resistor absorption to reduce the voltage of cells with excessively high capacity (or voltage), thereby improving consistency. However, this method is energy-intensive and carries a high risk of thermal runaway, so it is not commonly used. Active equalization actively analyzes the capacity of each cell and optimizes consistency by transferring high-capacity cells to low-capacity cells using a "high-capacity release, low-capacity compensation" approach. This method is more efficient, achieving an equalization efficiency of 80%-90%.

[0004] Furthermore, there are two main existing active balancing methods:

[0005] One method is manual equalization, which is currently used by most manufacturers and is typically performed once a month. This method transfers charge to each cell one by one according to their arrangement, without skipping cells. The charge transfer efficiency between adjacent cells is usually between 80% and 90%, so after multiple charge transfers, the charge is depleted, thus limiting the number of cells that can be equalized, generally not exceeding 16 individual cells. Increasing the number of cells requires more complex equalization circuits, which increases costs and the failure rate. Therefore, this method suffers from high labor costs, susceptibility to human error in equalization effectiveness, lack of real-time capability, and a limited number of cells that can be equalized.

[0006] Another method is the shared inductor method, where multiple cells store electricity in an inductor via an inverter, and then the electricity is automatically transferred to the cell with the lower voltage. This method also suffers from a limitation on the number of cells that can be balanced; generally, a maximum of 16 individual cells can be balanced. Increasing the number of cells requires a more complex balancing circuit.

[0007] Therefore, designing a technical solution for efficient balancing of cells within a battery pack without manual intervention, and with no limit on the number of cells to be balanced, is an urgent problem to be solved. Utility Model Content

[0008] The purpose of this invention is to provide a cell balancing system that can achieve efficient balancing of each cell in a cell pack, with no limit on the number of cells to be balanced, low cost, and suitable for widespread application.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A cell balancing system includes a balancing module and a balancing control module. The balancing module includes multiple independently configured isolated power supply units and a power supply unit that supplies power to each of the isolated power supply units. Each cell in the cell pack is configured with one of the isolated power supply units, and each isolated power supply unit is connected to a balancing control module. The balancing control module is used to send independent balancing control signals to each of the isolated power supply units. Under the control of the balancing control module, each isolated power supply unit starts or stops charging its corresponding cell to achieve capacity balancing among the cells in the cell pack. The cell pack includes multiple cells connected in series, and the cell pack forms a loop with a bidirectional inverter to achieve charging and discharging operations between the bidirectional inverter and the power grid. The cells are lithium iron phosphate batteries.

[0011] Further design of the equalization control module: The first scheme is that the equalization control module includes a power supply unit and a DC / DC unit, wherein: the power supply unit is divided into two paths, one path is connected to each of the isolated power supply units through the DC / DC unit, and sends an equalization control signal to each of the isolated power supply units to start the charging operation, and the other path is directly connected to each of the isolated power supply units to supply power to each of the isolated power supply units.

[0012] The second approach involves a balancing control module comprising a power supply unit and multiple metering units. These metering units are connected in series to form a loop with the CPU. Each battery cell within the battery pack is equipped with one metering unit. The metering unit detects the voltage across the battery cell and feeds back the detected voltage information to the CPU. The CPU is connected to each of the isolated power supply units. Based on the voltage information fed back by the metering units, the CPU controls each isolated power supply unit to start or stop charging a corresponding battery cell, thereby achieving capacity balancing among the batteries within the battery pack. The power supply unit provides power to the CPU and each metering unit.

[0013] Furthermore, the isolated power supply unit includes a DC / DC conversion chip, an isolation transformer, and a charging circuit. The DC / DC conversion chip receives the equalization control signal from the equalization control module. The DC / DC conversion chip is connected to the charging circuit via the isolation transformer. The positive and negative output terminals of the charging circuit are connected to the positive and negative terminals of the corresponding battery cells. Preferably, the charging circuit includes a TP5000 chip.

[0014] The advantages of this utility model are:

[0015] This invention, through the design of physically isolated power supply units, enables independent charging and equalization of each individual cell within the battery pack. The individual cells do not affect each other, resulting in high equalization efficiency, effectively suppressing cell dispersion, facilitating the full release of the battery pack's capacity, extending the battery pack's service life, and improving safety. Furthermore, there is no limit to the number of individual cells that can be equalized simultaneously.

[0016] This invention is low in cost, easy to implement, and its balancing effect is not affected by human factors. It can achieve high efficiency and real-time balancing. Compared with the prior art, it greatly reduces power consumption loss, generates less heat, has a small size, and has no influence between cells. The number of cells to be balanced is unlimited, and the balancing efficiency can exceed 90%. It is suitable for lithium batteries, especially lithium iron phosphate batteries. Attached Figure Description

[0017] Figure 1 This is a general block diagram of the battery cell balancing system of this utility model.

[0018] Figure 2 This is a block diagram of the first embodiment of the battery cell balancing system of this utility model.

[0019] Figure 3 This is a block diagram of the second embodiment of the cell balancing system of this utility model.

[0020] Figure 4 This is a block diagram of the isolated power supply unit.

[0021] Figure 5 This is the circuit diagram of the charging circuit for the isolated power supply unit.

[0022] Figure 6 This is the circuit schematic of the DC / DC converter chip and isolation transformer of the isolated power supply unit.

[0023] Figure 7 This is the circuit diagram of the metering unit. Detailed Implementation

[0024] This invention proposes a cell balancing system for balancing the capacity of cells 11 within a cell pack 10 to ensure consistency among the cells 11. Figures 1 to 7 As shown, the battery cell balancing system of this utility model includes a balancing module 30 and a balancing control module 20. The balancing module 30 includes multiple independently configured isolated power supply units 31 and power supply units (not shown in the figure) that supply power to each isolated power supply unit. Each battery cell 11 in the battery cell pack 10 is equipped with an isolated power supply unit 31, and each isolated power supply unit 31 is connected to a balancing control module 20. The balancing control module 20 is used to send independent balancing control signals to each isolated power supply unit 31. Under the control of the balancing control module 20, each isolated power supply unit 31 starts or stops charging the corresponding battery cell 11 to achieve capacity balancing among the batteries 11 in the battery cell pack 10, wherein: as shown in the figure. Figure 1 The cell pack 10 includes multiple cells 11 connected in series. All the cells 11 connected in series in the cell pack 10 form a circuit with the bidirectional inverter 40 for charging and discharging operations with the grid through the bidirectional inverter 40. The cells are lithium iron phosphate batteries.

[0025] In this invention, the power supply unit is implemented using a conventional power supply circuit.

[0026] As can be seen from the above, this utility model designs an independent isolation power supply unit 31 for each battery cell 11. That is to say, each isolation power supply unit 31 in the equalization module 30 is independent. Whether to charge a certain battery cell 11 to achieve equalization is independently controlled and has nothing to do with other battery cells 11. On the other hand, the equalization process of battery cell 11 is unrelated to the battery cells 11 located before and after it and will not consume the charge of other battery cells 11. Therefore, there is no problem of charge exhaustion. Many battery cells 11 can be equalized at the same time, and the number of battery cells 11 is not limited, for example, hundreds or thousands.

[0027] In actual implementation, the battery cell balancing system of this utility model should perform balancing processing on the battery cell pack 10, but it can perform balancing processing on multiple battery cell packs 10 at the same time.

[0028] Figure 2An embodiment of the cell balancing system of this utility model is shown. For example... Figure 2 The equalization control module 20 includes a power supply unit 21 and a DC / DC unit 22. The power supply unit 21 is divided into two paths. One path is connected to each isolated power supply unit 31 through the DC / DC unit 22 to send an equalization control signal to each isolated power supply unit 31 to start the charging operation. The other path is directly connected to each isolated power supply unit 31 to supply power to each isolated power supply unit 31 (this connection path is not shown in the figure).

[0029] In this utility model, the power supply unit 21 is implemented using a conventional power supply circuit, and the DC / DC unit 22 is implemented using a conventional DC-DC conversion circuit, which will not be described in detail here.

[0030] Figure 3 Another embodiment of the cell balancing system of this utility model is shown. For example... Figure 3 The equalization control module 20 includes a power supply unit (not shown in the figure) and multiple metering units 24. The metering units 24 are connected in series to form a loop with the CPU 23. Each cell 11 in the cell pack 10 is equipped with a metering unit 24. The metering unit 24 is used to detect the voltage across the two ends of the cell 11 and feed back the detected voltage information to the CPU 23. The CPU 23 is connected to each isolation power supply unit 31. Based on the voltage information fed back by the metering unit 24, the CPU 23 controls each isolation power supply unit 31 to start or stop charging the corresponding cell 11 so that the capacity of each cell 11 in the cell pack 10 is balanced. The power supply unit supplies power to the CPU 23 and each metering unit 24.

[0031] In the actual design, the metering unit 24 includes a microcontroller, preferably a PY32 series microcontroller. The circuit schematic of the metering unit 24 is shown below. Figure 7 As shown.

[0032] Here, on the one hand, the selection of PY32 series microcontrollers reduces the cost of a single core to below 5 yuan, making it extremely inexpensive and suitable for widespread adoption. On the other hand, in addition to monitoring voltage parameters, PY32 series microcontrollers can also be used to monitor parameters such as the cell's own temperature (multi-point measurement is possible for more accurate detection), ambient temperature, and current. If any of these parameters becomes abnormal, an alarm can be triggered in a timely manner.

[0033] In actual design, optical couplers (not shown in the figure) are provided between adjacent metering units 24, and between CPU 23 and its adjacent metering unit 24.

[0034] In this invention, voltage information feedback adopts a ring network approach. That is, each metering unit 24, under the instruction of the CPU 23, detects the voltage across the corresponding battery cell 11 or does not detect it (the detected voltage information is empty). After detection, the detected voltage information is transmitted to the next metering unit 24, and so on. Finally, the last metering unit 24 feeds back the voltage information detected by all metering units 24 to the CPU 23, which processes and analyzes the voltage information to issue appropriate equalization control signals to each isolated power supply unit 31. Practical application shows that this ring network approach has many advantages: it avoids excessive cable connections; the metering unit 24 and the battery cell 11 can form a modular system; furthermore, the metering unit 24 can be flexibly expanded without restriction as the number of battery cells 11 increases.

[0035] In the actual design, the power supply unit also supplies power to each optocoupler isolator, and the power supply unit is implemented using a conventional power supply circuit.

[0036] like Figure 5 and Figure 6 As shown, the isolated power supply unit 31 includes a DC / DC converter chip 311, an isolation transformer 312, and a charging circuit 313. The DC / DC converter chip 311 receives the equalization control signal sent by the equalization control module 20. The DC / DC converter chip 311 is connected to the charging circuit 313 via the isolation transformer 312. The positive and negative output terminals of the charging circuit 313 are connected to the positive and negative terminals of the corresponding battery cell 11.

[0037] In this invention, the isolation transformer 312 enables the isolation power supply unit 31 to have an isolation function, and during the process of balancing each battery cell 11, the battery cells 11 achieve the effect of independent charging.

[0038] In the actual design, the charging circuit 313 includes the TP5000 chip.

[0039] This invention is applicable to lithium batteries, especially lithium iron phosphate batteries. Figure 5 The circuit diagram of the charging circuit 313 is shown. Figure 5 The values ​​of resistors and other components shown are suitable for lithium iron phosphate batteries. For other types of lithium batteries, the values ​​of resistors and other components can be adjusted according to actual needs.

[0040] In this invention, the DC / DC converter chip 311, the isolation transformer 312, and the TP5000 chip are implemented using devices well known in the art.

[0041] In actual implementation, the DC / DC converter chip 311 sends a start or stop signal to the isolation transformer 312 based on the equalization control signal received from the equalization control module 20. When the start signal is sent, the isolation transformer 312 converts the high-voltage AC signal (such as a 24V AC signal) output by the DC / DC converter chip 311 into a low-voltage DC signal (such as a 5V DC signal), and outputs the low-voltage DC signal to the TP5000 chip, which then charges the battery cell 11 to achieve capacity equalization.

[0042] Specifically, because Figure 2 and Figure 3 The configurations of the equalization control modules 20 shown are different, so the equalization processes and effects achieved by the two are slightly different. The following explanation uses a lithium battery as an example, but is not limited to this example.

[0043] for Figure 2 The cell balancing system of this invention, as shown, has a power supply unit 21 of the balancing control module 20 continuously sending a balancing control signal to the DC / DC conversion chip 311 to initiate charging operation via the DC / DC unit 22. The isolation transformer 312 then converts the high-voltage AC signal (24V AC signal) output by the DC / DC conversion chip 311 into a low-voltage DC signal (5V DC signal), and outputs the converted low-voltage DC signal to the TP5000 chip. Therefore, under the action of the low-voltage DC signal (indicating the start of charging operation), the TP5000 chip directly charges the cell 11 (lithium battery) to its nominal voltage (3.6V). In other words, after the cell pack 10 has been used for a period of time, the balancing control module 20 sends a balancing control signal to the balancing module 30 to initiate charging operation, actively charging each cell 11 to its nominal voltage (3.6V) in a timely manner, thus quickly achieving capacity balancing among the cells 11. Here, the ability of the lithium battery to be directly charged to 3.6V is determined by the characteristics of the TP5000 chip itself. Figure 2 The battery cell balancing system shown in this utility model is simple, practical, and inexpensive, and is suitable for situations where automatic balancing of differences between battery cells is required.

[0044] Figure 2 The battery cell balancing system shown in this utility model, through the design of the TP5000 chip, ensures that the battery cell 11 will not exceed the nominal voltage. That is, it directly eliminates the problem of overcharging of the battery cell 11 at the hardware level, thereby improving the safety of the battery cell 11.

[0045] for Figure 3The battery cell balancing system of this invention, as shown, allows the user to pre-set the desired voltage value after balancing the battery cells 11 via the CPU 23. This is referred to as the target voltage (the target voltage should not exceed the nominal voltage, such as 3.2V). During the use of the battery cell pack 10, each metering unit 24 monitors the voltage across each battery cell 11 in real time. When the voltage across a battery cell 11 drops below the target voltage, the CPU 23 sends a balancing control signal to the DC / DC converter chip 311 to initiate the charging operation. The isolation transformer 312 then converts the high-voltage AC signal (24V AC signal) output by the DC / DC converter chip 311 into a low-voltage DC signal (5V DC signal) and outputs the converted low-voltage DC signal to the TP5000 chip. Under the action of the low-voltage DC signal (indicating the start of the charging operation), the TP5000 chip charges the battery cell 11 (lithium battery). When the voltage across cell 11 is detected to have reached the target voltage, the CPU 23 sends a balancing control signal to the DC / DC converter chip 311 to stop charging. The TP5000 chip then stops charging cell 11. This ensures that the voltage across cell 11 remains at the target voltage. Accordingly, all cells 11 within the cell pack 10 maintain their target voltage through this method, effectively achieving capacity balancing among the cells 11. Figure 3 The battery cell balancing system of this invention perfectly meets the various needs of users for the voltage value after battery cell balancing.

[0046] Figure 3 The battery cell balancing system of this invention has dual protection functions. First, by real-time detection of the voltage across the battery cell 11 by the metering unit 24, it ensures that the battery cell 11 will not continue charging after reaching the target voltage, that is, the battery cell 11 will not exceed the nominal voltage. Second, thanks to the design of the TP5000 chip, even if the target voltage fails, it can still ensure that the battery cell 11 will not exceed the nominal voltage. That is, overcharging of the battery cell 11 is directly eliminated at the hardware level, improving the safety of the battery cell 11. The battery cell balancing process performed by this invention includes the following steps: the balancing control module 20 sends balancing control signals to each isolated power supply unit 31, so that each isolated power supply unit 31 starts or stops charging the corresponding battery cell 11 according to the received balancing control signal, thereby completing the capacity balancing of each battery cell 11 in the battery cell pack 10.

[0047] against Figure 2The cell balancing system of this utility model, as shown, includes the following steps in its cell balancing process: the power supply unit 21 of the balancing control module 20 sends a balancing control signal to each isolated power supply unit 31 through the DC / DC unit 22 to initiate a charging operation. Under the action of the balancing control signal, each isolated power supply unit 31 initiates a charging operation on its corresponding cell 11, directly charging the cell 11 (lithium battery) to its nominal voltage (3.6V), thereby completing the capacity balancing of each cell 11 within the cell pack 10. In practical implementation, this cell balancing method is suitable for automatic execution after the cell pack 10 has been used for a period of time, ensuring that the capacity of each cell 11 within the cell pack 10 remains balanced at all times.

[0048] against Figure 3 The cell balancing system of this utility model shown includes the following steps in its cell balancing process:

[0049] Each metering unit 24 monitors the voltage across each cell 11 in real time. For a cell 11 whose voltage drops below the target voltage, the CPU 23 of the equalization control module 20 sends an equalization control signal to the corresponding isolation power supply unit 31 to start charging, so that the isolation power supply unit 31 charges the cell 11. For a cell 11 whose voltage is equal to or higher than the target voltage, the CPU 23 of the equalization control module 20 sends an equalization control signal to the corresponding isolation power supply unit 31 to stop charging, so that the isolation power supply unit 31 stops charging the cell 11.

[0050] The voltage across each cell 11 is always maintained at the target voltage, thereby achieving capacity balance among the cells 11 within the cell pack 10. The target voltage is the voltage value that the user wants to achieve after the cells 11 are balanced, as set in advance by the CPU 23.

[0051] In practice, this cell balancing method can be implemented when the cell pack 10 is in use or during non-time periods, so as to keep the capacity of each cell 11 in the cell pack 10 balanced according to user needs.

[0052] This utility model has the following beneficial effects:

[0053] 1. This utility model, through the design of physically isolated power supply units, enables independent charging and equalization of each individual cell in the battery pack. The individual cells do not affect each other, resulting in high equalization efficiency, effectively suppressing cell dispersion, facilitating the full release of the battery pack's capacity, extending the battery pack's service life, and improving safety. Furthermore, there is no limit to the number of individual cells that can be equalized simultaneously.

[0054] 2. This utility model has low cost, is easy to implement, and the balancing effect is not affected by human factors. It can achieve high efficiency and real-time balancing. Compared with the existing technology, the power consumption loss is greatly reduced, the heat generation is less, the size is small, there is no influence between the cells, the number of cells to be balanced is unlimited, and the balancing efficiency can exceed 90%.

[0055] 3. This utility model incorporates a TP5000 chip with charging protection function within the isolated power supply unit, directly eliminating the risk of overcharging at the hardware level and improving the safety of the battery cell.

[0056] 4. This utility model uses a PY32 series microcontroller to measure the voltage at both ends of the battery cell, which is low in cost and suitable for widespread application.

[0057] The above describes the preferred embodiment of this utility model and the technical principles used therein. For those skilled in the art, any obvious changes such as equivalent transformations or simple substitutions based on the technical solution of this utility model without departing from the spirit and scope of this utility model shall fall within the protection scope of this utility model.

Claims

1. A cell balancing system, characterized by, It includes an equalization module and an equalization control module; the equalization module includes multiple independently configured isolated power supply units and a power supply unit that supplies power to each of the isolated power supply units, each of the battery cells in the battery pack is configured with one of the isolated power supply units, and each of the isolated power supply units is connected to an equalization control module; the equalization control module is used to send independent equalization control signals to each of the isolated power supply units. Under the control of the equalization control module, each isolated power supply unit starts or stops charging one of its corresponding cells to achieve capacity equalization among the cells in the cell pack. The cell pack includes multiple cells connected in series, and the cell pack forms a loop with the bidirectional inverter to achieve charging and discharging operations between the bidirectional inverter and the power grid. The cells are lithium iron phosphate batteries.

2. The cell balancing system of claim 1, wherein, The equalization control module includes a power supply unit and a DC / DC unit, wherein: the power supply unit is divided into two paths, one path is connected to each of the isolated power supply units through the DC / DC unit, and sends an equalization control signal to each of the isolated power supply units to start the charging operation; the other path is directly connected to each of the isolated power supply units to supply power to each of the isolated power supply units.

3. The cell balancing system of claim 1, wherein, The equalization control module includes a power supply unit and multiple metering units. The metering units are connected in series to form a loop with the CPU. Each cell in the cell pack is equipped with one metering unit. The metering unit is used to detect the voltage across the two ends of the cell and feed back the detected voltage information to the CPU. The CPU is connected to each of the isolated power supply units. Based on the voltage information fed back by the metering units, the CPU controls each isolated power supply unit to start or stop charging the corresponding cell, so as to achieve capacity equalization among the cells in the cell pack. The power supply unit supplies power to the CPU and each metering unit.

4. The cell balancing system of claim 3, wherein, The metering unit includes a microcontroller.

5. The cell balancing system of claim 4, wherein, The microcontroller in question is a PY32 series microcontroller.

6. The cell balancing system of claim 4, wherein, Optical isolators are provided between adjacent metering units, and between the CPU and adjacent metering units.

7. The cell balancing system of claim 2 or 3, wherein, The isolated power supply unit includes a DC / DC conversion chip, an isolation transformer, and a charging circuit. The DC / DC conversion chip receives the equalization control signal from the equalization control module. The DC / DC conversion chip is connected to the charging circuit via the isolation transformer. The positive and negative output terminals of the charging circuit are connected to the positive and negative terminals of the corresponding battery cells.

8. The cell balancing system of claim 7, wherein, The charging circuit includes a TP5000 chip.

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