Lithium battery equalization control circuit

Abstract

The utility model discloses a lithium battery equalization control circuit, and mainly relates to the field of lithium battery charging. Comprising a voltage conversion assembly which is connected with an external power supply, and a direct charging circuit comprises a first switch which is connected with a power supply management system; the first switch is connected in series with the plurality of battery cells; the conversion circuit comprises a second switch and a plurality of voltage converters which are connected with the power management system; the number of the voltage converters is matched with that of the battery cells, the voltage converters are connected with the battery cells in parallel, and the second switch is connected with the battery cells and the voltage converters in series; the power management system controls the first switch and the second switch to be turned on and off in sequence according to the voltage of the battery cell. Compared with the prior art, the lithium battery charging device has the advantages that the lithium battery charging device is used for charging a lithium battery, a traditional charging mode and a control method of a BMS system are changed, so that the lithium battery can be quickly charged without overcharging the lithium battery, heating of the lithium battery during charging can be reduced, and the heating is concentrated on a charger instead of the lithium battery.

Description

Technical Field

[0001] The utility model relates to the field of lithium battery charging, in particular to a lithium battery balancing control circuit. Background Art

[0002] The statements in this section merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] Lithium-ion battery balancing technology is a crucial component of a battery management system (BMS). Its primary function is to ensure that multiple series-connected lithium-ion battery cells maintain the same voltage level during charge and discharge, thereby extending the overall lifespan of the battery pack, improving energy efficiency, and ensuring safety. In lithium-ion battery packs, due to differences in internal resistance, capacity, and self-discharge rate among battery cells, voltage inconsistencies can occur after repeated charge and discharge cycles. Low-voltage cells may not fully discharge, while high-voltage cells may not fully charge. This phenomenon is known as cell imbalance. Without balancing, the overall performance of the battery pack will be limited by the weakest cell, potentially leading to overcharging or over-discharging of some cells, reducing capacity, damaging the battery, and even causing safety issues.

[0004] Current lithium battery balancing technologies primarily include active balancing and passive balancing. Active balancing uses an active control circuit to transfer excess energy from high-voltage cells directly to low-voltage cells (partially charged), charging the partially charged cells. This method, however, suffers from long charging times, low efficiency, complex equipment, and heat generation in the converter. Passive balancing discharges fully charged cells, then discharges the fully charged cells to the partially charged cells, charging the partially charged cells. However, this method takes a long time to charge, generates significant heat, has low charging efficiency, and uses low current. Furthermore, this method is limited by the capacity of the fully charged cells, especially after a period of use, as the capacity of the cells decreases. Therefore, the entire process is affected by the cell capacity. The first drawback of both of these lithium battery balancing methods is the high heat generation (especially passive balancing). Heat is the most significant factor affecting lithium battery safety and lifespan. Second, the balancing efficiency is low and the balancing time is long. Passive balancing, due to load heat generation, limits the current draw, requiring only a small current draw. Recharging the charger only as much as the current draw decreases, resulting in a lengthy charging process. Active balancing takes time to recover the current of a fully charged cell. After the recovery, it is tested again and the battery with the lowest voltage is charged. This process is repeated over and over again, which increases the time. The flow of current in and out will also increase the heat of the cell. In addition, the equipment is relatively complex and the failure rate is relatively high. Utility Model Content

[0005] The purpose of this utility model is to provide a lithium battery balancing control circuit for controlling cell voltage balancing during the lithium battery charging process. This circuit significantly reduces the balancing time during the lithium battery charging process and lowers the temperature generated by the battery management system (BMS) by switching between two circuits. It also enables rapid charging of lithium batteries without overcharging, and reduces heating during charging, concentrating the heat on the charger rather than the batteries themselves. The overall circuit structure is simple and practical, and it efficiently achieves lithium battery balancing.

[0006] In order to achieve the above-mentioned purpose, the present invention is realized through the following technical solutions:

[0007] A lithium battery balancing control circuit includes multiple battery cells and a power management system, wherein the power management system is connected to each battery cell. The lithium battery balancing system also includes a direct charging circuit and a conversion circuit; the direct charging circuit includes a first switch connected to the power management system; the first switch is connected in series with the multiple battery cells;

[0008] The conversion circuit includes a second switch connected to a power management system and multiple voltage converters. The number of voltage converters matches the number of battery cells, the voltage converters are connected in parallel with the battery cells, and the second switches are connected in series with the battery cells and the voltage converters. The power management system controls the first and second switches to open and close sequentially based on the battery cell voltage. When the voltage of any battery cell is lower than the saturation voltage, the power management system controls the first switch to close and the second switch to open. When the voltage of any battery cell is equal to the saturation voltage, the power management system controls the first switch to open and the second switch to close.

[0009] Only one of the first switch and the second switch can be closed.

[0010] A plurality of the voltage converters are connected in parallel, and the voltage converters are DC-DC modules.

[0011] Compared with the prior art, the beneficial effects of the present invention are:

[0012] This control controls the cell voltage equalization during lithium-ion battery charging, significantly improving traditional battery equalization methods. By switching between two circuits, it significantly reduces the equalization time during the charging process and lowers the temperature generated by the battery management system (BMS). It also enables rapid charging without overcharging, and reduces heat generation during charging, concentrating the heat on the charger rather than the battery itself. The overall circuit structure is simple and practical, and it efficiently achieves battery equalization. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Attachment Figure 1 This is a view of the utility model.

[0014] Reference numerals shown in the accompanying drawings:

[0015] 1. Battery cell; 2. Power management system; 3. Charger; 4. First switch; 5. Second switch; 6. Voltage converter. DETAILED DESCRIPTION

[0016] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art may make various changes or modifications to the present invention, and that these equivalent forms also fall within the scope defined in this application.

[0017] The present invention describes a lithium battery balancing control circuit, comprising a plurality of battery cells 1 and a power management system 2 connected to each battery cell 1. In existing lithium battery balancing systems, voltage monitoring is mostly performed on one battery cell 1, rather than all of them. This results in the existing lithium battery balancing system being charged based on one battery cell 1, whether it is active balancing or passive balancing, so this application improves it. The battery management system (BMS) is a key component in electric vehicles and lithium batteries, and is mainly responsible for monitoring and regulating the operating status of the battery. Its core functions include status monitoring, balancing control, fault diagnosis and protection, communication interface management, thermal management, charging and discharging control, data recording and storage, and user interface interaction to ensure the safety, stability and life of the battery. The BMS in this article is mainly used to monitor the voltage of the battery cell 1 to avoid overcharging of the battery cell 1, and can more reasonably distribute the charging process of the lithium battery cell 1. The conversion of the two circuits of the charging device is controlled by the battery management system. The following is described according to the control process, as shown in the accompanying drawings of the specification. Figure 1 As shown:

[0018] S1. After the lithium battery balancing system is charged by the external charger 3, the power management system 2 detects and determines the voltage of the battery cell 1. After determination, it selects between the direct charging circuit and the conversion circuit. The direct charging circuit and the conversion circuit specifically include: the direct charging circuit includes a first switch 4 connected to the power management system 2, and the first switch 4 is connected in series with multiple battery cells 1; the conversion circuit includes a second switch 5 connected to the power management system 2 and multiple voltage converters 6; the number of voltage converters 6 matches the number of power cells 1, each voltage converter 6 is connected in parallel with a battery cell 1, and the second switch 5 is connected in series with the battery cell 1 and the voltage converter 6. The voltage converter 6 is a DC-DC module, a device that converts electrical energy of one voltage value into electrical energy of another voltage value in a DC circuit. It uses microelectronics technology to integrate small surface-mount integrated circuits with microelectronic components.

[0019] S2: After the battery management system determines that the voltage of any battery cell 1 is lower than the saturation voltage, the power management system 2 controls the first switch 4 to close and the second switch 5 to open. The power supply connected to the charger 3 is charged through the direct charging circuit. The charger 3 steps down the power supply voltage to a voltage suitable for the lithium battery cell 1 group, and then charges the multiple battery cells 1. During the charging process, the power management system 2 monitors the voltage of each battery cell 1. When any battery cell 1 is fully charged, the voltage will reach the saturation voltage. After reaching the saturation voltage, the conversion circuit needs to be activated.

[0020] S3: When the voltage of any battery cell 1 reaches the saturation voltage, the power management system 2 controls the first switch 4 to open and the second switch 5 to close. At this point, the direct charging circuit is disconnected and replaced by a conversion circuit. After the conversion, the connected power source converts the voltage to a voltage compatible with direct charging of the battery cell 1 through the voltage converter 6 connected in parallel with the battery cell 1, thereby enabling the charger 3 to directly charge the battery cell 1. For battery cells 1 that have reached the saturation voltage, the battery management system controls the battery cells 1, preventing the charger 3 from charging fully charged battery cells 1 and charging battery cells 1 that have not yet reached the saturation voltage until all battery cells 1 reach the saturation voltage.

[0021] The battery management system controls the opening and closing of first switch 4 and second switch 5 in the same order, and the direct charging circuit and the conversion circuit cannot operate simultaneously. When charging directly with the conversion circuit, the battery is at a low charge. At this time, the charging current through the conversion circuit is large, and the voltage converter 6 generates heat. Compared to charging with the direct charging circuit, the heat is mainly generated by the charger 3, not the lithium battery itself. Therefore, the lithium battery is charged first through the direct charging circuit. When one of the battery cells 1 is fully charged, it is then charged through the conversion circuit. At this time, the charging power is reduced, and the heat generation is reduced.

[0022] In summary, this application is used to control the cell voltage balancing method during lithium battery charging, which changes the traditional lithium battery balancing method. By switching between two circuits, it greatly reduces the balancing time during the lithium battery charging process and reduces the temperature generated by the BMS. It can also quickly charge lithium batteries without causing overcharging, and can reduce the heating of lithium batteries during charging, with the heat being concentrated in the charger 3 rather than the lithium batteries themselves. The overall circuit structure is simple and practical, and it can achieve efficient lithium battery balancing.

Claims

1. A lithium battery balancing control circuit, comprising a plurality of battery cells (1) and a power management system (2), characterized in that: The power management system (2) is connected to each battery cell and also includes a direct charging circuit and a conversion circuit; The direct charging circuit comprises a first switch (4) connected to a power management system (2); the first switch (4) is connected in series with a plurality of battery cells (1); The conversion circuit comprises a second switch (5) connected to the power management system (2) and a plurality of voltage converters (6); the number of the voltage converters (6) matches the number of the battery cells (1), the voltage converters (6) are connected in parallel with the battery cells (1), and the second switch (5) is connected in series with the battery cells (1) and the voltage converters (6); The power management system (2) controls the first switch (4) and the second switch (5) to open and close in sequence according to the voltage of the battery cell (1); When the voltage of any battery cell (1) is lower than the saturation voltage, the power management system (2) controls the first switch (4) to be closed and the second switch (5) to be opened; When the voltage of any battery cell (1) is equal to the saturation voltage, the power management system (2) controls the first switch (4) to be disconnected and the second switch (5) to be closed.

2. The lithium battery balancing control circuit according to claim 1, characterized in that: Only one of the first switch (4) and the second switch (5) can be closed.

3. The lithium battery balancing control circuit according to claim 1, characterized in that: A plurality of the voltage converters (6) are connected in parallel with each other, and the voltage converters (6) are DC-DC modules.

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