A high-sensitivity battery capacity balancing system and balancing method

Abstract

The present invention discloses a highly sensitive battery capacity balancing system and balancing method. The balancing system includes a balancing trigger judgment module, a balancing position processing module, and a balancing start-stop control module. The balancing trigger judgment module is used to compare the difference between each battery cell and the minimum battery voltage when the battery charging reaches the balance start judgment voltage. When the set starting balance voltage difference is met, the balancing position processing module is used to record the battery position to be balanced and the battery position currently starting balancing. The balancing start-stop control module is used to obtain the battery position to be balanced based on the upper-level judgment processing and directly control the start and stop of battery balancing. Through this balancing system and balancing method, the BMS can also start battery balancing even when the voltage difference is not obvious. It has high balancing sensitivity and effectively improves balancing efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery capacity balancing, and in particular relates to a high-sensitivity battery capacity balancing system and a balancing method. Background Art

[0002] Battery capacity balancing refers to the process of maintaining a consistent state of charge (SoC) among all cells in a multi-battery system through certain technical means. Due to differences in manufacturing processes, material properties, and operating conditions, even batteries of the same model and specification can exhibit inconsistent performance over long-term use. For example, some cells may age or wear out faster than others. This inconsistency can lead to decreased performance of the entire battery pack and even shorten its service life.

[0003] The premise of battery capacity balancing is to detect the state of charge of each battery. In the existing technology, the state of charge of the battery is generally detected by detecting the battery output voltage. However, the relationship between voltage and capacity of lithium iron phosphate batteries within a certain capacity range is not obvious. In this range, it is difficult to make an effective balance judgment based on voltage differences. In addition, the capacity range with obvious differences between voltage and capacity is small, resulting in a short time for voltage balancing and low efficiency. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defect in the prior art that the capacity of lithium iron phosphate batteries cannot be effectively detected by voltage, resulting in difficulty in battery balancing, thereby providing a high-sensitivity battery capacity balancing system and balancing method.

[0005] A high-sensitivity battery capacity balancing method comprises the following steps:

[0006] Step S1: Obtain the balancing starting voltage a, the starting balancing battery voltage difference b, and calculate the cumulative charging current voltage threshold c;

[0007] Step S2: Real-time monitoring of the voltage and current of each battery. During the charging process, when any battery reaches the balance start voltage a, the battery is compared with the battery with the lowest voltage. If the voltage difference between the two exceeds the battery voltage difference b, it is recorded that the battery needs to start balancing. All batteries are cycled and judged to obtain the balance position data d;

[0008] Step S3: Based on the previously acquired balancing position data d, to avoid balancing adjacent cells at the same time, an adjacent determination process is performed to obtain the voltage position e at which balancing is to be performed;

[0009] Step S4: Based on the obtained voltage position e, the MCU is controlled to communicate with the front-end chip to notify the front-end chip to turn on the balancing circuit of the corresponding battery position. The front-end chip then controls the battery to discharge to the balancing resistor through the internal circuit to control the balancing of the corresponding battery;

[0010] Step S5: When the charging voltage of any battery reaches the voltage threshold c for calculating the cumulative charging current, the battery starts to calculate the cumulative charging current f, and the battery starts to accumulate the balancing current h;

[0011] Step S6: After charging stops, the battery position that needs balancing is continuously obtained based on the voltage a at the start of balancing. At the same time, if the cumulative charging current f of the battery is greater than the cumulative balancing current h, balancing is continued at the battery position.

[0012] Step S7: When the accumulated charging current f of the battery minus the accumulated balancing current h is equal to 0, or the battery voltage is lower than the balancing stop voltage P, balancing is stopped at the battery position.

[0013] Furthermore, the following steps are included: Step S8: when charging after discharging for a period of time, the balance is judged again.

[0014] Furthermore, in step S1, the equilibrium starting voltage a is calculated by charging at different ambient temperatures with a charging current of a preset capacity rate, taking a preset capacity ratio of SOC as a voltage point, and obtaining the equilibrium starting voltage values ​​corresponding to different temperatures:

[0015] Get the current temperature value T and calculate the balanced startup voltage a according to the linear formula.

[0016] Furthermore, in step S1, the method for calculating the battery voltage difference b for starting balancing is: comparing the differences between different temperatures at different preset voltage values, combining sampling errors, and setting the battery voltage difference b for starting balancing.

[0017] Furthermore, in step S1, the cumulative charging current voltage threshold c is calculated by setting the cumulative charging current voltage threshold c to the full charge voltage.

[0018] Furthermore, in step S5, the calculation method of the accumulated balancing current h of the battery is:

[0019] ;

[0020] Where h is the accumulated current, t1 and t2 are the accumulation start time and accumulation end time, respectively, and I(t) is the current value.

[0021] A high-sensitivity battery capacity balancing system is provided, wherein the battery capacity balancing system completes battery capacity balancing through the above-mentioned battery capacity balancing method.

[0022] Furthermore, it includes a balance trigger judgment module, a balance position processing module and a balance start-stop control module;

[0023] The balancing trigger judgment module is used to compare the difference between each battery cell and the minimum battery voltage when the battery charging reaches the balance starting judgment voltage, and record the position of the battery that needs to be balanced when the set starting balance voltage difference is met;

[0024] The balancing position processing module is used to record the position of the battery that needs to be balanced and the position of the battery that is currently starting balancing;

[0025] The balancing start and stop control module is used to obtain the position of the battery that needs to be balanced according to the upper layer judgment processing, and directly control the start and stop of the battery balancing.

[0026] Furthermore, it also includes a battery capacity balancing module, which includes an MCU, a front-end chip, a capacitor-resistor circuit, a switching device and a balancing resistor. The MCU is communicatively connected to the front-end chip, and the front-end chip controls the switching of the switching device through the capacitor-resistor circuit; the switching device is connected in series with the balancing resistor and in parallel to the battery module.

[0027] Beneficial effects: The present invention discloses a highly sensitive battery capacity balancing system and balancing method. The balancing system includes a balancing trigger judgment module, a balancing position processing module, and a balancing start-stop control module. The balancing trigger judgment module is used to compare the difference between each battery and the minimum battery voltage when the battery charging reaches the balance start judgment voltage, and record the battery position that needs to be balanced when the set starting balance voltage difference is met; the balancing position processing module is used to record the battery position that needs to be balanced and the battery position currently starting the balance; the balancing start-stop control module is used to obtain the battery position that needs to be balanced based on the upper-level judgment processing, and directly control the start and stop of the battery balance. Through this balancing system and balancing method, the BMS can start battery balancing even when the voltage difference is not obvious. It has high balancing sensitivity and effectively improves the balancing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1Schematic diagram of the steps of the battery capacity balancing method of the present invention;

[0030] Figure 2 The figure is a schematic block diagram of the structure of the battery capacity balancing system of the present invention. DETAILED DESCRIPTION

[0031] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0032] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0034] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0035] In this application, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0036] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0037] Example 1:

[0038] Reference Figure 1 As shown, this embodiment provides a high-sensitivity battery capacity balancing method, including the following steps:

[0039] Step S1: Obtain the balancing starting voltage a, the starting balancing battery voltage difference b, and calculate the cumulative charging current voltage threshold c;

[0040] In step S1, the method for calculating the equilibrium starting voltage a is as follows: charging at different ambient temperatures with a charging current of a preset capacity multiple, taking a preset capacity ratio of the SOC as a voltage point, and obtaining the equilibrium starting voltage values ​​corresponding to different temperatures:

[0041] Get the current temperature value T and calculate the balanced startup voltage a according to the linear formula.

[0042] Specifically, since the battery's SOC will have a clear voltage increase step when the SOC is 60%, the differences in different capacities and voltages are distinguished at the 60% capacity position.

[0043] Charging at a charging current of 0.3 times the capacity at different ambient temperatures, taking the voltage point where the SOC is 60%, obtains the equilibrium starting voltage values ​​corresponding to different temperatures. The test data of the battery in Table 1 below is used to obtain a two-dimensional array temperature t-voltage v table:

[0044] Table 1

[0045] Temperature t Voltage v 0 3426 25 3388 45 3374

[0046] Take the current temperature value T, obtain the two previous and next temperatures t0, t1 and voltages v0, v1 from the temperature t-voltage v table, and use the linear formula to obtain the balanced startup voltage a = v1 + (v0 – v1)*(T – t1) / (t0– t1). For example, the balanced startup voltage a at 30°C is = 3374 + (30 - 45)*(3388 - 3374) / (25 - 45) = 3384.5mV.

[0047] In step S1 , the method for calculating the battery voltage difference b for starting balancing is to compare the differences between different temperatures at different preset voltage values, combine the sampling error, and set the battery voltage difference b for starting balancing.

[0048] Specifically, in this embodiment, based on the 60% SOC battery voltage characteristics, combined with the SOC error within a 5% range, the difference between the voltage value at 55% and the voltage value at 60% at various temperatures is compared, with a maximum difference of approximately 15mV. Combined with the maximum sampling error of 10mV, the battery voltage difference b for starting balancing is set to 25mV.

[0049] In step S1 , the cumulative charging current voltage threshold c is calculated by setting the cumulative charging current voltage threshold c to the full charging voltage.

[0050] Based on the specifications and test results of lithium iron phosphate batteries, when the battery is charged to 3550mV, it is basically consistent with the designed nominal capacity. Therefore, the full charge voltage is set to 3550mV, and the voltage starts at 3550mV. The capacity difference will make the voltage change more obvious. The voltage threshold c for calculating the cumulative charging current is set to 3550mV.

[0051] Step S2: Real-time monitoring of the voltage and current of each battery. During the charging process, when any battery reaches the balance start voltage a, the battery is compared with the battery with the lowest voltage. If the voltage difference between the two exceeds the battery voltage difference b, it is recorded that the battery needs to start balancing. All batteries are cycled and judged to obtain the balance position data d;

[0052] Specifically, if (cell n voltage - maximum cell voltage) > cell voltage difference b, then the balancing position data d = d + (1 >> n). For example, if the voltage difference indicates that the cells to be balanced are cells 1, 2, 5, 6, and 7, then the balancing position data d = 0x73.

[0053] Step S3: Based on the previously acquired balancing position data d, to avoid balancing adjacent cells at the same time, an adjacent determination process is performed to obtain the voltage position e at which balancing is to be performed;

[0054] In this embodiment, if the balancing data d = 0x73, the balancing voltage position e is equal to 0x51 or 0x22, switching alternately between the two values. To avoid balancing adjacent cells, since the internal balancing circuit forms a loop with the circuits of adjacent cells to discharge, if the balancing circuits of adjacent cells are turned on simultaneously, the balancing resistor impedance will change, affecting the balancing effect and the stability of the sampled voltage.

[0055] Step S4: Based on the obtained voltage position e, the MCU is controlled to communicate with the front-end chip to notify the front-end chip to turn on the balancing circuit of the corresponding battery position. The front-end chip then controls the battery to discharge to the balancing resistor through the internal circuit to control the balancing of the corresponding battery;

[0056] Step S5: When the charging voltage of any battery reaches the voltage threshold c for calculating the cumulative charging current, the battery starts to calculate the cumulative charging current f, and the battery starts to accumulate the balancing current h;

[0057] In step S5, the calculation method of the balancing current h accumulated by the battery at the beginning is:

[0058] ;

[0059] Where h is the accumulated current, t1 and t2 are the accumulation start time and accumulation end time, respectively, and I(t) is the current value.

[0060] Step S6: After charging stops, the battery position that needs balancing is continuously obtained based on the voltage a at the start of balancing. At the same time, if the cumulative charging current f of the battery is greater than the cumulative balancing current h, balancing is continued at the battery position.

[0061] Step S7: When the accumulated charging current f of the battery minus the accumulated balancing current h is equal to 0, or the battery voltage is lower than the balancing stop voltage P, balancing is stopped at the battery position.

[0062] Regarding the selection of the balancing stop voltage P, it can be seen from the SOC and voltage correlation curve that when the voltage is lower than 3250mV, the SOC is lower than 20% under various current conditions, which is no longer suitable for balancing. Therefore, the balancing stop voltage P is 3250mV.

[0063] Step S8: When charging again after discharging for a period of time, the balance is judged again.

[0064] Example 2:

[0065] Reference Figure 2 As shown, this embodiment provides a high-sensitivity battery capacity balancing system, which completes battery capacity balancing through the above-mentioned battery capacity balancing method.

[0066] The battery capacity balancing system includes a balancing trigger judgment module, a balancing position processing module, and a balancing start-stop control module;

[0067] The balancing trigger judgment module is used to compare the difference between each battery cell and the minimum battery voltage when the battery charging reaches the balance starting judgment voltage, and record the position of the battery that needs to be balanced when the set starting balance voltage difference is met;

[0068] The balancing position processing module is used to record the position of the battery that needs to be balanced and the position of the battery that is currently starting balancing;

[0069] The balancing start and stop control module is used to obtain the position of the battery that needs to be balanced according to the upper layer judgment processing, and directly control the start and stop of the battery balancing.

[0070] It also includes a battery capacity balancing module, which includes an MCU, a front-end chip, a capacitor-resistor circuit, a switching device and a balancing resistor. The MCU is communicatively connected to the front-end chip, and the front-end chip controls the switching of the switching device through the capacitor-resistor circuit; the switching device is connected in series with the balancing resistor and in parallel to the battery module.

[0071] This embodiment discloses a highly sensitive battery capacity balancing system, including a balancing trigger judgment module, a balancing position processing module, and a balancing start-stop control module. The balancing trigger judgment module is used to compare the difference between each battery cell and the minimum battery voltage when the battery reaches the balance start judgment voltage. When the set starting balancing voltage difference is met, it records the position of the battery that needs to be balanced. The balancing position processing module is used to record the position of the battery that needs to be balanced and the position of the battery currently starting balancing. The balancing start-stop control module is used to obtain the position of the battery that needs to be balanced based on the upper-level judgment processing and directly control the start and stop of battery balancing. This balancing system and balancing method can enable the BMS to initiate battery balancing even when the voltage difference is not obvious, has high balancing sensitivity, and effectively improves balancing efficiency.

[0072] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A high-sensitivity battery capacity balancing method, characterized in that: The following steps are involved: Step S1: Obtain the balancing starting voltage a, the starting balancing battery voltage difference b, and calculate the cumulative charging current voltage threshold c; Step S2: Real-time monitoring of the voltage and current of each battery. During the charging process, when any battery reaches the balance start voltage a, the battery is compared with the battery with the lowest voltage. If the voltage difference between the two exceeds the battery voltage difference b, it is recorded that the battery needs to start balancing. All batteries are cycled and judged to obtain the balance position data d; Step S3: performing adjacent determination processing based on the acquired balancing position data d to avoid balancing adjacent cells at the same time, and obtaining the voltage position e to be performed for balancing; Step S4: Based on the obtained voltage position e, the MCU is controlled to communicate with the front-end chip to notify the front-end chip to turn on the balancing circuit of the corresponding battery position. The front-end chip then controls the battery to discharge to the balancing resistor through the internal circuit to control the balancing of the corresponding battery; Step S5: When any battery reaches the voltage threshold c for calculating the cumulative charging current, the battery starts to accumulate the charging current f and the balancing current h. Step S6: After charging stops, the battery position that needs balancing is continuously obtained based on the voltage a at the start of balancing. At the same time, if the cumulative charging current f of the battery is greater than the cumulative balancing current h, balancing is continued at this battery position. Step S7: When the cumulative charging current f of the battery minus the cumulative balancing current h is equal to 0, or the battery voltage is lower than the balancing stop voltage P, balancing is stopped at the battery position.

2. A high-sensitivity battery capacity balancing method according to claim 1, characterized in that: The following steps are also included: Step S8: When charging again after discharging for a period of time, the balance is judged again.

3. A high-sensitivity battery capacity balancing method according to claim 1, characterized in that: In step S1, the method for calculating the equilibrium starting voltage a is as follows: charging at different ambient temperatures with a charging current of a preset capacity multiple, taking a preset capacity ratio of the SOC as a voltage point, and obtaining the equilibrium starting voltage values ​​corresponding to different temperatures: Get the current temperature value T and calculate the balanced startup voltage a according to the linear formula.

4. A high-sensitivity battery capacity balancing method according to claim 1, characterized in that: In step S1 , the method for calculating the battery voltage difference b for starting balancing is to compare the differences between different temperatures at different preset voltage values, combine the sampling error, and set the battery voltage difference b for starting balancing.

5. The high-sensitivity battery capacity balancing method according to claim 1, characterized in that: In step S1 , the cumulative charging current voltage threshold c is calculated by setting the cumulative charging current voltage threshold c to the full charging voltage.

6. A high-sensitivity battery capacity balancing method according to claim 1, characterized in that: In step S5, the calculation method of the current h at which the battery starts to accumulate balancing is: ； Where Q is the accumulated current, t1 and t2 are the accumulation start time and accumulation end time, respectively, and I(t) is the current value.

7. A high-sensitivity battery capacity balancing system, characterized in that: The battery capacity balancing system completes battery capacity balancing by the battery capacity balancing method according to any one of claims 1 to 6.

8. The high-sensitivity battery capacity balancing system according to claim 7, characterized in that: It includes a balance trigger judgment module, a balance position processing module and a balance start-stop control module; The balancing trigger judgment module is used to compare the difference between each battery cell and the minimum battery voltage when the battery charging reaches the balance starting judgment voltage, and record the position of the battery that needs to be balanced when the set starting balance voltage difference is met; The balancing position processing module is used to record the position of the battery that needs to be balanced and the position of the battery that is currently starting balancing; The balancing start and stop control module is used to obtain the position of the battery that needs to be balanced according to the upper layer judgment processing, and directly control the start and stop of the battery balancing.

9. The high-sensitivity battery capacity balancing system according to claim 8, characterized in that: It also includes a battery capacity balancing module, which includes an MCU, a front-end chip, a capacitor-resistor circuit, a switching device and a balancing resistor. The MCU is communicatively connected to the front-end chip, and the front-end chip controls the switching of the switching device through the capacitor-resistor circuit; the switching device is connected in series with the balancing resistor and in parallel to the battery module.

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