High-sensitivity battery capacity equalization system and equalization method

Abstract

The invention discloses a high-sensitivity battery capacity equalization system and method, the equalization system comprises a balance trigger judgment module, a balance position processing module and a balance start-stop control module, and the balance trigger judgment module is used for comparing the difference between each battery 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 position of the battery needing to be balanced is recorded; the balance position processing module is used for recording the position of a battery needing to be balanced and the position of a battery currently starting balance; and the balance start-stop control module is used for directly controlling the balance start and stop of the battery according to the position of the battery needing to be balanced obtained through upper layer judgment processing. Through the equalization system and the equalization method, the BMS can also start battery equalization when the voltage difference is not obvious, the equalization sensitivity is high, and the equalization efficiency is effectively improved.

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 keeping the state of charge (SoC) of each battery consistent through certain technical means in a multi-battery system. Due to differences in manufacturing processes, material properties, and usage conditions, even batteries of the same model and specification may have inconsistent performance during long-term use. For example, some batteries may age or wear out faster than other batteries. This inconsistency will cause the performance of the entire battery pack to deteriorate, and even shorten the service life of the entire battery pack.

[0003] The premise of battery capacity balancing is to detect the state of charge of each battery. In the prior art, the state of charge of the battery is generally detected by detecting the output voltage of the battery. However, the relationship between the voltage and capacity of lithium iron phosphate batteries in a certain capacity range is not obvious. It is difficult to make an effective balance judgment based on the voltage difference in this range, and 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: Step S1: obtaining the balancing start voltage a, the starting balancing battery voltage difference b, and calculating 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 judged in a cycle to obtain the balance position data d. Step S3: Based on the previously acquired balancing position data d, to avoid balancing adjacent batteries at the same time, an adjacent judgment process is performed to obtain the balancing voltage position e to be performed; Step S4: According to the obtained voltage position e, the MCU is controlled to communicate with the front-end chip to notify the front-end chip to open the balancing circuit corresponding to the battery position, and the front-end chip controls the battery to discharge to the balancing resistor through the internal circuit to control the balance of the corresponding battery; Step S5: When 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; Step S6: After charging is stopped, the battery position that needs to be balanced is continuously obtained according to the voltage a at the start of balancing. Meanwhile, if the accumulated charging current f of the battery is greater than the accumulated balancing current h, balancing should continue to be started at the battery position. Step S7: When the accumulated charging current f of the battery minus the accumulated balancing current h equals 0, or the battery voltage is lower than the balancing stop voltage P, balancing stops at the battery position.

[0006] Furthermore, the following steps are included: Step S8: when charging is performed again after discharging for a period of time, the balance is judged again.

[0007] Furthermore, in step S1, the calculation method of the balanced starting voltage a is: charging at different ambient temperatures with a charging current of a preset capacity multiple, taking a preset capacity ratio of SOC as a voltage point, and obtaining the balanced 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.

[0008] Furthermore, in the step S1, the method for calculating the battery voltage difference b for starting balancing is: comparing the differences between various temperatures at different preset voltage values, combining sampling errors, and setting the battery voltage difference b for starting balancing.

[0009] Furthermore, in the step S1, the calculation method of the cumulative charging current voltage threshold c is: setting the cumulative charging current voltage threshold c to the full charging voltage.

[0010] Furthermore, in step S5, the calculation method of the balancing current h accumulated by the battery at the beginning is: ; Wherein, 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.

[0011] A high-sensitivity battery capacity balancing system is disclosed, wherein the battery capacity balancing system completes battery capacity balancing through the above-mentioned battery capacity balancing method.

[0012] Further, 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 and the minimum battery voltage when the battery charging reaches the balancing start judgment voltage, and record the position of the battery that needs to be balanced when the set starting balancing 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 that currently starts 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.

[0013] 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.

[0014] 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 balancing start judgment voltage, and record the battery position that needs to be balanced when the set starting balancing 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 that currently starts balancing; the balancing start-stop control module is used to obtain the battery position that needs to be balanced according to the upper-level judgment processing, and directly control the battery balancing start and stop. Through this balancing system and balancing method, the BMS can also start battery balancing when the voltage difference is not obvious, with high balancing sensitivity, which effectively improves the balancing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying creative work.

[0016] Figure 1 A schematic diagram of the steps of the battery capacity balancing method of the present invention; Figure 2 The figure is a schematic block diagram of the structure of the battery capacity balancing system of the present invention. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0018] 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 referred device or element 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.

[0019] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0020] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0021] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature 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. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0022] 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 a central 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 a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0023] Embodiment 1: Reference Figure 1 As shown, this embodiment provides a high-sensitivity battery capacity balancing method, comprising the following steps: Step S1: obtaining the balancing start voltage a, the starting balancing battery voltage difference b, and calculating the cumulative charging current voltage threshold c; In step S1, the calculation method of the balanced starting voltage a is: charging at different ambient temperatures with a charging current of a preset capacity multiple, taking a preset capacity ratio of SOC as a voltage point, and obtaining the balanced 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.

[0024] Specifically, because the battery's SOC will have an obvious voltage rise step when the SOC is 60%, the differences in different capacities and voltages are distinguished at the 60% capacity position.

[0025] Charging at different ambient temperatures with a charging current of 0.3 times the capacity, taking the voltage point of 60% SOC, obtains the equilibrium starting voltage values ​​corresponding to different temperatures, as shown in Table 1 below, the test data of the battery, and obtains the temperature t-voltage v table of the two-dimensional array: Table 1 Temperature Voltage 0 3426 25 3388 45 3374 Take the current temperature value T, obtain the two temperatures t0, t1 and voltages v0, v1 from the temperature t-voltage v table, and obtain the balanced startup voltage a = v1 + (v0 – v1)*(T – t1) / (t0– t1) according to the linear formula. For example, the balanced startup voltage a = 3374 + (30 - 45)*(3388 - 3374) / (25 - 45) = 3384.5mV at 30℃.

[0026] In the step S1, the method for calculating the battery voltage difference b for starting balancing is: comparing the differences between various temperatures at different preset voltage values, combining the sampling error, and setting the battery voltage difference b for starting balancing.

[0027] Specifically, in this embodiment, according to the 60% SOC battery voltage characteristics, combined with the SOC error within the 5% range, the difference between the voltage value at 55% and the voltage value at 60% at each temperature is compared, the maximum is about 15mV, and combined with the maximum sampling error of 10mV, the battery voltage difference b for starting balancing is set to 25mV.

[0028] In the step S1, the calculation method of the cumulative charging current voltage threshold c is: setting the cumulative charging current voltage threshold c to the full charging voltage.

[0029] 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.

[0030] 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 judged in a cycle to obtain the balance position data d. Specifically, if (voltage of battery n - maximum battery voltage) > battery voltage difference b, then the balancing position data d = d + (1 >> n). For example, based on the voltage difference, the batteries that need to be balanced are batteries 1, 2, 5, 6, and 7, then the balancing position data d = 0x73.

[0031] Step S3: Based on the previously acquired balancing position data d, to avoid balancing adjacent batteries at the same time, an adjacent judgment process is performed to obtain the balancing voltage position e to be performed; In this embodiment, the balancing data d = 0x73, then the balancing voltage position e is equal to 0x51 or 0x22, and the two values ​​are switched alternately. To avoid balancing adjacent batteries, since the internal balancing circuit forms a loop with the circuit of the adjacent battery cell to discharge, if the balancing circuits of the adjacent battery cells are turned on at the same time, the impedance of the balancing resistor will change, affecting the balancing effect and the stability of the sampling voltage.

[0032] Step S4: According to the obtained voltage position e, the MCU is controlled to communicate with the front-end chip to notify the front-end chip to open the balancing circuit corresponding to the battery position, and the front-end chip controls the battery to discharge to the balancing resistor through the internal circuit to control the balance of the corresponding battery; Step S5: When 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; In step S5, the calculation method of the balancing current h accumulated by the battery at the beginning is: ; Wherein, 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.

[0033] Step S6: After charging is stopped, the battery position that needs to be balanced is continuously obtained according to the voltage a at the start of balancing. Meanwhile, if the accumulated charging current f of the battery is greater than the accumulated balancing current h, balancing should continue to be started at the battery position. Step S7: When the accumulated charging current f of the battery minus the accumulated balancing current h equals 0, or the battery voltage is lower than the balancing stop voltage P, balancing stops at the battery position.

[0034] 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 and is no longer suitable for balancing. Therefore, the balancing stop voltage P is 3250mV.

[0035] Step S8: When charging again after discharging for a period of time, the balance is judged again.

[0036] Embodiment 2: Reference Figure 2 As shown, this embodiment provides a high-sensitivity battery capacity balancing system, and the battery capacity balancing system completes battery capacity balancing through the above-mentioned battery capacity balancing method.

[0037] The battery capacity 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 balancing start judgment voltage, and record the position of the battery that needs to be balanced when the set starting balancing 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 that currently starts 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.

[0038] It also includes a battery capacity balancing module, which includes an MCU, a front-end chip, a capacitor-resistor circuit, a switch device and a balancing resistor. The MCU is communicatively connected to the front-end chip, and the front-end chip controls the switch of the switch device through the capacitor-resistor circuit; the switch device is connected in series with the balancing resistor and in parallel to the battery module.

[0039] 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 and the minimum battery voltage when the battery charging reaches the balancing start judgment voltage, and record the battery position that needs to be balanced when the set starting balancing 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 that currently starts balancing; the balancing start-stop control module is used to obtain the battery position that needs to be balanced according to the upper-level judgment processing, and directly control the battery balancing start and stop. Through this balancing system and balancing method, the BMS can also start battery balancing when the voltage difference is not obvious, with high balancing sensitivity, effectively improving the balancing efficiency.

[0040] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0041] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A high-sensitivity battery capacity balancing method, characterized in that: The following steps are involved: Step S1: obtaining the balancing start voltage a, the starting balancing battery voltage difference b, and calculating 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 judged in a cycle to obtain the balance position data d. Step S3: performing adjacent judgment processing according to the acquired equilibrium position data d to obtain the equilibrium voltage position e to be executed; Step S4: According to the obtained voltage position e, the MCU is controlled to communicate with the front-end chip to notify the front-end chip to open the balancing circuit corresponding to the battery position, and the front-end chip controls the battery to discharge to the balancing resistor through the internal circuit to control the balance of the corresponding battery; Step S5: When 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; Step S6: After charging is stopped, the battery position that needs to be balanced is continuously obtained according to the voltage a at the start of balancing. Meanwhile, if the accumulated charging current f of the battery is greater than the accumulated balancing current h, balancing should continue to be started at the battery position. Step S7: When the accumulated charging current f of the battery minus the accumulated balancing current h equals 0, or the battery voltage is lower than the balancing stop voltage P, balancing stops 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 calculation method of the balanced starting voltage a is: charging at different ambient temperatures with a charging current of a preset capacity multiple, taking a preset capacity ratio of SOC as a voltage point, and obtaining the balanced 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 the step S1, the method for calculating the battery voltage difference b for starting balancing is: comparing the differences between various temperatures at different preset voltage values, combining the sampling error, and setting the battery voltage difference b for starting balancing.

5. A high-sensitivity battery capacity balancing method according to claim 1, characterized in that: In the step S1, the calculation method of the cumulative charging current voltage threshold c is: 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 balancing current h accumulated by the battery at the beginning is: ； Wherein, 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.

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

8. A high-sensitivity battery capacity equalization 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 and the minimum battery voltage when the battery charging reaches the balancing start judgment voltage, and record the position of the battery that needs to be balanced when the set starting balancing 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 that currently starts 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. A high-sensitivity battery capacity equalization 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 switch device and a balancing resistor. The MCU is communicatively connected to the front-end chip, and the front-end chip controls the switch of the switch device through the capacitor-resistor circuit; the switch device is connected in series with the balancing resistor and in parallel to the battery module.

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