An adaptive protection algorithm for BMS performance parameters of battery cells

Abstract

The present invention provides a BMS adaptive protection algorithm for the performance parameters of a battery cell, comprising the following steps: real-time voltage monitoring: the BMS monitors the voltage of each battery cell in real time through a voltage sensor; charging state judgment: when the battery cell voltage is close to the preset charging cut-off voltage, the BMS gradually reduces the charging current according to the charging curve control strategy and enters the constant voltage charging stage; multiple condition judgment: in addition to voltage monitoring, the BMS combines other parameters for comprehensive judgment; protection action execution: once it is determined that an overcharge has occurred, the BMS immediately cuts off the charging circuit and stops charging; fault recording and subsequent processing: recording detailed information of the overcharge event, including the time of occurrence, battery cell voltage, and charging current, for subsequent analysis of the cause of the fault. The present invention can adaptively adjust the charging current or mode to avoid overcharging of these batteries, and accurately judge the overcharge threshold of each battery cell by continuously learning and analyzing the performance of the battery cell.

Description

Technical Field

[0001] The present invention relates to the technical field of battery cell protection, and in particular to an adaptive protection algorithm of a BMS for performance parameters of a battery cell. Background Art

[0002] The battery management system (BMS) has a crucial impact on the performance parameters of the battery cell. During the charging process, the BMS monitors the battery cell voltage in real time. When the voltage reaches the set charging cut-off voltage, the BMS will cut off the charging circuit in time to prevent the battery cell from overcharging. The BMS can dynamically adjust the charging current according to the state of the battery cell, such as temperature, SOC (state of charge), etc. When the battery cell temperature is low or the SOC is high, the charging current is appropriately reduced to avoid damage to the battery cell caused by high current charging. At the same time, the BMS uses active balancing or passive balancing technology to keep the SOC of each battery cell in the battery pack consistent, avoiding the capacity and performance of the entire battery pack affected by the rapid decay of the capacity of individual batteries, and extending the overall service life of the battery pack.

[0003] The prior art lacks precise voltage, current and temperature control over the performance parameters of battery cells. When the internal resistance is small or the capacity is low, the battery cell voltage will rise quickly. When the battery cell approaches its personalized overcharge threshold, if the charging circuit cannot be cut off in time, the overcharge problem will cause safety accidents such as battery fire and explosion. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a BMS adaptive protection algorithm for the performance parameters of battery cells to solve the problems raised in the above background technology. The present invention can adaptively adjust the charging current or mode to avoid overcharging of these battery cells, and accurately determine the overcharging threshold of each battery cell through continuous learning and analysis of battery cell performance.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solution: a BMS adaptive protection algorithm for the performance parameters of the battery cell, comprising the following steps:

[0006] S1. Real-time voltage monitoring: BMS monitors the voltage of each battery cell in real time through the built-in voltage sensor, and reduces the impact of battery internal resistance on voltage measurement through voltage compensation. The process uses the following formula:

[0007] V actual =V measured +I·R internal

[0008] Among them, the voltage V measured , charge and discharge current I and battery internal resistance R internal To calculate the actual battery voltage V actual .

[0009] S2, charging status judgment: When the cell voltage is close to the preset charging cut-off voltage, the BMS will gradually reduce the charging current according to the charging curve control strategy and enter the constant voltage charging stage to avoid a sharp rise in voltage;

[0010] S3. Multiple condition judgment: In addition to voltage monitoring, BMS will also make a comprehensive judgment based on other parameters, such as charging time, battery temperature, charging current, etc., and monitor the actual voltage based on the battery temperature, using the following formula:

[0011] R interna (T) = R0(1+α(T-T0))

[0012] Where R interna (T) is the battery internal resistance at temperature, R0 is the internal resistance at reference temperature T0, and α is the temperature coefficient. Combining the basic formula, a more accurate voltage compensation formula can be obtained:

[0013] V actual =V measured +I·R0(1+α(T-T0))

[0014] S4, protection action execution: Once overcharging is confirmed, the BMS will immediately cut off the charging circuit and stop charging. At the same time, an overcharging alarm signal is sent to the external device through the communication interface to remind the user or system to take corresponding measures;

[0015] S5. Fault recording and subsequent processing: Record detailed information of the overcharging event, including the time of occurrence, battery cell voltage, and charging current, for subsequent analysis of the cause of the fault.

[0016] Furthermore, in S1, the monitored voltage value is continuously compared with a preset charging cut-off voltage threshold during the charging process.

[0017] Furthermore, during the charging process, the BMS continuously compares the real-time voltage value of each battery cell with the preset charging cut-off voltage threshold. Once the voltage of a battery cell reaches or approaches the threshold, the BMS immediately initiates the corresponding protection measures.

[0018] Furthermore, when it is monitored that the battery cell voltage is close to the threshold, the BMS will first gradually reduce the charging current to achieve constant voltage charging; if the battery cell voltage continues to rise and exceeds a certain range of the threshold despite the reduction in charging current, the BMS will decisively cut off the charging circuit and stop charging.

[0019] Furthermore, in S3, if the charging time reaches the preset maximum charging time limit, charging will be stopped even if the voltage does not exceed the cutoff value; if the battery temperature is too high and exceeds the set safety temperature threshold, charging will also be stopped immediately.

[0020] Furthermore, the voltage sensor continuously obtains the voltage value of each battery cell. The collected data is first pre-processed by filtering to remove possible interference signals to obtain stable and accurate real-time voltage data. These data are then associated with the corresponding battery cell number and other identification information for storage.

[0021] Furthermore, the current sensor monitors the current flowing into the battery during the charging process in real time. The collected data is converted and compared with the preset current range after processing to determine whether the current charging current is in a normal state.

[0022] Furthermore, in S5, after the overcharge protection, the state of the battery cell is evaluated, and corresponding treatment measures are taken as needed, such as testing the voltage again after standing for a period of time, or performing balanced charging.

[0023] Furthermore, in S4, when the BMS determines that overcharging has occurred through monitoring and judging various battery parameters, its built-in control module will immediately generate a control signal to cut off the charging circuit. This signal will be transmitted to the relay control circuit connected to the charging circuit in the form of a digital signal in accordance with the CAN bus protocol.

[0024] Furthermore, after receiving the cut-off signal from the BMS, the relay control circuit drives the corresponding relay to operate. At this time, the electromagnetic coil inside the relay will be energized, causing the contacts to quickly switch from a closed state to an open state, thereby cutting off the current path in the charging circuit.

[0025] Beneficial effects of the present invention:

[0026] 1. The BMS's adaptive protection algorithm for the performance parameters of the battery cells accurately controls the charging and discharging process according to the actual performance parameters of the battery cells, such as capacity, internal resistance, etc., and can adaptively adjust the charging current or mode to avoid overcharging of these battery cells.

[0027] 2. The BMS's adaptive protection algorithm for the performance parameters of the battery cells monitors the voltage, current and other parameters of the battery cells in real time, and performs dynamic protection based on the characteristics of the battery cells. By continuously learning and analyzing the performance of the battery cells, it accurately determines the overcharge threshold of each battery cell. When the battery cell voltage approaches its personalized overcharge threshold, the charging circuit is cut off in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a schematic structural diagram of the appearance of an adaptive protection algorithm for performance parameters of a BMS for a battery cell. DETAILED DESCRIPTION

[0029] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0030] See also Figure 1 The present invention provides the following technical solutions: a BMS adaptive protection algorithm for the performance parameters of the battery cell,

[0031] (1) Real-time voltage monitoring: BMS monitors the voltage of each battery cell in real time through a built-in voltage sensor. During the charging process, the monitored voltage value is continuously compared with the preset charging cut-off voltage threshold. In this embodiment, a battery pack is provided, which consists of 10 battery cells connected in series. The charging cut-off voltage threshold preset by BMS is 4.20V for each battery cell, and the voltage sensor accuracy in BMS is ±0.02V, and the sampling frequency is 1 time per second. During a certain charging process, at a certain moment, the voltage values ​​of the 10 batteries collected by BMS are: 4.18V, 4.19V, 4.20V, 4.17V, 4.19V, 4.21V, 4.20V, 4.18V, 4.19V, 4.20V.

[0032] (1.1) The BMS collects the voltage value of each battery cell in real time at a sampling frequency of once per second and converts it into a digital signal for processing by the microcontroller unit (MCU).

[0033] (1.2) The MCU compares each collected cell voltage value with the preset charge cut-off voltage threshold of 4.20V.

[0034] (1.2.1) For the first cell, the voltage value is 4.18V. Since 4.18V<4.20V, the cell has not reached the charge cut-off voltage.

[0035] (1.2.2) For the second battery cell, the voltage value is 4.19V. Similarly, 4.19V<4.20V, and the cut-off voltage has not been reached.

[0036] (1.2.3) The voltage of the third cell is 4.20V, which is exactly equal to the preset charge cut-off voltage threshold. At this time, the BMS will pay close attention to the status of this cell and adjust it according to the overall charging strategy. Similarly, all 10 cells are compared and judged to obtain the status of each cell.

[0037] (1.3) Since the voltage sensor accuracy is ±0.02V, special attention should be paid to voltage values ​​close to the threshold. For example, the voltage of the sixth cell is 4.21V. Although it is greater than the threshold of 4.20V in terms of value, its actual voltage may be between 4.19V and 4.23V considering the sensor error. Therefore, the BMS will not immediately determine that the cell is overcharged, but will continue to observe its voltage change trend in the next few samplings.

[0038] S2. Charging status judgment: When the cell voltage is close to the preset charging cut-off voltage, the BMS will gradually reduce the charging current according to the charging curve control strategy and enter the constant voltage charging stage to avoid a sharp rise in voltage.

[0039] In this embodiment, at the beginning of charging, the BMS controls the charger to perform constant current charging on the battery pack at a current of 0.5C (25A). In this stage, the battery voltage gradually rises, and the BMS collects the voltage value of each single cell in the battery pack every 10 seconds. As charging progresses, when the BMS monitors that the voltage of a single cell in the battery pack reaches 4.15V, it is already close to the voltage threshold of 4.2V in the constant voltage charging stage. According to the preset charging curve control strategy, the BMS begins to gradually reduce the charging current.

[0040] The BMS first reduces the charging current from 25A to 20A. In the next few sampling cycles, the battery voltage changes will continue to be monitored. If the voltage rises still too fast and exceeds the preset slope limit, it means that the current is still too large, and the BMS will reduce the charging current again, for example, to 15A. When the BMS reduces the charging current to 10A, after multiple samplings, it is found that the rate of increase of the battery voltage has slowed down significantly and gradually stabilized at around 4.2V. At this time, the battery officially enters the constant voltage charging stage. During the constant voltage charging stage, the BMS will continue to monitor the battery voltage and current, and dynamically adjust the charging current according to small fluctuations in voltage to keep it in a constant voltage state.

[0041] S3. Multiple condition judgment: In addition to voltage monitoring, BMS will also make comprehensive judgments based on other parameters, such as charging time, battery temperature, charging current, etc. If the charging time reaches the preset maximum charging time limit, charging will be stopped even if the voltage does not exceed the cutoff value; if the battery temperature is too high and exceeds the set safety temperature threshold, charging will also be stopped immediately.

[0042] In this embodiment, when charging starts, the charger charges the battery pack at a constant current of 0.5C (30A), and the BMS collects charging current data every 5 seconds. At this stage, the charging current is basically stable at around 30A, and the battery voltage gradually rises; as the battery voltage increases, when the battery voltage reaches the preset constant voltage charging voltage value (assuming 4.2V / cell), the charger enters the constant voltage charging mode, and the charging current begins to gradually decrease. The BMS continuously monitors the changes in the charging current and finds that the current gradually decreases from 30A.

[0043] During the constant voltage charging process, the charging current continues to decrease over time. When the BMS detects that the charging current has dropped to 5A, it is close to the set cut-off current threshold of 3A. At this time, the BMS begins to pay closer attention to current changes, and at the same time makes a comprehensive judgment based on other parameters such as battery voltage and temperature. When the charging current further drops to 3A, the BMS determines that the battery is basically full according to the preset control strategy. At the same time, the BMS checks that the battery temperature is within the normal range, and the battery voltage is also stable at around 4.2V, meeting the conditions for stopping charging. Therefore, the BMS sends a stop charging instruction to the charger, the charger stops working, and the charging process ends.

[0044] S4, protection action execution: Once overcharging is determined, the BMS will immediately cut off the charging circuit and stop charging. At the same time, it will send an overcharging alarm signal to the external device through the communication interface to remind the user or system to take corresponding measures.

[0045] In this embodiment, when the temperature exceeds the set safety threshold of 60°C, the BMS will immediately start the heat dissipation device, including increasing the circulation speed of the coolant in the battery cooling system and starting the high-speed operation mode of the cooling fan, trying to reduce the battery temperature as quickly as possible so that the battery operates within a normal temperature range.

[0046] If after a period of time, which is set to 5 minutes in this embodiment, the battery temperature remains high and continues to rise, reaching the critical value of 70°C, the BMS will decisively cut off the charging circuit and the power output circuit. In this state, even if there is a charging current input request, the BMS will not respond to these requests, preventing the battery from continuing to work and charge and discharge, and preventing accidents such as thermal runaway of the battery caused by high temperature.

[0047] S5. Fault record and subsequent processing: Record the detailed information of the overcharge event, including the time of occurrence, battery cell voltage, and charging current, for subsequent analysis of the cause of the fault. After the overcharge protection, evaluate the battery cell status and take appropriate processing measures as needed, such as testing the voltage again after a period of rest, or performing balanced charging.

[0048] In this embodiment, when the BMS detects that the battery is over-discharged, the data acquisition module in the BMS will immediately start the information recording function to collect various data, including the specific time when the over-discharge occurred, which is accurate to milliseconds in this embodiment, the remaining battery power percentage at that time, the actual voltage value of each single cell, the ambient temperature of the battery, the device where the battery is located, and other related information.

[0049] The data is then organized into a specific data format and stored in the BMS's built-in Flash memory to ensure that the data will not be lost even if the system loses power unexpectedly. At the same time, the BMS can transmit data to an external server in real time or periodically, which facilitates subsequent remote centralized analysis and management. The transmission method is through the wired CAN bus.

[0050] The basic principles and main features of the present invention and the advantages of the present invention are shown and described above. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention.

[0051] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A BMS adaptive protection algorithm for the performance parameters of a battery cell, characterized by: The following steps are involved: S1. Real-time voltage monitoring: BMS monitors the voltage of each battery cell in real time through the built-in voltage sensor, and reduces the impact of battery internal resistance on voltage measurement through voltage compensation. The process uses the following formula: V actual =V measured +I·R internal Among them, the voltage V measured , charge and discharge current I and battery internal resistance R internal To calculate the actual battery voltage V actual ; S2, charging status judgment: When the cell voltage is close to the preset charging cut-off voltage, the BMS gradually reduces the charging current according to the charging curve control strategy and enters the constant voltage charging stage to avoid a sharp rise in voltage; S3. Multiple condition judgment: In addition to voltage monitoring, BMS makes a comprehensive judgment based on other parameters, such as charging time, battery temperature, charging current, etc., and monitors the actual voltage based on the battery temperature, using the following formula: R interna (T)=R0(1+α(T-T0)) Where R interna (T) is the battery internal resistance at temperature, R0 is the internal resistance at reference temperature T0, and α is the temperature coefficient. Combining the basic formula, a more accurate voltage compensation formula can be obtained: V actual =V measured +I·R0(1+α(T-T0)) S4, protection action execution: Once overcharging is determined, the BMS immediately cuts off the charging circuit and stops charging. At the same time, it sends an overcharging alarm signal to the external device through the communication interface to remind the user or system to take corresponding measures; S5. Fault recording and subsequent processing: Record detailed information of the overcharging event, including the time of occurrence, battery cell voltage, and charging current, for subsequent analysis of the cause of the fault.

2. According to claim 1, the BMS adaptive protection algorithm for the performance parameters of the battery cell is characterized by: In S1, the monitored voltage value is continuously compared with a preset charging cut-off voltage threshold during the charging process.

3. According to claim 2, the BMS adaptive protection algorithm for the performance parameters of the battery cell is characterized by: During the charging process, the BMS continuously compares the real-time voltage value of each battery cell with the preset charging cut-off voltage threshold. Once the voltage of a battery cell reaches or approaches the threshold, the BMS immediately initiates the corresponding protection measures.

4. The adaptive protection algorithm for the performance parameters of a BMS for a battery cell according to claim 3 is characterized in that: When it is monitored that the battery cell voltage is close to the threshold, the BMS first gradually reduces the charging current to achieve constant voltage charging; if the battery cell voltage continues to rise and exceeds the threshold within a certain range despite the reduction in charging current, the BMS decisively cuts off the charging circuit and stops charging.

5. The adaptive protection algorithm for the performance parameters of a BMS for a battery cell according to claim 1, characterized in that: In S3, if the charging time reaches the preset maximum charging time limit, charging will be stopped even if the voltage does not exceed the cutoff value; if the battery temperature is too high and exceeds the set safety temperature threshold, charging will also be stopped immediately.

6. The adaptive protection algorithm for the performance parameters of a BMS for a battery cell according to claim 5, characterized in that: The voltage sensor continuously obtains the voltage value of each battery cell. The collected data is first pre-processed by filtering to remove possible interference signals and obtain stable and accurate real-time voltage data. This data is then associated with the corresponding battery cell number and other identification information for storage.

7. The adaptive protection algorithm for the performance parameters of a BMS for a battery cell according to claim 6, characterized in that: The current sensor monitors the current flowing into the battery during the charging process in real time. The collected data is converted and compared with the preset current range after processing to determine whether the current charging current is in a normal state.

8. The adaptive protection algorithm for performance parameters of a BMS for a battery cell according to claim 1, characterized in that: In S5, after the overcharge protection, the state of the battery cell is evaluated, and corresponding treatment measures are taken as needed, such as testing the voltage again after standing for a period of time, or performing balanced charging.

9. The adaptive protection algorithm for the performance parameters of a BMS for a battery cell according to claim 8, characterized in that: In S4, when the BMS determines that overcharging has occurred through monitoring and judging various battery parameters, its built-in control module will immediately generate a control signal to cut off the charging circuit. This signal will be transmitted to the relay control circuit connected to the charging circuit in the form of a digital signal according to the CAN bus protocol.

10. The BMS adaptive protection algorithm for performance parameters of a battery cell according to claim 9, characterized in that: After receiving the cut-off signal from the BMS, the relay control circuit drives the corresponding relay to operate. At this time, the electromagnetic coil inside the relay will be energized, causing the contacts to quickly switch from a closed state to an open state, thereby cutting off the current path in the charging circuit.

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