Power lithium battery pack three-dimensional temperature imaging and active protection system

Abstract

The invention relates to a three-dimensional temperature imaging and active protection system for a power lithium battery pack. Through a distributed temperature array, three-dimensional temperature field reconstruction and intelligent half-bridge rapid isolation technology, the problems of temperature detection lag, insufficient spatial resolution and passive protection mechanism in the prior art are solved, and high-precision measurement of the surface temperature of the battery cell, rapid cutting off of abnormal current and visualization of the three-dimensional temperature field are realized. The system can early warn the thermal runaway risk in advance, and the safety and reliability of the battery pack are remarkably improved. According to the method, the early warning time is 8-12 minutes earlier than that of a traditional scheme, the abnormal battery cell can be cut off before thermal runaway, the abnormal battery cell is prevented from worsening the working state, and the overcurrent protection response time is not longer than 1 ms.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery pack management, and in particular to a three-dimensional temperature imaging and active protection system for a power lithium battery pack. Background Art

[0002] Traditional BMS temperature detection only arranges 1-2 temperature sensors at the electrode contacts of the battery cell, which cannot sense the temperature distribution inside and on the surface of the battery cell. There is a lack of distributed monitoring of the temperature field on the surface of the battery cell, making it difficult to locate local hot spots in a timely manner. Although the intelligent sensor, device and method for lithium battery temperature distribution with application number 202311038355.5 mentions the use of multiple point temperature measurement sensors to measure the temperature of lithium batteries, due to the point sensors, there will be a large number of blank areas between the sensors whose temperatures cannot be monitored. In addition, the temperature changes in the early stage of thermal runaway inside the battery cell cannot be detected in time through the electrode contacts. It takes time for heat to transfer from the inside to the surface, and the transfer speed is affected by the thermal conductivity and structure of the material. The temperature inside the battery cell is higher, and the temperature of the electrode contacts is lower. There is a temperature difference between the temperature of the battery cell electrode contacts and the inside of the battery cell, which leads to a delay in early warning.

[0003] In addition, the traditional solution relies on a global fuse and cannot isolate a single faulty cell, causing the system to shut down. The failure or performance degradation of a single chip will affect the overall performance of the battery pack and form a barrel effect. In the patent with application number 202211204986.5, a battery system and method with inter-battery state balancing and fault bypass functions are implemented with complex circuits. It does not have the function of comprehensive temperature detection on the surface of the battery cell. The use of a large number of power tubes and switch components will significantly increase the complexity and cost of the system, making it difficult to promote and apply. The main problem is that the current balancing capability of the active balancing circuit is significantly lower than 10 amperes, which is difficult to achieve the effect compared to the current of tens of amperes or hundreds of amperes when the battery pack is charging or discharging. The patent with patent number CN111478410B, a bidirectional active balancing BMS circuit and control method, uses a complex balancing circuit, but the current balancing capability is still very weak, significantly lower than 10 amperes. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention discloses a three-dimensional temperature imaging and active protection system for a power lithium battery pack, and the technical solution adopted is, including a central processing unit and a battery cell temperature measurement unit, the central processing unit is electrically connected to a display unit and an alarm unit, the battery cell temperature measurement unit includes a temperature measurement single chip microcomputer, the temperature measurement single chip microcomputer is electrically connected to a temperature measurement matrix circuit, a half-bridge switching circuit, and a lithium battery cell, the half-bridge switching circuit is electrically connected to the lithium battery cell, the upper battery cascade, and the lower battery cascade, the central processing unit and the temperature measurement single chip microcomputer are electrically connected to a radio frequency module respectively, and are used for communication between them. The radio frequency module adopts a Si24R1 wireless transceiver chip, performs data transmission based on the LoRa protocol, and constructs a star-shaped radio frequency network, each temperature measurement single chip microcomputer is used as a sub-node, the central processing unit is used as a master node, and the communication cycle is ≤50ms.

[0005] As a preferred solution of the present invention, the half-bridge switching circuit includes a half-bridge upper arm MOS tube and a half-bridge lower arm MOS tube, which are connected to the temperature measuring microcontroller through a driving circuit, and the first resistor V_cell_R1 and the second resistor V_cell_R2 are connected in series to form a first voltage divider circuit, and are connected in parallel with the battery cell bat to the half-bridge upper arm ON_Q, and the third resistor V_mid_R1 and the fourth resistor V_mid_R2 are connected in series to form a second voltage divider circuit, and are connected between the half-bridge upper arm ON_Q and the half-bridge lower arm OFF_Q.

[0006] As a preferred solution of the present invention, the temperature measurement matrix circuit is composed of NTC temperature sensors arranged and connected in a matrix of 5 NTC temperature sensors per row and 5 NTC temperature sensors per column. The NTC temperature sensors can be arranged in an array according to the actual number of battery cells. Each NTC temperature sensor is connected in series with a diode, and the diode is a Schottky diode. Each NTC temperature sensor is in close contact with the surface of the battery cell through a thermal conductive adhesive; the first voltage-dividing resistor R1, the second voltage-dividing resistor R2, the third voltage-dividing resistor R3, the fourth voltage-dividing resistor R4, and the fifth voltage-dividing resistor R5 are sequentially connected to the front end of each column of NTC temperature sensors to provide a voltage-dividing resistor for each column of NTC temperature sensors, and the voltage-dividing voltage is sent to the AD port of the temperature measurement microcontroller; the first transistor Q1, the second transistor Q2, the third transistor Q3, the fourth transistor Q4, and the fifth transistor Q5 are sequentially connected to the end of each row of NTC temperature sensors, and the grounding state of the horizontal NTC temperature sensors is controlled by the transistors, and the AD port is time-divided to reduce the resource occupation of the temperature measurement microcontroller.

[0007] The formula for the relationship between the resistance and temperature of the NTC temperature sensor is: Among them, R 0 is the temperature T 0 The resistance value of the NTC temperature sensor under the condition of 0is the reference temperature, usually 298k. The voltage divider voltage calculation formula for each column of NTC temperature sensor is V out =R T ·V cc / R T +R ref , where R T is the resistance of the NTC temperature sensor, V cc is the reference voltage, usually 3.3V, R ref The voltage divider resistor value is usually 10kΩ.

[0008] As a preferred solution of the present invention, the central processing unit receives data through the radio frequency module and generates a three-dimensional temperature distribution map, combines the threshold algorithm to implement abnormal alarm, displays the three-dimensional temperature distribution map through the display unit, and sends out alarm information through the alarm unit.

[0009] Beneficial effects of the present invention: The present invention solves the problems of temperature detection lag, insufficient spatial resolution and passive protection mechanism in the prior art through distributed temperature array, three-dimensional temperature field reconstruction and intelligent half-bridge fast isolation technology, and realizes high-precision measurement of battery cell surface temperature, rapid cutting off of abnormal current and three-dimensional temperature field visualization. The system can warn of thermal runaway risks in advance and significantly improve the safety and reliability of battery packs. The warning time of this method is 8-12 minutes earlier than that of traditional solutions. It can cut off abnormal batteries before thermal runaway occurs, prevent abnormal batteries from deteriorating their working state, and the overcurrent protection response time is no more than 1ms. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a system structure block diagram of the present invention;

[0011] Figure 2 is a schematic diagram of a half-bridge switching circuit of the present invention;

[0012] Figure 3 It is a schematic diagram of the temperature matrix circuit of the present invention;

[0013] Figure 4 It is a schematic diagram of the radio frequency module circuit of the present invention. DETAILED DESCRIPTION

[0014] Example 1

[0015] like Figures 1 to 4As shown, a three-dimensional temperature imaging and active protection system for a power lithium battery pack of the present invention includes a central processing unit and a battery cell temperature measurement unit, wherein the central processing unit is electrically connected to a display unit and an alarm unit, and the battery cell temperature measurement unit includes a temperature measurement single chip microcomputer, wherein the temperature measurement single chip microcomputer is electrically connected to a temperature measurement matrix circuit, a half-bridge switching circuit, and a lithium battery cell, wherein the half-bridge switching circuit is electrically connected to the lithium battery cell, the upper battery cascade, and the lower battery cascade, and the central processing unit and the temperature measurement single chip microcomputer are electrically connected to a radio frequency module respectively, and are used for communication between them. The radio frequency module adopts a Si24R1 wireless transceiver chip, performs data transmission based on the LoRa protocol, and constructs a star-shaped radio frequency network, wherein each temperature measurement single chip microcomputer is used as a sub-node, the central processing unit is used as a master node, and the communication cycle is ≤50ms. The communication data packet structure design: includes a temperature matrix (5×5 bytes), a voltage (12bit ADC value), a MOS status flag bit, and a CRC check.

[0016] The half-bridge switching circuit includes a half-bridge upper arm MOS tube and a half-bridge lower arm MOS tube, which is a dual MOS half-bridge topology. When working normally, the upper arm is turned on (R ds_on <=1mΩ), the lower arm is turned off, the upper arm is disconnected during isolation, and the lower arm is turned on to form a bypass channel. The selected half-bridge driver is TI UCC27517. Through the half-bridge driver connected to the temperature measuring microcontroller, when the upper arm ON_Q of the half-bridge is turned on, the battery cell bat can charge and discharge the outside. After the lower arm OFF_Q of the half-bridge is turned on, it can provide a current channel for the entire battery pack to prevent current interruption caused by the opening of the upper arm of the half-bridge. The first resistor V_cell_R1 and the second resistor V_cell_R2 are connected in series to form a first voltage divider circuit, and are connected in parallel with the battery cell bat to the upper arm ON_Q of the half-bridge, and the third resistor V_mid_R1 and the fourth resistor V_mid_R2 are connected in series to form a second voltage divider circuit, and are connected between the upper arm ON_Q of the half-bridge and the lower arm OFF_Q of the half-bridge. The first voltage divider circuit is connected to the AD channel of the temperature measuring microcontroller to collect the battery voltage, and the second voltage divider circuit is connected to the AD channel of the temperature measuring microcontroller to collect the midpoint voltage of the half-bridge. Because when the upper arm MOS tube of the half-bridge is turned on, the current will generate a voltage drop when passing through the internal resistance of the MOS tube. The temperature measuring microcontroller can determine whether the battery is in the charging state, discharging state or overcurrent state by comparing the difference between the midpoint voltage of the half-bridge and the battery voltage. For example, when the midpoint voltage of the half-bridge is greater than the battery voltage, it means that it is in the charging voltage. When the midpoint voltage of the half-bridge is less than the battery voltage, it means that it is in the discharging state. The size of the voltage difference is proportional to the current size. The size of the difference can also be used to determine whether the charging current and the discharging current are overcurrent. When the upper arm ON_Q of the half-bridge is turned off and the lower arm OFF_Q is turned on, the half-bridge circuit cuts off the charging and discharging circuit of the battery cell. By measuring the tube voltage drop when the lower arm is turned on, that is, the V_mid_AD voltage, the charging current size can be determined and whether the charging protection is required.

[0017] Overcurrent protection mechanism: Calculate the current by measuring the Vds conduction voltage difference of the MOS tube in real time: I = V ds / R ds_on , where I is the cell current, V ds is the MOS tube voltage drop, R ds_on It is the on-state resistance of the MOS tube, usually 1mΩ.

[0018] The temperature measurement matrix circuit is composed of NTC temperature sensors arranged and connected in a matrix, and the NTC temperature sensors can be arranged in an array according to the number of actual battery cells, and each NTC temperature sensor is in close contact with the surface of the battery cell through a thermal conductive adhesive; taking the matrix arrangement of 5 NTC temperature sensors in each row and 5 NTC temperature sensors in each column as an example, the first voltage-dividing resistor R1, the second voltage-dividing resistor R2, the third voltage-dividing resistor R3, the fourth voltage-dividing resistor R4, and the fifth voltage-dividing resistor R5 are sequentially connected to the front end of each column of NTC temperature sensors, providing a voltage-dividing resistor for each column of NTC temperature sensors, and sending the voltage-dividing voltage to the AD port of the temperature measurement single-chip computer; the first transistor Q1, the second transistor Q2, the third transistor Q3, the fourth transistor Q4, and the fifth transistor Q5 are sequentially connected to the end of each row of NTC temperature sensors. The first transistor Q1, the second transistor Q2, the third transistor Q3, the fourth transistor Q4, and the fifth transistor Q5 are turned on in sequence to measure any temperature sensor. For example, the first transistor Q1 is turned on, and the other transistors are turned off. The temperature measuring microcontroller collects the temperature of temp_AD1, and the collected temperature is the temperature equivalent value of the NTC1 temperature sensor. Although the temperature sensors NTC6, NTC11, NTC16, and NTC21 are also connected to the first voltage-dividing resistor R1, since the second transistor Q2, the third transistor Q3, the fourth transistor Q4, and the fifth transistor Q5 are in a disconnected state, the resistance value changes of the temperature sensors NTC6, NTC11, NTC16, and NTC21 do not affect the state of the temperature sensor NTC1, and do not affect the temperature collection of the NTC1 temperature sensor. Similarly, when the first transistor Q1 is turned on, the temperature measuring microcontroller collects the temperature of temp_AD2, and the collected temperature is the temperature of the NTC2 temperature sensor, which is not affected by other temperature sensors. Similarly, the temperature collection of any NTC temperature sensor can be completed. A diode is connected in series under each sensor in the circuit. The diode uses an ultra-low voltage drop Schottky diode. Its function is to prevent other sensors that are not measuring from backflowing into the NTC temperature sensor being measured, thereby avoiding interference.

[0019] The formula for the relationship between the resistance and temperature of the NTC temperature sensor is: Among them, R 0 is the temperature T 0The resistance value of the NTC temperature sensor under the condition of 0 is the reference temperature, usually 298k. The voltage divider voltage calculation formula for each column of NTC temperature sensor is V out =R T ·V cc / R T +R ref , where R T is the resistance of the NTC temperature sensor, V cc is the reference voltage, usually 3.3V, R ref The voltage divider resistor value is usually 10kΩ.

[0020] The central processing unit receives data through the radio frequency module and generates a three-dimensional temperature distribution map, combines the threshold algorithm to realize abnormal alarm, displays the three-dimensional temperature distribution map through the display unit, and sends an alarm message through the alarm unit. Alarm strategy: Level 1 alarm (temperature ≥ 60°C or current ≥ 150A): triggers the half-bridge protection of this battery cell, and the local temperature field is displayed in red. Level 2 alarm (abnormalities in ≥ 3 adjacent battery cells): cuts off the main circuit of the battery pack and pushes an emergency alarm to the vehicle terminal. The alarm information can also be pushed to the owner's mobile phone through the 5G module, or the alarm can be displayed outside the car body through sound and light.

[0021] Temperature field reconstruction algorithm: Based on the interpolation algorithm of finite element analysis, discrete temperature data is mapped into a three-dimensional thermal map of the battery cell surface. The system delay is <20ms, which is more than 5 times higher than the traditional solution.

[0022] Anomaly detection logic: The gradient threshold method identifies areas where the local temperature rise rate is greater than 3°C / s, and cross-validates with adjacent sensor data.

[0023] Interpolation formula (bilinear interpolation): Where T(x,y) is the temperature of the interpolation point, T 11 , T 21 , T 12 , T 22 is the temperature value of four adjacent NTC temperature sensors.

[0024] Workflow:

[0025] Temperature sampling stage: The temperature measuring microcontroller turns on the horizontal transistors Q1-Q5 in sequence, reads the vertical divided voltage value and calculates the temperature of each NTC sensor.

[0026] Safety decision-making stage: When it is detected that the temperature of ≥3 adjacent sensors exceeds the set threshold (such as 55°C) or the temperature rise rate is abnormal, the following procedures are immediately triggered:

[0027] a) Report to the central processing unit to generate a three-dimensional alarm image;

[0028] b) Turn off the upper arm MOS of this battery cell and turn on the lower arm MOS to form a bypass.

[0029] System self-recovery mechanism: After the abnormality is resolved, the battery cell health assessment is automatically performed and the battery is reconnected after passing the assessment.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" 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, or it can be the internal connection of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0032] Components not described in detail herein are prior art.

[0033] Although the specific embodiments of the present invention are described in detail above, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the purpose of the present invention, and modifications or deformations without creative labor are still within the protection scope of the present invention.

Claims

1. A three-dimensional temperature imaging and active protection system for a power lithium battery pack, characterized in that: It includes a central processing unit and a battery cell temperature measurement unit, the central processing unit is electrically connected to a display unit and an alarm unit, the battery cell temperature measurement unit includes a temperature measurement single chip microcomputer, the temperature measurement single chip microcomputer is electrically connected to a temperature measurement matrix circuit, a half-bridge switching circuit, and a lithium battery cell, the half-bridge switching circuit is electrically connected to the lithium battery cell, the upper battery cascade, and the lower battery cascade, the central processing unit and the temperature measurement single chip microcomputer are respectively electrically connected to a radio frequency module, and are used for communication between them.

2. A three-dimensional temperature imaging and active protection system for a power lithium battery pack according to claim 1, characterized in that: The half-bridge switching circuit includes a half-bridge upper arm MOS tube and a half-bridge lower arm MOS tube, which are connected to the temperature measuring microcontroller through a half-bridge driver. The first resistor V_cell_R1 and the second resistor V_cell_R2 are connected in series to form a first voltage divider circuit, and are connected in parallel with the battery cell bat to the half-bridge upper arm ON_Q. The third resistor V_mid_R1 and the fourth resistor V_mid_R2 are connected in series to form a second voltage divider circuit, and are connected between the half-bridge upper arm ON_Q and the half-bridge lower arm OFF_Q.

3. The three-dimensional temperature imaging and active protection system for a power lithium battery pack according to claim 1, characterized in that: The temperature measurement matrix circuit is composed of NTC temperature sensors arranged and connected in a matrix of 5 NTC temperature sensors in each row and 5 NTC temperature sensors in each column. Each NTC temperature sensor is connected in series with a diode, and the diode is a Schottky diode. Each NTC temperature sensor is in close contact with the surface of the battery cell through a thermal conductive adhesive. The first voltage-dividing resistor R1, the second voltage-dividing resistor R2, the third voltage-dividing resistor R3, the fourth voltage-dividing resistor R4, and the fifth voltage-dividing resistor R5 are sequentially connected to the front end of each column of NTC temperature sensors to provide a voltage-dividing resistor for each column of NTC temperature sensors, and the voltage-dividing voltage is sent to the AD port of the temperature measurement microcontroller. The first transistor Q1, the second transistor Q2, the third transistor Q3, the fourth transistor Q4, and the fifth transistor Q5 are sequentially connected to the end of each row of NTC temperature sensors.

4. The three-dimensional temperature imaging and active protection system for a power lithium battery pack according to claim 1, characterized in that: The radio frequency module adopts Si24R1 wireless transceiver chip and performs data transmission based on LoRa protocol.

5. The three-dimensional temperature imaging and active protection system for a power lithium battery pack according to claim 3, characterized in that: The voltage divider resistor for each column of NTC temperature sensor is calculated as V out =R NTC ·V cc / R NTC +R ref , where R NTC is the resistance of the NTC temperature sensor, V cc is the reference voltage, R ref The resistance value of the voltage divider resistor.

6. The three-dimensional temperature imaging and active protection system for a power lithium battery pack according to claim 1, characterized in that: The central processing unit receives data through the radio frequency module and generates a three-dimensional temperature distribution diagram, triggering a graded alarm.

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