CN212182485U - Battery management system of low-voltage lithium battery pack - Google Patents

Abstract

A low-voltage lithium battery pack battery management system, comprising a power supply module, a current sensor signal sampling module, a switch value acquisition module, a load relay driving module, a charging relay driving module, a temperature management relay driving module, a communication module, a single voltage sampling module, Module temperature acquisition module, passive equalization module, voltage monitoring module, MCU module, crystal oscillator module. The utility model has a simple structure, is stable and reliable, ensures the voltage consistency of the single cell, and avoids the overvoltage of the single cell at the same time; facilitates the sampling of voltage and resistance values; the principle of voltage value collection and calculation is simple, the cost is low, and the reliability is high; The on and off control of each load circuit; actively realize the heat dissipation or heating of the matched lithium battery pack; when the current is overcurrent, the battery management system actively disconnects the charging relay to protect the lithium battery pack.

Description

A low-voltage lithium battery pack battery management system

technical field

The utility model belongs to the technical field of electronic control, in particular to a low-voltage lithium battery pack battery management system.

Background technique

Lithium battery is a kind of battery that uses lithium metal or lithium alloy as negative electrode material and uses non-aqueous electrolyte solution. Due to the very active chemical properties of lithium metal, the processing, storage and use of lithium metal have very high environmental requirements. With the development of science and technology, lithium batteries have become the mainstream. Lithium-ion batteries have attracted more and more attention due to their high energy density, long life, and almost no environmental pollution. As an important energy storage power source, it is widely used in new energy vehicles, household energy storage, vehicle energy storage, grid energy storage, etc. Due to the narrow operating temperature range of lithium-ion batteries and the great impact on lifespan of overcharge and overdischarge, the function and performance of the battery management system directly restrict the application and promotion of energy-storage lithium-ion battery packs.

As a high-energy substance, lithium batteries must be used under certain technical conditions, including suitable ambient temperature, safe charge and discharge current, safe capacity usage range, and allowable monomer consistency, exceeding the technology allowed by lithium batteries. Use under certain conditions will affect the battery life, and serious thermal runaway will occur.

The current battery management system is generally used in high-voltage lithium battery pack systems, which are developed for new energy vehicles. The conventional battery management system is powered by an external low-voltage power supply. According to the function definition of the components, it includes the main management system module and the sub-management system module. The functions of the main management system module include vehicle communication protocol adaptation, nuclear charge calculation, and sub-management system modules. Functions include battery voltage monitoring, module temperature monitoring.

The high-voltage lithium battery pack for new energy vehicles supplies power for power batteries, high-voltage accessories, etc. When the vehicle control strategy coordinates the output of the power motor torque motor, the power battery is often overcharged or discharged due to the unreasonable torque output of the power motor. Charging or discharging, use at high temperature or low temperature will seriously affect the safety of lithium battery pack.

For this specific battery management requirement of low-voltage lithium battery packs, this type of controller requires external low-voltage power supply, and the matching flexibility is not high. At the same time, because there is no external power-consuming equipment control function, it cannot perform safety operations under abnormal use conditions. operation, there is a greater safety hazard.

Utility model content

Aiming at the problems existing in the above-mentioned prior art, the present invention aims to provide a low-voltage lithium battery pack battery management system, which aims to realize passive balance, discharge demand collection, discharge loop control, nuclear charge count through a single control unit Estimation, safety protection and other functions.

In order to achieve the above object, the utility model adopts the following technical solutions:

Aiming at the shortcomings of the battery management system in the prior art, such as single function, poor integration, scattered strategies, and no active current limiting, the utility model provides a low-voltage lithium battery with complete functions, high integration, centralized strategy, and priority-based current limiting. Battery pack battery management system.

In order to achieve the above object, the utility model adopts the following technical solutions:

A low-voltage lithium battery pack battery management system, comprising a power supply module, a current sensor signal sampling module, a switch value acquisition module, a load relay drive module, a charging relay drive module, a temperature management relay drive module, a communication module, a single voltage sampling module, Module temperature acquisition module, passive equalization module, voltage monitoring module, MCU module, crystal oscillator module.

The power module converts the external power supply voltage of the battery management system into the power supply low voltage of the internal chip, and provides power for the external current sensor at the same time.

The MCU module is the main controller unit of the battery management system, and is a physical device for policy execution.

The crystal oscillator module provides an accurate and reliable working clock for the MCU module.

The current sensor signal sampling module converts the signal input by the current sensor input from the outside into a signal type that can be processed by the MCU module.

The switch quantity collection module collects the power supply request of the load, and increases the number of channels according to the actual demand.

The load relay drive circuit outputs the drive signal of the external relay, controls the opening and closing of the relay, and increases the number of channels according to actual needs.

The charging relay driving circuit outputs a driving signal of the charging relay to control the opening and closing of the charging relay, and the signal type is the same as that of the above-mentioned load relay driving circuit.

The temperature management relay drive module has the same drive signal type as the above load relay drive circuit, and controls the opening and closing of the assembly power supply relay that can adjust the temperature of the lithium battery pack, such as fans, water pumps, and electric heating components outside the lithium battery pack.

The communication module realizes communication between the battery management system and other external assemblies, such as a display screen, an electrical load, and the like.

The cell voltage sampling module collects cell voltage signals of the matched lithium battery pack, and the number of channels is determined according to the cell pack data.

The module temperature acquisition module collects the temperature sensor signal inside the matched lithium battery pack, preferably a thermistor type temperature sensor, whose channel data is determined by the internal temperature sensor data of the lithium battery pack.

The passive equalization module realizes the protection of the passive equalization of the battery cells, and the number of channels is determined according to the data of the battery cells.

The voltage monitoring module realizes a specific point voltage to judge the working condition of the device, such as collecting the back-end voltage of the power supply output fuse of the lithium battery pack to judge whether the fuse is blown, and the number of channels is determined according to the actual demand.

Further, the current sensor power supply circuit of the power module is isolated from the internal chip power supply circuit.

Further, the power module and the negative electrode of the matched lithium battery pack share the same ground.

Further, the input signal of the current sensor signal sampling module is a voltage signal, which is compatible with different current sensors.

Further, it is preferable that the external switch signal type is a low-level active signal that shares the ground with the power management system, or it can be a high-level active signal with the power management system ground as a reference, and the high-level voltage is the same as the power management system voltage. The values are the same or similar.

Further, in the drive circuit of the load relay, preferably, the low-level terminal of the external load circuit relay and the negative power supply terminal of the battery management system share the same ground.

The drive output signal is a high-level drive signal with the ground wire of the power management system as a reference; an external relay can also be a high-level power supply voltage for the power management system, and the drive output signal and the battery management system share a low-level ground drive signal.

Further, the communication module preferably uses CAN communication, and can also be other communication bus methods such as RS232 and RS485; the interactive content includes but is not limited to the voltage of the lithium battery pack, the temperature of each temperature sensor, the battery value, and the battery core charge. data, load request signal, load relay control signal, total voltage of lithium battery pack, allowable discharge current of lithium battery pack, allowable charging current of lithium battery pack, etc.

Further, the single-cell voltage sampling module obtains the single-cell voltage by collecting the voltage value between the positive electrode and the common-ground level of the lithium battery pack by collecting the voltage value between the positive electrode and the common ground level of the voltage divider circuit of the lithium battery pack; a differential voltage circuit can also be used. Collect the voltage value between the positive and negative electrodes of the lithium battery cell to directly obtain the cell voltage.

Further, a passive equalization circuit constructed by a controllable precision voltage regulator, PNP transistor, NPN transistor, resistor and other components is used;

Further, the resistance includes a signal resistance and a power resistance; Q1 is a controllable precision voltage stabilizer, preferably TL431; Q3 is a PNP type triode, Q2 is an NPN type triode; wherein one end of R1, R3, R6 and the emission of Q3 The pole is connected to the positive pole of the single battery, one end of R2, the anode of Q1, and the emitter of Q2 are connected to the negative pole of the single battery; the reference pole of Q1 is connected to the other ends of R1 and R2; the two ends of R4 are respectively connected to the other end of R3 One end is connected to the base of Q3; one end of R5 is connected to the collector of Q3, and the other end is connected to the base of Q2; the other end of R6 is connected to the collector of Q2; each resistance value parameter is based on the matched lithium battery protection voltage The specific calculation steps are as follows:

Taking the passive balance voltage as V _bls , the balance voltage relationship is:

Among them, the TL431 type controllable precision regulator V _ref takes a fixed value: V _ref = 2.5V

Preferred value: R ₂ =220kΩ, according to the type of lithium battery, the passive balance voltage value is V _bls , and the calculation can be obtained

R ₃ , R ₃ and R ₅ are preferably: R ₃ =620Ω; R ₃ =R ₄ =200Ω according to the current characteristics of Q3 and Q2;

R ₆ and R ₇ are equalizing circuit discharge power diodes, and the equalizing discharge current is set as I _bls , at this time:

The beneficial effects of the present utility model are:

1. The battery management system includes a passive balancing circuit with a simple, stable and reliable structure, which can effectively protect the voltage of the battery cells from exceeding the set value, ensure the voltage consistency of the single cells, and avoid the overvoltage of the cells;

2. The negative pole of the power supply of the battery management system and the negative pole of the matched lithium battery pack are shared, and each circuit module is the same as the reference voltage of the lithium battery pack, which is convenient for voltage and resistance value sampling;

3. Use the voltage divider circuit with the total negative ground of the lithium battery pack to collect the voltage value between the positive electrode and the common ground level of each series cell, and calculate the difference value to obtain the voltage value of the cell. The principle is simple, low cost and reliable. high;

4. The battery management system collects the external switching signal of the load work request to accurately identify the external discharge request; it can control the relay of the load circuit to realize the on and off control of each load circuit;

5. According to the actual working characteristics of the matched lithium battery pack, the battery management system compares the current discharge current and the allowable discharge current in real time, and disconnects the load with lower priority when overcurrent, so as to achieve limited protection of the matched lithium battery pack ;

6. The battery management system has a temperature management relay drive module, which actively realizes the heat dissipation or heating of the matched lithium battery pack by controlling the cooling fan or electric heating device of the matched lithium battery pack;

7. The battery management system compares the current charging current and the allowable charging current in real time, and automatically disconnects the charging relay in case of overcurrent to protect the lithium battery pack.

Description of drawings

Figure 1 is a schematic diagram of the structure of a low-voltage lithium battery pack battery management system;

Figure 2 is a passive equalization circuit diagram of a low-voltage lithium battery pack battery management system;

Figure 3 is a matching schematic diagram of a low-voltage lithium battery pack battery management system.

Detailed ways

For ease of understanding, below in conjunction with the accompanying drawings, the technical solutions of the present utility model will be further described in detail through the embodiments:

As shown in Figures 1-3, a low-voltage lithium battery pack battery management system includes a power supply module, a current sensor signal sampling module, a switching value acquisition module, a charging relay drive module, a load relay drive module, a temperature management relay drive module, Communication module, single voltage sampling module, module temperature sampling module, passive equalization module, voltage monitoring module, MCU module, crystal oscillator module, wake-up switch, current sensor, load request switch, positive fuse, load loop relay, charging relay, charging terminals, cooling fan relays, electric heating relays, cooling fans, electric heaters, single battery series modules, temperature sensors and battery pack output terminals, etc.

The power supply module includes a wake-up circuit, an internal power supply circuit of the controller, and a current sensor power supply circuit. Preferably, the internal power supply circuit of the controller and the current sensor power supply circuit are isolated from each other; the power supply module is connected to the charging end.

The power module converts the external power supply voltage of the battery management system into the power supply low voltage of the internal chip, and provides power for the external current sensor at the same time; the current sensor power supply circuit of the power module is isolated from the power supply circuit of the internal chip; the power module and the matched negative pole of the lithium battery pack common ground.

The switch quantity acquisition module collects the power supply request of the load, preferably the switch quantity signal level is a common ground low level, and can also be a high level voltage that is the same as or close to the power supply voltage of the power management system. The switch value acquisition module increases the number of channels according to actual needs. Preferably, the external switch signal type is a low-level active signal that shares the ground with the power management system, or it can be a high-level active signal with the power management system ground as a reference. The high-level voltage is the same as the power management system voltage or similar.

The output drive signal of the temperature management relay drive module is the same as the load relay drive signal. Temperature management relay drive module: control the opening and closing of the assembly power supply relay that can adjust the temperature of the lithium battery pack, such as fans, water pumps, and electric heating components outside the lithium battery pack.

The load relay drive module outputs the drive signal of the external relay, and controls the opening and closing of the relay. The load relay drive module increases the number of channels according to actual needs. Preferably, the low-level terminal of the external load loop relay and the negative power supply terminal of the battery management system share the same ground, and the driving output signal is a high-level driving signal with reference to the ground wire of the power management system; the high level of the external relay can also be used for power management. The system power supply voltage, driving the output signal and the low-level driving signal of the battery management system.

Passive equalization module: realize the protection of the passive equalization of the single cell, and the number of channels is determined according to the data of the battery pack; the passive equalization circuit constructed by the controllable precision voltage regulator, PNP triode, NPN triode, resistor and other components is used. When the cell voltage exceeds the configuration threshold, the triode is actively turned on, and the power resistor is connected to the positive and negative electrodes of the single cell. R1, R2, R3, R4, R5 are signal resistors, R6 is power resistor; Q1 is a controllable precision voltage regulator, preferably TL431; Q3 is a PNP type transistor, Q2 is an NPN type transistor; One end and the emitter of Q3 are connected to the positive electrode of the single battery; one end of R2, the anode of Q1, and the emitter of Q2 are connected to the negative electrode of the single battery; the reference electrode of Q1 is connected to the other end of R1 and R2; the two ends of R4 They are respectively connected to the other end of R3 and the base of Q3; one end of R5 is connected to the collector of Q3, and the other end is connected to the base of Q2; the other end of R6 is connected to the collector of Q2; The lithium battery protection voltage value is calculated and obtained.

The voltage monitoring module monitors including but not limited to the back-end voltage of a specific fuse. The voltage monitoring module realizes a specific point voltage to judge the working condition of the device, such as collecting the back-end voltage of the output fuse of the lithium battery pack to judge whether the fuse is blown, and the number of channels is determined according to the actual demand.

The MCU module is the main controller unit of the battery management system and is the physical device for policy execution.

The MCU module estimates the number of core charges of the lithium battery pack. Preferably, when the current current value is lower than a certain threshold, the open-circuit voltage method is used, and when the current current value is higher than a certain threshold, the ampere-hour method is used. The MCU module calculates the charge and discharge capacity of the lithium battery pack in real time according to the temperature, cell voltage, and nuclear charge of the lithium battery pack.

The MCU module decides whether to close the load circuit relay through the load relay drive module according to the preset power of the corresponding load and the current output power limit of the battery.

The MCU module compares the current current value with the current allowable charging and discharging current value of the lithium battery pack in real time. When charging overcurrent, it actively disconnects the charging relay through the charging relay drive module; when discharging overcurrent, it actively drives the module through the load relay to disconnect the priority. Load loop with lower level until the real-time discharge current value is less than the allowable discharge current value.

The communication module includes but is not limited to a certain type of CAN bus, RS232 bus, and RS485 bus. The interactive content includes but is not limited to the voltage of the single battery, the temperature of the temperature sampling point, the current current, the number of nuclear charges, the allowable charging current value, Allowable discharge current value, load request signal, load relay control signal, thermal management component turn-on signal, etc. The communication module realizes the communication between the battery management system and other external assemblies, such as display screen, electrical load, etc. The communication module preferably uses CAN communication, but can also use other communication bus methods such as RS232 and RS485; the content of interaction includes but is not limited to For lithium battery cell voltage, temperature of each temperature sensor, battery value, battery core charge, load request signal, load relay control signal, total lithium battery voltage, lithium battery allowable discharge current, lithium battery allowable charging current, etc. information.

The crystal oscillator module provides an accurate and reliable working clock for the MCU module.

The input signal of the current sensor signal sampling module is a voltage signal, which is compatible with different current sensors; the current sensor signal sampling circuit converts the signal input by the external input current sensor into a signal type that the MCU module can process.

The charging relay driving module outputs the driving signal of the charging relay to control the opening and closing of the charging relay, and the signal type is the same as that of the above-mentioned load relay driving circuit.

The cell voltage sampling module collects the cell voltage signal of the matched lithium battery pack, and the number of channels is determined according to the cell pack data. The cell voltage sampling module preferably collects the voltage value between the cell positive electrode and the common ground level with the voltage divider circuit that shares the total negative ground of the lithium battery pack, and makes a difference to obtain the cell voltage; the differential voltage circuit can also be used to collect the single cell voltage value of the lithium battery pack. The voltage value between the positive and negative electrodes of the body directly obtains the cell voltage.

The module temperature acquisition module collects the temperature sensor signal inside the matched lithium battery pack, preferably a thermistor type temperature sensor, whose channel data is determined by the internal temperature sensor data of the lithium battery pack.

The positive pole of the single battery series module is connected to the sampling terminal of the current sensor and the positive fuse in sequence; the negative pole of the single battery series module and the negative pole of the battery management system share the same ground.

The power supply end of the current sensor is connected with the power supply module, and the signal end of the current sensor is connected with the current sensor signal sampling module.

One end of the wake-up switch is connected to the power module wake-up signal, and the other end is connected to the back end of the (temperature) sensor and the back end of the positive fuse.

One end of the load request switch is connected with the switch quantity acquisition module, and the other end is the common ground end.

The control end of the load circuit relay is connected with the load relay drive module, and the other end is the common ground end.

The charging relay driving module is connected with the control terminal of the charging relay, and the other terminal is a common ground terminal.

One end of the power end of the charging relay is connected to the charging end, and one end is connected to the rear end of the positive fuse.

The temperature sensor is arranged inside the single battery series module, and the output end of the temperature sensor is connected with the module temperature sampling module.

The voltage monitoring module is connected with the output terminal of the battery pack.

The MCU module is the policy execution unit of the battery management system. The MCU module is connected with the temperature management relay driver module. The temperature management relay driving module is connected with the electric heating relay. The temperature management relay driving module is connected with the cooling fan relay, and the cooling fan relay is connected with the cooling fan through wires.

When the wake-up switch is closed, the power module starts to work, supplying power to each module device in the battery management system, and supplying power to the current sensor at the same time.

The positive voltage of each cell in the single battery series module is input to the MCU module after being divided and limited by the cell voltage sampling circuit, and the MCU module analyzes and obtains the low voltage value of each cell in the single cell series module.

The module temperature sampling module collects the signals of each temperature sensor, and inputs it to the MCU module after conditioning. The MCU module analyzes and obtains the physical temperature value of the temperature sensor; when the temperature of the lithium battery pack is lower than the set threshold, the MCU module drives the module through the temperature management relay The electric heating relay is controlled to close, and the electric heater converts electric energy into heat energy for heating the lithium battery pack. When the temperature of the lithium battery pack is higher than the set threshold, the MCU module controls the cooling fan relay to close through the temperature management relay drive module, and the cooling fan dissipates heat for the lithium battery pack.

The current sensor signal is conditioned by the current sensor signal sampling module and then input to the MCU module. After the MCU module and analysis, the physical current value of the current sensor is obtained; the MCU module estimates the number of core charges of the lithium battery pack according to the current current value. When a certain threshold, the open-circuit voltage method is used to estimate the nuclear charge, and when the current value is higher than a certain threshold, the ampere-hour method is used to calculate the nuclear charge.

The MCU module calculates the charging and discharging capacity of the battery in real time according to the temperature, cell voltage, and nuclear charge of the lithium battery pack, including charging and discharging current and charging and discharging power.

The load request switch signal is adjusted by the switch value acquisition circuit and then input to the MCU module. The MCU module decides whether to close the load circuit relay through the load relay drive module according to the preset power of the corresponding load and the current output power limit of the battery.

The MCU module compares the current current value with the current allowable charging and discharging current value of the lithium battery pack in real time. When charging overcurrent, it actively disconnects the charging relay through the charging relay drive module; when discharging overcurrent, it actively drives the module through the load relay to disconnect the priority. Load loop with lower level until the real-time discharge current value is less than the allowable discharge current value.

The above-mentioned embodiments are only illustrations or explanations of the technical solutions of the present invention, and should not be construed as limitations on the technical solutions of the present invention. Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the present invention. New type of spirit and scope. If these modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention also includes these modifications and variations.

Claims (7)

1. A low-voltage lithium battery pack battery management system, characterized in that it comprises a power supply module, a current sensor signal sampling module, a switch quantity acquisition module, a load relay drive module, a charging relay drive module, a temperature management relay drive module, a communication module, Single voltage sampling module, module temperature acquisition module, passive equalization module, voltage monitoring module, MCU module, crystal oscillator module. 2 . The low-voltage lithium battery pack battery management system according to claim 1 , wherein the current sensor power supply circuit of the power module is isolated from the internal chip power supply circuit. 3 . 3 . The battery management system for a low-voltage lithium battery pack according to claim 1 , wherein the power module and the matched negative electrode of the lithium battery pack share a ground. 4 . 4 . The low-voltage lithium battery pack battery management system according to claim 1 , wherein in the load relay drive circuit, the low-level terminal of the external load circuit relay and the negative power supply terminal of the battery management system share the ground. 5 . 5. The low-voltage lithium battery pack battery management system according to claim 1, wherein the communication module uses CAN communication. 6 . The low-voltage lithium battery pack battery management system according to claim 1 , wherein the passive equalization circuit is constructed by a controllable precision voltage regulator, a PNP triode, an NPN triode, and resistance components. 7 . 7 . The battery management system for a low-voltage lithium battery pack according to claim 6 , wherein the resistance includes a signal resistance and a power resistance. 8 .

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