CN102303542A - Detection system for vehicular storage battery - Google Patents

Abstract

The invention discloses a battery detection system for vehicles, which is composed of a CPU, a signal acquisition and conversion module connected to it, a display interface, a keyboard interface, an alarm circuit, and a power supply circuit. The present invention can carry out real-time online detection on the important information of the bottom layer of the battery pack, mainly detects important information such as the terminal voltage of each single battery forming the battery pack, the discharge current, the charging current of the battery pack, and the temperature of the battery, and simultaneously collects environmental temperature for reference. The system can directly display these information. On this basis, a variety of analysis functions for the collected information are realized, mainly including battery imbalance judgment, abnormal temperature indication, overcharge, overdischarge, and deep discharge indication. And it can realize the indication of the remaining capacity and the judgment of the battery health status, and provide effective help for battery users to better use and maintain the battery.

Description

Vehicle battery detection system

technical field

The invention belongs to the technical field of accumulator management, in particular to a vehicle accumulator detection system .

Background technique

At present, power storage batteries are widely used in railway locomotives, electric vehicles, especially the very popular electric bicycles. Their common feature is that multiple identical batteries are connected in series to supply power to the load in groups. However, most of the current vehicle control systems are too simple to reflect the battery status information. Taking electric bicycles that are widely used at present as an example, the display only reflects the voltage of the entire battery pack to measure the remaining power of the current battery. On the one hand, the total voltage of the battery pack does not have a good linear relationship with the remaining capacity of the battery, and the reliability of the indication of the remaining capacity is not high. In actual use, it is found that when the power of the battery pack is actually not much, the power meter is still full. During the process, it was discovered that the indicator of the battery meter dropped rapidly, but it was already driving on the road at this time, because it was impossible to have a correct estimate of the remaining battery power in advance, which caused unnecessary trouble. On the other hand, the information indication is too single, which is not good for the effective maintenance of the storage battery. Because it is not clear how their own actions will affect the battery during actual driving, users often use electric vehicles blindly, so most batteries are damaged or scrapped without knowing it.

Contents of the invention

In order to solve the above problems, the present invention provides a vehicle battery detection system, which can perform real-time online detection, display and alarm for the important bottom information of the battery pack.

Technical scheme of the present invention is as follows:

A vehicle battery detection system, composed of a CPU and a signal acquisition and conversion module connected to it, a display interface, a keyboard interface, an alarm circuit, and a power supply circuit;

The signal acquisition and conversion module is composed of a voltage acquisition circuit, a current acquisition circuit, a temperature acquisition circuit and an A/D conversion circuit; the voltage acquisition circuit is composed of a voltage access circuit and a photoelectric coupling circuit. For collection, the voltage is converted into a 0~5V signal by an optocoupler circuit and input to the A/D conversion circuit; the current collection circuit uses a TBC06DS Hall-type current sensor, and the current is converted into a 0~5V signal by the Hall sensor and input to the A/D D conversion circuit; A/D conversion circuit adopts TLC2543CN analog-to-digital conversion chip to convert voltage and current signals into digital quantities and send them to the CPU for processing; the temperature acquisition circuit adopts DS18B20 digital temperature chip to be directly read by the CPU;

CPU, STC11F60XE single-chip microcomputer with 8051 core, is the core part of the system, responsible for various data processing and logic judgment tasks;

The display interface adopts TFT LCD, 240×320 true color dot-matrix liquid crystal, which is directly connected with the CPU data line;

The keyboard interface adopts a 5-button structure, which constitutes up, down, left, and right navigation keys and confirmation keys, which are used to operate the system interface. The keys are connected to the CPU in an interrupt mode, and the low-level active signals of the 5 keys generate an interrupt signal through the AND gate. ;

The alarm circuit includes a buzzer and a triode. The CPU drives the triode, and the base of the triode controls on-off at a low level to drive the buzzer to sound.

The power supply circuit adopts LM2576 chip and IL1117 chip. The power supply voltage is taken from the 12V voltage of the last battery in the series battery pack. 5V voltage is generated by LM2576 to supply power to the system, and then 3.3V low voltage is generated by IL1117 to supply power to the LCD screen.

The beneficial technical effect of the present invention is:

The present invention can carry out real-time online detection on the important information of the bottom layer of the battery pack, mainly detects important information such as the terminal voltage of each single battery forming the battery pack, the discharge current, the charging current of the battery pack, and the temperature of the battery, and simultaneously collects environmental temperature for reference. The system can directly display these information. On this basis, a variety of analysis functions for the collected information are realized, mainly including battery imbalance judgment, abnormal temperature indication, overcharge, overdischarge, and deep discharge indication. And it can realize the indication of the remaining capacity and the judgment of the battery health status, and provide effective help for battery users to better use and maintain the battery.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the drawings used in the embodiments are briefly introduced below. These drawings constitute a part of this application and do not limit the present invention.

Fig. 1 is an overall block diagram of the system of the present invention.

Figure 2 is a schematic diagram of the voltage access circuit.

Figure 3 is a schematic diagram of the optocoupler isolation circuit.

Figure 4 is a schematic diagram of the current acquisition circuit.

Figure 5 is a graph showing the relationship between the output voltage and the input current.

Figure 6 is a schematic diagram of the temperature acquisition circuit.

Fig. 7 is a schematic diagram of a multi-point temperature measurement system.

Fig. 8 is a schematic diagram of a minimum system of a single chip microcomputer.

FIG. 9 is a functional block diagram of an AD conversion circuit.

Fig. 10 is a schematic diagram of the interface between the AD conversion circuit and the single-chip microcomputer.

Fig. 11 is a schematic diagram of 5 keys of the keyboard.

Figure 12 is a schematic diagram of the interface between buttons and interrupts and the microcontroller.

Figure 13 is a schematic diagram of the interface between the display and the single-chip microcomputer.

Figure 14 is a schematic diagram of the alarm circuit.

Fig. 15 is a schematic diagram of a power supply circuit.

Fig. 16 is a functional schematic diagram of the system of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be comprehensively described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

System overall description

In order to realize the system function, the present invention is composed of CPU, a signal acquisition and conversion module connected to the CPU, a display interface, a keyboard interface, an alarm circuit, and a power supply circuit (not shown in Fig. 1 ) for supplying power to the system and the display. The overall block diagram of the hardware system is shown in Figure 1.

The signal acquisition and conversion module is composed of a voltage acquisition circuit, a current acquisition circuit, a temperature acquisition circuit and an A/D conversion circuit; the voltage acquisition circuit is composed of a voltage access circuit and a photoelectric coupling circuit. For collection, the voltage is converted into a 0~5V signal by the optocoupler circuit and input to the A/D conversion circuit; the current collection circuit uses a TBC06DS Hall-type current sensor, and the current is converted into a 0~5V signal by the Hall sensor and input to the A/D conversion circuit; The A/D conversion circuit adopts TLC2543CN analog-to-digital conversion chip, which converts the voltage and current signals into digital quantities and sends them to the CPU for processing; the temperature acquisition circuit adopts DS18B20 digital temperature chip to be directly read by the CPU. CPU, STC11F60XE single-chip microcomputer with high-speed 8051 core, is the core part of the system, responsible for various data processing and logic judgment tasks. The display interface adopts TFT LCD, 240×320 true color dot-matrix liquid crystal, and is directly connected with the CPU data line. The keyboard interface adopts a 5-button structure, which constitutes up, down, left, and right navigation keys and confirmation keys, which are used to operate the system interface. The keys are connected to the CPU in an interrupt mode, and the low-level active signals of the 5 keys generate an interrupt signal through the AND gate. The alarm circuit, its function is composed of two parts: the display flashing alarm and the buzzer sounding alarm. The display flashing alarm part is completed by the display screen; the buzzer sounding alarm part includes the buzzer and the triode, the CPU drives the triode, the triode The base low level controls the on-off and drives the buzzer to sound. The power module adopts LM2576 s-5.0 chip and IL1117-3.3 chip. The power supply voltage is taken from the 12V voltage of the last battery in the series battery pack. 5V voltage is generated by LM2576 to supply power to the 5V system, and then 3.3V low voltage is generated by IL1117 for power supply. The LCD display is powered.

Each circuit module in the present invention will be described one by one below:

Voltage Acquisition Circuit

The battery pack is composed of several batteries, and the inside of a single battery is composed of multiple single batteries. The single battery is the basic unit of the battery pack. Generally, the voltage of a single battery is 2V, and 6 single batteries are connected in series to form a 12V battery. Due to the inconsistency of the production process and the production process, the capacity of the single cells inside the battery varies, which directly leads to the deviation of the capacity between the batteries.

Since the batteries are used in series, if there is an imbalance in the capacity of each battery, it is inevitable that some batteries in the entire battery pack will be overcharged, overdischarged or undercharged. This in turn will increase the further deterioration of battery performance, leading to a further increase in the imbalance between batteries, entering a vicious circle.

Therefore, it is of great significance to find out the imbalance of the battery pack in time and effectively, and find out the backward battery (that is, the battery with a relatively low voltage) to maintain the performance of the battery.

The general method for judging battery imbalance is to track, detect and compare the voltage of the single battery. However, the general single-cell battery packs the internal 6 cells and provides terminals for the outside, so it is not easy to measure the terminal voltage of the cells. Therefore, the general practice is to detect the terminal voltage of a single battery in a battery pack. The basis for this is that if a single cell in a battery fails, it is difficult to be covered by the averaging effect, that is, the fault condition of the internal single cell can be reflected by a single battery, and the battery The smallest unit of group fault handling is a single battery. The usual practice is to replace the lagging single battery in the battery pack. Therefore, when performing unbalance detection, we adopt the method of comparing the consistency of the single battery terminal voltage.

The system collects the voltage of each battery in the battery pack, and the collection is divided into two parts: the voltage access part and the photoelectric coupling part. The voltage access part connects each single-cell terminal of the battery to the system, and protects it through a fuse at the front end of the system, and then uses a diode to indicate that the voltage access is valid for the connected voltage.

The voltage access circuit is shown in Figure 2. The fuse adopts a 4A fuse. If a short circuit occurs in the system, the fuse can quickly cut off the battery, thus playing a protective role. After the battery is connected, the light-emitting diode lights up, indicating that the battery connection is valid. If the fuse is blown or the battery terminal voltage is too low, the diode will not light up, indicating that the battery connection is invalid. The fuse should be checked or the battery should be replaced.

After the above treatment, the 12V battery voltage is isolated by the photoelectric coupling circuit shown in Figure 3. Because the analog-to-digital converter requires the common ground of the measurement signal, and the battery is connected in series, it will inevitably generate a high common-mode voltage, so it is necessary to use photoelectric isolation to transmit the voltage signal. In addition, the optocoupler isolation can also prevent the strong electrical signal of the main circuit from entering the weak electrical system and improve system security.

As shown in Figure 3, the optocoupler device uses HCNR201, which is a high-precision linear optocoupler with a nonlinearity of 0.05%, ensuring the accuracy of voltage acquisition.

The working principle of the optocoupler is to apply the voltage signal of the detected circuit to the LED, and the LED emits infrared light to irradiate the photodiode to generate current. The change of the applied voltage signal causes the change of the light intensity of the LED, which leads to the change of the current flowing through the photodiode. , so as to realize the electrical-optical-electrical conversion of the signal. Due to the use of optical signal coupling, the direct electrical connection between the circuits is completely cut off, thereby realizing the isolation of the signal.

Generally, the pre-stage voltage signal applied by the optocoupler or the current of the LED and the current generated by the photodiode are nonlinear. The linear optocoupler adds a photodiode PD1 with the same parameters as the original on the basis of the ordinary optocoupler to adjust the signal feedback of the previous stage, so as to realize the linear transmission of the optocoupler.

Its main principle is the principle of negative feedback. As shown in Figure 3, the input part of the front stage, the op amp A1 forms a negative feedback. The negative feedback process is: when the output of A1 increases (decreases), the LED current increases (decreases), the LED light becomes stronger (weaker), the PD1 current increases (decreases), and the R1 voltage drop increases (decreases). Small), the input of the op amp decreases (increases), and the output of the op amp decreases (increases). Under the regulation of negative feedback, the input of the previous stage reaches balance. According to the characteristics of virtual short and virtual break after negative feedback of the op amp, the positive input terminal voltage is the ground potential G1, that is, the negative terminal potential of a single-cell battery, and the PD1 current is:

近似等于

，有关系： And the parameters of PD1 and PD2 are the same, and the illumination is almost the same, then

approximately equal to

,There are relationships:

in The typical value of is 1, and the absolute error is within 0.05. The two can be considered equal.

At the output terminal, A2 converts the current signal into a voltage signal. Also according to the characteristics of virtual short and virtual break, the potential of the reverse input terminal of A2 is ground potential G2, which is the ground of the 5V system. This ground is completely isolated from the ground potential of the previous stage input. Then the output voltage is:

To sum up, the relationship between the pre-stage voltage signal and the output voltage is:

，则

。 this system

,but

.

Linearly convert the 0-15V monomer voltage to 0-5V voltage.

The acquisition of one voltage is completed above, and the other acquisition channels are exactly the same. Since the front-stage operation adopts single op amp LM321, which is directly powered by a single battery, it solves the problem of common mode high voltage. The common ground problem of the differential mode voltage of the group monomers.

Current Acquisition Circuit

As shown in Figure 4, the TBC06DS Hall-type current sensor is used for current acquisition. The sensor has a wide measurement range and can measure positive and negative currents. The unidirectional current measurement range is 0-19.2A, which fully meets the measurement needs of the working current of electric vehicles. The secondary power supply only needs 5V power supply, and no negative power supply is needed, which simplifies the system power supply design. High output linearity, accurate measurement, output voltage range 0-5V, directly A/D conversion without adjustment.

The relationship between the output voltage of the sensor and the input current is shown in Figure 5.

Temperature Acquisition Circuit

As shown in Figure 6, the system uses a single bus device DS18B20 as a temperature sensor. DS18B20 is a single bus digital temperature sensor. Only one data cable is needed to communicate with the CPU, and multiple chips can be mounted on one data cable at the same time. Each chip has a unique 64-bit ROM number, and the chip can be identified by comparing the number. The chip has the advantages of miniaturization, low power consumption, high performance, strong anti-interference ability, and easy allocation of processors. It can directly communicate with the single-chip microcomputer through a 1-bit data line serial communication, and its unique internal chip number is especially suitable for forming a multi-point measurement system, and when the number of chips is less than 8, it can be directly powered by the data line, only during the idle period of bus transmission Just pull the data line high.

This system adopts TO-92 package chip, which is small in size and easy to install, and the chip contacts can fully contact with the battery electrodes, which is convenient for accurately measuring the temperature of the battery.

Under normal temperature measurement conditions, the temperature detection range of the chip can reach -55°C to +125°C, and the inherent resolution can reach 0.5°C. This system measures the temperature of 4 batteries, plus the ambient temperature, a total of 5 temperature channels, so 5 DS18B20 are used, and they are directly connected to a bus. The chip is powered by a data line, which reduces the number of transmission lines. The multi-point temperature measurement system composed of chip and single-chip computer is shown in Figure 7.

CPU (Single-chip microcomputer minimum system)

CPU is the core part of the system, responsible for various data processing and logic judgment tasks. The invention adopts a single-chip microcomputer as a central controller, and the single-chip microcomputer is small in size, low in price, and rich peripheral resources are integrated in the chip, and the minimum system can be conveniently formed.

STC11F60XE microcontroller with 8051 core. The single-chip microcomputer is a high-speed chip, 1 machine cycle/clock cycle, and the instruction execution speed is 8-12 times faster than the ordinary 8051 single-chip microcomputer, and the maximum can reach 24 times, which can conveniently drive high-speed peripherals such as LCD.

On-chip ROM or program memory has a capacity of up to 60KB and 1280 bytes of RAM, so there is no need for memory expansion.

The chip only needs to be connected with an external power-on reset circuit, that is, a crystal oscillator, to form the smallest system of a single-chip microcomputer. Since the P0 port is an open-drain output, it must be connected with an external 10K pull-up resistor when used as a port. The minimum system of the one-chip computer is shown in Fig. 8 .

AD conversion circuit

The voltage and current signals are converted into voltages in the range of 0-5V by the acquisition circuit, and these signals are converted into digital quantities by the analog-to-digital converter and then sent to the single-chip microcomputer for processing.

Its internal structure block diagram is shown in Figure 9, and the analog-to-digital conversion chip adopts TLC2543CN. This model is a 12-bit high-precision digital-to-analog converter, which communicates with the processor through the SPI bus, and only needs two data lines and one clock signal line to complete data transmission and reception. Internal multiple switches can collect up to 11 analog signals. The conversion period is short, and it only takes 10us to complete a conversion, which can complete the high-speed sampling of the signal.

The reference voltage is 5V, which can be directly connected to the 5V system power supply without designing a special voltage reference circuit.

the

Since the 8051 MCU does not have an SPI bus hardware interface, we use the MCU port to simulate the SPI bus timing to complete the communication between the MCU and the AD. The conversion end signal is connected to the MCU No. 0 interrupt, and the MCU controls the AD conversion through the interrupt mode. The interface between AD and microcontroller is shown in Figure 10.

keyboard interface

The system is equipped with a keyboard for operating the system interface. In order to simplify the input operation, the keyboard adopts a 5-key structure, which constitutes up, down, left, and right navigation keys and a confirmation key, as shown in Figure 11.

The interface between buttons and interrupts and the microcontroller is shown in Figure 12. The buttons are connected to the single-chip microcomputer by means of an independent keyboard, that is, each button is assigned a P port for reading the button status. The keyboard and the microcontroller are connected in an interrupt mode, and the low-level active signals of the five keys are generated by an AND gate to generate an interrupt signal. The interrupt generation condition is that as long as there is a low-level signal on the 5 keys, a low-level interrupt request signal is generated, and the AND gate can realize this function. In order to realize the logical judgment of the 5-way signal, the 74HC21D double four-input AND gate is used to realize this function. The specific method is that the 4-way signal is connected to a four-input AND gate, and the output signal is then ANDed with the fifth-way signal to realize the 5-way Phase and function of signals.

Display interface

Interface display We choose LCD dot matrix liquid crystal as the display module. LCD selects 2.4-inch TFT type 240×320 resolution color liquid crystal. The liquid crystal adopts ILI9325 as the controller.

The color of one pixel of the LCD is 16-bit 565 format RGB true color, the bit width of the data bus is set to 8 bits, and it is directly connected to the 8-bit data line of the single-chip microcomputer. The interface between LCD and microcontroller is shown in Figure 13.

Alarm circuit

For the alarm of abnormal condition, the present invention utilizes the buzzer to send out the alarm. The buzzer is controlled on and off by a single-chip microcomputer. Due to the large driving current, it is driven by a triode. The alarm driving circuit is shown in Figure 14, in which the 8550 is a PNP triode, the base is low-level to control conduction, and the buzzer sounds.

power circuit

As shown in Figure 15, the main chip of the system needs 5V power supply, and the LCD backlight needs 3.3V. The power supply voltage is taken from the 12V voltage of the last battery in the series battery pack, which is regulated by LM2576 to form 5V voltage, and then regulated by IL1117 to 3.3V.

System function description of the present invention

The main process of the present invention is that the voltage, current, and temperature signals of the storage battery are collected and sent to the system, and the system performs related processing on the data to realize related functions and obtain the data to be displayed, and send them to the interface for display.

As shown in Figure 16, the system functions are divided into five modules, which are the display of operating status, viewing of battery-related information, alarm triggering, discharge test environment, and historical file records.

(1) Running status display

This function indicates the important data of the electric vehicle during the driving process, and it works when the battery is actually applied with the actual load. It mainly displays the current remaining power of the battery and the current discharge current, that is, the load intensity. And predict how long the battery can still work according to the current discharge current. Considering that the user does not need to care about the value of the specific current and the ampere-hour of the battery capacity during use, these two pieces of information are qualitatively displayed graphically, and specific values are given for the remaining time of discharge. In addition, for easy reference, the battery discharge time of this time is also displayed.

During the running process, it also gives the balance situation of each battery in the battery pack in real time.

(2) Check battery related information

This part is used to display some original information that does not require the user's direct attention during operation and some information that does not need to be displayed in real time. It is mainly used to view specific values such as battery voltage, current, temperature, and SOC, SOH information.

(3) Alarm triggered

This part of the function is used to check various abnormal conditions in real time and generate alarm signals. When the voltage difference between single cells exceeds the set value, a battery imbalance alarm will be generated. By comparing the battery terminal voltage with the set upper and lower limit values, an overcharge and over discharge alarm will be generated. If the current exceeds a predetermined value, a deep discharge alarm will be generated. Abnormal temperature, low battery, and battery failure will all generate corresponding alarms.

(4) Discharge test environment

This module specially sets up a software environment for checking the discharge test of the battery. In this environment, only need to fully charge the battery and then connect an external constant current load to perform the check discharge test. This function can complete the drawing of the corresponding discharge curve, obtain the actual capacity of the battery pack and the SOH information of the battery pack.

(5) Historical archives and records

This function mainly stores some important information during the use of the battery. Such as the total usage hours, abnormal records and other relevant information.

These modules are connected by navigation blocks, which can be easily switched between each other.

In summary, the present invention can perform real-time online detection of the important information of the bottom layer of the battery pack, that is, it mainly detects important information such as the terminal voltage of each single battery that constitutes the battery pack, the discharge current, the charging current of the battery pack, and the temperature of the battery. , and at the same time collected the ambient temperature for reference. The system can directly display these information. On this basis, a variety of analysis functions for the collected information are realized, mainly including battery imbalance judgment, abnormal temperature indication, overcharge, overdischarge, and deep discharge indication. For the indication of the remaining capacity, the combination of the ampere-hour integral method and the open circuit voltage method is adopted, the actual capacity difference under different currents is considered, and the charging and discharging efficiency and temperature correction are introduced to predict the current capacity more accurately. The judging function of battery state of health (SOH) is also designed. These functions will provide effective help to battery users to better use and maintain batteries. As additional functions, related functions such as drawing battery charging and discharging curves, checking and discharging tests of batteries, archiving and viewing historical data, etc. are supplemented.

What is described above is only a preferred embodiment of the present invention, and the present invention is not limited to the above examples. It can be understood that other improvements and changes directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention. the

Claims (1)

1. A battery detection system for vehicles, characterized in that: it is composed of CPU and a signal acquisition and conversion module connected thereto, a display interface, a keyboard interface, an alarm circuit, and a power supply circuit; The signal acquisition and conversion module is composed of a voltage acquisition circuit, a current acquisition circuit, a temperature acquisition circuit and an A/D conversion circuit; the voltage acquisition circuit is composed of a voltage access circuit and a photoelectric coupling circuit. For collection, the voltage is converted into a 0~5V signal by an optocoupler circuit and input to the A/D conversion circuit; the current collection circuit uses a TBC06DS Hall-type current sensor, and the current is converted into a 0~5V signal by the Hall sensor and input to the A/D D conversion circuit; A/D conversion circuit adopts TLC2543CN analog-to-digital conversion chip to convert voltage and current signals into digital quantities and send them to the CPU for processing; the temperature acquisition circuit adopts DS18B20 digital temperature chip to be directly read by the CPU; CPU, STC11F60XE single-chip microcomputer with 8051 core, is the core part of the system, responsible for various data processing and logic judgment tasks; The display interface adopts TFT LCD, 240×320 true color dot-matrix liquid crystal, which is directly connected with the CPU data line; The keyboard interface adopts a 5-button structure, which constitutes up, down, left, and right navigation keys and confirmation keys, which are used to operate the system interface. The keys are connected to the CPU in an interrupt mode, and the low-level active signals of the 5 keys generate an interrupt signal through the AND gate. ; The alarm circuit includes a buzzer and a triode, the CPU drives the triode, and the base of the triode controls on-off at a low level to drive the buzzer to sound; The power supply circuit adopts LM2576 chip and IL1117 chip. The power supply voltage is taken from the 12V voltage of the last battery in the series battery pack. 5V voltage is generated by LM2576 to supply power to the system, and then 3.3V low voltage is generated by IL1117 to supply power to the LCD screen.

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