Hardware design technology of power lithium-ion battery management system

The hardware design technology of the electric battery management system. An electric vehicle is a car driven by an electric motor either completely or partially. There are now three types of pure electric vehicles, hybrid vehicles and fuel-powered battery vehicles. The commonly used power for electric vehicles now comes from lead-acid batteries, lithium batteries, and nickel-metal hydride batteries. Lithium batteries have high voltage, high specific energy and high energy density. But it is precisely because of the high energy density of lithium batteries that when misuse or abuse occurs, safety accidents can occur. The battery handling system can handle this problem. When the battery is in a charge overvoltage or discharge undervoltage state, the processing system can actively block the charge and discharge circuit, and its power balance function can ensure that the voltage difference of a single battery is maintained within a very small plan. In addition, it also has over-temperature, over-current and remaining power estimation functions. What this text is planning is a battery processing system based on single-chip microcomputer [1]. 1. The hardware composition of the battery processing system The hardware circuit of the system can be divided into a single chip microcomputer module, a detection module and an equalization module. 1.1 SCM module SCM is the core of system control. The single-chip microcomputer used in this article is M68HC08 series GZ16 single-chip microcomputer. All series of single-chip microcomputers use enhanced M68HC08 central processing unit (CP08). The microcontroller has the following features: (1) Internal bus frequency is 8MHz; (2) 16kb built-in flash memory; (3) Two 16-bit timer interface modules; (4) Clock generator that supports 1MHz~8MHz crystal oscillator; ( 5) Enhanced serial communication interface (ESCI) module. 1.2 Detection module The detection module will introduce voltage detection, current detection and temperature detection modules. 1.2.1 Voltage detection module In this system, the total voltage and single voltage of the battery are tested by the single-chip microcomputer. There are two methods to detect the total voltage of the battery pack: (1) Select a specific voltage detection module, such as a Hall voltage sensor; (2) Use precision resistors in the resistor divider circuit. The cost of using a dedicated voltage detection module is high, and a dedicated power supply is required, and the process is more complicated. Therefore, the voltage divider circuit is selected for detection. The voltage change method of 10 series lithium manganate battery pack is 28v~42v. Use 3.9 meters? Fat and 300k? to divide the redundant resistors into voltages, and the modification method of the collected voltage signals is 2v~3v, and the corresponding AD conversion results are 409 and *. For the detection of single batteries, flying capacitors are the preferred technique. The schematic diagram of the capacitor flight skills is shown in Figure 1 [2], the battery protection circuit diagram after 4 days, the four-channel switch array can unscrupulously collect the battery voltage of the 14-cell single-chip microcomputer, the single-chip microcomputer outputs the drive signal, and controls the MOS tube to turn on and Turn off, then battery charge and discharge protection. As shown in Figure 1, it is a circuit diagram of the 4-stage protection circuit after the battery pack. Through the four-channel switch array, the voltage of any segment of the battery is collected into the MCU, and the MCU outputs the drive signal to control the turn-on and shutdown of the MOS tube, and protect the charging and discharging of the battery pack. The above six batteries can be completed by switching the array through two three-way switches. MAX309 is a four-to-one, dual-channel multiplexer, the selected channel after selection. Switches S5, S6, S7 are used to connect the positive pole of the battery to the positive pole of the flying capacitor. Switches S2, S3 and S4 are used to connect the negative pole of the battery to the negative pole of the flying capacitor. The structure of the three-way switch switch array is similar to that of the four-way switch switch array, except that the number of channels is one less. During operation, the single-chip microcomputer announces the channel position signal so that the battery of the positive and negative electrodes is connected to the capacitor, the capacitor is charged, and then the channel switch is disconnected, connected to the expansion of the switch, and the voltage of the single-chip capacitor is quickly detected, thereby completing a battery voltage detection . If the detection voltage is found to be less than 2.8v, it can be inferred that the battery may have a short circuit, and the battery is broken in the detection line of the discharge or protection system, and the microcontroller will immediately announce that the signal is blocking the main loop MOS tube. If the above process is repeated, the microcontroller will complete the detection of the battery handled by the module. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. 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