Introduce lithium-ion battery and nickel-cadmium battery charging system

Explain the design goals of the lithium-ion battery and nickel-cadmium battery charging system: 1. It can charge and discharge four sets of 8.4v lithium-ion batteries or 9.2v nickel-cadmium batteries at the same time. 2. It can communicate with the chip in the battery to determine the chemical nature of the battery. 3. Batteries with different chemical properties adopt corresponding charging methods. 4. It can communicate with the chip in the battery to obtain the battery's voltage, charging current, capacity and other parameters. 5. The charger is equipped with an LCD display that can display various data of the battery. Signal conditioning circuit design In order to enable the LTC4002 to charge the battery with a constant current greater than 8.4v and adjust the charging current, a signal conditioning circuit is added between the BAT of the LTC4002 and the detection terminal and the sampling resistor. The important function of this circuit is to calculate the signal at both ends of the sampling resistor and send the corresponding signal to the battery LTC4002 with different chemical properties. System software overall design The single-chip microcomputer in the charging unit is mainly responsible for the control of the charging process and the communication with the main control board. The procedure flow is shown as in Fig. 4. The charging device first determines whether there is a battery. If there is a battery, it determines the state of charge and discharge. The default state is the charging state, which can be changed by the main control unit. If the charging device is in a charging state, continue to determine the chemical nature of the battery, and adopt different charging methods for different batteries. If the battery is in a discharged state, discharge it until the battery voltage is lower than the threshold voltage, and then charge it. Pulse charging and discharging circuit design Because of the LTC4002 constant current charging control chip, a single-chip microcomputer must be used to control its charging pin COMP. When the LTC4002 wants to output charging pulses, the port that controls the COMP pin will become a high impedance state, and the COMP pin will automatically rise over 360mv, and then the charging current will be output. When discharging, must pull down the compensation pin, make LTC4002 close the charging current. Then, open the discharge circuit. The microcontroller is PIC16F873, which is an 8-bit microcontroller based on Flash. Internal timer, watchdog circuit, 10-bit ADC and other modules. The design and realization of the whole control unit The whole control unit is composed of single-chip microcomputer PIC16F873 and keyboard control chip ZLG7289A. The important task is to communicate with each charging unit, process user input and LCD display information. The keyboard control chip is responsible for 6 keys and 12 leds. The two-way communication between ZLG7289A and the one-chip computer is carried out through SPI bus. The main control unit queries the charging unit every second to obtain information about whether the current charging unit has a battery, battery properties, and battery voltage. Then it is displayed to the user through the LCD 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. Previous post: The issue of the recycling and reuse of power lithium batteries is put on the agenda