Analysis on the Design of Lithium Battery Charging System

An analysis of the design and data display of the lithium battery charging system analyzes the coexistence of nickel-cadmium batteries and lithium batteries with the market. This article plans to choose two kinds of batteries that the charger can carry charge, and choose the pulse charging method to use constant current for nickel-cadmium batteries and lithium batteries. The charging method is based on the different mechanisms and plans of the battery. A machine amphibious is truly completed. This is the innovation of the charger, and it is also a difficult point in the planning. The charger's widescreen LCD display can simultaneously display the charging status of 4 sets of chargers, or separately display the battery parameters of a set of chargers, so as to realize real-time monitoring of the battery charging process. System overall planning The goals of the system planning are: 1. Four groups of 8.4v lithium batteries or 9.2v nickel-cadmium batteries can be charged and discharged at the same time. 2. It can communicate with the chip in the battery to determine the chemical nature of the battery. 3. For batteries with different chemical properties, select the corresponding charging method. 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 a liquid crystal display, which can display various data of the battery. The functional block diagram of the charger is shown as in Fig. 1. Figure 1 System overall planning structure diagram System hardware planning plan and completion of the main control unit The entire control unit is composed of the single-chip microcomputer PIC16F873 and the 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 can control 6 keys and 12 leds. ZLG7289A communicates with the single-chip microcomputer through the SPI bus. The main control unit queries the charging unit every second to obtain information about whether the current charging unit has a battery, the nature of the battery, and the battery voltage. Then display the LCD module to the user. The planning and completion of the charging unit TP8002 lithium battery charging control chip TP8002 is an efficient independent switching lithium battery charging controller. The controller has two versions, 4.2v and 8.4v. The tp882-8.4 with 500kHz switching frequency is a high-efficiency current form of PWM controller. It is driven by an external p-channel MOSFET and can supply up to 90% power 4A charging current. The output voltage is set to 8.4v, the final floating voltage is 1%, and the charging accuracy is 5%. In addition, the device can operate various wall adapters in the range of 9V to 22V. Compared with the hysteresis charger, tp882-8.4's fast operating frequency and current structure make it possible for small inductors and capacitors. The overall planning of the lithium-ion/nickel-cadmium battery charging unit is based on the previous analysis of the TP8002. The chip is a charging controller for the lithium battery. The nickel-cadmium battery should solve the following problems. First of all, TP8002 monitors the battery voltage to ensure that the battery voltage does not exceed 8.4v. As for nickel-cadmium batteries, the charge cut-off voltage can reach 9.2v. Secondly, when the nickel-cadmium battery is charged, the battery should be charged at 30% and 10% of the normal current. So, the second requirement is how to control the current in the constant current charge. In addition, nickel-cadmium batteries should be pulsed. That is to say, with 1s as the cycle, 95% of the time is used for charging, 1% is used for discharging, and the rest of the time is not charging and discharging. Finally, how to judge whether a battery is a lithium battery or a nickel-cadmium battery? If the lithium battery is mistaken for a nickel-cadmium battery, the charging voltage will exceed 8.4v, which is very dangerous for the lithium battery. If nickel-cadmium batteries are misdiagnosed as lithium batteries, the batteries may be underestimated. Therefore, it is necessary to ensure a very low miscalculation rate. 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 article: How to improve the fast charge and discharge performance of lithium batteries?