Analyze the design of low-power lithium battery management system

The design summary of the low-power lithium battery management system analyzes the planning method of a low-temperature intelligent lithium battery processing system, which is composed of 32 20Ah4 series and 8 parallel cells. This method has functions such as base protection, power measurement, charging balance, and defect recording. Experiments show that the system has perfect functions and meets the planning requirements. Current battery processing systems are mostly planned for large-capacity battery packs and applications with short battery life. This production system serves high power consumption equipment, the battery cycle is short, the power consumption of the production system itself is not low, and it is not suitable for low-power surface applications. On the remote monitoring surface of gas, the current of the uniform system is only a few milliamps, and it needs to work continuously for more than 6 months at low temperature. In order to meet the application of this project, this paper analyzes a planning method for a low-temperature intelligent lithium battery processing system. It has the functions of base protection, power measurement, charging balance, defect recording and so on. Experiments show that the system has perfect functions and meets the planning requirements. 1. The overall structure of the system The low-temperature lithium battery processing system is mainly composed of a base protection circuit, a fuel gauge, a balance circuit and a secondary protection, as shown in Figure 1. According to the consideration of low power consumption, a lot of low power consumption devices were selected in the plan, such as MSP430FG439 low power consumption single-chip microcomputer as the processor. The reference voltage is REF3325, the power consumption is extremely low, only 3.9db; the operational amplifier uses LT1495, the working current is only 1.5a; the digital potentiometer uses AD5165, the quiescent current is as low as 50nA. The power processing circuit is added to the intermittent operation circuit, the operation current is large, and the energy consumption is reduced. The low-temperature battery pack has a rated voltage of 14.8v and is composed of 4 batteries in series, each with 8 single cells. The normal working voltage is 2.5-4.2v. Each collection period collects the voltage of each group of batteries, and the processor issues instructions to the protection circuit according to the voltage, and performs corresponding protection actions. The equalization circuit is realized by a single chip microcomputer and a triode instead of a dedicated equalization chip. The system records abnormal information such as the maximum voltage, current, temperature, battery usage time, and remaining power in the storage device. The processor supplies the TTL communication interface, and the on-site computer reads the log in the storage device through the TTLRS232 conversion module. In order to prevent the MCU from crashing and other abnormal conditions during the charging process, a protection fault occurs. A new secondary protection circuit is added. If the voltage exceeds the preset value, the secondary protection circuit will be activated and the three-terminal fuse will be blown to prevent the occurrence of faults. 2 Hardware Planning 2.1 Protection Implementation Circuit The protection execution circuit is the actuator of the protection action, CH is the charge control switch, and DISCH is the discharge control switch. The corresponding protection actions are performed by controlling CH and DISCH, as shown in the circuit diagram in Figure 2. CH and DISCH are set to low level during normal operation, when M1 and M2 are opened at the same time. When discharge overcurrent or overdischarge occurs, set DISCH to high level, disconnect Q2, and proceed to Q3. Perform charge-sensitive discharge on the gate capacitance of M2, make M2 close instantaneously, and the protection ends. When charging overcurrent or overcharging occurs, set CH to high level and turn off M1. The MOSFET circuit chooses IRF4310, the on-resistance of the MOSFET is only 7k, and the flow rate is as high as 140. 2.2 Balance circuit and secondary protection Figure 3(a) shows the schematic diagram of a battery charging balance circuit, which consists of four units in series Become. The ADV terminal voltage is collected by the single-chip microcomputer to obtain the voltage of this group of batteries. During the charging process, if the charging voltage exceeds 4.2v, the BLA of the MCU control pin is set to a high level. At this time, this group of batteries is short-circuited, and the charging current is charged to other groups of batteries through R4, thus ensuring that the charge of each group of batteries has good consistency. The secondary protection is irreversible and can only be activated when a major danger occurs. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Simple analysis of the structure and working principle of lithium batteries