This paper introduces the design of low power consumption lithium ion battery ma
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2023/03/31 11:43:09
Abstract: The planning method of a low temperature intelligent lithium-ion battery processing system is introduced. The system is composed of 32 20Ah4 series and 8 parallel monomers. This method has the functions of base protection, power metering, charge balance and defect recording. The experiment shows that the system has perfect function and meets the requirements of planning.
Current battery processing systems are planned for applications with large capacity batteries and short battery life. This machining system is used for high-power equipment, the battery cycle is short, and the power consumption of the machining system is not low, so it is not suitable for low-power surface application. At the remote monitoring surface of the gas, the uniform system has a current of only a few milliamps, and has to operate continuously at low temperatures for more than six months. In order to meet the application of this project, a planning method of low temperature intelligent lithium-ion battery processing system is introduced in this paper. It has the functions of base protection, power measurement, charge balance, defect record and so on. The experiment shows that the system has perfect function and meets the requirements of planning.
1. Overall structure of the system
The low-temperature lithium-ion battery treatment system is mainly composed of base protection circuit, coulometer, balance circuit and secondary protection, as shown in Figure 1.
According to the consideration of low power, many low power devices are selected in the planning, such as MSP430FG439 low power MCU as the processor. The reference voltage is REF3325, and the power consumption is very low, only 3.9db; The operation amplifier uses LT1495, the working current is only 1.5a; Digital potentiometer AD5165, static current as low as 50nA. Add power processing circuit in intermittent operation circuit, running current is large, reduce energy consumption. The low-temperature battery pack has a rated voltage of 14.8v and consists of four batteries in series. Each battery has eight individual batteries. Normal operating voltage is 2.5-4.2v.
The voltage of each group of batteries is collected in each collection period, and the processor sends instructions to the protection circuit according to the voltage and executes the corresponding protection action. Balancing circuit is realized by single chip microcomputer and transistor instead of special balancing chip. The system records the maximum voltage, current, temperature, battery life, and remaining power of the storage device. The processor provides TTL communication interface, and the field computer reads the logs in the storage device through TTLRS232 conversion module. In order to prevent the MCU in the process of charging crash and other abnormal situations, there is a protection fault. A new secondary protection circuit is added. If the voltage exceeds the preset value, the secondary protection circuit will be started and the three fuses will be blown to prevent the occurrence of faults.
2 Hardware Planning
2.1 Protect the implementation circuit
The protection executive circuit is the executive mechanism of the protection action, CH is the charging control switch, DISCH is the discharge control switch, and the corresponding protection action is carried out by controlling CH and DISCH, as shown in Figure 2 circuit diagram.
CH and DISCH are set to low during normal operation, when M1 and M2 are on at the same time. When discharge overcurrent or overdischarge occurs, set DISCH to high level, disconnect Q2, and proceed with Q3. Charge sensitive discharge is carried out on the M2 grid capacitor, so that M2 closes instantaneously and the protection ends. When overcurrent or overcharge occurs, set CH to high level and turn off M1. The MOSFET circuit is IRF4310. The on-off resistance of MOSFET is only 7k and the flow rate is up to 140.
2.2 Balance circuit and secondary protection
Figure 3(a) shows the schematic diagram of a battery charge balancing circuit, which consists of four units in series. ADV terminal voltage is collected by MCU to get the voltage of this group of batteries. During the charging process, if the charging voltage exceeds 4.2v, BLA of MCU control pin is set to high level. At this time, the battery is short-circuited, and the charging current is charged to the other battery groups through R4, thus ensuring that the charge of each battery group has a good consistency. Secondary protection is irreversible and can only be activated in the event of major danger.
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