Design of low power consumption lithium ion battery management system
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2023/03/30 11:42:01
In order to satisfy the application of micro power plane and improve the safety function, a planning method of the ultra low power Li-ion battery processing system was proposed. In this method, a bidirectional high-end microcurrent detection circuit is selected, and an open circuit voltage and charge integration algorithm are combined to complete the electric quantity detection. Select button batteries instead of DC/DC step-down circuits to reduce maximum power consumption. The system has the functions of base protection, residual power detection and defect recording. The lithium-ion battery treatment system shows good stability and reliability on the surface, and the working current is only 145A uniformly.
With the rapid development of electronic technology, the application range of instruments is expanding, and battery power has become an important choice. Battery handling system is a powerful guarantee for the safe operation of batteries. Most current battery handling systems plan to use high-capacity battery packs and short battery life. The device served by this processing system has high power consumption, short battery cycle, and the power consumption of the processing system itself is not low, so it is not suitable for low-power surface applications. 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.
FIG. 1 Structure of low-temperature Li-ion battery treatment system
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 cryogenic battery pack has an additional voltage of 14.8v and consists of four cells in series, each containing eight individual cells. Normal operating voltage 2.5v~4.2v. The voltage of each group of batteries is collected in each collection cycle, and the processor instructs the protection implementation circuit according to the voltage and executes the corresponding protection action. The equalization circuit ends in a single chip microcomputer and a transistor, rather than a dedicated equalization chip. The system records the maximum value of abnormal information such as voltage, current, temperature, battery life, and remaining power in 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 microcontroller breakdown during charging, protection failure. New secondary protection circuit. If the voltage exceeds the preset value, the secondary protection circuit is started to fuse the three-end fuse to prevent the occurrence of accidents.
2. Plan hardware
2.1 Protect the implementation circuit
The protection executive circuit is the executive mechanism of the protection action, CH is the charge control switch, DISCH is the discharge control switch. Corresponding protection actions can be realized by controlling CH and DISCH, as shown in Figure 2.
Protection circuit implementation
Figure 2 Protection implementation circuit
CH and DISCH are set to low during normal operation, when M1 and M2 are on at the same time. DISCH is set to high when overcurrent or overdischarge occurs. At this point, Q2 is disconnected and the charge of the M2 grid capacitor is sensitively discharged through Q3, causing M2 to close instantaneously and the protection to end. When there is a charging stream, CH can be set to high level and M1 can be turned off. The circuit's MOSFET of choice is IRF4310. The on-off resistance of MOSFET is only 7k, and the current can be as high as 140.
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