Design of low power consumption lithium ion battery management system
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2023/08/29 15:29:09
In order to satisfy the application of micro-power surface and improve the safety function, the planning method of ultra-low power Li-ion battery processing system is proposed. This method selects bidirectional high-end microcurrent detection circuit, combines open circuit voltage and charge integration algorithm to complete power detection. Select button batteries instead of DC/DC buck circuits to reduce maximum power consumption. The system has the functions of base protection, residual power detection, defect recording and so on. The lithium-ion battery treatment system shows good stability and reliability on the surface, with a uniform operating current of only 145A.
With the rapid development of electronic technology, the application range of instruments and meters continues to expand, and battery power has become an important choice. The battery handling system is a strong guarantee for the safe operation of the battery. Most current battery handling systems are planned 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, which is not suitable for low-power surface applications. At the remote monitoring surface of the gas, the current of the uniform system is only a few milliamps, and it needs to work continuously at low temperatures for more than six months. In order to meet the application of this project, this paper introduces a low temperature intelligent lithium-ion battery processing system planning method. With base protection, power measurement, charge balance, defect record and other functions. The experiment shows that the system has perfect function and meets the requirement of planning.
1. Overall structure of the system
The low-temperature lithium-ion battery treatment system is mainly composed of a 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 consumption, many low-power devices were 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; The digital potentiometer uses the AD5165 with static current as low as 50nA. The power processing circuit is added to the intermittent operation circuit, the running current is large, and the energy consumption is reduced.
The low temperature battery pack has an additional voltage of 14.8v and is formed by 4 cells in series, each cell contains 8 individual cells. Normal operating voltage 2.5v~4.2v. Each collection cycle collects the voltage of each group of batteries, and the processor instructs the protection realization circuit according to the voltage and executes the corresponding protection action. The end of the equalization circuit is 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 log in the storage device through TTLRS232 conversion module. In order to prevent the MCU from crashing during the charging process, the protection fails. 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 Protection 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 the circuit diagram 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 discharge overcurrent or overdischarge occurs. At this time, Q2 is disconnected, and the charge of the M2 gate capacitor is sensitively discharged through Q3, so that M2 is instantly closed and the protection ends. When there is a charging stream, CH can be set to a high level and M1 can be turned off. The circuit MOSFET is selected IRF4310, the MOSFET on-resistance is only 7k, and the current can be as high as 140.
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