Reserach On The Battery Management System Of Lithium Battery

Because of the energy shortage and the environmental pollution, it has become an inevitable trend that the electric vehicles will replace the fuel vehicles. As an important component of the electric vehicle, the battery management system(BMS) naturally become the focus of research. The battery management system mainly provides detection and management for electric vehicles when they are moving. BMS includes the sampling of the voltage and the current, the sampling of the temperature, the estimation of State of Charge and the balancing of the battery. It has important significance to the health of electric cars, so the power management system is necessary to study. The main contents of this paper include the following aspects:1. This paper is about lithium batteries. It introduces the composition structure, chemical properties and the equivalent circuit of the lithium batteries. It also introduces the basics of the power management system, including the battery sampling, battery balancing and SOC estimation.2. In this paper, the extended Kalman filter method is used for the SOC estimation of lithium battery and the calculation process of the extended Kalman filter method was deduced in detail. By identifying the equivalent circuit model of the lithium battery, we get the value of the equivalent components through simulation. Combining the equivalent circuit with extended Kalman filter method, we get the waveform of SOC.3. The sampling system, including the single battery voltage sampling, the total voltage and current sampling, the temperature sampling is designed. In the experiment, the design of the single voltage sampling is based on the chip named LTC6804-2. The design of total voltage and current sampling is based on separate components. The design of the temperature sampling is based on a temperature sensor chip. We complete the design of hardware and software.4. We analyze the bi-directional flyback converter which is the most widely used circuit for cell balancing. Then we get its’ simulation waveform. In the experiment, the design of the cell balancing circuit is based on the balancing chip named LTC3300-1. We complete the design of hardware and software.