Design Of Equalization System And Research On Method For Lithium Battery Pack

In recent years, the energy crisis and environment deterioration have become increasingly prominent, the traditional automobile not only consumes fossil fuel but also causes great pollution.Therefore, electric vehicles powered by batteries are getting more and more attention.Power batteries for electric vehicles need to connect in series and/ or in parallel to achieve the voltage, power and energy requirements of electric vehicles. If the phenomenon of single cell inconsistency occurs in the battery pack, the battery power will down and the utilization rate is reduced.This topic is based on "Research on the key technology of explosion-proof trackless rubber tyred electric vehicle used in mine" which is from Beijing Municipal Science and Technology Commission, and the main task is to put forward the practical solution to the battery pack imbalance.This paper introduces the equivalent circuit model of battery firstly, then tests the performance parameters of LiFePO4 battery and lithium titanate battery. Meanwhile, it mainly analyzes the effects of DC resistance, polarization voltage, SOC and battery capacity on the unbalance of batteries.The equalization system design is mainly divided into online equalization system and the off-line equalization system,according to the analysis of existing equalization circuits and strategies, the two systems chose the circuit of energy consumption based on voltage equalization strategy.In this paper, we have completed the design of the equalization system in two ways, online and off-line, respectively. The online equalization system takes the LTC6804-1 and Freescale single-chip as the core.The main function of acquisition and equalization board is collecting cell voltage, measuring monomer temperature, balancing battery capacity and communicating with external device.The function and module design of off-line equalization system is proposed in this paper.Function design includes support for various types of lithium batteries, Support for the two battery pack structures,support for automatic balancing and manual balancing mode and support for changing balancing current.After the completion of the design, the paper tests the function of two equalization systems with EVTS ARBIN and off-line equalization device in three kinds of unbalanced conditions for lithium titanate battery pack and LiFePO4 battery pack. At last,the function of the equalization system is verified and the experimental data are analyzed.