| Energy and environment are the foundation of subsistence and development of human society. Power battery as a typical entity of new energy development has been widely applied to various fields. In order to meet the demand of the wide application in market, power battery usually adopts multiple single cells in series group to supply energy. In the process of mass production, the manufacturing process of each monomer battery is basically same. But the internal resistance, voltage of battery is not exactly the same, the temperature of battery which works in the same work environment is also different. And the initial capacity of each monomer battery is slightly biased, and this difference of performance would be increased in the process of charging and discharging. Finally the difference leads to the overall performance of power battery decrease obviously, and shortens the life of cycle use. For electric vehicles, the cost of battery’s replacement occupies the main part of operation and maintenance of the electric vehicles. In order to reduce the cost, the balance of battery must be improved, which can ensure the safe and stable operation and the value of electric vehicles for a long time.The research object of this topic is power battery, which is made up of lithium batteries. This paper deeply researches the imbalance problem of the series battery and designs a suitable charging mode and balanced control strategy of the power battery.First of all, the characteristics and working principles of lithium-ion batteries are introduced in this paper. The view point of modeling is considered, and combined with the experimental analysis of lithium batteries’ voltage, characteristic of capacity, temperature and other important factors; this paper designs a second-order RC equivalent circuit and researches the improvement of equivalent circuit as a power battery model.Secondly, this paper introduces the charging ways of power battery and control technology of balance charging. The influence of fast charging method to the battery’s life has not yet been determined. After comparing and analyzing the advantages and disadvantages of conventional charging methods, this paper chooses the constant current/constant voltage charging method. Although the battery has high compatibility before use, but the imbalance of cycle charging and discharging still cannot be solved. This paper compares the existing technology of power battery equalization charging which applies in the circuit, analyzes the each equalization of circuit, and sums the non dissipative energy equalization circuit which has a bigger superiority compare with the other balance control methods. This paper designs a kind of equalization charging circuit with central symmetrically distributed energy storage inductors.What’s more, this paper designs the equilibrium charging control system. This paper adopts the TMS320LF2407A of TI Company as a main controller, introduces the entire system of voltage, current, temperature detection circuit, balanced control circuit, power supply and charging protection circuit and so on in detail and designs the main program and the important subroutine of equalizing charge system.Finally, in order to verify the feasibility of this content, this paper uses six section lithium battery series as equalizing charge object to experiment. The result shows that the equalization circuit and the control method can balance the battery effectively, efficiency is high and the result is ideal. |
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