The Battery Soc Estimation Strategy Study

Under the background of the research on hybrid hydraulic excavator in this paper, according to the circular task of the hydraulic excavator and the special variational discharge work condition of the drive-battery in the system, analyzed the traditional estimation strategy of SOC and pointed out that those method are inapplicable under large and variational discharge work condition. This paper presents a new estimation strategy of SOC based on the law of conservation of energy and four-line's measurement for battery internal resistor. Not only can this strategy fit for steady small and large discharge current, but also be adaptive to variational discharge work condition and the estimated value whose warp less than 5% has acceptable precision.There are three main sections about the thesis as follows.First of all, this paper presents a new estimation strategy of SOC based on the law of conservation of energy and four-line's measurement for battery internal resistor. The strategy modifies and compensates the rating capacity in accordance with the relationship between the capacity and life times, temperature. Also we simulated the new estimation strategy with MATLAB/Simulink.The second section is to design the hardware which based on ATMEGA16 singlechip and software which programmed with C language to implement the new strategy. By this work, the new strategy is successfully implemented and also we can compare the new strategy with Ah strategy and the strategy that only based on the law of conservation of energy.The third section is the experiment. The main experiment we did for acid-lead battery as follows: the relationship between OCV and SOC; experiment of small discharge current; experiment of large discharge current in different temperature; experiment of intermittence large discharge current ; experiment of variational discharge current and so on. The experiment results under the condition as described indicate that the estimated values of the new strategy of SOC have acceptable precision and are very close to the real SOC of the battery. That is to say, the new strategy is correct and feasible.