Research On Algorithm Of Estimation Of SOC For Battery Management System

SOC (State Of Charge) is one of the most important parameters for EVs (Electric Vehicles) and HEVs (Hybrid Electric Vehicles). SOC is the basis for EVs to prevent over-charging and/or over-discharging, while for HEVs, it is important in control algorithm. This paper reviewed now existing SOC estimating algorithms and compared their advantages and disadvantages, as well as the different requirement of SOC estimation in different operation environment.After doing a lot of charging and discharging experiments, we got plenty data of battery. By analyzing these data, combining with battery theories, we developed a new battery model, and make it fit the real battery more precisely through different battery experiment. In order to achieve the minimal covariance estimation, we developed the state-space model of the battery pack, and adopted Kalman Filter to make the estimation of SOC more precisely. Then we use different experiments to make this algorithm works better. Finally, this algorithm of estimating SOC evolved to an algorithm that does not require the initial value to be precise.In order to make the algorithm embedded, we designed the hardware and software of the battery management system, which can estimate SOC online and in real time.The BMS has been installed in HEV, and tested for more than 1 year. And the test shows that the algorithm for SOC estimation is proper and stable.