**4. Conclusions**

To investigate the effect of different operating conditions on the SOC estimation results, a DPM and a FOM were established in this study, taking into account the prediction accuracy and structural complexity of a battery model. Further, based on these two battery ECMs, an HKF was used to estimate the SOC of the battery, utilizing the Ah integration method, KF, and EKF. The SOC estimation results of the DPM and the FOM under DST, FUDS, and HPPC test cycle conditions were compared and analyzed through six sets of experiments. Simulation results showed that the SOC estimation accuracy of both models was satisfactory, and the errors were within the range of ± 0.06. Under any operating condition, the SOC estimation error of the FOM was always less than that of the DPM, but the adaptability of the FOM was not as good as that of the DPM. In future work, we consider combining several typical working conditions to form a new working condition, then identify the parameters of the battery models to make them more adaptable in different operating conditions.

**Author Contributions:** Conceptualization, M.H.; methodology, M.H.; validation, G.J.; formal analysis, G.J., L.L., and Y.X.; investigation, G.J., L.L., Y.X., and D.Q.; writing—original draft, G.J. and L.L.; writing—review and editing, M.H. and C.F.; supervision, M.H. and C.F.; project administration, L.L. and Y.X.; funding acquisition, D.Q., M.H. and C.F. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the National Key R&D Program of China [No. 2018YFB0106102], and the Major Program of Chongqing Municipality [No. cstc2018jszx-cyztzxX0007].

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
