The purpose of this paper is presenting a reliable modelling of sodium-nickel chloride battery in order to have a powerful tool which is able to foresee the steady state battery behaviour in both discharge and charge operations. The proposed modelling approach allows representing both constant current operations and variable charge or variable discharge current ones, but it does not allow passing instantaneously from one battery mode to another one. This method is based on experimental measures. All the main modelling steps are described and a comparison between the model results and real battery measures, with the same conditions, is presented. The very good agreement between measures and model confirms the robustness of the approach for steady state applications. The paper proposes to adopt a set of standard battery measures from which it is possible to infer a simple but very precise modelling structure.