Parameter estimation for a single cell sodium-nickel chloride battery model using experimental data

At this work the parameters of three different equivalent electrical circuit battery model were estimated to a single cell sodium-nickel chloride battery model. The three different models are the first, second and third order Thevenin model. A pulse discharge test was conducted to excite the battery at different state of charge levels. The pulses were applied at every 10% of the state of charge level, so the discharge and rest curves of every pulse were used to estimate the model parameters. The model parameters were estimated using the non-linear least squares as a function of the state of charge. The worst case was observed in the first order model, with a minimum r-square of 0.6672, while the best value was obtained for the third order model, achieving 0.999 r-square in several curves. Other values are presented and compared in this work.