This paper studies the effect of the granularity of a cell model on the voltage accuracy. A multi-coupled cell model with varying parameters is compared with a simpler one (varying voltage source and equivalent series resistance). The first model implies a very long and complex characterization process. The second one is very simple. Experiments are performed at different temperatures by applying a current profile corresponding to a driving cycle of an electric vehicle. Experimental results show both models can be used for 25°C and 10 °C ambient temperatures with reasonable accuracy. Nevertheless, when the temperature is cold the multi-coupled model is more accurate.